Gülfem Ünal

Microstructural, textural, and sensory characteristics of probiotic yogurts fortified with sodium calcium caseinate or whey protein concentrate

The influence of milk protein-based ingredients on the textural characteristics, sensory properties, and microstructure of probiotic yogurt during a refrigerated storage period of 28 d was studied. Milk was fortified with 2% (wt/vol) skim milk powder as control, 2% (wt/vol) sodium calcium caseinate (SCaCN), 2% (wt/vol) whey protein concentrate (WPC) or a blend of 1% (wt/vol) SCaCN and 1% (wt/vol) WPC. A commercial yogurt starter culture and Bifidobacterium lactis Bb12 as probiotic bacteria were used for the production. The fortification with SCaCN improved the firmness and adhesiveness. Higher values of viscosity were also obtained in probiotic yogurts with SCaCN during storage. However, WPC enhanced water-holding capacity more than the caseinate. Addition of SCaCN resulted in a coarse, smooth, and more compact protein network; however, WPC gave finer and bunched structures in the scanning electron microscopy micrographs. The use of SCaCN decreased texture scores in probiotic yogurt; probably due to the lower water-holding capacity and higher syneresis values in the caseinate-added yogurt sample. Therefore, the textural characteristics of probiotic yogurts improved depending on the ingredient variety.

In vitro determination of calcium bioavailability of milk, dairy products and infant formulas.

In this study, the aim was to determine the in vitro calcium bioavailability of different dairy products and to investigate the effect of dry matter, fat, acidity and calcium content on calcium bioavailability of the products. For this purpose, the dry matter, fat, acidity and calcium content of different kinds of milk, yogurt, cheese and infant formulas were analysed. Then, calcium bioavailability of products was determined by an in vitro method that involves simulating gastrointestinal digestion of the product with pepsin–HCl and pancreatin–biliary salts, and then measuring the fraction of element that dialyses through a membrane of a certain pore size. Each of the product groups was examined statistically and no difference was found among milk, yogurt and infant formula groups in terms of calcium bioavailability. However, there were differences among cheese kinds according to the results of the Duncan test; all cheese kinds were considerably different from each other (P < 0.05). Moreover, it was found that calcium, dry matter, fat content and acidity did not affect the calcium bioavailability (P < 0.05). According to the results of statistical analysis that was applied to all product groups, it was found that the yogurt group was different from the other products and that the acidity affected calcium bioavailability (P < 0.05).

Influence of fortification with sodium–calcium caseinate and whey protein concentrate on microbiological, textural and sensory properties of set-type yoghurt

The effect of fortification of yoghurt with sodium–calcium caseinate (SCC) and whey protein concentrate (WPC) on some properties of set-type yoghurt were investigated. The addition of WPC enhanced the viability of Lactobacillus delbrueckii subsp. bulgaricus more than SCC. The highest firmness values were obtained from SCC-fortified yoghurts, whereas yoghurts fortified with WPC had the highest water-holding capacity during storage. The yoghurts fortified with 4% w/w SCC or 4% w/w WPC had the highest viscosity. Yoghurts fortified with 2% w/w SMP, SCC or WPC showed similar taste and overall acceptability scores; however, samples containing 4% w/w SCC or 4% w/w WPC had the lowest scores.

Enrichment of probiotic ice cream with different dietary fibers: Structural characteristics and culture viability

This study evaluated the effect of 5 dietary fibers (apple, orange, oat, bamboo, and wheat) on the physicochemical, rheological, and textural characteristics; sensory properties; and culture viability of probiotic ice cream stored at -18°C for 180 d. The presence of orange and apple fibers increased the titratable acidity, decreased the lightness (color) value of the ice creams, and enhanced the red and yellow coloration. Compared with the control sample, the consistency indices and apparent viscosities of the experimental samples increased with the addition of all dietary fibers except oat fiber. The highest viscosity was obtained in the sample fortified with apple fiber, whereas the ice cream containing orange fiber showed the highest hardness after d 60 of storage. The addition of orange and apple fibers significantly increased melting resistance; however, panelists did not generally like these samples in terms of taste-flavor. All ice creams had viable counts of Lactobacillus acidophilus of ≥7 log cfu/g during storage except the samples with orange and bamboo fiber. Bifidobacterium lactis counts were also found to be >6 log cfu/g in those samples until d 150 of storage.

Effect of Supplementation with Green and Black Tea on Microbiological Characteristics, Antimicrobial and Antioxidant Activities of Drinking Yoghurt

The influence of supplementation with green and black tea on microbiological properties, antimicrobial and antioxidant activities of drinking yoghurt were investigated during 21 days of storage. The samples supplemented with 2% either green or black tea had higher viable counts of both yoghurt starter bacteria than those of infused by the ratio of 4%. Both green and black tea extracts showed antimicrobial activity on E. coli, B. cereus, S. aureus and C. albicans however this effect was detected higher in samples containing green tea. The samples added green tea extract had the highest DPPH scavenging activity when compared to those supplemented with black tea extract throughout the storage. Green tea had a superior effect than black tea in terms of total phenolic content of drinking yoghurt samples.

EFFECTS OF DIFFERENT PREBIOTICS ON VIABILITY UNDER IN VITRO GASTROINTESTINAL CONDITIONS AND SENSORY PROPERTIES OF FERMENTED MILK

The effect of inulin, polydextrose and Hi-maize resistant starch on probiotic viability under simulated gastrointestinal conditions and sensory characteristics of ABT (Lactobacillus acidophilus La-5 and Bifidobacterium animalis subsp. lactis Bb-12, and Streptococcus thermophilus) fermented milk was investigated during 28 days. B. animalis presented higher survival rates under gastrointestinal stress than L. acidophilus. Although inulin addition enhanced viable counts of L. acidophilus more than those of other prebiotics during the gastric and enteric-1 phases, all samples showed similar L. acidophilus survival after the enteric-2 phase. The supplementation with Hi-maize indicated a protective effect on B. animalis tolerance to simulated gastrointestinal conditions on the 14th and 28th days. Inulin or Hi-maize did not affect the sensory properties of fermented milk whereas the product supplemented with polydextrose had the lowest scores specifically at the end of the storage period.

Yeşil ve Siyah Çay İlavesinin İçilebilir Yoğurdun Viskozitesi ve Duyusal Özellikleri Üzerine Etkisi

Siyah ve yesil cayin icilebilir yogurdun viskozitesi ve duyusal ozellikleri uzerine etkisi arastirilmistir. Calismada iki cay infuzyon konsantrasyonu (%2 ve %4) kullanilirken herhangi bir ilave yapilmayan icilebilir yogurt kontrol ornegi olarak yer almistir. En yuksek viskozite degerleri kontrol orneginde tespit edilirken cay ekstrakti ilave edilen icilebilir yogurtlar arasinda 14.gun disinda onemli bir fark bulunamamistir. %4 oraninda cay ilave edilmesi %2 orani ile kiyaslandiginda tat puanlarini olumsuz yonde etkilemistir. %2 yesil cay ile muamele edilen icilebilir yogurt kontrol ornegine benzer renk ve tekstur degerleri gostermistir. %2 siyah veya yasil cay ilave edilen orneklerde toplam kabul edilebilirlik acisindan istatistiksel olarak herhangi bir fark belirlenememistir.