Course Compendium Sensory and Related Techniques for Evaluation of Dairy Foods 23rd Short Course Organized under the aegis ofCentre of Advanced Studies in Dairy Technology 17thJune, 2008 to 7th July, 2008 Course Director Dr. Dharam Pal Course Coordinator Dr. Ashish Kumar Singh Centre of Advanced Studies Dairy Technology Division National Dairy research Institute Karnal 132001 (Haryana), India 2008 Published by Dr. A. A. Patel Head, Dairy Technology Division Director, CAS Course Director Dr. Dharam Pal Course Coordinator Dr. Ashish Kumar Singh Editing and Compilation Dr. Dharam Pal Dr. V.K. Gupta Dr. R.R.B. Singh Dr. Mrs. Latha Sabikhi Dr. A.K. Singh Dr. Sumit Arora All Right Reserved Nopartofthislecturecompendiummaybereproducedor transmitted in any form or by any means, electronic or mechanical, includingphotography,recordingoranyotherinformationstorage andretrievalsystemwithoutthewrittenpermissionfromthe Director, NDRI, Karnal Cover Design and Page Layout Mr. Avneet Rajoria & Mr. Ramesh Modi i ii Committees for the Course Organization ORGANIZING COMMIITTEE Dr A. A. Patel (Director, CAS) Dr. S. Singh Dr. G. K. Goyal Dr. V. K. Gupta Dr. S.K. Kanawjia Dr. D. K. Thompkinson Dr. Dharam Pal (Course Director) Dr. Ashish Kumar Singh (Course Coordinator) RECEPTION COMMITTEETECHNICAL COMIITTEE Dr. G. K. Goyal (Chairman)Dr. V. K. Gupta (Chairman) Dr. Ashish Kumar SinghDr. R. R. B. Singh Mr. Ram Swaroop Dr. (Mrs.) Latha Sabikhi HOSPITALITY COMMITTEEPURCHASE COMMITTEE Dr. S. K. KanawjiaDr. D. K. Thompkinson(Chairman)(Chairman) Dr. (Mrs.) Latha SabikhiMr. F. C. Garg Mr. Lahiri SinghMr. M. K. Trehan iiiShort Courseon Sensory and Related Techniques for Evaluationof Dairy Foods 17th June-7 July, 2008 17.06.2008 (TUESEDAY) 10.:00 AM- 10.15 AMRegistrationDr. Ashish Kumar Singh 10.15 AM-10.50 AMVisit to ATICMr. M. K. Trehan 11.00 AM-11.45 AMInauguration of Course 11.45 AM-1.00 PMVisit to Experimental Dairy PlantMr. M. K. Trehan 1.00 PM- 2.00 PMLunch 2.15 PM -3.30 PMVisit to Model DairyMr. M. K. Trehan 3.30 PM- 3.45 PMTea 3.45 PM- 4.30 PMVisit to LibraryMr. M. K. Trehan 18.06.2008 (WEDNESDAY) 9:45 AM-10.45 AMRequirements for Sensory Evaluation of Foods (Theory) Dr. Dharam Pal 10.45 AM-1.00 PMDeterminationofTastethreshold (Practical) Dr. Dharam Pal Mr. Ramswaroop 1.00 PM 2.00 PMLunch 2.15 PM- 3.15 PMDeterminationofOdourthreshold (Practical) Dr. Dharam Pal Mr. Ramswaroop 3.15 PM - 3.30 PMTea3.30 PM 4.30 PMLibrary Consultation - 19.06.2008 (THURSDAY) 9:45 AM- 10.45 AM Sensory Methods and their Applications in Evaluating Quality of Foods (Theory) Dr. Dharam Pal 10.45 AM- 1.00 PM SensoryEvaluationofMilk(Theory& Practical) Dr. Dharam Pal Mr. Ramswaroop 1.00 PM- 2.00 PMLunch 2.15 PM- 3.15 PMSensory Evaluation of Dried Milk and Milk Products (Theory) Dr. V. K. Gupta 3.15 PM - 3.30 PMTea3.30 PM 4.30 PMLibrary Consultation 20.06.2008 (FRIDAY) 9:45 AM- 1.00 PMDetermination of Water Activity of Foods (Theory & Practical) Dr. R. R. B. Singh Mr. Avneet Course Programme ivRajoria 1.00 PM 2.00 PMLunch 2.15 PM- 3.15 PMPrinciples of Good Laboratory Practice (Theory) Dr. Rajan Sharma 3.15 PM-3.30 PMTea 3.30 PM-4.30 PMLibrary Consultation- 21.06.2008 (SATURDAY) 9:45 AM- 10.45 AMChemistry of Flavour Development in Cheese (Theory) Dr. Sumit Arora 10.45 AM-1.00 PMMicrostructure of Dairy Products (Theory & Practical) Dr. S. K. Tomar 1.00 PM 2.00 PMLunch 2.15 PM- 3.15 PMConsumer Acceptance Studies (Theory)Dr. (Mrs.) Latha Sabikhi 3.15 PM - 3.30 PMTea 3.30 PM 4.30 PM Colour Measurement of Foods (Practical) Dr. Ashish Kumar Singh Mr. .Avneet Rajoria 23.06.2008 (MONDAY) 9:45 AM- 1.00 PM Sensory Attributes of Ice-cream and Frozen Dessert (Theory & Practical) Mr. F. C. Garg Mr. Ramswaroop 1.00 PM 2.00 PMLunch 2.15 PM- 3.15 PMViscoelastic Characteristics of Foods (Theory) Dr. G. R. Patil 3.15 PM -4.30 PMSensoryEvaluationofMilkChocolate (Practical) Dr. Ashish Kumar Singh Mr. Modi Ramesh 24.06.2008 (TUESDAY) 9:45 AM- 10.45 AMStatistical Techniques for Analysis of Sensory Data (Theory) Dr. R. Malhotra 10.45 AM-1.00 PMSensoryEvaluationofDriedMilks (Practical) 1.00 PM 2.00 PMLunch 2.15 PM- 4.30 PMTexture Measurement of Dahi & Yoghurt (Practical) Dr. Dharam Pal Mr. N. Raju 25.06.2008 (WEDNESDAY) 9:45 AM- 10.45 AMAnalytical techniques for Characterization of Flavoring Compounds in Dairy Products (Theory)Dr. Rajesh Bajaj 10.45 AM-1.00 PMDescriptive Sensory Analysis of foods (Practical) Dr. Ashish Kumar Singh 1.00 PM 2.00 PM11Lunch 2.15 PM- 4.30 PMSensory evaluation of Paneer and Un-ripened Cheeses (Theory & Practical) Dr. S. K. Kanawjia v 26.06.2008 (THURSDAY) 9:45 AM- 1.00 PMSensory and Rheological Properties of Fermented Milks (Theory & Practical) Dr. (Mrs.) Latha Sabikhi Mr. Ram Swaroop1.00 PM 2.00 PMLunch 2.15 PM- 4.30 PMSensory Evaluation of Khoa & Khoa based Sweets (Theory & Practical) Mr. F. C. Garg Mr. Ram Swaroop27.06.2008 (FRIDAY) 9:45 AM- 10.45 AMBiosensors in Chemical Quality Assessment of Dairy and Food Products (Theory) Dr. Rajan Sharma 10.45 AM-11.15 AMNutritional and Therapeutic Assessment Techniques for Dairy Products(Theory) Dr. (Mrs.) Suman Kapila 11.15 AM-11.30 AM Tea break 11.30 AM-1.00 PMTexture Profile Analysis of Dairy Products (Practical) Dr. R. R. B. Singh Mr. Avneet Rajoria 1.00 PM 2.00 PMLunch 2.15 PM- 4.30 PMSensory Characteristics of Milk Protein Products (Theory) Dr. V. K. Gupta 28.06.2008 (SATURDAY) 9:45 AM- 1.00 PMStatistical Software for Analysis of Sensory Data (Theory & Practical) Dr. R. Malhotra 1.00 PM 2.00 PMLunch 2.15 PM-4.30 PMSensoryCharacteristicsofConcentrated and UHT Milk (Theory & Practical) Dr. R. R. B. Singh 30.06.2008 (MONDAY) 9:45 AM- 10.45 AMInfluence of Packaging Materials on Sensory Quality of Dairy Products (Theory) Dr. G. K. Goyal 10.45 AM-1.00 PMTestingofPackagingMaterialsforDairy Foods (Practical) Dr. G. K. Goyal Mr. Ram Swaroop1.00 PM 2.00 PMLunch 2.15 PM- 3.15 PMChemistry of Quality Attributes in Heat Processed Dairy products (Theory) Dr. (Mrs.) Bimlesh Mann 3.15 PM-3.30 PM Tea 3.30 PM-4.30 PMLibrary Consultation 1.07.2008 (TUESDAY) 9:45 AM- 1.00 PMDescriptive Sensory Analysis of Dairy Foods (Theory & Practical) Dr. Ashish Kumar Singh & Ms. Rekha Chawla 1.00 PM 2.00 PMLunch 2.15 PM- 4.30 PMRole of Starter and Adjunct Cultures on Quality Characteristics of Fermented Dairy Products (Theory) Dr. Rameshwar Singh vi2.07.2008 (WEDNESDAY) 9:45 AM- 10.45 AMRole of Primary Senses in Sensory Evaluation of Foods (Theory) Prof. V. K. Joshi 10.45 AM- 11.00 AMTea 11.00 AM- 1.00 PMTechniques for Sensory Evaluation of Beverages (Theory & Practical) Prof. V. K. Joshi 1.00 PM 2.00 PMLunch 2.15 PM- 4.30 PMJudging Contest for ParticipantsDr. Dharam Pal Mr. Ramswaroop 3.07.2008 (THURSDAY) 9:45 AM- 1.00 PM Sensory Characteristics of Fat-rich Dairy Products (Theory & Practical) Dr. A. A. Patel Mr. Ramswaroop 1.00 PM 2.00 PMLunch 2.15 PM- 3.15 PMEmerging Concepts in Sweet Taste (Theory) Dr. Sumit Arora 3.15 PM-3.30 PMTea 3.30 PM- 4.30 PMRheological & Textural Characteristics of Solid Foods (Theory) Dr. A. A. Patel 4.07.2008 (FRIDAY) 9:45 AM- 1.00 PMBasic Concepts of Rheology and Texture Measurement of Foods (Theory) Dr. D. S. Sogi 1.00 PM 2.00 PMLunch 2.15 PM- 4.30 PMProperties of Food Powders (Theory & Practical) Dr. R. R. B. Singh Mr. Avneet Rajoria 5.07.2008 (SATURDAY) 9:45 AM- 10.45 AM Concept of Colour Measurement and Sampling Techniques for Quality Evaluation of Food (Theory)Dr. S. N. Jha 10.45 AM- 1.00 PMSensory Characteristics of Ripened Varieties of Cheeses (Theory & Practical) Dr. S. Singh 1.00 PM 2.00 PMLunch 2.15 PM- 3.15 PMNondestructive methods for Quality Evaluation of Dairy and Food Products (Theory) Dr. S. N. Jha 3.15 PM - 3.30 PMTea & Discussion 3.30 PM 4.30 PM 7.07.2008 (MONDAY) 9:45 AM- 10.45 AMCourse Evaluation 10.45 AM-11.15 AMInteraction with the Course Faculty 11.15 AM-1. 00 PM1.00 PM 2.00 PMLunch 2.30 PM- 3.30 PMValedictory function ForewordDr. A.K. Srivastavai Committees for Course the Course Organization ii CourseProgrammeiii 1RequirementsforSensoryEvaluationof Foods Dr. Dharam Pal1 2SensoryMethodsandtheirApplications in Evaluating Quality of Foods Dr. Dharam Pal10 3Sensory Evaluation of MilkDr. A.K. Singh18 4Sensory Characteristics of Fresh CheeseDr. S.K. Kanawjia25 5Sensory Attributes of Ice CreamMr. F.C. Garg33 6SensoryEvaluationofDairyProducts withSpecialEmphasisonFlavour Lexicon V. Pathak & Z.F. Bhat40 7SensoryAttributesofConcentratedMilk and their Evaluation Dr. R.R.B. Singh48 8SensoryAttributesofFermentedMilk Products Dr. Latha Sabikhi56 9Application of e-tongue in monitoring Sensory quality of foods Dr. S.K. Kanawjia65 10Role of Packaging Materials In Enhancing Sensory Quality of Dairy Products Dr. G.K. Goyal 77 11Consumer Acceptance StudiesDr. Latha Sabikhi83 12ChemistryofFlavourDevelopmentIn Cheese Dr. Sumit Arora86 13AnalyticalTechniquesfor CharacterizationofFlavouring Compounds In Dairy Products Dr.RajeshKumar, Dr.R.B.Sangwanand Dr. Bimlesh Mann 97 14SensoryAttributesofMilkProtein Products Dr. Vijay Kumar Gupta 104 15SensoryEvaluationofDriedMilkand Milk Products Dr. Vijay Kumar Gupta 110 16ApplicationofRheologyinQuality Assurance in Food Processing Dr. Dalbir Singh Sogi 116 CONTENTS 17NondestructiveMethodsforQuality Evaluation of Dairy and Food Products Dr. S. N. Jha 126 18GoodLaboratoryPracticesGenesis& Concept Dr. Rajan Sharma135 19ChemistryofQualityAttributesinHeat Processed Dairy Products Dr. (Mrs.) Bimlesh Mann 144 20DeterminationofSorptionIsothermsand Generation of Sorption Data Dr. R. R. B. Singh 155 21BiosensorinChemicalQuality Assessment of Dairy and Food Products Dr. Rajan Sharma165 22SoftComputingModelswith Applications to Dairying Dr. A. K. Sharma177 23MicrostructureofCulturedDairy Products:An Update Dr. Sudhir Tomar184 24NutritionalandTherapeuticAssessment for Functional Dairy Products Dr. Suman Kapila196 25Viscoelastic Behaviour of FoodsDr. G. R. Patil208 26Fundamentals of RheologyDr. Dalbir Singh Sogi214 27SwitchingSweetenersASweet Approach Dr. Sumit Arora 221 28ConceptofColourMeasurementand SamplingTechniquesforQuality Evaluation of Food Dr. S. N. Jha 227 29SensoryEvaluationofRipenedVarieties of Cheese Dr. S. Singh245 30StatisticalTechniquesforAnalysisofSensory Data Dr. Ravinder Malhotra254 31Descriptive Sensory AnalysisDr. A. K. Singh267 Sensory and Related Techniques for Evaluation of Dairy Foods1 Dr. Dharam Pal Principal Scientist Division of Dairy Technology National Dairy Research Institute, Karnal. 1.0 INTRODUCTION Anumberofqualityassuranceproceduresareusedtoexamineandmaintain qualityofadairyproduct.Thetestingstartsfromreceptionofrawmaterial,for example,milk,tocloseexaminationoffinalizedproduct.Thesetestsarephysical, chemical,microbiological,instrumentalandsensory.Inourcountry,thedairy industry so far considers the chemical and microbiological quality as the sole criteria ofdecidingfoodquality.Withtheavailabilityofmoremilk,increasedcompetition andconsumersawarenessaboutquality,thesignificanceofsensoryevaluationis being realized and it is emerging as an important analytical tool in fast growing dairy industry.Sensoryevaluation maybedefined as a scientific discipline used to evoke, measure, analyze and interpret results of those characteristics of foods and materials as they are perceived by the senses of sight, smell, taste, touch and hearing. Thesensoryevaluationisveryimportantinproductevaluationonaccountof following advantages: i)It is a simple analytical tool, ii)It identifies the presence or absence of perceptible differences in terms of flavour, texture, colour and appearance, iii)Theseimportantqualityattributesaremeasuredinafastandquantifiable manneremployingsensorytechniques.Theuseofchemicaland instrumentalmethodsforexaminingsensorycharacteristicsaretime consuming, complicated and expensive, iv)Itenablesidentificationofaparticularproblemordefectthatcannotbe detected by other analytical techniques, v)Sensoryevaluationtechniqueshelpinensuringthattheconsumersgeta non defective and enjoyable product. Inrecentyears,thecompetitioninfood/dairycorporatehastremendously increased.Thefoodprocessingcompaniesaremakingveryfastchangesintheir existing product in terms of ingredients, value addition, packaging etc. or developing newproductstograblargerglobalmarketshare.Inallthesesituations,sensory REQUIREMENTS FOR SENSORY EVALUATION OF FOODSSensory and Related Techniques for Evaluation of Dairy Foods2 evaluationplaysacriticalrole.Thevariousapplicationsofsensoryevaluationare given as below: Inspection of raw materials New product developmentimprovement/reformulation of existing productCost reduction Quality assuranceSelection of packaging material Shelf life studiesEstablishing analytical/ instrumental/ sensory relationships 2.0REQUIREMENTS Asuccessfulimplementationofsensoryevaluationprogrammerequires following three major components: Proper laboratory facilities Sensory panels and their rigorous training programmes Statistician 2.1 Laboratory Set UpMany designs of the sensory evaluation laboratory are available. The sensory laboratorysetupnormallyconsistsofareceptioncumbriefingroom,panelbooths andpreparationroom.Sensoryevaluationshouldbeconductedinquietandwelllit rooms free from any odours. The dominant motive of constructional details should be tohavecomfortforconcentratedprolongedtestingandeaseofcleaning.Pleasing neutralshadesandmaintenanceofcomfortabletemperatureandhumidityconditions ofthewholeareaoratleastthepanelroomaredesirable.Thetestingareawhere booths are located should be separated from sample preparation room and wash room and store by a complete partition. 2.1.1 Reception and briefing room Itshouldbesodesignedastoensuremaintenanceofpleasantattitudesand minimizetraffictothebooths.Panelmembersshallassemblehere,register,receive the evaluation card and briefed about the test. 2.1.2Testing booths/area: This is the area where panel members carry out actual sensory evaluation of dairy products. Testing area shall be located separately but in the immediate vicinity of the preparationarea.Thisareaisnormallydividedinsmallbooths(numberofbooths between 5 to 10) so that each panel member can independently evaluate the product. Following conditions have to be maintained in testing area for obtaining best results: -Thetemperatureandrelativehumidityshallbeconstant,controllableand comfortableforevaluators.Atemperatureofabout20oCand62%relative humidity are considered to be optimum. Sensory and Related Techniques for Evaluation of Dairy Foods3 -Noise level shall be kept to a minimum during the tests. The movement of persons shall also be restricted in the area. -Thetestingareashallkeepfreefromodours.Aslightpositivepressuremaybe created in the testing area to reduce inflow of odorous air from other area. -Lightingisveryimportantinallsensorytesting.Itisparticularlyimportantin colour examination of dairy products. Lighting particularly in testing booths shall beuniform,shadowfree,controllableandofsufficientintensitytopermit effective evaluation of the colour and appearance of samples. In most cases, lights havingacorrelatedcolourtemperatureof6500K(or110candlefootlight)are desirable.Inordertomaskdifferencesincolourandotherappearance characteristicsspeciallightingdevices,suchasadimmerdevice,colored lamps/filters or sodium vapour lamps, may be provided. -Thesizeofeachtestingboothshallbesufficientlylargetoaccommodatethe samples, utensils, sink, rinsing agents and score sheet/card. An area of 0.9 m wide and0.6mdeepisconsideredoptimumforthispurpose.Theheightofworking space in the booth should be appropriate to allow comfort to the evaluator. -Acounterontheserving/distributionareasideshallbeprovided.Openings, coveredbyslidingdoors,ofconvenientsizemaybeprovidedforsupplying samples into the booths from the serving counter. A system, such as light bulb on the counter side, is devised for evaluator to signal to the operator when he is ready for a sample. 2.1. 3Preparation room It shall be suitably separated from the testing room and should be equipped for preparingandservingfoodsamples.Theroomshouldhavethefacilityforcooking range hot and cold storage cabinet. The ventilation should be proper and the cooking odours should not penetrate the panel booth area. The samples shall be passed to the testboothsthroughhatchinthepartition.Thehatchontheservicecountershould preferablybeconstructedinsuchamannerthatthereshallbenorecognitionof individual or either side of partition. Thelaboratoryfacilityshouldbeflexibleenoughtohandleenoughtohandle current and future testing activities as well as to provide a workable environment for thestaff.Theuseofcomputers has beenrecommendedforsensoryevaluationwork. Inthatcase,sensoryevaluationlaboratoryshouldincludespacefordataprocessing equipment. 3.0SELECTION OF SENSORY PANELISTS Analysisofsensorypropertiesoffoodinvolvestheuseofhumansubjectsin thelaboratory/processingplantenvironment.Thesensitivityandexperienceofan evaluator (panelist) influence the accuracy of results. The evaluator should work like a calibrated instrument and provide reproducible results. The selection of most stable Sensory and Related Techniques for Evaluation of Dairy Foods4 andsensitivepanelmembersandtheirtraining,istherefore,veryessentialfor efficient conduct of sensory analysis of dairy products. 3.1Types of panel Thesensorypanelsareclassifiedintothreecategoriesviz.,trained,semi trainedandconsumerpanel.Thepanelistsareselectedandtrainedbythesensory leader/coordinator depending on the type of the product. Trained Panel: They should be carefully selected and trained, and need not be expert panelists.Thetrainedpanelshouldbeusedtoestablishtheintensityofasensory characteroroverallqualityofafood.Atrainedpanelshouldcompriseofsmall numberofmembersvaryingfrom5to10andmaybeusedinalldevelopmental, processingandstoragestudies.Asmallhighlytrainedpanelwillgivemorereliable results than a large untrained panel. Semi-TrainedPanel(D&CPanel):Thistypeofpanelshouldbeconstitutedfrom persons normally familiar with quality of milk and different classes of dairy products. This panel is capable of discriminating differences and communicating their reactions, thoughitmaynothavebeenformallytrained.Inasemi-trainedpanelindividual variationscanbebalancedoutbyinvolvinggreaternumberofpanelists.Thepanel, shouldnormallyconsistofabout25to30members,andshouldbeusedasa preliminaryscreeningprogrammetoselectafewproductsforlargescaleconsumer trials. ConsumerPanel:Themembersoftheconsumeroruntrainedpanelshouldbe selectedatrandomandensureduerepresentationtodifferentage,sex,raceand income groups in the potential consumer population in the market area. More than 80 members are required to constitute a consumer panel. Two channels can be adopted for screening and selection of sensory panel members. First,fromthequalitycontrol/researchlaboratoryandsecondsourceisfromthe processingunit.Anotheroptionistohaveamixedsourcei.e.someofthemembers from quality control laboratory/research laboratory and the remaining from processing sections.Normallydoublethenumbers of panelists finally required are selected. For example,if7membersareneededinthefinalpanelatleast15shouldbeinitially screened 3.1.2Qualification for Screening a Panelist Interest and motivation:Candidates who are interested in sensory analysis and have investigating curiosity are likely to be more motivated and will do better jobs. Attitudestofoods:Candidateshavingstronglikingordislikingtowardsadairy product should not be screened. Knowledgeandaptitude:Theevaluatorsshouldhavecapacitytoconcentrateandto remainunaffectedbyexternalinfluences.Heshouldhaveknowledgeaboutbasic aspects and principles of milk and its processing into products. Sensory and Related Techniques for Evaluation of Dairy Foods5 Health: Candidates should be in good general health. They shall not suffer from any disabilities,whichmayaffecttheirsenses,orfromanyallergiesorillnessandshall not take medication, which might impair their sensory capacities. AbilitytoCommunicate:Theabilityofcandidatestocommunicateanddescribethe sensations they perceive when judging a food product is particularly important. Availability:Candidatesshallbeavailabletoattendbothtrainingandsubsequent evaluation.Personnelwhotravelfrequentlyorhaveheavyworkloadsareoften unsuited for sensory work. Table 1.Examples of materials/substances and their concentration for identification/ matching test Taste or odourMaterial Concentration in water (taste material) or ethanol* (odorous material) at room temperature (g/litre) Taste SweetSucrose16 Acid/ sourTartaric acid or citric acid1 BitterCaffeine0.5 SaltySodium chloride5 Astringent Tannic acid orpotassium aluminium sulfate (alum)1 0.5 MetallicFerrous sulfate**, hydrates, FeSO4.7H2O 0.01 Odour Lemon, freshCitral (C10H15O)1 x 10-3 VanillaVanillin (C8H8O3)1 x 10-3 ThymeThymol (C10H14O)5 x 10-4 Floral, JasmineBenzyl acetate (C8H12O2)1 x 10-3 * Stock solutions are prepared with ethanol, but the final dilution is made with water and shall not contain more than 2% of alcohol. **To mask yellow colour, present the solutions in closed opaque containers or under dim or colouring light. TestforDetectionofBasicTaste:Solutionsoffourbasictastesolutions,namely sweet,sour,saltandbitterarepreparedoftheconcentrationasshownintable2 below: Sensory and Related Techniques for Evaluation of Dairy Foods6 Table 2. Concentration of taste solutions used to examine the acuity of candidates MaterialTaste Quality Concentration in water at room temperature CaffaineBitter0.27 g/ litre Citric AcidSour0.60 g/ litre Sodium ChlorideSalt2 g/ litre SucroseSweet12 g/ litre 3.1.3Screening and Selection Sensory panelists can be screened and selected by adopting several tests. The followings are the most commonly used tests: determine impairment of primary senses (colour, vision, ageusia and anosmia) matching test for taste and odour substancesability to detect basic taste and odour acuity determine ability to characterized texture performance in comparison with other candidates ColourVision:Candidateswithabnormalcolourvisionorcolourblindnessare unsuitableforjudgingofdairyproducts.Assessmentofcolourvisioncanbecarried out by a qualified optician. Matching Test:Samples of sapid and/ or olfactory materials, depending on the nature of product for which the panel members are to be trained later, at well above threshold levelsoftheexpectedpanelistsareprepared.Theexamplesofthesematerialsare given in table 1. Each sample is allotted a different, random, three digit code number. Candidates are presented with one sample of each type and are allowed to familiarize themselveswiththem.Theyarethenpresentedwithaseriesofthesamematerials labelled with different code numbers. They may be asked to match each of them with oneoftheoriginalsetanddescribethesensationtheyareexperiencing.Forthe substances and their concentration given in table 1, candidates who make fewer than 80% correct answers should not be chosen as selected panelists. Thesetestmaterialsalongwithblank(water)arepresentedtothecandidates andaskedthemtodetectthetastequality.Preferablycandidatesshouldhave100% correct responses as the concentrations test materials are at the super threshold level. Inabilitytodetectdifferencesandidentifythetastequalityafterseveralrepetitions indicate that the candidates have poor sensitivity and unsuitable to judge the samples on the basis of taste. OdourRecognitionTest:Candidatesarepresentedmany(about10ineachlot) odoriferous substances. Some of these materials are familiar (those we use daily such as tea, coffee, onion, garlic, curd, orange, spices, etc.) and others unfamiliar (table 3). Theodorousfoodmaterialsmaybepresentedpreferablyinformofliquidextractor assuch(inatesttubeininvisibleform).Theconcentrationshouldbeabovethe Sensory and Related Techniques for Evaluation of Dairy Foods7 recommendedthresholdlevel.Candidatesaregradedaccordingtocorrectanswers. Those recognize less than 65% of odorous substances/odour are unsuitable as panelist for this type of test. Table 3.Examples of unfamiliar odorous material for odour recognition test MaterialName most commonly associated with the odour BenzaldehydeBitter almonds, cherry, .. Octene-3-OlMushroom, Phenyl-2-ethyl acetateFloral, Diallyl sulphideGarlic, CamphorCamphor, medicine, MentholPeppermint, Butyric acidRancid butter, Acetic acidVinegar, Isoamyl acetateFruit, banana, ThymolSpices, VanillinVanilla, Texturalcharacterization:Thistypeoftestishighlybeneficialforselectingthe panelistsforjudgingthedairyproductswheretextureisanimportantattributelike cheese,paneer,butter,icecream,khoaetc.Inthistest,allrangeofproductshaving typicaltexture(table4)isgiventothecandidates.Theyhavetoarrangethese products according to the nature and level of textural properties, such as hard, elastic (spongy), adhesive (sticky/pasty), brittle, gummy, cohesive, chewy etc. A satisfactory levelofsuccessinthistaskcanbespecifiedonlyinrelationtotheproductsused. Candidates who achieve less than 65% of the maximum score are unsuitable. Table 4.Food products with typical textural attributes Food productTextural attribute most commonly associated Carrot (raw)Hard, crunchy ButterSoft ToffeeGummy Meat/ PaneerChewy BiscuitBrittle RasogollaSpongy OrangesJuicy, cellular particles Chest nut pureePasty SemolinaGrainy SaltGritty/ coarse Sensory and Related Techniques for Evaluation of Dairy Foods8 3.1.4Training Thepurposeoftrainingistoincreasesensoryacuityofpanelistsandprovidethem with rudimentary knowledge of procedures used in sensory evaluation. Training also developstheabilityofpanelmemberstodetect,recognizeanddescribesensory stimulirelatedtofoodproducts.Ageneralstep-wiseapproachfortrainingin food/dairy product is summarized as below: a)Sensorypanelists(assessorsorevaluators)shouldbeexplainedthebasic requirements of sensory evaluation i.e. what they should do and what not to do. b)Assessors shall be acquainted with the: -desirable and undesirable attributes of the product -correct terminology -use of score card -scoring technique/ sequence of observations c)Samplesusedfortrainingandtestingshallbecharacteristicoftheirorigin,style andquality,andrepresentativeoftherangegenerallyfoundinthemarket(all defects may be simulated in the samples under laboratory conditions). A reference (having most desirable characters) is always provide with test samples. d)Difficultiesofthetestaresoadjustthethatthegroupasawholewillfind difference between the samples, but some panelists will fail. e)Start with the large group and reject those who are insensitive or under perform. f)Finally a trained panel comprising of 5-6 members is retained. 4.0STATISTICIAN The role of a statistician is very important in sensory evaluation programme at each stage starting from designing of experiments till drawing valid conclusions from the sensory data. A statistician help in planning of experiment coding and presentation ofsamples,statisticalanalysisofdatabyapplyingappropriatedesignand interpretationofresults.Though,nowadaysseveralsoftwaresareavailablefor statisticalanalysis,theroleofstatisticianintabulationofdataanddrawingof inferences is equally important. 5.0 SAMPLING REQUIREMENTS i)Samplingshouldbecarriedoutbyatrainedandexperiencedpersonanditis essential that the sample should be representative of the lot. ii)A procedure of sample preparation which is most likely to bring out the difference in the particular quality attribute under evaluation shall be selected. Care shall be taken that no loss of flavor occurs and no foreign tastes or odours are imported by the procedure during preparation, storage, serving, etc. Depending upon the nature ofthematerialandaimofthetest,theneedforamediumintestingauxiliary itemsshouldbedecided.Foodslikehotsauce,spices,vinegar,etc.mayrequire dilution with some medium because of their intense physiological efforts. Sensory and Related Techniques for Evaluation of Dairy Foods9 iii) Thepanelistshouldbeallowedtohavesufficientsamplenecessarytomake judgment.Unless,onlyonesampleistobetested,fullnormalservingquantities shall not be served even though the material is available. iv)Thetemperatureofservingshouldbeclosetothatrecommendedforthefood product. The samples shall be served in utensils of the same type and appropriate size, shape and colour and they shall not import any taste or odour to the sample. The test should be carried out at least one hour before or after lunch. v)Use of materials which are likely to vitiate results such as smoking, chewing, pan (betel-vine)andtakingintoxicantsbyapanelistshouldhaveatimelapseofat leasthalf-an-hourbeforethetest.Useofstrongodoriferoussubstancessuchas cosmetics, flowers, hair oil should be avoided. vi) The number of samples served in any session shall depend upon the nature of the testproductandupontheevaluationmethoduse.Incasethetestproductexert mildsensoryeffects,largenumberoftheproductsexertingstrongprolonged sensory effects, the number of samples may be reduced to less than 5. vii) Sincecodingisnecessarytoobscuretheidentityofthesample,amultipledigit codegeneratedfromatableofrandomnumbersshouldbeused.Avoidconstant use of certain codes or a set of codes to expedite tabulation of results. 6.0 EVALUATION CARD Theevaluationcardshouldbeclearlyprintedandthemattershouldbe arrangedinlogicalsequenceforexaminationwhichisexpectedundereachtest. Appropriate terminology without ambiguity shall be used. The evaluation card should besimple,brief,easytofollowandrecordwhatisexactlyrequired.Dueweightage should be given to all the sensory attributes. 7.0 REFERENCES Amerine,M.A.,Pangborn,R.M.andRoessler,E.B.(1965).PrinciplesofSensory Evaluation of Food Academic Press, New York. ASTM (1986). Manual on Sensory Testing Methods. STP 434, American Society for Testing and Materials, Philadelphia, U.S.A. Bodyfelt, F.W., Tobias, J. and Trout, G.M. (1988). The Sensory Evaluation of Dairy Products, AVI Publ. Co., New York. Dharam Pal, Sachdeva, S. and Singh, S. (1995). Methods for determination of sensory quality of foods: A critical appraisal. J. Fd. Sci. Technol. 32 (5):357-367. Russell,G.M.(1984).Somebasicconsiderationincomputerizingthesensory laboratory. Food Technol. 38(9): 67-70. Stone,H.andSidel,J.(1993).SensoryEvaluationPractices,AcademicPress,Inc. London. Sensory and Related Techniques for Evaluation of Dairy Foods10 SENSORY METHODS AND THEIR APPLICATIONS IN EVALUATING QUALITY OF FOODS Dr. Dharam Pal Principal Scientist Division of Dairy Technology National Dairy Research Institute, Karnal. 1.0 INTRODUCTION Sensory tests are conducted to meet the following purposes: Select qualified judges and study human perception of food attributes. Correlate sensory with chemical and physical measurement. Studyprocessingeffects,maintainquality,evaluaterawmaterial selection, establish storage stability or reduce costs. Evaluate quality or Determine consumer reaction. Eachofthesepurposesrequiresappropriatetests.Thereareasubstantial number of test methods and new methods continue to be developed. Stone and Sidel (1993) have classified these methods into following categories. S.No.CategoryTest Type 1.Discriminative Pairedcomparison,Duotrio,Triangle,Dualstandard, Multiple standard, etc. 2.DescriptiveFlavorprofile,TextureprofileandQuantativeDescriptive Analysis (QDA) 3.AffectiveAcceptance/preference:9-pointsHedonicscale,Consumer studies 4.OthersScoring, Ranking 2.0 DISCRIMINATIVE TESTING Thisisoneofthemostusefulanalyticaltoolsavailabletothesensory professionals.Itisonthebasisofaperceiveddifferencebetweentwoproductsthat onecanjustifyproceedingtoadescriptivetestinordertoidentifythebasisforthe difference.Withinthisgeneralclassisvarietyofspecificmethodsasgiveninthe table above. The main objective of all these methods is to answer a simple question. Are the products perceived as different? Obviously the response to this question can have majorconsequences.Iftheconclusionsfromadiscriminationtestaretobeaccepted by management as reliable, valid and believable, then it is important that each test be Sensory and Related Techniques for Evaluation of Dairy Foods11 conductedwithproperconsiderationforallaspectsofthetestdesign,product preparation and handling, implementation, data analysis and interpretation. 2.1 Paired Comparison Test The paired comparison procedure is the earliest example of the application of discriminationtestingtofoodandbeverageevaluation.Ithasalsobeenused successfullyfordeterminationsofthresholdforbasictastesolutions.Thepaired comparison test is a two product test, and thepanelist task is to indicate the one that hasmoreofadesignatedcharacteristicsuchassweetness,tendernessorskinniness. Thismethodisalsoidentifiedasadirectionalpairedcomparisontest,the directionalcomponentalteringthepanelisttoaspecifictypeofpairedtest.The paired comparison test is relatively easy to organize and to implement. The two coded products(AA,BB,ABandBA)areservedsimultaneouslyandthesubjecthasto decidewhetherthereisdifferenceorthereisnodifference.Requiringa difference response in all cases has been found to give better results. AnotherversionofthepairedtestistheA-not-Aprocedure.Thesubjectis presentedwithasinglesampleforevaluation,whichisthenreplacedbyasecond sample.Thesubjectthenmakesadecisionastowhethertheproductsaresame(or different).Thisparticulartestprocedurehasconsiderablemeritinthosesituations where non test variables such as a colour difference may influence results. 2.2 Duo-trio and Triangle test Thesetestshavebeendiscussedearlier.TheDuo-triotestissuitablefor products that have relatively intense taste, odour and / or kinaesthetic effects such that the sensitivity is significantly reduced. It lends itself to use for quality control and for selection of judges for superior discrimination. The chance probability associated with theduo-triotestisidenticalwiththatoftheothertwoproducttests.Whenever productsarebeingcomparedwithacurrentfranchise(i.e.productnowbeing manufactured), the duo-trio, constant-reference test method, is most appropriate. The chance probability associated with the three product (triangle) test is only 1/3,whichaccountsforitsclaimofgreatersensitivity.Thetriangletestismore difficulttestbecausethesubjectmustrecallthesensorycharacteristicsoftwo products before evaluating a third and then making a decision. In fact, the test can be viewed as a combination of three paired tests (A-B, A-C and B-C). Products that have intense flavours and aromas that are spicy and/or are difficult to remove from palate, or that have physiological effects (distilled beverages) usually preclude the use of the triangle test. 2.3 Multiple Sample Test Testsinvolvingmorethan3stimuliareclassifiedasmultiplesampletests. Theymayhaveequal(symmetrical)orunequal(asymmetrical)numbersofeach stimulus.Whentheyareappliedastruedifferencetests,thejudgeisrequiredto separatethesamplesintotwogroupsorlikesamples.Whentheyareappliedas Sensory and Related Techniques for Evaluation of Dairy Foods12 directional tests, the judge is asked to identity the groups of higher or lower intensity oragivencriterion.Differencetestdesignsinvolvingmorethanthreestimulihave hadonlylimiteduse.Thelimitationisbasedontheincreaseinpsychological complexity and physiological fatigue which accompanies an increase in the number of stimuli. In addition, large quantities of samples are required and more time is needed forobservertomakeadecision,thesetestsappeartobemostapplicabletovisual discrimination,wherethejudgedoesnotrelyonmemoryandfatigueisalmostnon-existent. 2.4 Dual Standard Test The dual standards method was proposed for use in quality control situations. The subject is served four products; two are identified as references A and B and two are coded. The subjects must match the reference product with the coded product. The designationofthetworeferencescouldreflectqualitycontrollimitsorcurrent production and product outside the limit. 2.5 Multiple Standards Test Thistestwasdevelopedforodourevaluationwhenanon-uniformstandard was to be compared with an unknown. Any numbers of the questionable standards are presented simultaneously with the unknown and the subject is asked to designate the onewhichismostdifferent.Thechanceprobabilityofidentifyingtheunknown correctly is ones over the total number of samples involved. Theliteratureprovidesasomewhatconflictingselectionofconclusions regardingthesensitivityofthevarioustestmethods;somesensoryprofessionals suggest that the triangle is more sensitive than the duo-trio and the paired tests, while others have arrived at contrary conclusions. The various difference tests can be ranked intermsofincreasingsensitivityas:paired,dualstandard,duo-trio,triangleand multiplestandard(Amerineetal,1965).RecentlyStoneandSidel(1993)have concluded that all discrimination tests are equally sensitive. 3.0 DESCRIPTIVE ANALYSIS Descriptiveanalysisisasensorymethodologythatprovidesquantitative descriptions of products based on the perceptions of a group of qualified subjects. It is atotalsensorydescriptiontakingintoaccountallsensationsthatareperceived visual,auditory,olfactory,kinaestheticandsoon-whentheproductisevaluated. Descriptiveanalysisresultsprovidecompletesensorydescriptionsofanarrayof productsandprovideabasisfordeterminingthosesensoryattributesthatare important to acceptance. The results enable one to relate specific process variables to specificchangesinsomeofthesensoryattributesofaproduct.Fromtheproduct developmentviewpoint,descriptiveinformationisessentialinfindingoutthose product variables that are different and from which one can establish cause and effect relationships. Sensory and Related Techniques for Evaluation of Dairy Foods13 Adescriptivetestinvolvesrelativelyfewsubjectswhohavebeenscreened. Screeningshouldbeproductcategoryspecificasisthesubsequenttrainingeffort. Trainingisprimarilyfocusedondevelopmentofdescriptivelanguagewhichisused asabasisforscoringtheproduct.Apartfromthistheotherimportantactivitiesthat arepartoftrainingincludethegroupingofattributesbymodality(i.e.appearance attributes,aromaattributesandsoon),listeningthembyoccurrence,developinga definition for each attribute, identifying helpful references for use during training, and familiarizingthesubjectswiththescoringprocedure.Therearenumerous applicationsfordescriptiveanalysis,includingmonitoringcompetition,storage stability/shelflife,productdevelopment,qualitycontrol,physical/chemicaland sensory correlation, etc. Dependinguponthetestmethodsusedthetrainingcanbequitedifferent. Some of the descriptive methods described in the literature are summarized here. 3.1 Flavour Profile The flavor profile method is the only formal qualitative descriptive procedure and is probably the most well known of sensory test methods. This utilizes a panel of fourtosixscreenedsubjectswhofirstexamineandthendiscusstheproductinan opensession.Onceagreementisreachedonthedescriptionoftheproductthepanel leadersummarizestheresultsinreportform.Themethodhasconsiderableappeal because results could be obtained rapidly and would obviate the need for statistics. 3.2 Texture Profile Thismethodrepresentsadvancementindescriptiveanalysiswithrespectto developmentofthedescriptiveterminology,thescalesforrecordingintensitiesand theword/productanchorsforeachscalecategory.Indevelopingthemethod,the objective was to eliminate problems of subject variability, allow direct comparison of resultswithknownmaterialsandprovidearelationshipwithinstrumentmeasures. There is considerable appeal to the direct link between specific instrumental measures oftheserheologicalpropertiesofaproductandtheresponsesofapanelofspecific sensoryattributes,forexample,texturometerunitsandhardnesssensoryratings. However,separationoftexturefromothersensorypropertiesofaproductsuchas colour,aroma,testsandsoforthlimitsthetotalperceptionoftheproductssensory properties. 3.3 Quantitative Descriptive Analysis Thequantitativedescriptiveanalysis(QDA)methodwasdevelopedwithan approachthatwasprimarilybehaviouralin orientationwithaconsensusapproachto languagedevelopment,useofreplicationforassessingsubjectandattribute sensitivity,andforidentifyingspecificproductdifferencesanddefinedstatistical analysis.Thedevelopmentofmethodevolvedfromanumberofconsiderationsto ensure that it would: Sensory and Related Techniques for Evaluation of Dairy Foods14 Be responsive to all the sensory properties of a product Rely on a limited number of subjects for each test Use subjects qualified before participation Be able to evaluate multiple product in individual booths Use a language development process free from leader influence Be quantitative and use a repeated trials design Have a useful data analysis system InaQDAtest,thesubjectsevaluatealloftheproductsonanattributeby attribute basis on more than a single occasion. 4.0OTHER METHODS Many more descriptive methods have been described in the literature which is moreorlessonthelinesofthetestmethodsdiscussedabove.Thespectrum descriptive analysis, for example, involves extensive training activities, reflecting the basicflavorandtextureprofileprocedures,withparticularrelianceontrainingthe subjectswithspecificstandardsofspecifiedintensities.Freechoiceprofilingis anotherapproachinwhichnosubjectscreeningortrainingarerequiredandthe subjectcanuseanywordstheywanttodescribetheproductsbeingevaluated.The timeadvantagemay,however,actuallynotbetheresincetheexperimenterrequires spending time explaining the testing procedures to the subjects. 4.1 Scoring The most frequently used of all sensory testing systems is scoring because of its diversity, apparent simplicity and ease of statistical analysis. Scoring methods have mostextensivelybeenusedbythedairyindustryforproductdevelopmentand improvements,shelflifestudiesandassessingsuitabilityofpackagingmaterials. Scorecardsbasedon100pointsgenerallyusedforjudgingandgradingofdairy products.Mostrecently25pointsscorecardshavebeensuggested(Bodyfelt,etal, 1988). It is believed that numerical rating tests give morecomplete information than eitherrankingtestsordescriptiveratingtests,butthejudgesmustbetrained.Since thereisnoindicationoflikingtothetestproduct,palatabilitynormsshouldbe established.Thescorecardmustbeproperlydevelopedgivingdueweightagetoall the sensory attributes. 4.2Ranking Ranking tests require that judges arrange a series of two or more samples in an ascendingordescendingorderofintensityofaspecificattribute.Inrankingtestfor quality,theusualobjectiveistoselectoneortwoifthebestsamplesratherthanto test all samples thoroughly. Ranking is often used for screening inferior from superior experimental samples in product development and occasionally in training judges. Samplesmayberankedinorderofdegreeofacceptabilityorinorderof generalquality,orbyspecificattributesofcolour,volume,textureorflavour intensity.Judgesshouldbethoroughlyfamiliarwithallaspectsofthesample Sensory and Related Techniques for Evaluation of Dairy Foods15 characterizationunderconsideration.Thismaynotbeeasilyachievedinpractice, because stimuli may vary along several dimensions simultaneously, complicating the interpretationofthecriteriausedtodifferentiate.Thisproblemarisesnotonlyin ranking tests but in most methods. 5.0 AFFECTIVE/ACCPTANCE TESTING Acceptancetesting,avaluableandnecessarycomponentofeverysensory programmeisperformedatconsumerslevels.Itreferstomeasuringlikingor preferenceforaproduct.Preferencecanbemeasureddirectlybycomparisonoftwo ormoreproductswitheachother,thatis,whichoneofthetwoormoreproductsis scoredsignificantlyhigherthananotherproductinamultiproducttest,orwhich product is scored higher than another by significantly more people. The two methods mostfrequentlyusedtodirectlymeasurepreferenceandacceptancearethepaired comparisontestandtheninepointhedonicscale.Othermethodsareeither modificationsofthesetwomethodsoraretypesofqualityscales:forexample, excellent to poor and palatable to unpalatable. 5.1 Hedonic Scale The nine point hedonic scale has been used extensively since its development withawidevarietyofproductsandwithconsiderablesuccess.Thescaleiseasily understood by nave consumers with minimal instruction and the product differences arereproduciblewithdifferentgroupsofsubjects.Theresultsfromuseofthisscale aremostinformativesincecomputationswillyieldmeans,variancemeasuresand frequencydistributions,allbyorderofpresentationandmagnitudeofdifference betweenproductsbysubjectandbypanelandthedatacan beconvertedtoranksas well, which yields product preferences. As an example of the scale is given below: Like extremely:9 Like very much :8 Like moderately : 7 Like slightly : 6 Neither liked nor disliked :5 Dislike slightly: 4 Dislike moderately : 3 Dislike very much :2 Dislike extremely:1 The sensory acceptance test is a very cost-effective resource that has a major roletoplayinthedevelopmentofsuccessfulproduct.Properlyused,itcanhavea significant impact on the growth and long term development of sensory evaluation. 5.2Consumer evaluation With the increase in competition, availability of many brands of same product inthemarketandthechoiceofconsumers,itishighlydesirableforthefood/dairy industry to study the acceptance/preference and needs of consumers. In some cases it Sensory and Related Techniques for Evaluation of Dairy Foods16 ispossibletocreatemarketsforcertaindairyproductswhennoneexistedearlier.In manyothersituations,suchasalterationsinexistingformulations,changein packaging materials, use of some additives or adoption of a new technology, the food processorhastogotoconsumerswiththeirproducttostudytheir acceptance/preference.Whileconductingtheconsumerstudies,thesensory leader/organizershouldconsiderallthefactorsthatareimportantinachievingthe desired results. Some of these factors are: clear objectives, target population, start and completiondates,representativetestsamples,numberofproductsnumberof responsespersampling,samplecodingprocedures,questionnaire,instructionon servingandpre-screening,dataanalysisandprocessingprocedure,andproposed reportingschedule.Asfaraspreferenceandacceptanceofconsumersisconcerned the factors are grouped into two categories viz. 1) the attitude of the dairy product and 2) of the consumer. AttitudeoftheDairyProduct:Thisisrelatedtotheproductitselfinrespectof availability;utility;convenience;price;storagestability/requirements;safetyand nutritional value; and sensory properties, which of course is very important. AttitudeoftheConsumer:Religionpreference;nationalityandrace;ageandsex; education,socio-economics;psychologicalmotivationsuchassymbolismoffood, advertising, etc. and physiological motivation, such as thirst, hunger, deficiencies and pathological conditions. Whiledesigningconsumerstudiesandinterpretingtheresults,theroleofabove factors may be considered. Questionnaire for Consumer Studies:A well developed questionnaire for obtaining desired information, including preference, from the consumers is very important. The important considerations for developing a questionnaire are that it should be: simple and clear realistic use appropriate terms avoid stereotype answers OneexampleofsuchaquestionnaireforseekingconsumeropiniononControlmilk sample (A) and on experimental milk sample fortified with Vit A. (B) is given below: 1.Prefer sample A. Prefer sample B . 2.Why do you prefer the sample of your choice (Tick mark one or more): Preferred milk sample has Richer taste . Sweeter taste . Sensory and Related Techniques for Evaluation of Dairy Foods17 Smoother body . Rich consistency . Other . 3.Ifyouprefertobuythepreferredsample,howmuchmore(ifany)perlitre would you be willing to pay: 25 paise . 50 paise . Re. 1 . None . Theabovequestionnaireshowstherelationshipbetweenpreferenceformilk and willingness to pay more for the preferred sample. 6.0 REFERENCES Amerine,M.A.,Pangborn,R.M.andRoessler,E.B.(1965).PrinciplesofSensory Evaluation of Food, Academic Press, New York. ASTM (1986). Manual on Sensory Testing Methods. STP 434, American Society for Testing and Materials, Philadelphia, U.S.A. Bodyfelt, F. W., Tobias, J. and Trout, G. M. (1988). The Sensory Evaluation of Dairy Products, AVI Publishing Co. New York. Dharam Pal, Sachdeva, S. and Singh, S. (1995). Methods for determination of sensory quality of foods: A critical appraisal. J. Fd. Sci. Technol. 32 (5):357-367. Stone,H.andSidel,J.(1993).SensoryEvaluationPractices,AcademicPressInc. London. Sensory and Related Techniques for Evaluation of Dairy Foods18 Dr. Ashish Kumar Singh Senior Scientist Dairy Technology Division NDRI, Karnal 1. INTRODUCTION Thesensoryevaluationofmilkisofutmostimportance.Packagedandretail saleoffreshmilkcomprisesamajorshareofIndianDairyindustry(bothinthe organizedandunorganizedsectors).Sincefluidmilkisconsumedbymosteveryone everydayitisbeingassesseddairyforitsquality.Iftheflavourofmilkisnot appealing or appetizing less of it will be consumed. Thesensorycharacteristicsof any dairy product are dependent on the quality attributesofmilkingredientsused.FINISHEDMILKPRODUCTSCANNOTBE BETTERTHANTHEINGREDIENTSFROMWHICHTHEYAREMADE.Ifthe raw milk supply is properly assessed for its sensory quality all off-flavour defects due to raw milk could be minimized if not eliminated. Amongdairyproductjudgesthescoringordifferentiationofmilkinto differentqualityclassesdemandskeener,morefullydevelopedsensesofsmelland taste than in the sensory evaluation of other dairy products. Many of the off-flavours present in fluid milk are more delicate, less volatile or more elusive than those present in other milk products. Milk,mayberaworpasteurized,skimorwhole,tonedordoubletoned, standardizedorfullfat,coworbuffalo.Forthepurposeofpresentdiscussion,milk wouldmeanPASTEURIZED,STANDARDIZED(MIXED)MILKunlessotherwise specified. Pasteurization is effected by heating the milk to 72oC for 15 sec or 63oC for 30 min in HTST or LTLT respectively. Pasteurizedmilkcommonlypossessessomedegreeofaheatedorcooked flavourespeciallyimmediatelyafterprocessing,buttheintensityofcookedflavour diminishes during storage. The flavour of milk is affected by: a.heating-up and cooling time. b.temperature difference between the product and heating medium c.velocity of the product in a continuous system SENSORY EVALUATION OF MILK Sensory and Related Techniques for Evaluation of Dairy Foods19 d.occurrence of product burn on and e.direct Vs indirect heating methods. Theflavourofpasteurizedunhomogenizedmilkundergoesflavourchanges during storage as below: HEATED--> NORMAL--> FLAT--> METALLIC--> OXIDISED The extent of flavour deterioration depends on the storage time, session of the year,typeofroughagefedtothecowandbuffaloesandrelativelevelsofcupricor ferric ions. 2. MILK SCORE CARD Theoriginalscorecard(100pointscale)developedbytheADSAhasbeen extensivelymodifiedandispresentedonthenextpage.Bacterialcounts,milk temperatureandsedimentationtestareimportantdatatobeprovidedbylab. Evaluationofthecontainer/closureisalsoavalidquantitycriterionthatshouldbe evaluatedwhenrequired.Flavouronthenewscorecardisevaluatedona10-point scale. 100 point score card can still be used provided the milk has a bacterial content of 20,000 ml and a maximum temperature of 7.2oC. Familiarity with the score and use of scorecard guide is important for milk product judging. SCORE CARD FOR MILK Product _______________Date__________ ------------------------------------------------------------------------------------------------- Sample number FLAVOUR10Criticism1234 acidScore astringent barmy NO CRITICISMbitter 10cooked cowy feed NORMAL RANGEfermented/fruity 1-10flat foreign garlic/ onion UNSALEABLElacks freshness malty oxidized light-induced oxidized metal induced rancid Sensory and Related Techniques for Evaluation of Dairy Foods20 salty unclean ------------------------------------------------------------------------------------------------------------ SEDIMENT 3 ------------------------------------------------------------------------------------------------------ PACKAGE 5 ------------------------------------------------------------------------------------------------------ dented/defective NO CRITICISMdirty inside/outside 5leaky/not full NORMAL RANGEheat seal defective 1-5illegible printing UNSALEABLElabeling/code incorrect 0 ------------------------------------------------------------------------------------------------------ BACTERIA 5 ------------------------------------------------------------------------------------------------------- TEMPERATURE 2 ------------------------------------------------------------------------------------------------------- TOTAL SCORE Signature of the judge Fig. 1 The modified ADSA scorecard for milk 3.JUDGING OF MILK & MILK PRODUCTS Table 1. Suggested scoring guide for flavour for milk Intensity of flavour defect Slight ModerateDefiniteStrong Pronounced Astringent876-- Barmy54321-0 Sensory and Related Techniques for Evaluation of Dairy Foods21 Bitter54321-0 Cooked98765-0 Cowy65432-0 Feed98765-0 Fermented/fruity32100 Flat987-- Foreign32100 Garlic / onion54321-0 High acid32100 Lacks freshness87600 Malty54321-0 Metallic54321-0 Oxidized Light induced65432-0 Metal induced54321-0 Rancid43210 Salty87624-0 Unclean32100 3. SOME MILK SCORING TECHNIQUES 3.1 Preparation of samples for evaluation Thisdependsonthepurposeorobjectivesofevaluation,numberof participants and the quality criteria to be assessed. If several persons are to judge the milksamplesforflavour,containerandclosure,sedimentandothercriteriathen severalcontainersofeachindividuallotofmilkmustbeprovided.Thesediment test/bacterial count of each sample should be provided. 3.2 Order of examination and scoring 3.2.1 Sediment test Sensory and Related Techniques for Evaluation of Dairy Foods22 Itshouldbeperformedfirst.Thekind,amountandsizeofsedimentparticles should be carefully observed and scored against a chart or mental image. 3.2.2 Closure Closure should be carefully observed. Now a days bottles or cartons (not used inIndia)arenottheusualpackagingmaterial.Themilkisbeingpackaged polyethylene sachets. Hence the evaluator must see that the packaging properly sealed to prevent leakage/pilferage. 3.2.3 Container Container as stated above, since plastic bags is now in vogue; these should be examinedforextentoffullness,cleanlinessandfreedomfromcuts/nicks/pinholes from leakage. 3.2.4 Flavour The milk should be properly tempered between 13 to 18oC preferably 15.5oC. Milk samples should be poured into clean, odourless glasses or paper/plastic cups. 10 to 15 ml milk should be poured and a sip taken, rolled around the mouth and flavour sensation noted and then expectorated. Sometimes, any aftertaste may be enhanced by drawingabreathoffreshairveryslowlythroughthemouthandthenexhaling through the nose slowly. A full WHITE of air should be taken soon after the sample is placed in the container for any off-odour that may be present. 3.3 Evaluation temperature Pasteurized milk should at 7.2oC but lower than 4.4oC is preferred. A 2-point scalemaybeused.Ifthetemperatureisabove7.2oCthesamplemaybescored ZERO. Samples at 4.4oC or below should be scored a perfect or 2 score. 3.4 Evaluation of sediment Consumerswantthatthemilkshouldbefreefromforeignmatter.A3-point scalemaybeemployed.Presenceofanysedimentisseriousandshouldreceivea ZERO score. One Possible scoring system could be: No sediment3 < 0.02 mg/disc2 0.025mg/disc1 >0.025mg/disc0 3.5 Evaluation of milk flavour Sensory and Related Techniques for Evaluation of Dairy Foods23 Typically the flavour of milk should be PLEASANTLY SWEET AND POSSESS NEITHERAFORETASTENORANAFTERTASTEotherthenthatimpartedbythe natural richness due to milk fat and milk solids. Whenmilkclearlyexhibitsthesoc-calledTASTEthereisusuallysomething WRONGwiththeflavourofthemilksample.Thusmilkisconsideredtohavea defectifithasanodour,fore-orafter-tasteanddoesnotleavethemouthinclean, sweet,pleasantcondition,followingtasting.Thescoringguidelistsmorefrequently observed off-flavours. The defects should be described while scoring. 4. UNDESIREABLE FLAVOURS 4.1 Acid Sourdetectedbytasteandsmell-duetomicrobialconversionoflactoseto lactic acid, which imparts a tingling effect. 4.2 Astringent Not common in milk. 4.3 Barny Transmittedoff-flavourduetopoorventilation,foulsmellingenvironment. Perceived by sniffling and tasting. Characteristic aftertaste. 4.4 Bitter Associatedwithotherdefectslikeastringency,rancidityduetoweedsand microbial growth specially psychrotrophs.. 4.5 Cooked Heat-induced defect appears when milk is heated to 76oC or more. There are 4 typesofheatinducedflavours:COOKED/SULPHUROUS;HEATEDORRICH; CARAMELISEDandSCORCHEDHeatedandcookedflavorsareeasilyidentified, reaction time is quick, and sensation remains after expectoration. Cooked flavour may also be noted through smell. 4.6 Cowy (acetone) Distinct,persistentunpleasant,medicinalchemicalaftertastewithacetone bodies in milk i.e. ketosis in cows. 4.7 Feed Imparts aromatic taints to milk when fed -3 hours prior to milking. The off-flavourisaromaticsometimespleasant(e.g.alfa-alfa),detectedbysmellvarieswith feed. To prevent such feeds should not be fed 3 hours prior to milking. 4.8 Fermented/Fruity Duetomicrobes,resemblesvinegar,pineapple,apple.Foundinold pasteurized milk, due to growth of Pseudomonas sp. (P. fragii). Sensory and Related Techniques for Evaluation of Dairy Foods24 4.9 Flat Flat taste/mouthfeellack of richness. 4.10 Foreign Smelledortasted,duetochemicals/detergents,disinfectants,sanitizers, exposuretofumesofpetrol,diesel,kerosene,insecticides,ointments,medicationto cows etc. 4.11 Garlic/onion (weedy) Pungent odour and persistent aftertaste. 4.12 Lacks freshness (stale) Tastereactionindicateslossoffinepleasingtaste.Slightlychalky.Maybe forerunnerofeitheroxidizedorrancidoff-flavouroroff-flavourcausedby pshychrotrophs. 4.13 Malty Flavour definite or pronounced, suggestive of malt caused by the growth of S lactisvar.Maltigenesat>18.2oCfor2-3hourscanbesmelledortasted.Bacterial population in millions, followed by acid/sour taste. 4.14 Metal-induced oxidized off-flavour Duetolipidoxidation-metalcatalyzed.Metallic,oily,cardboardy,cappy, stale, tallowy, painty and fishy are used to describe this off-flavour. The off-flavour is quickly perceived in the mouth and has a relatively short adaptation time. 4.15 Light-induced oxidized off-flavour Describedasburnt,burntprotein,burntfeathers,cabbagy,medicinalor chemical-like,light-activatedorsunlightflavourorsunshineflavour,lightcatalyzed lipid oxidation as well as protein degradation both are involved. It requires riboflavin that is naturally present in milk. Homogenized milk is more susceptible but is resistant tooxidizedoff-flavour(duetolipidoxidation)theoppositeistruefornon-homogenized milk. 4.16 Rancid Extremelyunpleasant,duetovolatilefattyacidsformedthroughenzymatic hydrolysisoffat.Soapy,bitteranduncleanaftertaste.Flavourisnauseatingand revolting. 4.17 Salty Perceived quickly in the mouth 4.18 Unclean Due to growth/activity of psychrotrophs at 7.2oC Sensory and Related Techniques for Evaluation of Dairy Foods25 Dr. S. K. Kanawjia, Sanjeev Kumar** and Hitesh Gahane* Principal Scientist, Division of Dairy Technology NDRI, Karnal **Ph.D. Scholar and * M.Tech (DT) 1. Introduction Cheese,thenatureswonderfoodandtheclassicalproduct ofbiotechnology, is highly nutritious food with good keeping quality, enriched pre-digested protein with fat,calcium,phosphorus,riboflavinandothervitamins,availableinaconcentrated form. It is the most important category of fermented foods, has been reported to have therapeutic,anticholesterolemic,anticarcinogenicandanticariogenicproperties beyondtheirbasicnutritivevalue.They,contributingtoavarietyinourgustative desire,havebeenrecognizedtoprovideimportantnutrientsandconsideredsuperior over non-fermented dairy products in terms of nutritional attributes as the micro flora presentproducesimplecompoundslikelacticacid,aminoacidsandfreefattyacids thatareeasilyassimilable.Someofthecheeseflorahasbeenreportedtoinhibitthe growth of certain toxin-producing bacteria in the intestine. Soft unripened cheeses are commonly known as Fresh Cheese and are made bycoagulatingeitherwholemilk,partlyskimmedmilk,skimmilkorcream; eliminating a large part of the liquid portion (whey) and retaining the coagulated milk solids.Theamountofwaterretainedinthecurdgreatlyinfluencestherelative softnessofunripenedcheesemadefrommilkhavingconstantcasein-to-fatratio. Softnessofcheesealsodependsontheextentofproteinhydrolysissaltcontentand theamountofmilkfatincheese.Softunripenedcheesederivetheirflavourmainly fromthecultureandthecreamdressing.Cottagecheese,Creamcheese,Mozzarella cheese, Ricotta cheese, paneer etc are some of the common varieties of fresh cheese. Theydifferfromeachotherintheirmethodofmanufacturewithrespecttotypeof milk,treatmentgiventomilk,typeofculture,amountofculturemethodof coagulation, cutting of curd, cooking of curd, pressing of curd etc. Consequently,theydifferinsensoryaswellaschemicalattributes.The desirablesensoryattributesoffreshcheeses,defectsandtheirprobablecausesand remedies with special reference to cottage cheese are described in this lecture note. 2. Scenario of Cheese Production in India Scenario of cheese production in India is quite bright because of the facts that cheese has all the beneficial attributes of an ideal dairy product and the emergence of SENSORY CHARACTERISTICS OF FRESH CHEESESensory and Related Techniques for Evaluation of Dairy Foods26 newglobaleconomicreformsbasedonglobalizationandliberalizationinthe marketing arena that has unfastened the door to the Indian dairy industry to penetrate the international cheese market. There has been a steady increase in the consumption of cheese in most countries worldwide, the annual growth rate in cheese consumption being over 3 per cent with an acceleration being expected due to worldwide trend of adopting Western consumption habits with a high level of cheese in the diet list. In Indiacheese,productionhasbeenacceleratingquitesteadily,being1000tonnesin 1980 to 40000 tonnes in 2007, against the world production of 16 million tonnes. Tillabout8-10yearsback,theonlymajorregional/nationalplayersinthe cheese market were Amul, Verka, and Vijaya all from the cooperative sector. These plantsarecontinuingtoexpandtheircheesemanufacturingcapacitiesslowlyintune with the demand growth for cheese. Many new players like Dynamix and Dabur, and entrepreneurs, such as Vadilal, Vintage, Chaudharys Miraj, Kodai, etc have ventured incheeseproductioninrecentyears.AtpresentAmulhastargetedopeningof3000 Pizza retail franchise outlets all over the country by the year-end, which would boost the annual sets of Mozzarella cheese to 5000 tonnes. 3. Cottage Cheese Cottage cheese is a fresh, soft, unripened cheese made from sweet, pasteurized skim milk by lactic culture with or without the addition of rennet. The curd is cut and cookedtofacilitatewheyexpulsionanddevelopmentofpropercurdconsistency. Whenthecurdhasattainedthedesiredconsistency,wheyisdrainedoff,curdis washedandsalted.Subsequently,thecurdisdressedwithcreaminthecaseof creamedcottagecheesewhichcontains4%fat.Cottagecheesecontains80% moisture. 3.1 Desired sensory attributes 3.1.1 Appearance and colour The curd particles of cottage cheese should be distinctly separate and uniform insizeandshape.Thecheeseshouldpossessmoderatelyglossysheenandcreamy whitecolour.Thecreamdressingshouldbereasonablyviscousandfoamfree,and bulk of it should adhere to the curd particles. The excess dressing should form only a uniformandsmoothcoatingonthecurdparticles.Freecream,freewhey,lackof uniformityandthepresenceoflumpsorcurddustareconsideredascommon appearance defects in cottage cheese caused mostly by faulty method of manufacture viz.,excessivecooking,insufficientwashing,cuttingofcurdattoohighortoolow pH, rapid cooking, uneven cutting or cutting with a faulty knife or aggressive stirring lowTSmilk,excessiveheattreatmentofskimmilk,useofexcessivecoagulator, severestirringororughhandlingofcurdduringcookingetc.Appropriatecorrective measures during manufacture of cottage cheese eliminate these defects. Sensory and Related Techniques for Evaluation of Dairy Foods27 3.1.2 Body and texture of cottage cheese Ideally,creamedcottagecheeseshouldhaveatenderbody,andsmoothand meatliketexture.Curdparticlesshouldmaintaintheirshapeandindividualidentity butshouldnotbetoofirm,rubberyortoosoft.Smooth,meatyandtendercurd particlesexhibitgoodcapillarydesiredforcompleteabsorptionofcreamdressing common body & texture defects are listed below: 3.1.2.1 Too firm body: Firmorrubberybodiedcurdparticlesofcottagecheeseresistcrushing between tongue and roof of the mouth. This defect occurs due to over use of rennet or othermilkcoagulator;cookingofcurdattoohightemperatureandfortoolong;or cutting of curd at a pH more than 4.7 3.1.2.2 Mealy/Grainy/Gritty: Presenceofthisdefectgivesacornmeallikesensationinthemouthwhen masticatedcurdispressedbythetongueagainsttheroof.Also,adryroughand serratedcurdmassisobservedwhenthewashedcurdparticlesofcreamedcottage cheesearekneadedandsmearedbetweentheforefingerandthumb.Thedefectmay becausedbyoverdevelopingtheacidduringcurdformation;retentionoftoolow moisture,non-uniformcuttingofcoagulum,unevenheating,toorapidcooking, inadequate stirring, and curd particles coming in contact milk extremely hot surfaces during cooking. 3.1.2.3 Gelatinous: Gelatinouscheesehasajelly-likeandstickycharacter.Oftenthisdefectis associatedwithabitterflavourandtranslucentappearance.Thisdefectiscausedby psychotropic bacteria. 3.1.2.4 Weak/soft/mushy: Thisdefectischaracteristicofhighmoisture,low-solidcottagecheese.Itis caused by faulty manufacturing methods, which favour retention of whey in the curd. On storage such cheese may become pasty and bitter. 3.1.2.5 Over stabilized dressing: Whenthisdefectoccursthecreamedcottagecheeseappearsdryandsome individualcurdparticlesaresurroundedbyathick,pasty,coating.Thisusually happensduetotheuseofexcessiveamountofnon-fatdrymilk,stabilizersand/or emulsifiers. Sensory and Related Techniques for Evaluation of Dairy Foods28 3.1.3 Flavour: Cottage cheese should have a fresh, clean, pleasant delicate (balanced culture) flavour that cleans up well immediately after the sample has been eliminated from the mouth.Thisflavorismadeupofcharacteristiccurdflavouranditsacidity,volatile products by lactic acid organisms. Addition of cream and salt enhance the flavour of creamed cottage cheese. The probable cottage cheese being high perishable product is proving to the development of specific flavour defects as discussed below: 3.1.3.1 Acid/high acid/sour: Acidtasteiscleanandsharpwhilesourtasteispronouncedandmaybe associatedwithotherbacterialdefectslikefruity,fermentedetc.Excessiveacid development and/or insufficient washings of the curd cause this defect. Such product is sometimes also criticized for flavour defect like whey taint. 3.1.3.2 Bitter: Bitterflavourischaracterizedbyitsrelativelyslowreactiontime;tasteator nearthebackofthetongueonly;freedomfromastringency;andpersistenceafter expectoratingthesample.Thedefectismostfrequentlyencounteredinoldcottage cheeseorinthesamplestoredatatemperaturefavourableforthegrowthof Pseudomonas organisms. 3.1.3.3 Flat: Absenceofcharacteristicflavouroraromaistermedasflatflavour.Adry, unsalted andwashedrennetcurdyields a distinctly flat taste during the intermediary stages of oxidized flavour development. 3.1.3.4 Lacks freshness: Theflavourofcottagecheeseisitsbestimmediatelyaftermanufacture. Cottage cheese progressively deteriorates in flavour during storage. Often this defect isreferredasstorageflavourbecausethearomaofcheeseissimilartothatofthe refrigerator in which it was stored. 3.1.3.5 Fruity/Fermented: Thisdefectischaracterizedbythepresenceofapleasantaromaticflavour suggestiveofpineapple,apple,bananaorstrawberryanddistinctivelingering aftertaste.Thecottagecheesestoredatelevatedorfavourabletemperaturesforthe psychrotrophic bacteria may develop this defect. Sensory and Related Techniques for Evaluation of Dairy Foods29 3.1.3.6 Yeasty: Yeastyandvinegarlikeflavourshaveapeculiararomaticqualityinaddition tohighacidity.Yeastsandvariousothercontaminantsincludingpsychrotrophic bacteria are generally responsible for causing this flavour defect. Other flavour defects in cottage cheese include malty, musty, oxidized, rancid, salty and unclean flavours. 4. Cream Cheese Cream cheese is a soft, unripened cheese made by coagulating cream (12-30% milk fat) either by lactic acid bacteria aided by milk coagulating enzymes or by direct acidificationfollowedbyremovalofwheybycentrifugationorpressingthecurdin clothbags.Thefatcontentinthefinalproductvariesfrom3to40%.Neufchatel cheeseisasimilarproductmadefromwholemilkofhighfatcontents.Itcontains about 20-25% fat. 4.1 Desirable sensory attributes 4.1.1 Flavour: Creamcheeseshouldhaveafullrich,cleanandmilkacidicflavour. Neufchateltypecheesemayhaveamoderateacidtaste.Morecommonflavour defects in various types of cream cheese may be flat, sour or too high acid, metallic, yeasty and unclean after taste. 4.1.2 Body and texture: Soft yet sufficiently firm body to retain its shape is the characteristic of cream cheese.Thetextureshouldbesomewhatbutteryandsilkysmooth.Itshouldpossess bothspreadingaswellasslicingcharacteristics.Creamcheesepreparedfromcream containing16%fatexhibitsmostdesirablebodyandtextureproperties.Insuch cheeses the moisture and fact content may vary in the ranges of 50-54% and 37-42%, respectively.Creamcontaininglessfatyieldsacreamcheesewhichiscriticizedas having grainy texture and crumbly body. Increased fat content of cream (20%) results inexcessivesmoothnessandstickiness.Otherbodyandtexturedefectsofcream cheese include coarse, grainy, too firm and too soft. 5. Mozzarella Cheese ItisasoftunripenedvarietyofcheeseofItalianorigin.Itisproducedfrom whole or partly skimmed milk to which small amounts of starter or organic acids are added,followedbyrennetextract.Thecurdiscut,allowedtofirmupinthewarm wheywithoccasionalstirringandthewheyisdrainedoff.Whenthecurdhas developed the desired plasticity and fibrous texture and the whey acidity 0.65-0.70% LA,itismilded.Thecurdpiecesareimmersedinhotwaterkneaded,stretchedand Sensory and Related Techniques for Evaluation of Dairy Foods30 moulded.Saltingofcheeseisdonebydippingthecheeseinbrinesolutionforfew days. The cheese can be consumed after the brine treatment is complete. 5.1 Desirable sensory attributes 5.1.1 Colour and appearance: Mozzarellacheeseshouldhaveauniformwhitetolightcreamcolor.Faulty manufacturingmethodandmicrobialcontaminationmaysometimescausecolour defects in the product. Use of too high salt may cause discoloration. Development of browningmaybecausedbyusingstarterculturecontainingonlyThermophilus. ContaminationwithPsuedomonasspp.Causesdevelopmentofsuperficialreddish marks. 5.1.2 Body and Texture: Mozzarellacheeseshouldhaveasoft,elastic,waxyandmoistbodywith typicalstructureofpulledcurdcheese.Itshouldhaveafibroustexturewithnogas holes. It should possess a good slicing as well as melting properties. Use of too high saltorgrowthofLactobacilluscaseimaycausepoormeltingquality.Undesirable microbialcontaminationmaycausedevelopmentofdefects,likepigmentation,hole formationandother texturaldefects. Rapid evaporation of moisture from the surface leads to the development of granular texture. 5.1.3 Flavour: Bland,pleasantbutmildlyacidicwithslightlysaltytasteisthecharacteristic ofmozzarellacheese.Buffalomilkcheeseisamorepiquantandaromaticthancow milkcheese.Microbialcontamination,particularlywithPseudomonasspeciesmay leadtothedevelopment offlavourdefects like putrid smell, bitter flavour etc. Other flavourdefectsmaybeofabsorbedorchemicalnatureasinthecaseofcottage cheese. 6. Ricotta Cheese ItisyetanothervarietyofsoftunripenedcheeseofItalianorigin.Inthe manufacture of ricotta cheese, mixture of whey and skim milk is acidified to a critical pHwithlacticacid,aceticacidoracidwheypowderandthenheated.Theresulting curdisrecoveredandoverfilledinperforatedtincontainers,cooledandallowedto drainfreewhey.Cheeseisnowreadyforconsumption.Ricottacheesemadefrom wholemilkisconsumeddirectlywhilemadefromskimmilkorwheyskimmilk mixture is highly suited for pastry manufacture. Ricotta cheese from whole milk resembles highly creamed, cottage cheese but has a softer and more fragile texture. A mixture of skim milk whey yields a firmer and drier product which lacks its distinctive nutty flavour. In general ricotta cheese is soft, and creamy with a delicate, pleasant and slight caramel flavour. Sensory and Related Techniques for Evaluation of Dairy Foods31 Ricotta cheese is highly susceptible to spoilage due to microbial contamination leadingtoflavourdefectslikesour,fermented,fruityetc.Excessivegasformation may also cause blowing of the lid of the container. 7. Paneer Paneer is an indigenous milk product made by coagulating heated milk preferably buffalo milk (6% fat) acid solution and/or sour whey. The whey is drained and the curd filled in hoops and pressed. The pressure is removed after 10-15 and the paneer is cut into pieces and immersed in chilled water for cooling. 7.1 Desirable sensory characteristics 7.1.1 Colour and appearance: Paneershouldhaveuniformwhitecolourwithgreenishtingeifmadefrom buffalo milk and light yellow it prepared from cow milk. Paneer may develop colour and appearance defects as listed below: 7.1.1.1 Dull: This defect is recognized by its dead, unattractive appearance and suggest lack of cleanliness in manufacture. 7.1.1.2 Dry surface: Use of milk containing excessive amount of fat gives paneer with dry surface and unattractive appearance. 7.1.1.3 Surface skin: Exposureofpaneerwhilehottotheatmospherecausesrapidevaporationof moisture from the surface resulting into the formation an undesirable yellow skin on the surface. 7.1.1.4 Visible dirt/ Foreign Matter: Thisdefectmayoccurduetoimproperstrainingofmilk,useofdirtywater, dirty, windy surrounding, poor packaging and careless handling of paneer. 7.1.1.5 Mouldy surface: Longstorageofproductinhumidatmospherecoupledwithhighermoisture content flavours development of moulds on the paneer surface. 7.1.2 Body and texture Thebodyofpaneershouldneitherbetoofirmnortoosoft.Itshouldremain retainitsshape.Thetextureofthehighgradepaneershouldbecompact,smooth elastic and velvety. Paneer develops body and texture defects due to faulty manufacturing methods and microbial contamination. Excessive retention of moisture due to low coagulation temperature,delayedstrainingorincorrectpHofcoagulationoftengivesapaneer Sensory and Related Techniques for Evaluation of Dairy Foods32 withsoftbodyandpastytexture.Lowmoisturecontentinpaneercausedbyhigher coagulationtemperature,incorrectpHatcoagulation,useoflowfatmilk,yieldhard andrubberybodiedpaneer.Suchpaneermayalsohaveamealytexture.Frozen storage of paneer causes crumbly body and coarse/mealy texture in paneer. 7.1.3 Flavour Flavourofpaneerisacharacteristicblendoftheflavourofheatedmilkcurt, andacid.Theflavourofthehigh-gradepaneershouldbepleasant,mildlyacidic, slightsweetandnutty.Commonflavourdefectsobservedinpaneeraresimilarto thoseasobservedinotherfreshcheeseandcanbeeliminatedbyfollowingproper manufacturing, method, sanitation, packaging, storage and handling. 8.References Bodyfelt,F.W.;Tobias,J.andTrout,G.M.1988.TheSensoryEvaluationofDairy Products. Van Nostrand Reinhold, NY. DharamPalandGupta,S.K.1985.SensoryevaluationofIndianMilkProducts. Indian Dairyman, 37: 465 Kanawjia,S.K.andSingh,S.1996.SensoryandTexturalchangesinPaneerduring storage. Buffalo J. (Thailand) 12: 329-32 Khurana,H.andKanawjiaS.K.2007.Recenttrendsinfermentedmilks.Current Nutrition Food Sci. (USA) 3: 91-108 Makkal,S.andKanawjiaS.K.2003.PreservationofCottageCheese:Areview Indian J. Dairy Sci. 56: 1-12 Nelson,J.N.andTrout,G.M.1964.JudgingofDairyProducts.OlsenPubl.Co. Milwaukee. Wis., USA. Tiwari,B.D.1996.Sensoryattributesoffreshcheese.Compendium:Sensory evaluation and rheology of milk and milk products. CAS, DT Division, NDRI, Karnal: 52-57. Sensory and Related Techniques for Evaluation of Dairy Foods33 Dr. F.C. Garg Dairy Technology Division NDRI, Karnal 1. Introduction Icecreamisadelicious,wholesomenutritiousfrozendairyfood.Ithas evolved over a period spanning about five centuries. The great technological progress madeinthefieldofdairyinginthenineteenthcenturysuchasthedevelopmentof centrifugal separator, mechanical refrigeration, better understanding of chemistry and bacteriology provided stimulus to the development of a large ice-cream industry that we see today. Ice cream has occupied a unique place in the diet of western people and isgainingsteadilyinpopularityallovertheworld.Forinstance,theannual productionoficecreaminUSAhasreachedmorethan3770millionlitres.Other countriesrankinghighinannualproductionofIcecreamandrelatedproductsare Japan: (750 million litres), Canada (476), Australia (331), and UK (218). India is the thirdlargestproduceroficecreamintheworldwithproductionofover513million litres annually. It has been estimated that 0.6 per cent of total milk production in our country is utilized for making ice cream and Kulfi. The ice cream industry in India is expanding very fast witnessing an estimated growth rate of 25 to 35 per cent per year. ProductionofexcellentqualityIcecreamisessentialtothesuccessandprogressof theice-creamindustry.Thequalityoficecreamisjudgedbytheconsumeronthe basis of its sensory attributes i.e. flavour, body and texture, melting behaviour, colour and the appearance of package or container. Besides, the product should also comply withlegalstandardswithregardtoitschemicalcompositionandbacteriological quality.Icecreamnotpossessingdesirablesensorypropertiescausediminished consumer goodwill, sales and income to the manufacturer. 2. Factors Affecting Sensory Attributes of Ice-cream Thequalityoficecreamdependsnotonlyoncompositionofice-cream,but alsoonthequalityofrawmaterialsused,methodsofmanufacture,distributionand sale of the product these factors are under the control of the ice cream maker. A full knowledgeofthefactorsbywhichthequalitymaybeattainedorcontrolledis therefore,essentialfortheproductionoficecreampossessingdesirablesensory attributes. Therearemanydifferingconceptsofperfectice-cream.Individual preferencescancauselargevariationsinwhatpeopleconsidertobeicecreamof highest quality. Some prefer ice cream with a low fat content, while others will want highfat.Somewilllikeverysmoothtexturedice-cream,othersmaypreferitbenot toosmooth.Variationsexistintherequiredsweetnesslevelandsoon.Therefore, SENSORY ATTRIBUTES OF ICE-CREAM Sensory and Related Techniques for Evaluation of Dairy Foods34 desirablesensoryattributesoficecreamcanbebestexplainedbygivingdetailsof defects and faults which may be found in ice cream, and show how these faults occur and how they may be overcome. 3. Judging of Ice-cream The available methods of determining the sensory attributes of ice cream rely mainlyontastingandusingascorecard.Suchscorecardsgivemaximaforvarious aspectsoftheice-creamqualitysuchasflavour,texture,bodyandcolour.The American Dairy Association has stipulated a scorecard for ice cream, which carries a maximum score of 10 for flavour, 5 for body and 5 for colour and appearance, 3 for melting quality and 2 for bacterial content. The recommended scoring guide is given in Table 1. Table 1. The ADSA scoring guide for sensory defects of ice cream Intensity of Defect ____________________________________________________________________ Criticisms SlightDefinitePronounced Flavour Acid (sour)420 Cooked975 Flavouring: Lacks flavoring987 Too high887 Unnatural864 Lacks fine flavour987 Lack freshness876 Metallic642 Old ingredient 642 Oxidized641 Rancid 420 Salty875 Storage764 Sensory and Related Techniques for Evaluation of Dairy Foods35 Sweetener: Lacks987 Too high987 Syrup Flavour 975 Whey764 Body and texture Coarse/Icy 421 Crumbly (brittle, friable)432 Fluffy (foamy)321 Gummy (pasty, sticky)421 Sandy210 Soggy (heavy, pudding-like)432 Weak (watery)421 Table 2. Flavour defects of ice-cream, their causes and remedies DefectsCausePrevention AHigh flavourPresenceoflarge amountofflavouring material Addingrightamountofflavoring material. BLow flavourPresenceofinsufficient amountofflavouring material Addingrightamountofflavoring material. CAcid flavourPresence of an excessive amountoflacticacid (developed) Using fresh dairy products Prompt,efficientcooling of mix Avoidingprolonged storageofmixathigh storage temperature DBitter flavourUse of inferior productsUsing true flavour extract Avoidinguseofdairy Sensory and Related Techniques for Evaluation of Dairy Foods36 productsstoredforlong period at low temperature Usingproductsfreefrom off flavour ECooked flavour Overheating the mix. Using overheated concentrated dairy products Carefullycontrolling pasteurization process Usingconc.Productsfree of cooked flavour FFlat flavourUseofinsufficient flavour,sugarormilk solids Usingrightamountof these ingredients GMetallic flavour Copper contamination Bacterial action Avoidingcopper contaminationofmix during processing. Avoidinguseofproducts have metal flavour. HUnnatural flavour Flavour not typical to ice cream Usinghighquality flavouring products. Using high quality dairy and non-dairy products. IOxidized flavour Usingoxidized flavoureddairy products. Metallic contamination. Usingfreshdairy products. Usingonlystainlesssteel equipment. Using antioxidants. Pasteurizingthemixat high temperatures. Whenicecreamisbeingjudgedorganolepticallyitisimportantthatthe serving temperature should be correct. If it is too cold the palate will be deadened, and itwillnotbepossibleeithertoenjoytheicecreamortojudgeanyofitssensory characteristics.Ifitistoowarmitwillhavemeltedpartiallyjudgingofbodyand texture will be almost impossible. A consumer judges the quality or sensory attributes oficecreamonthebasisofseveralcharacteristicstheseareflavour,body,texture and appearance of the product and the package. 3.1 Flavour Ice cream is a mixture of fat, sugar and milk solids-not-fat together with added flavour and colour. An increase in total solids increases the richness of the ice cream and normally improves the flavour, texture and body. Some if these ingredients have markedflavour,othersaremorenearlyneutralorbland.However,theflavourofno singleingredientshouldpredominate,buteachshouldblendtogethertoforma Sensory and Related Techniques for Evaluation of Dairy Foods37 harmoniouswhole,creamysweetsensationwithaslightflavour,leavingapleasant after taste which must not be excessive. Many possible flavour defects may arise due to use of faulty ingredients. The more common flavour defects are given in Table 2. Table3. Body and texture defects of ice cream NameCausesPrevention ACrumbly bodyLow T.S. Content Insufficient Stabilizer Excessive overrun Improper homogenization Increasing T.S. Content Increasing Stabilizer Decreasing overrun Proper homogenization BSoggy body Low overrun High sugar content Excessive amount of stabilizer Proper overrun Optimum suggest content Right amount of stabilizer CShrunken body (The ice cream shrinks away from the sides and top of the container) Fluctuating temperatures during storage Excessive overrun Protein instability Rough transportation Avoiding fluctuating temperature during storage Reducing overrun Avoiding high acidity in mix Avoiding rough transportation. DWeak bodyLow T.S. content Insufficient stabilizer Increasing T.S. content Increasing stabilizer EButtery textureImproper homogenization High fat content Slow freezing Proper homogenization Optimum fat content Fast freezing FCoarse or ice texture Low T.S. content Insufficient stabilizer Slow freezing Slow hardening Insufficient ageing Increasing T.S. content Increasing stabilizer Fast freezing Fast hardening Sufficient ageing Avoiding heat shocking Avoiding prolonged Sensory and Related Techniques for Evaluation of Dairy Foods38 Heat shocking Prolonged storage storage GFluffy textureExcessive overrun Low T.S. content High emulsifier content Decreasing overrun Increasing T.S. content Decreasing emulsifier content HSandy textureHigh M.S.N.F. (Lactose) content Fluctuating temp. in retail cabinets Long storage Period Decreasing M.S.N.F. (Lactose) content Avoiding fluctuating temperatures in retail cabinets Reducing storage periods 3.2 Body and texture Boththebodyandtextureoficecreammaybedeterminedreadilybythe sensesofsightandtouch.Thedesiredbodyinicecreamisthatwhichisfirm,has substance,respondsreadilytodippingandmeltsdownatordinarytemperaturestoa creamyconsistency.Thedesiredtextureisthatwhichisfine,smooth,velvetyand carriestheappearanceofcreaminessthroughout.Thepossiblebodyandtexture defects which may be encountered in ice cream are presented in Table 3. 3.3 Melting Quality High quality ice cream should show little resistance toward melting when it is exposed to room temperature. During melting the mix should drain away as rapidly as itmeltsandformasmooth,uniformhomogeneousliquid.Anyvariationsfromthis behaviourmayleadtheconsumertobesuspiciousofitsquality.Thedefectsin melting quality frequently observed in judging ice cream are given in Table 4. Table 4. Melting quality defects of ice cream NameCausesPrevention a)Curdy meltdownHigh acidity of mix.Using fresh dairy products b)Slow melting*Excessive amount of stabilizer *Improper homogenization. * Reducing the amount of stabilizer. * Proper homogenization Sensory and Related Techniques for Evaluation of Dairy Foods39 c)Whey leakage*Poor quality dairy products * Improperly balanced mix. * Improperly stabilized mix.* Using fresh dairy products * Balancing the mix properly. * Using more effective stabilizer d)Foamy melt down * Excessive overrun. * Excessive amount of emulsifier.* Reducing overrun * Reducing amount of emulsifier. 3.4 Colour The colour of the ice cream should be attractive and pleasing. The ideal colour is characteristic of the flavour, true in shade and neither too pale nor too intense. For example, vanilla ice cream should have a creamish yellow to white colour. Uniform, naturalcolourisdesirableinicecream.Excessivecolouristheresultofaddingtoo muchartificialcolourtothemix.Anunevencolourresultsifthecolourisnot properly added and also if care is not exercised when changing flavours. An unnatural colour is caused by (a) carelessness in adding the colour, (b) improper use of colours, or (c) use of foreign materials. 4. Conclusion Therefore, an excellent quality of Ice-cream can be made only from good mix ingredientsproperlybalancedtoproduceadesirablecompositionalongwithproper processing, freezing, hardening and distribution, under proper sanitary conditions. All thesefactorsareimportantandmustbecarefullycontrollediftheicecreamhaving desirablesensoryattributesistobeproduced.Itmustberememberedthatproduct inferiorityconstitutesoneofthegreatestmenacestothesuccessandprogressofthe icecreamindustry.TheconsumerhaslearnttodependuponIcecramasasafe, enjoyable, energy-giving, nourishing and refreshing food. References Arbuckle, W.S. (1986) Ice cream, 4th Edn., Van Nostrand Reinhold Co. NY Bodyfelt,F.W.,Tobias,J.andTroutG.M.(1988)ThesensoryevaluationofDairy products. Van Nostrand Reinhold, NY. Hyde,K.A.andRothwell,J.(1973)Icecream.ChurchullLivingstone,Edinburgh, UK. Sensory and Related Techniques for Evaluation of Dairy Foods40 SENSORYEVALUATIONOFDAIRYPRODUCTSWITHSPECIALEMPHASISONFLAVOURLEXICON V. Pathak and Z. F. Bhat Associate Proffesor & Head Division of Livestock Products Technology F.V.Sc. & A.H., SKUAST-J Introduction: Sensoryevaluationofafoodreferstoitsscientificevaluationthroughthe applicationofhumansenses.Itinvolvesdevelopmentanduseofprinciplesand methods for measuring human responses to products and ingredients. These principles and methods have broad application for a variety of products. The common element in these tasks is the use of humans as evaluators. It is this link, the human evaluator, that suggestssensoryevaluation'sproximityto,ifnotrelianceon,thebehavioraland socialsciences.Sensoryevaluationcomplieswiththeprinciplesofscienceandis differentfromorganolepticevaluationastheresultsareoftenreproducibleand comparable.Thisnewfieldisfoundedprincipallyonthebehavioralandsocial sciences, rather than chemistry, microbiology, and engineering, the principal scientific fieldsinwhichtraditionaldairyscientistshavebeentrained.Behavioralresearchin perception, learning, cognition, psychophysics, and psychometrics, to mention only a few, provides the basis for the principles and methods the sensory scientist uses today.Onethingincommontoallsensoryassessmentmethodsisthattheyuse humans as the measuring instrument. Even though sophisticated and highly sensitive measuringinstrumentssuchasgaschromatographs,massspectrometers,nuclear magneticresonancespectrometers,IRandUVspectrophotometers,etc.,arenow available,theimportanceofsensoryanalysishasgrownratherthandiminished.The problem with instruments is that one instrument will analyse only single component at atimewhichdoesnotfulfillourrequirementasweareinterestedingettingtotal sensory impression of a processed food product at the same time. The dairy industry has come a long way since the early 1900s, when it began developingtechniquesforjudgingdairyproductstostimulateinterestandeducation in dairy science. Since then sensory analysis techniques have developed into powerful toolsforunderstandinghowtheappearance,flavorandtextureattributesofdairy products drive consumer preferences. In the traditional methods that emerged, judging and grading dairy products normally involved one or two trained experts assigning qualityscoresontheappearance,flavorandtextureoftheproductsbasedonthe presenceorabsenceofpredetermineddefects.Modernsensorytechniquescanhelp dairy processors develop new products that are highly appealing to consumers; enable processorstooptimizeaproductsflavor,textureandcolortoattractspecifictarget audiences as wel