8/14/2019 Ozkan, 2007

1/6

Antioxidant activities of Satureja cilicica essentialoil in butter and in vitro

Gulcan Ozkan *, Bedia Simsek, Hakan Kuleasan

Suleyman Demirel University, Faculty of Agriculture, Department of Food Engineering, 32260 Isparta, Turkey

Received 14 November 2005; accepted 12 April 2006Available online 4 May 2006

Abstract

Satureja(Labiatae) species are a well-known aromatic plant which is used to produce essential oil and aromatic water in the mountainregions of the Mediterranean part of Turkey. In our study, it was aimed to determine antioxidant activities ofSatureja cilicicaessentialoil in butter and in vitro. Antioxidant activities of the oils at different concentrations were evaluated using the 1,1-diphenyl-2-pic-rylhydrazyl (DPPH) radical scavenging and phosphomolybdenum methods. Also the essential oil with 0.5%, 1.0% and 2.0% were addedin butter as antioxidants and were assayed during 60 days storage of butter at +4 and +20 C. For this reason, it was analyzed peroxidevalue, pH, titratable acidity and total lactic acid bacteria as a criterion to assess the antioxidant activity of essential oil at 20th, 40thand 60th days of storage. Antiradical activity was found as IC50= 32.02 0.58lg/ml and in vitro antioxidant capacity was101.16 3.32 lg/ml by phosphomolybdenum methods. On the other hand, the essential oil ofS. cilicicaexhibited a strong antioxidantactivity in butter. Antioxidant activities of oils were higher when the essential oil concentration was increased. In addition to that per-oxide value pH, titratable acidity and number of viable lactic acid bacteria were compared to the control. In addition, titratable acidityand total number of lactic acid bacteria of samples stored at +20 C were determined higher than the other storage temperature duringthe storage time. According to our results, essential oil ofS. cilicicacould be used as both natural antioxidant and aroma agent in butter.2006 Elsevier Ltd. All rights reserved.

Keywords: Satureja cilicica; Essential oil; Butter; Starter culture

1. Introduction

Satureja cilicica L. is an aromatic and endemic medici-nal plant belonging to the Lamiaceae family. The aerialmaterial has a distinctive taste and can be added to stuffing,meat pies, sausages and some milk products as a seasoning.

Fresh sprigs can be boiled with pulses, such as peas, beansor lentils, for flavouring or, alternatively, they can be usedinstead of parsley and chervil as a garnish. The leaves,flowers and stems of Satureja species are used as herbaltea, in production of traditional medicine, to treat variousailments, such as cramps, muscle pains, nausea, indiges-tion, diarrhea and infectious diseases (Baydar, Sagdic,

Ozkan, & Karadogan, 2004; Gulluce et al., 2003; Hajhas-hemi, Sadraei, Ghannadi, & Mohseni, 2000).

Herbs and derivatives have been used as culinary andmedicinal purposes for a long time and added in the foodto prevent the formation of undesirable oxidationproducts. Not only are many of the flavours and aromas

distinctively pleasant, but they can also be used to concealoff-flavours and odors. The researches conducted on theopportunity of antioxidant and antimicrobial agent ofherbs in vitro an in food generally focused on their essentialoils in the last 1520 years (Tainter & Grenis, 1993).

The oxidation of lipids is very important with respect tothe shelf life of a product. In the first stage of oxidation,peroxides are formed by the reaction between unsaturatedfatty acids and oxygen molecule. Butter is also a milk prod-uct with relatively longer shelf life. In butter making, thefat content of the milk is concentrated approximately

0260-8774/$ - see front matter 2006 Elsevier Ltd. All rights reserved.

doi:10.1016/j.jfoodeng.2006.04.020

* Corresponding author. Tel.: +90 246 2111666; fax: +90 246 2370437.E-mail address:gozkan@ziraat.sdu.edu.tr(G. Ozkan).

www.elsevier.com/locate/jfoodeng

Journal of Food Engineering 79 (2007) 13911396

mailto:gozkan@ziraat.sdu.edu.trmailto:gozkan@ziraat.sdu.edu.tr

8/14/2019 Ozkan, 2007

2/6

20 times. By contrast, the other constituents in milk, i.e.protein, lactose, salts and water are reduced. Butter is pro-duced from milk, cream and yoghurt in different areas ofTurkey (Konar & Hayaloglu, 1999). The rate of consump-tion of butter is about 2.6% for each person in Turkey(Atamer, 1993). In addition, lactic acid bacteria are com-

monly used as starter cultures to provide diacetyl whichis the major aroma compound in the production of variousdairy products. They cause rapid acidification of the rawmaterial with the production of organic acids, mainly lacticacid. Their production of acetic acid, ethanol, aroma com-pounds, and several enzymes is also important. In this waythey enhance shelf life, microbial safety, improve texture,and contribute to the pleasant sensory profile of the endproduct. The characteristics and or fatty acid compositionof butter and milk fat have been investigated by manyresearchers (Bilgin, 1996; Collomb, Butikofer, Sieber, Jean-gros, & Bosset, 2002; Glew, Okolo, Chuang, Huang, &Vanderjagt, 1999; Sagdic, 2000; Sagdic, Arici, & Simsek,

2002). But according to our knowledge there were a littleliterature on opportunity of herb essential oil as both nat-ural antioxidant and aroma agent in butter.

The aim of this study was to determine the antioxidantactivities and aromatic properties of S. cilicica essentialoil when it is used in butter production. In addition, theeffect of essential oil on oxidation, chemical propertiesand stability of butter was determined. Since the presenceof starter culture is crucial for the aroma development ofbutter, the effect of essential oil on viability ofLactococciused as starter culture was also investigated.

2. Materials and methods

2.1. Essential oil

Essential oil of S. cilicica was obtained from thebi-national project of Deutscher Akademischer Aust-auschdienst (DAAD) in Bonn, Germany (reference num-ber: A/04/17627). Schulz, Ozkan, Baranska, Kruger, andOzcan (2005)were reported in their article from this projectthatS. cilicicamain components were the thymol (22.76%),carvacrol (18.90%), p-cymene (19.52%) and c-terpinene(13.40%).

2.2. Butter production

For butter production, cream and butter were producedin Suleyman Demirel University, Un-Sut Dairy Plant. Thefirst, cream was analyzed, after cream was standardized35% fat and pasteurized at 90 C for 15 min and cooledto 1011C, cream churned. After churning cream wasinoculated with butter culture (2%) (Wiesby, Probat 505,Germany). After fermentation, the butters were dividedinto two parts (A: +4 C stored and B: +20 C stored)and each part was divided into four parts again. essentialoil was added into each part (1UA, 0.5%; 2UA, 1.0%;

3UA, 2%; KA, control: non-essential oil; 1UB, 0.5%;

2UB, 1.0%; 3UB, 2%; KB, control: non-essential oil). Thenthe samples were packaged as 100 g and stored at 4 and20 C for 60 days until analysis. All determinations weredone in duplicate.

2.3. Determination of antiradical activity

The free radical scavenging activity of essential oil wasexamined by comparing to those of known antioxidantsuch as BHT by 1,1-diphenyl-2-picrylhydrazyl (DPPH)using the method ofLee et al. (1998). Briefly, a 1.0 ml solu-tion of the essential oil in methanol (10 ppm) was mixedwith 2.0 ml of methanolic solution of DPPH (10 mg/l).The mixture was shaken vigorously and allowed to standat room temperature for 5 min. Then the absorbance wasmeasured at 517 nm against methanol as the blank in aspectrophotometer. Lower absorbance of the reaction mix-ture indicated higher free radical scavenging activity. Thepercent of DPPH discoloration of the samples was calcu-

lated according to the formula:Antiradical activity (%) = 100 (absorbance of con-

trol absorbance of sample/absorbance of control).Extract concentration providing 50% inhibition (IC50)

was calculated from the plot of inhibition percentageagainst extract concentration. Tests were carried out intriplicate.

2.4. Evaluation of antioxidant activity

The antioxidant activity of essential oil was evaluated bythe formation of phosphomolybdenum complex method

according to Prieto, Pineda, and Aguilar (1999). Briefly,an aliquot of 0.4 ml of sample solution (10 ppm in metha-nol) was combined in a vial with 4 ml of reagent solution(0.6 M sulfuric acid, 28 mM sodium phosphate and4 mM ammonium molybdate). The blank solution con-tained 4 ml of reagent solution and the 1 ml of methanol.The vials were capped and incubated in a water bath at95 C for 90 min. After the samples had cooled to roomtemperature, the absorbance of the mixture was measuredat 695 nm against a blank. The antioxidant activity wasexpressed relative to that of ascorbic acid. All determina-tions were done in triplicate.

2.5. Peroxide value analysis

The antioxidant activity of the essential oil was tested inbutter and expressed as the decrease in the rate of peroxideformation. And its peroxide value was also found as0.35 mequiv/kg. Oil (2 g) was accurately weighted and theessential oil was added directly to the oil at a concentrationof 0.5%, 1% and 2% (v/wt). Control samples of butter with-out antioxidant were also placed under same conditions.All samples were incubated in 100 ml capped plastic beak-ers at +4 and +20 C in the dark. The peroxide values ofthe samples were determined at 20th, 40th and 60th days

of storage in terms of the method of the American Oil

1392 G. Ozkan et al. / Journal of Food Engineering 79 (2007) 13911396

8/14/2019 Ozkan, 2007

3/6

Chemists Society (AOAC, 1990). All determinations weredone in triplicate.

2.6. Physicochemical analyses of butter and cream

The pH value of butter and cream were determined by

pH meter (WTW instruments, pH 330-Germany). Titrat-able acidity (as lactic acid %) of cream and butter wasdetermined as suggested by Anonymous (1975, 1989).Moisture was found by heating in an over at 102 C, untila constant weight was obtained. The contents of fat (%)and non-fat solid of cream and butter were measuredaccording to the standard methods (Anonymous, 1975,1989). All determinations were done in triplicate.

2.7. Lactic acid bacteria counts

Commercial butter starter which contains Lactococcusand Leuconostoc species were added in butter to develop

desired flavour. Lactic acid bacteria counts were done inevery 20 days of storage period. For this purpose 10 mlbutter sample was taken into sterile tubes and melted in a45 C water bath. Then proper dilutions were done andeach dilution was plated on MRS agar plates in triplicates.After incubation at 30C for 24 h, colony counts wererecorded. The same experimental procedures were appliedto both samples stored at 4 and 20 C. The results were pre-sented as average of three counts.

2.8. Statistical analysis

Results of the research were tested for statistical signifi-cance by one-way ANOVA. Differences were consideredstatistically significant at the P< 0.05 level.

3. Results and discussion

In our study, antiradical activity and antioxidant capac-ity of the essential oil obtained fromS. cilicicawere studiedas in vitro and in food. Antiradical activity of essential oilfrom S. cilicica tested by the DPPH model system and theantiradical activity of essential oil was found asIC50= 32.02 0.58 lg/ml. BHT used as a synthetic anti-oxidant in food industry showed lower antiradical activity(IC50= 96,13 0.01 lg/ml) when it was compared to thesame concentration of essential oil. The model of scaveng-ing the stable DPPH radical is a widely used method toevaluate antioxidant activities in a relatively short timecompared with other methods (Gulcin, Sat, Beydemir,Elmastas, & Kufrevioglu, 2004). The addition of the essen-tial oil to the DPPH solution caused a rapid decrease in theoptical density at 517 nm. The degrees of discolorationindicate the scavenging capacity of the essential oil. Freeradicals cause autoxidation of unsaturated lipids in food(Kaur & Perkins, 1991). The effect of antioxidant on DPPHradical scavenging was thought to be due to their hydrogen

donating ability or radical scavenging activity (Baumann,

Wurn, & Bruchlausen, 1979). Antioxidants cease the freeradical chain of oxidation and to donate hydrogen fromthe phenolic hydroxyl groups. Therefore formed stableend-product does not permit further oxidation of the lipid(Sherwin, 1978). The antioxidant capacity of the essentialoil (equivalent to ascorbic acid) was found as 101.16

3.32 lg/ml by phosphomolybdenum method. The phosp-homolybdenum method is based on the reduction ofMo(VI) to Mo(V) by the antioxidant compounds and theformation of a green Mo(V) complex with a maximalabsorption at 695 nm (Prieto et al., 1999). The antioxidantsbreak the free radical chain by donating a hydrogen atom(Gordon, 1990).Jayaprakasha, Selvi, and Sakariah (2003)were reported that the antioxidant activity of the essentialoil depends on the presence of polyphenols which may actas reductons. According to our knowledge, there was noavailable literature on antiradical activities and antioxidantproperties of essential oil from S. cilicica for a furtherdiscussion.

Peroxide value is a widely used measure of the primarylipid oxidation indicating the amount of peroxides formedin fats and oils during oxidation. Antioxidant activity ofthe essential oil, compared with control samples, wastested. The results given in Figs. 1 and 2 showed that allconcentrations of essential oil reduced the oxidation rateof butter at +4 and +20 C in terms of formation perox-ides. After 60 days all essential oil showed antioxidanteffect in varying degrees in butter compared with the con-trol. Peroxide value of control sample increased from0.35 mequiv/kg to 1.00 and 1.14 mequiv/kg at +4 and+20 C, respectively. In terms of retarding the formation

of oxidation products, the effectiveness of the essential oilwas determined at 2% concentration. The essential oil atall concentration was found more effective than the controland the peroxide value of butter stored at +4 C had lowervalue than at +20C. Effectiveness of essential oil concen-tration (%) at days of 60th can be put into the followingorder: 2 > 1 > 0.5% and with the values of 0.50, 0.65 and0.71 mequiv/kg at +4 C and 0.69, 0.94 and 1.04 mequiv/kg at +20 C, respectively. Some researchers are alsoreported that herb and propolis extract had high antioxi-dant activity in butter (Ayar, Ozcan, Akgul, & Akin,2001; Ozcan & Ayar, 2003).

Before the production of butters, the physicochemicalcharacteristic of cream was analyzed. The fat, solid-non- fat, pH, titratable acidity and moisture values of creamwere determined as 72.666 0.2880%, 8.9766 0.3534%,4.713 0.0115, 0.2566 0.0011% and 18.3566 0.0702%,respectively. And then, the fat, solid-nonfat, pH, titratableacidity and moisture values of butters were analyzed andfound as 84.166 0.2880%, 1.5366 0.2663%, 6.373 0.0115, 0.028 0.0005% and 14.2976 0.0321%, respec-tively (first days). The titratable acidity value of buttersadded essential oil decreased according to control duringthe storage period.

This value increased at control samples during the stor-

age period. The lactic acid (%) value of samples stored at

G. Ozkan et al. / Journal of Food Engineering 79 (2007) 13911396 1393

8/14/2019 Ozkan, 2007

4/6

+20 C was higher than other storage temperature duringthe storage time. The pH value of samples added essential

oil at +20

C was lower than other storage temperature.This value was degreased at control samples during thestorage period at both +4 and +20 C. There was an insig-nificant difference between titratable acidities and pH ofthe butters (Table 1). Butter samples stored at +4 C weremore stable than those kept at +20 C. The results of phys-icochemical characteristics were similar to those given bySagdic et al. (2002) and Sagdic et al. (2003).

As a result, the antiradical and antioxidant activities ofthe herb extracts and essential oils are generally ascribed tothe diterpenes and polyphenols (Couladis, Tzakou, Veryk-okidou, & Harvala, 2003; Lu & Foo, 2001; Miliauskas,Venskutonis, & van Beek, 2004; Yildirim et al., 2004).

The main components of essential oil sample used in ourstudy were the thymol (22.76%), carvacrol (18.90%), p-

cymene (19.52%) and c-terpinene (13.40%) (Schulz et al.,2005). The antioxidant properties could be attributed tothese diterpenes and phenolics, especially thymol and car-vacrol. The results showed that antiradical and antioxidantactivity of essential oil may depend on not only the essen-tial oil content but also different concentrations. Because2% concentration of essential oil was found the most effec-tive to reduce the oxidation of butter. In addition to itsantioxidant activity, the essential oil did not show anyundesired effect on the viability of starter cultures whichare necessary for development of aroma in butter andchemical properties analyzed. As it is shown in the Figs.3 and 4there was a slight decrease in the number of lactic

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0 20 40 60

Storage time, days

Peroxidevalue

,permeqkg

KB

1 UB

2 UB

3 UB

Fig. 2. Peroxide values of essential oil fromS. cilicicaat 2%, 1% and 0.5% and control during storage at 20 C for up to 60 days in the dark.

Table 1Titratable acidities and pH values of the butter samples (mean standard deviation)

Butter Lactic acid pH

20th day 40th day 60th day 20th day 40th day 60th day

KA 0.095 0.002 0.0988 0.00 0.103 0.00 4.99 0.02 4.62 0.02 4.91 0.561UA 0.067 0.002 0.0665 0.00 0.075 0.00 5.09 0.03 4.93 0.03 4.83 0.042UA 1.067 0.002 0.0639 0.00 0.069 0.00 5.16 0.03 5.07 0.05 4.90 0.043UA 0.058 0.002 0.1113 0.00 0.114 0.00 4.52 0.02 5.19 0.01 4.98 0.05KB 0.101 0.002 0.1113 0.00 0.114 0.00 4.50 0.05 4.36 0.02 4.28 0.041UB 0.086 0.002 0.0874 0.00 0.093 0.00 4.97 0.05 4.55 0.05 4.49 0.052UB 0.083 0.002 0.0832 0.00 0.088 0.00 4.86 0.07 4.53 0.01 4.51 0.02

3UB 0.080 0.002 0.0821 0.00 0.087 0.00 5.13 0.05 4.78 0.01 4.72 0.02

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0 20 40 60

Storage time, days

Peroxidevalue,permeqkg

KA

1 UA

2 UA

3 UA

Fig. 1. Peroxide values of essential oil from S. cilicicaat 2%, 1% and 0.5% and control during storage at 4C for up to 60 days in the dark.

1394 G. Ozkan et al. / Journal of Food Engineering 79 (2007) 13911396

8/14/2019 Ozkan, 2007

5/6

acid bacteria in the first 20 days of storage. After 20 days,the numbers increased and the viable numbers of lactic acid

bacteria reached from 105 to 106 cfu/ml.The results also showed that there was an insignificant

difference between the samples stored in refrigeration tem-perature and those which stored in high temperatureregarding the viable numbers of lactic acid bacteria. Whendifferent concentrations of essential oils added in buttersamples were compared, similar results were obtainedwhich indicates that essential oil even at high concentra-tions did not affect viability of starter thus aroma develop-ment of the product.

The results of the present study indicate that S. cilicicaessential oil could be used as easily accessible source of nat-

ural antioxidant and aroma agent for butters.

References

Anonymous. (1975). Sour cream standard TS 1864. Ankara, Turkey: TSE(Turkish Standards Institute).

Anonymous. (1989). Butter standard TS 1331. Ankara, Turkey: TSE(Turkish Standards Institute).

AOAC (1990). Official methods of analysis (15th ed.). Washington, DC:Association of Official Analytical Chemists.

Atamer, M. (1993). Butter technology. Class notes: 380. Ankara Univer-sity, Agricultural Faculty, Ankara, Turkey.

Ayar, A., Ozcan, M., Akgul, A., & Akin, N. (2001). Butter stability asaffected by extracts of sage, rosemary and oregano. Journal of Food

Lipids, 8(1), 1525.

Baumann, J., Wurn, G., & Bruchlausen, F. V. (1979). Prostaglandinsynthetase inhibiting O2-radical scavenging properties of some flavo-

noids and related phenolic compounds, Naunyn, Schmiedebergs.Archives of Pharmacology, 308, 2732.

Baydar, H., Sagdic, O., Ozkan, G., & Karadogan, T. (2004). Antibacterialactivity and composition of essential oils fromOriganum,ThymbraandSatureja species with commercial importance in Turkey. Food Control,15, 169172.

Bilgin, B. (1996). A research on the determination of some sensory,physical, chemical and microbiological properties during the storageperiod of butters produced by souring with sweet and four differentculture combinations. Ph.D. Thesis, Graduate School of Natural andApplied Science, Trakya University, Tekirdag, Turkey.

Collomb, M., Butikofer, U., Sieber, K., Jeangros, B., & Bosset, J. O.(2002). Composition of fatty acids in cows milk fat produced inlowlands, mountains and highlands of Switzerland using high resolu-tion gas chromatography. International Dairy Journal, 12(8), 649659.

Couladis, M., Tzakou, O., Verykokidou, E., & Harvala, C. (2003).Screening of some Greek aromatic plants for antioxidant activity.

Phytotherapy Research, 17(2), 194195.Glew, R. H., Okolo, S. N., Chuang, L., Huang, Y. S., & Vanderjagt, D. J.

(1999). Fatty acid composition of Fulani butter oil made from cowsmilk. Journal of Food Composition and Analysis, 12, 235240.

Gordon, M. F. (1990). The mechanism of antioxidant action in vitro. InB.J.F.Hudson (Ed.),Food antioxidants (pp. 118). London: ElsevierApplied Science.

Gulcin, I., Sat, I. G., Beydemir, S., Elmastas, M., & Kufrevioglu, O. I.(2004). Comparison of antioxidant activity of clove (Eugeniacaryophylata Thunb) buds and lavender (Lavandula stoechasL.). FoodChemistry, 87, 393400.

Gulluce, M., Sokmen, M., Daferera, D., Agar, G., Ozkan, H., Kartal, N.,et al. (2003). In vitro antibacterial, antifungal, and antioxidant

activities of the essential oil and methanol extracts of herbal parts

4.5

5

5.5

6

6.5

7

7.5

0 20 40 60

Storage time, days (20 C)

Lacticacidbacteriacounts(logcfu/ml)

KA

1 UA

2 UA

3 UA

Fig. 4. Viable number of lactic acid bacteria during 60 days of storage at 20 C with control and essential oil from S. cilicica.

4.5

5

5.5

6

6.5

7

7.5

0 20 40

60

Storage time, days (4 C)

Lacticacidba

cteriacounts(logcfu/ml)

KB

1 UB

2 UB

3 UB

Fig. 3. Viable number of lactic acid bacteria during 60 days of storage at 4 C with control and essential oil from S. cilicica.

G. Ozkan et al. / Journal of Food Engineering 79 (2007) 13911396 1395

8/14/2019 Ozkan, 2007

6/6

and callus cultures ofSatureja hortensisL. Journal of Agricultural andFood Chemistry, 51(14), 39583965.

Hajhashemi, V., Sadraei, H., Ghannadi, A. R., & Mohseni, M. (2000).Antispasmodic and antidiarrheal effect of Satureja hortensis L.essential oil. Journal of Ethnopharmacology, 71(12), 187192.

Jayaprakasha, G. K., Selvi, T., & Sakariah, K. K. (2003). Antibacterialand antioxidant activities of grape (Vitis vinifera) seed extracts. FoodResearch International, 36, 117122.

Kaur, H., & Perkins, J. (1991). The free radical chemistry of foodadditives. In O. I. Aruoma & B. Halliwell (Eds.), Free radicalsand food additives (pp. 1735). England, London: Taylor and FrancisLtd.

Konar, A., & Hayaloglu, A. (1999). Tereyag Uretim Yontemleri, Kremave Yogurttan Elde edilen Tereyaglarin Fizikokimyasal, Mikrobiyolojikve duyusal Nitelikleri-II. Standard, 448, 5358.

Lee, S. K., Mbwambo, Z. H., Chung, H. S., Luyengi, L., Games, E. J. C.,Mehta, R. G., et al. (1998). Evaluation of the antioxidant potential ofnatural products. Combinatorial Chemistry and High-ThroughputScreening, 1, 3546.

Lu, Y., & Foo, Y. L. (2001). Antioxidant activities of polyphenols fromsage (Salvia officinalis). Food Chemistry, 75, 197202.

Miliauskas, G., Venskutonis, P. R., & van Beek, T. A. (2004). Screening ofradical scavenging activity of some medicinal and aromatic plantextracts. Food Chemistry, 85, 231237.

Ozcan, M., & Ayar, A. (2003). Effect of propolis extracts on butterstability. Journal of Food Quality, 26(1), 6573.

Prieto, P., Pineda, M., & Aguilar, M. (1999). Spectrophotometricquantitation of antioxidant capacity through the formation of aphosphomolybdenum complex: specific application to the determina-tion of vitamin E. Analytical Biochemistry, 269, 337341.

Sagdic, O., Arici, M., & Simsek, O. (2002). Selection of starters for atraditional Turkish yayik butter made from yoghurt. Food Microbi-ology, 19, 303312.

Sagdic, O., Donmez, M., & Demirci, M. (2003). Comparison ofcharacteristics and fatty acid profiles of traditional Turkish yayikbutters produced from goats, ewes or cows milk. Food control, 15,485490.

Sagdic, O. (2000). A research on the using of lactic acid bacteria isolatedfrom yayik butters as butter cultures. Ph.D. Thesis, Graduate Schoolof Natural and Applied Science, Trakya University, Tekirdag, Turkey.

Schulz, H., Ozkan, G., Baranska, M., Kruger, H., & Ozcan, M. (2005).Characterisation of essential oil plants from Turkey by IR and Ramanspectroscopy. Vibration Spectroscopy, 39(2), 249256.

Sherwin, E. R. (1978). Oxidation and antioxidants in fat and oilprocessing. Journal of American Oil Chemical Society, 55, 809814.

Tainter, D. R., & Grenis, A. T. (1993). Recent spice research. In D. R.Tainter & A. T. Grenis (Eds.), Spices and seasonings (pp. 140). NewYork: VCH.

Yildirim, A., Cakir, A., Mavi, A., Yalcin, M., Fauler, G., & Taskesenligil,Y. (2004). The variation of antioxidant activities and chemicalcomposition of essential oils ofTeucrium orientale L. var. Orientaleduring harvesting stages. Flavour and Fragrance Journal, 19, 367372.

1396 G. Ozkan et al. / Journal of Food Engineering 79 (2007) 13911396