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Featured researches published by Zeynep B. Guzel-Seydim.


Critical Reviews in Food Science and Nutrition | 2011

Review: Functional Properties of Kefir

Zeynep B. Guzel-Seydim; Tugba Kok-Tas; Annel K. Greene; Atif C. Seydim

Kefir is a unique cultured dairy product due to combined lactic acid and alcoholic fermentation of lactose in milk. Kefir is produced by microbial activity of “kefir grains” which have a relatively stable and specific balance of lactic acid bacteria and yeast. Due to the claimed health benefits of kefir which include reduction of lactose intolerance symptoms, stimulation of the immune system, lowering cholesterol, and antimutagenic and anticarcinogenic properties, kefir has become an important functional dairy food and consequently, research on kefir has increased in the past decade. In the following review, recent studies on the functional properties of kefir are reviewed.


Journal of Food Science | 2014

Functional Properties of Vinegar

Nilgün H. Budak; Elif Aykın; Atif C. Seydim; Annel K. Greene; Zeynep B. Guzel-Seydim

A variety of natural vinegar products are found in civilizations around the world. A review of research on these fermented products indicates numerous reports of health benefits derived by consumption of vinegar components. Therapeutic effects of vinegar arising from consuming the inherent bioactive components including acetic acid, gallic acid, catechin, ephicatechin, chlorogenic acid, caffeic acid, p-coumaric acid, and ferulic acid cause antioxidative, antidiabetic, antimicrobial, antitumor, antiobesity, antihypertensive, and cholesterol-lowering responses. The aims of this article are to discuss vinegar history, production, varieties, acetic acid bacteria, and functional properties of vinegars.


Journal of the Science of Food and Agriculture | 2010

Antioxidant activity and phenolic content of wine vinegars produced by two different techniques

Havva Nilgun Budak; Zeynep B. Guzel-Seydim

BACKGROUND The presence of phenolics in fruit, red wine and vinegar has positive health effects due to their significant antioxidant activity. The aim of the study was to determine the effects of two different vinegar production methods on antioxidant activity and phenolic level of vinegars derived from Ulugbey Karasi grapes. Traditional surface and industrial submerge methods were used to make vinegar. Samples were taken from fresh red grape juice, maceration, wine, traditional vinegar and industrial vinegar. RESULTS Total phenolic content of traditional and industrial vinegar samples were 2690 mg L(-1) and 2461 mg L(-1) GAE, respectively. ORAC values of traditional and industrial vinegar samples were 10.50 micromol mL(-1)and 8.84 micromol mL(-1) TE, respectively. Antioxidant activity values of traditional and industrial vinegars were 13.50 mmol L(-1) and 10.37 mmol L(-1) TEAC, respectively. Gallic acid, catechin, epicatechin, chlorogenic acid, caffeic acid, syringic acid, p-coumaric acid and ferulic acid were detected in grape juice, wine and vinegar samples. The content of catechin in industrial vinegar (27.50 mg L(-1)) was significantly higher than that of in traditional vinegar (13.76 mg L(-1)) (P < 0.05). Traditional vinegar had higher amounts of chlorogenic and syringic acids than the industrial vinegar (P > 0.05). CONCLUSION Results of this study showed that different production methods affected the functional constituents of wine vinegars.


Journal of Agricultural and Food Chemistry | 2011

Effects of Apple Cider Vinegars Produced with Different Techniques on Blood Lipids in High-Cholesterol-Fed Rats

Nilgün H. Budak; Duygu Kumbul Doguc; Cagri M. Savas; Atif C. Seydim; Tugba Kok Tas; Metin I. Ciris; Zeynep B. Guzel-Seydim

Red delicious apples were used to produce natural apple cider with and without inclusion of maceration. Traditional surface and industrial submersion methods were then applied to make vinegar from apple ciders. Apple cider vinegar samples produced with inclusion of maceration in the surface method had the highest total phenolic content, chlorogenic acid, ORAC, and TEAC levels. Cholesterol and apple vinegar samples were administered using oral gavage to all groups of rats except the control group. Apple cider vinegars, regardless of the production method, decreased triglyceride and VLDL levels in all groups when compared to animals on high-cholesterol diets without vinegar supplementation. Apple cider vinegars increased total cholesterol and HDL and LDL cholesterol levels and decreased liver function tests when compared to animals on a high-cholesterol diet without vinegar supplementation. A high-cholesterol diet resulted in hepatic steatosis. VSBM and VSB groups significantly decreased steatosis.


Journal of the Science of Food and Agriculture | 2010

Effect of fat replacers on kefir quality.

Bilge Ertekin; Zeynep B. Guzel-Seydim

The purpose of the study was to determine the effects of fat replacers on the quality of non-fat kefir. Skim milk fortified with Dairy Lo (DL) and inulin (INU) was fermented with kefir grains to manufacture kefir. The results of compositional, microbiological, rheological and sensorial analyses were compared with whole kefir (WK) and non-fat kefir (NFK) controls. Results for dry matter, pH and lactic acid ranged between 82.4 and 109.1 g kg(-1), 4.26 and 4.40, and 7.0 and 9.2 g L(-1), respectively. Acetaldehyde and ethanol contents of samples were between 2.89 and 7.28 mg L(-1), and 151.46 and 323.89 mg L(-1), respectively. In all samples, Lactobacillus spp., Streptococcus spp. and yeast counts were between 9.1 and 9.9, 9.3 and 9.9, and 5.2 and 5.6 log cfu mL(-1), respectively. Kefir samples had non-Newtonian behaviour and pseudoplastic fluid with thixotropy. At the first day, DL had the highest apparent viscosity (3.119 Pa s) while NFK had the lowest value (1.830 Pa s). In the sensory evaluation, odour and taste scores of samples were not different. Dairy Lo and inulin could be used without any adverse effect for the production of non-fat kefir.


Journal of Dairy Science | 2013

Effects of different fermentation parameters on quality characteristics of kefir.

Tugba Kok-Tas; Atif C. Seydim; Barbaros Özer; Zeynep B. Guzel-Seydim

The main objective of the study was to determine the effects of different fermentation parameters on kefir quality. Kefir samples were produced using kefir grains or natural kefir starter culture, and fermentation was carried out under normal or modified atmosphere (10% CO(2)) conditions. The microbiological (lactobacilli, lactococci, Lactobacillus acidophilus, Bifidobacterium spp., and yeasts), chemical (pH, lactic acid, total solids, protein, ethanol, exopolysaccharide contents), rheological, and sensory properties of kefir samples were investigated during a 21-d storage period. The use of different fermentation parameters or the choice of grain versus natural kefir starter culture did not significantly affect the content of microorganisms. Lactobacilli, lactococci, and yeast contents of kefir samples varied between 9.21 and 9.28, 9.23 and 9.29, and 4.71 and 5.53 log cfu/mL, respectively, on d 1 of storage. Contents of L. acidophilus and Bifidobacterium spp. were between 5.78 and 6.43 and between 3.19 and 6.14 log cfu/mL, respectively, during 21 d of storage. During the storage period, pH, lactic acid (%), total solids (%), protein (%), acetaldehyde, and ethanol contents of kefir samples ranged from 4.29 to 4.53, from 0.81 to 0.95%, from 7.81 to 8.21%, from 3.09 to 3.48%, from 3.8 to 23.6 mg/L, and from 76.5 to 5,147 mg/L, respectively. The exopolysaccharide contents of the samples decreased during 21 d of cold storage; the samples fermented under modified atmosphere had relatively higher exopolysaccharide contents, indicating higher potential therapeutic properties. The kefir samples exhibited non-Newtonian pseudoplastic flow behavior according to the power law model. According to the sensory results, kefir produced from natural kefir starter culture under CO(2) atmosphere had the highest overall evaluation score at d 1.


Journal of Dairy Science | 2011

Effect of different growth conditions on biomass increase in kefir grains

Zeynep B. Guzel-Seydim; Tugba Kok-Tas; B. Ertekin-Filiz; Atif C. Seydim

Kefir is a functional dairy product and the effects of kefir consumption on health have been well documented. Kefir grains have naturally high numbers of lactic acid bacteria and yeasts and are used in manufacturing kefir. The biomass of kefir grains slowly increases after successive fermentations. The effects of adding whey protein isolate, modified whey protein (MWP, fat replacer; Carbery Inc., Cork, Ireland), or inulin to milk and different atmospheric conditions (ambient or 6% CO(2)) during fermentation on the increase in biomass of kefir grains were investigated. Reconstituted milks (10% milk powder) enriched with whey protein isolate (2%), MWP (2%), and inulin (2%) were inoculated with kefir grains and fermented in ambient and 6% CO(2) incubators at 25°C until a final pH of 4.6 was reached. Biomass increments of kefir grains were determined weekly over 30 d. Lactic acid bacteria and yeast contents of kefir grains were also determined. The highest biomass increase (392%) was found in kefir grains grown in milk supplemented with whey protein isolate under ambient atmospheric conditions. Application of CO(2) did not provide a significant supporting effect on the biomass of kefir grains. Addition of MWP significantly accelerated the formation of kefir grain biomass (223%). The use of whey protein isolate, MWP, or inulin in milk did not cause any adverse effects on the microbial flora of kefir grains.


Journal of Analytical Chemistry | 2011

Optimization of the experimental conditions for macrolide antibiotics in high performance liquid chromatography by using response surface methodology and determination of tylosin in milk samples

Senem Şanlı; Ismail Murat Palabiyik; Nurullah Şanli; Zeynep B. Guzel-Seydim; Güleren Alsancak

The simple, rapid and sensitive liquid chromatographic separation of five macrolides (tilmicosin, erythromycin, tylosin, roxithromycin and josamycin) widely used in food producing animals was developed. Response surface methodology was used as an optimization method of mobile phase, column temperature and pH to provide the best resolution of these analytes. The separation was performed by using an end-capped X-Terra RP-18 column (250 × 4.6 mm I.D × 5 m) with an isocratic system of 15 mM hydrochloric acid (pH 2.5)-acetonitrile as the mobile phase at a temperature of 30°C and flow-rate of 1.0 mL/min. The suitability of the method for multi-residue determination of the macrolides is demonstrated by the analysis of milk samples spiked with tylosin. Roxithromycin was used as internal standard. The recovery of tylosin was quite good as 90.8%. The limit of quantification and detection limit were 0.024 and 0.007 μg/mL, respectively. The method was successfully applied to determination of macrolides at levels below the maximum concentration legally allowed in milk samples.


Food Science and Biotechnology | 2015

Effect of Gluconacetobacter spp. on kefir grains and kefir quality

Nilgün Özdemir; Tugba Kok-Tas; Zeynep B. Guzel-Seydim

Microbial, chemical, physical, and sensorial analyses of kefir samples produced using kefir grains embedded with Gluconacetobacter spp. were investigated using kefir samples with Gluconacetobacter spp. inclusion (KA), and regular kefir grains (control, KC) lacking Gluconacetobacter spp. The genus Gluconacetobacter, (identified using PCR) isolated from apple cider vinegar, was embedded in kefir grains. Inclusion of Gluconacetobacter spp. provided a significant biomass increase (p<0.01). The Lactobacillus spp., Lactococcus spp., yeast, Lactobacillus acidophilus, and Bifidobacterium spp. contents of KA were similar to KC. The acetic acid bacterial content of KA was 3.86 log CFU/mL. A significant (p<0.05) increase was observed in the exopolysaccharide content and viscosity of KA compared with KC. Inclusion of a different useful bacterium not naturally present in kefir grains is herein reported. Kefir grains can be an important carrier for microorganisms.


Journal of The American College of Nutrition | 2015

Bioactive Components of Mother Vinegar

Elif Aykın; Nilgün H. Budak; Zeynep B. Guzel-Seydim

Objective: Mother vinegar is extracellular cellulose and is a thick, hard layer formed by the acetic acid bacteria on the surface of vinegar. The aim of the study was to determine the bioactive components of mother vinegar produced from various vinegars. Methods: Mothers of vinegar were produced during vinegar productions using surface culture method from apple and pomegranate juices. Titration acidity, pH, total dry matter, ash, mineral substances, total carbohydrate, total phenolic substance, phenolic components, and total antioxidant activity were determined in samples. Results: It was found that mother of pomegranate vinegar had higher antioxidant capacity and total phenolic substance compared to samples of mother of apple vinegar. According to standards, gallic acid and chlorogenic acid were dominant phenolic compounds in mother of apple vinegar, whereas gallic acid was the major phenolic compounds in mother of pomegranate vinegar. The mother vinegars had high Fe contents. Conclusion: It was concluded that mother of vinegar produced by natural acetic acid bacteria contains significant bioactive substances.

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Atif C. Seydim

Süleyman Demirel University

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Tugba Kok-Tas

Süleyman Demirel University

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Nilgün H. Budak

Süleyman Demirel University

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Bilge Ertekin

Süleyman Demirel University

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Özge Duygu Okur

Süleyman Demirel University

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Ayşegül Kubilay

Süleyman Demirel University

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