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Yeast and molds Yeast and molds Lactic Lactic Fermentation Fermentation

Yeast and Molds Lactic Fermentation

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Yeast and molds Yeast and molds Lactic Lactic

FermentationFermentation

Yeast-lactic Yeast-lactic fermentationfermentation

Fermented milk products which are made Fermented milk products which are made from certain strains of lactic acid bacteria from certain strains of lactic acid bacteria and yeasts are called yeast-lactic and yeasts are called yeast-lactic fermentationfermentation

E.g :- E.g :-

1.Kefir 1.Kefir

2.Related products like Koumiss and 2.Related products like Koumiss and Acidophilus yeast milkAcidophilus yeast milk

These products are also known as These products are also known as alcoholic milk beveragesalcoholic milk beverages

Cont…..Cont….. Yeast-lactic fermented products are Yeast-lactic fermented products are

originated in central Asia between originated in central Asia between caucasus mountains and Mongolia.caucasus mountains and Mongolia.

These are very popular in many These are very popular in many countries liky former USSR, Poland, countries liky former USSR, Poland, Hungary, Bulgaria and some Hungary, Bulgaria and some Scandinavian countries.Scandinavian countries.

The popularity of the alcoholic milk The popularity of the alcoholic milk beverages help their consumption and beverages help their consumption and promote these products as good for promote these products as good for health.health.

Kefir Kefir Kefir is a fermented milk drink that Kefir is a fermented milk drink that

originated with Shepherds of the north originated with Shepherds of the north caucasus regioncaucasus region

Kefir is white or yellowish fermented milk Kefir is white or yellowish fermented milk having balanced yeasty aroma with acidic having balanced yeasty aroma with acidic flavour but have pleasant and refreshing flavour but have pleasant and refreshing charactersccharactersc

It have elastic consistencyIt have elastic consistency Lactic acid, volatile acids, diacetyl, COLactic acid, volatile acids, diacetyl, CO22 and and

ethanol are main compounds influencing ethanol are main compounds influencing the sensory properties of kefir.the sensory properties of kefir.

Kefir grainsKefir grains

Appearance and chemical compositionAppearance and chemical composition Size range # 0.3-2.0cm or more in Size range # 0.3-2.0cm or more in

diameterdiameter The kefir grains are irregular, folded or The kefir grains are irregular, folded or

uneven surface resembling cauliflower uneven surface resembling cauliflower florets in shape and colourflorets in shape and colour

White or slightly yellowish in colour and a White or slightly yellowish in colour and a characterstic smellcharacterstic smell

These grains have specific biological These grains have specific biological functionfunction

Microflora of Kefir Microflora of Kefir grainsgrains Complex microfloraComplex microflora Lactic acid bacteria, Yeast, Acetic Lactic acid bacteria, Yeast, Acetic

acid bacteria and Mouldsacid bacteria and Moulds According to Polish standardsAccording to Polish standards

Lactobacilli- 80%Lactobacilli- 80%

Yeasts-12%Yeasts-12%

Lactococci-8%Lactococci-8%

Lactic acid Lactic acid bacteriabacteria

Main LAB microfloraMain LAB microflora LactococcusLactococcus spp mainly spp mainly L.lactis subsp lactisL.lactis subsp lactis LactobacilliusLactobacillius spp spp Streptococcus thermophilusStreptococcus thermophilus Leuconostoc Leuconostoc spp spp Lb. delbrueckii subsp bulgaricus, Lb. Lb. delbrueckii subsp bulgaricus, Lb.

helveticus, Lb. casei subspp helveticus, Lb. casei subspp pseudoplantarum, Lb.brevis pseudoplantarum, Lb.brevis are also found.are also found.

Yeasts Yeasts

Kluyeromyces marxianus var. lactisKluyeromyces marxianus var. lactis Saccharomyces cerevisiaeSaccharomyces cerevisiae Candida inconspicuaCandida inconspicua Candida marisCandida maris

Kluyeromyces Kluyeromyces spp are permanently spp are permanently present on grains and responsible present on grains and responsible for yeasty aroma in the productsfor yeasty aroma in the products

Acetobacter aceti Acetobacter aceti and and Acetobacter Acetobacter rasensrasens

Mould- Mould- Geotrichum candidumGeotrichum candidum LactococcusLactococcus spp is located on the spp is located on the

surface of the kefir grain while surface of the kefir grain while lactobacilli and yeasts are present in lactobacilli and yeasts are present in the deepers layer of the grain.the deepers layer of the grain.

Cont….

Different microflora in Different microflora in kefir and kefir grainskefir and kefir grains

Organisum In kefir In Organisum In kefir In grainsgrains

Lactococci and 80% 5-25%Lactococci and 80% 5-25%

LeuconostocLeuconostoc spp. spp. Yeasts 10-15% 10-Yeasts 10-15% 10-

15%15% Lactobacilli 5-10% 60-Lactobacilli 5-10% 60-

80%80%

Mechanism Mechanism

The mechanisms responsible for the The mechanisms responsible for the production of flavor compounds are production of flavor compounds are results of metabolismresults of metabolism

Yeast metabolism in kefir is not well Yeast metabolism in kefir is not well establishedestablished

Lipolysis of fat in milk results in Lipolysis of fat in milk results in formation of free fatty acid which is formation of free fatty acid which is precursors of flavour compounds in kefirprecursors of flavour compounds in kefir

Methylketones, alcohols, lactones and Methylketones, alcohols, lactones and estersesters

Cont…Cont…

Protein hydrolysisProtein hydrolysis Yeasts also degrade casein to small Yeasts also degrade casein to small

peptides and free amino acids and peptides and free amino acids and latter these are converted to latter these are converted to alcohols aldehydes, volatile acids, alcohols aldehydes, volatile acids, ester and Sulphur-containing ester and Sulphur-containing compoundscompounds

Production of Production of exopolysaccharidesexopolysaccharides

Microflora held togther in a matrix of Microflora held togther in a matrix of protein and polysaccharideprotein and polysaccharide

EPS produce by LAB contribute to EPS produce by LAB contribute to texture of grain and fermentatetexture of grain and fermentate

EPS produce by LAB is known as KefiranEPS produce by LAB is known as Kefiran Kefiran material posses anti cancer Kefiran material posses anti cancer

activityactivity EPS produce by LAB can affect EPS produce by LAB can affect

rheological properties of products like rheological properties of products like improve the texture and mouth feel improve the texture and mouth feel

Also exhibit biological properties Also exhibit biological properties such as such as

ImmunostimulatoryImmunostimulatory AntimutagenicAntimutagenic AntitumourAntitumour Anti-ulcer activitiesAnti-ulcer activities Act as a prebiotic compoundAct as a prebiotic compound

Cont…

Production Production

Traditionally kefir was produced in Traditionally kefir was produced in animal skin bags in which fresh milk animal skin bags in which fresh milk seeded with kefir grains, as the seeded with kefir grains, as the products consumed, fresh milk was products consumed, fresh milk was added.added.

Current methodsCurrent methods 1.Traditional method based on the 1.Traditional method based on the

use of kefir grainsuse of kefir grains 2.Industrial process using DVI or 2.Industrial process using DVI or

DVS kefir cultureDVS kefir culture

Chemical Chemical compositioncomposition

Based on FAO/WHOBased on FAO/WHO Protein contents not less than Protein contents not less than

2.7g/100g2.7g/100g Fat level not more than 10g /100gFat level not more than 10g /100g Titratable acidity not less than Titratable acidity not less than

0.6mL /100mL0.6mL /100mL Bacterial count in 1g not specifiedBacterial count in 1g not specified Yeast count not less than 10 cfu/ gYeast count not less than 10 cfu/ g

Metabolic pathway of Metabolic pathway of YeastYeastLactoseLactose

Citrate Citrate COCO22 COCO22, Acetate, Acetate

Pyruvate D-Pyruvate D-LactateLactate

COCO22 AC-TPPAC-TPP CoCo22 L-Lactate L-Lactate

Acetaldehyde Acetaldehyde αα-Acetolactate-Acetolactate COCO22 COCO22

Ethanol Ethanol Acetoin Diacetyl Acetoin Diacetyl

Nutritional valueNutritional value According to Halle et al., Kefir contain (g 100g) According to Halle et al., Kefir contain (g 100g) 3.0-3.4 protein3.0-3.4 protein 1.5 fat1.5 fat 2.0-3.5 lactose2.0-3.5 lactose Vitamins in kefir made using grains and milk from Vitamins in kefir made using grains and milk from

different spp of mammals increased by 20% like-different spp of mammals increased by 20% like- Thiamine(B1)only in ewe’s milk kefirThiamine(B1)only in ewe’s milk kefir Pyridoxine (B6) in ewe’s milk+ goat’s milkPyridoxine (B6) in ewe’s milk+ goat’s milk Folic acid in all kefir except mare’s milkFolic acid in all kefir except mare’s milk Increase in biosynthesis of riboflavin(B2) and Increase in biosynthesis of riboflavin(B2) and

ascorbic acid when oxygen is injected into medium ascorbic acid when oxygen is injected into medium during fermentationduring fermentation

Therapeutic Therapeutic propertiesproperties

Antibacterial activityAntibacterial activity Used in the treatment of Used in the treatment of

tuberculosis, cancer, gastrointestinal tuberculosis, cancer, gastrointestinal tract disorders and a variety of tract disorders and a variety of diseasesdiseases

KoumissKoumiss

First mentioned in the 5First mentioned in the 5thth century as century as drink of goddrink of god

In 7In 7thth century koumiss became an century koumiss became an everyday drink of the Mongolian tribeseveryday drink of the Mongolian tribes

Traditional it is produced by mare’s milk Traditional it is produced by mare’s milk

In Mongolia by camel’ milkIn Mongolia by camel’ milk

In Europe and North America from In Europe and North America from full and full and

skimmed milkskimmed milk

MicrofloraMicroflora

Lactobacilli( Lactobacilli( Lb.delbrueckii subsp Lb.delbrueckii subsp bulgaricusbulgaricus and and Lb. acidophilusLb. acidophilus) ) lactose fermented yeasts lactose fermented yeasts ((Saccharomyces spp, candida Saccharomyces spp, candida koumisskoumiss

Non-lactose fermenting yeast Non-lactose fermenting yeast S.cartilaginosusS.cartilaginosus

Non-carbohydrate fermenting yeasts Non-carbohydrate fermenting yeasts ((MycodermaMycoderma))

ProductionProduction

Traditional mare milking starts early in Traditional mare milking starts early in the morning and takes place every 2 the morning and takes place every 2 hrs, means six times milking in a dayhrs, means six times milking in a day

In the evening, fresh milk is added in In the evening, fresh milk is added in the already fermented milk in a wooden the already fermented milk in a wooden pots to provide ongoing fermentationpots to provide ongoing fermentation

Traditional milk was fermented in Traditional milk was fermented in horse-hide bags known as chochuur or horse-hide bags known as chochuur or tursuks or burduks. tursuks or burduks.

At present, wooden containers are used, At present, wooden containers are used, which is also contain previous season which is also contain previous season microfloramicroflora

When fresh milk is added to fermentate, When fresh milk is added to fermentate, mixture is stirred vigorously for 1hr using mixture is stirred vigorously for 1hr using special implement to introduce air which special implement to introduce air which cause good growth conditions for yeastscause good growth conditions for yeasts

The amounts of yeasts determines the alochol The amounts of yeasts determines the alochol in the productsin the products

More alcohol is produces, better the quality of More alcohol is produces, better the quality of KoumissKoumiss

Cont..

Industrialised processIndustrialised process

The protein content of mare’s milk is The protein content of mare’s milk is very low compared to cow’s milk so very low compared to cow’s milk so that fermentate does not coagulatethat fermentate does not coagulate

Cow milk is used for the production Cow milk is used for the production of koumiss due to the limited of koumiss due to the limited availability of mare’s milkavailability of mare’s milk

Protein and lactose contents of Protein and lactose contents of mare’s milk are different from cow’s mare’s milk are different from cow’s milkmilk

Fresh mare’s milk or Cow milk

Heating (90-920C)

Cooling (26-280C)

Inoculation with 30% starter (1 part L.bulgaricus at 370C

for 7 hr+ 2 parts Torula spp.

at 300C for 15 hr)

Acidity 1.4% in mare’s milkIncubation (280C till acidity 0.7-0.8%)

Agitation every 1-2 hr

Cooling (200C)

Packaging

Storage (4-50C for 24 hr)

Manufacture of Kumiss

According to Tamime and Marshall According to Tamime and Marshall to modify cow’s milk composition for to modify cow’s milk composition for the manufacture of koumiss include the manufacture of koumiss include followingfollowing

Addition of 2.5g sucrose 100g to Addition of 2.5g sucrose 100g to skimmed milkskimmed milk

Blending different powders9 whole Blending different powders9 whole milk, skimmed milk, cheese whey)milk, skimmed milk, cheese whey)

Cont…

Nutritional propertiesNutritional properties Apart from nitrogenous compound in Apart from nitrogenous compound in

koumiss including free essential amino koumiss including free essential amino acidsacids

Starter culture microflora exhibits Starter culture microflora exhibits bacteriocidal and bacteriostatic bacteriocidal and bacteriostatic properties against many pathogens such properties against many pathogens such as E.coli, bacillus cereus and as E.coli, bacillus cereus and mycobacterium sppmycobacterium spp

Some of the yeast spp present in Some of the yeast spp present in koumiss also exhibit an antibiotic koumiss also exhibit an antibiotic activity against S.aureus, b.cereusactivity against S.aureus, b.cereus

Miscellaneous productsMiscellaneous products

Acidophilus-yeast milkAcidophilus-yeast milk CalpisCalpis Korean alcoholic fermented prodctsKorean alcoholic fermented prodcts BulgarosBulgaros AwasiAwasi TogwaTogwa SkyrSkyr

Mold-lactic Mold-lactic fermentationfermentation

Apart from mold-ripened cheeses, Apart from mold-ripened cheeses, there are few dairy products that there are few dairy products that deliberately include mold in the deliberately include mold in the

microflora,microflora,such as Viilisuch as Viili

ViiliViili Viili is a cream layer with white mold

growing on the surface that give productv velvety apperance

viili is mildly sour, aromatic in taste, and stretchy, and it can be cut easily with a spoon

The flavor of Viili is similar to other types of buttermilk product, but with a slightly musty aroma that is attributed by G. candidum

The mold layer on the surface of the product may be advantageous in preventing the growth of spoilage microorganisms

Types and starter cultureTypes and starter culture Three types of ViiliThree types of Viili 1. Low-fat viili1. Low-fat viili 2.Whole-fat villi2.Whole-fat villi 3.Cream viili3.Cream viili Starter cutureStarter cuture Lactobacillus lactis subsp lactisLactobacillus lactis subsp lactis Leuconotoc mesenteroides subsp Leuconotoc mesenteroides subsp

cremoriscremoris and a mold and a mold Geotrichum candidumGeotrichum candidum

Production Production

Viili is made from non-fortified and fat Viili is made from non-fortified and fat standardised milkstandardised milk

Milk is not homogenize or aeratedMilk is not homogenize or aerated But heat-treated at 95But heat-treated at 9500C for 5 minsC for 5 mins Then cooled at 20Then cooled at 2000C and inoculated by C and inoculated by

3-6ml 100ml of starter culture3-6ml 100ml of starter culture Inoculated milk is packaged, placed Inoculated milk is packaged, placed

on trays, palletised and transferred to on trays, palletised and transferred to a ripening tunnela ripening tunnel

The containers are incubated 20The containers are incubated 200 0 C for 18-C for 18-24hrs at pH below 4.624hrs at pH below 4.6

Because the milk base was not homogenized, the fat and mold spores rise to the surface during the incubation period.

The mold grows on the surface of the milk to give rise to the velvet-like appearance of the product

Natural Viili consists of two layers (i.e., the coagulated milk and a cream layer plus the mold growth)

Cont…