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    Characterisation of probiotic properties of yeast strains isolated from kefir samples
    (WILEY, 2021) Göktaş, Hamza; Dikmen, Hilal; Demirbas, Fatmanur; Sagdic, Osman; Dertli, Enes
    This study aimed to isolate and identify yeast species from kefir samples and to determine their probiotic characteristics in comparison with commercial probiotic yeast Saccharomyces boulardii. The microbial flora of traditional kefir samples were dominated by Saccharomyces cerevisiae and Kluyveromyces marxianus. Kefir isolates demonstrated higher auto-aggregation, hydrophobicity and antioxidant properties compared to S. boulardii although S. boulardii demonstrated the highest survival rate under in vitro gastrointestinal digestion conditions followed by two kefir yeasts K. marxianus and Kazachstania unispora. Importantly, kefir isolates revealed strong antifungal activities against mould species except Penicillium roqueforti. These findings suggest probiotic and functional roles of yeast strains isolated from traditional kefir samples.
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    Characteristics of functional ice cream produced with probiotic Saccharomyces boulardii in combination with Lactobacillus rhamnosus GG
    (Elsevier, 2022) Göktaş, Hamza; Dikmen, Hilal; Bekiroğlu, Hatice; Çebi, Nur; Dertli, Enes
    Ice creams have big potential to be used as probiotic food carrier. In this respect, this study aimed to produce ice creams with addition of Saccharomyces boulardii and Lactobacillus rhamnosus GG. Probiotic strains were added to the ice cream mixes before and after aging steps of ice cream production and were inoculated as single or mix cultures. Probiotic ice cream products were then characterized and the survival of the probiotic strains were determined during storage period. Both probiotic strains successfully survived during storage period and their numbers were above 6.18 log CFU/g at final date of storage. The rheological parameters of ice cream products improved with the co-inoculation of S. boulardii and L. rhamnosus both before and after aging step. Importantly the aroma profile of ice cream samples altered with probiotic inoculation and ethanol was the major volatile compound in ice cream samples produced with S. boulardii added before aging step. Inoculation of S. boulardii and L. rhamnosus as single cultures also resulted in formation of distinct aroma compounds in ice cream products. The highest overall acceptability score in sensorial evaluation of ice cream products was obtained from the ice cream products produced with inoculation of probiotics after aging step.
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    The stabilisation of low-fat mayonnaise by whey protein isolate-microbial exopolysaccharides (weissella confusa W-16 strain) complex
    (Wiley, 2023) Yalmancı, Dilara; Dertli, Enes; Tekin Çakmak, Zeynep Hazal; Karasu, Salih
    This study aims to evaluate the fat-substituting feature of the complex of whey protein isolate (WPI) and dextran structure exopolysaccharide (EPS) synthesised by Weissella confusa JCM 1093 strains in mayonnaise samples. The flow behaviour, frequency sweep and three interval thixotropy test properties of the samples were compared with the control groups. Thermal loop test was applied to determine the emulsion stability of the samples. Oxidative stability was tested with OXITEST, and induction period values were compared. K values of the samples varied between 20.05 and 169.13 Pa.s(n) and the n values vary between 0.133 and 0.383. Samples showed pseudoplastic behaviour (n < 1). G' of all samples is greater than G, meaning that all samples showed a solid-like behaviour like conventional mayonnaise. The complex of 2% EPS and 5% WPI provided a solid structure and improved the physical stability of low-fat mayonnaise. The results showed that the samples had high physical stability when they experienced thermal stress at low and high temperatures. As a result, the WPI and EPS complex can be used as a fat replacer for improving the rheological properties, emulsion and oxidative stability in low-fat mayonnaise samples.
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    Utilization of exopolysaccharide produced by Leuconostoc lactis GW-6 as an emulsifier for low-fat mayonnaise production
    (Elsevier B.V., 2023) Yalmancı, Dilara; Dertli, Enes; Tekin Çakmak, Zeynep Hazal; Karasu, Salih
    This study aimed to investigate the potential usage of exopolysaccharide (EPS) produced by Leuconostoc lactis GW-6 species as an emulsifier in a low-fat mayonnaise by the formation of a complex with whey protein isolate (WPI) to improve rheological properties, emulsion, and oxidative stability. For the determination of rheological properties, the flow behavior, frequency sweep, and 3-ITT rheological properties of low-fat mayonnaise samples were studied. All samples showed shear thinning, viscoelastic solid-like, and recoverable character. The K and n values for the mayonnaise samples were determined as 24.529-174.403 Pa.sn and 0.166-0.304, respectively, indicating that shear-thinning characters could be improved with WPI-EPS interaction. The higher K' and K? values of all low-fat samples prepared with EPS-WPI than the low-fat control sample explained the synergistic effect of EPS and WPI. Importantly, no effect was observed when WPI was used as alone as an emulsifier. Oxidative stability was tested by OXITEST and IP values of samples prepared by WPI and EPS were compared to control samples. In conclusion, the results of this study showed that the EPS and WPI interaction can significantly affect the rheological properties and emulsion and oxidative stability of mayonnaise samples.