Browsing by Author "Saygili, D"

Now showing 1 - 9 of 9
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    Analysis of some physicochemical, rheological, sensorial properties, and probiotic viability of fermented milks containing Enterococcus faecium and Enterococcus durans strains
    Yerlikaya, O; Akpinar, A; Saygili, D
    The aim of this research was to observe the combined usability of Enterococcus faecium and Enterococcus durans strains, which are resistant to adverse environmental conditions, together with commercial probiotic starters in the production of probiotic fermented milk. Accordingly, eight different probiotic fermented milks were produced; AF:Lactobacillus acidophilus + Enterococcus faecium, BF:Bifidobacterium animalis subsp. lactis + Enterococcus faecium, CF:Lactobacillus casei + Enterococcus faecium, RF:Lactobacillus rhamnosus + Enterococcus faecium, AD:Lactobacillus acidophilus + Enterococcus durans, BD:Bifidobacterium animalis subsp. lactis + Enterococcus durans, CD:Lactobacillus casei + Enterococcus durans, RD:Lactobacillus rhamnosus + Enterococcus durans. As a result of the data obtained in the study, it was found that fermented dairy products containing Enterococcus faecium and Enterococcus durans had no negative effects on the physicochemical, rheological properties and probiotic viability, and positively affected the sensory properties of the samples. The viscosity and hardness values of probiotic fermented milk produced by combining with E. durans were higher than by combining with E. faecium and serum separation was not occurred. Also, probiotic bacteria viability was higher than 7 log cfu/ml level at the end of the storage period. Practical applications Enterococci are found naturally in the human intestinal microbiota and are highly resistant to adverse environmental conditions. Enterococcus strains that produce antimicrobial peptides such as enterocin were found to be able to effectively inhibit the development of many food pathogens when they are added to some foods including cheese. They are microbial additives that are thought to be used in many foods to improve food safety. The bacteriocin called enterocin could act as natural bio-preservatives in foods. This study will guide the use of Enterococcus species as bio-preservative in foods such as dairy products and the possibility of the continuation of probiotic viability.
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    The effect of using different yeast species on the composition of carbohydrates and volatile aroma compounds in kefir drinks
    Saygili, D; Yerlikaya, O; Akpinar, A
    Kefir is a fermented dairy product known for its high content of lactic acid bacteria and various types of yeast. The yeast microorganisms present in kefir cultures play a crucial role in shaping the distinctive characteristics of kefir. This study aimed to investigate the impact of different yeast species commonly used in industrial kefir production on the carbohydrate and volatile aroma components of kefir during the storage period. To this end, kefir cultures with various yeast species, including Debaryomyces hansenii (DH), Kluyveromyces marxianus (KM), Candida colliculosa (CC), Yarrowia lipolytica (YL), Saccharomyces bouardii (SB), Saccharomyces cerevisiae (SC), Kluyveromyces lactis (KL), and Geotricum candidum (GC), were prepared and utilized in kefir production. The study findings revealed significant effects of different yeast species on the composition of carbohydrate and volatile aroma components in kefir (p < 0.05), with Klyveromyces spp. having particularly notable effects. It was observed that kefir drinks containing ethanol exhibited negligible lactose content, while their ethanol content was high. Kefir drinks containing minimal Klyveromyces marxianus contained glucose and galactose, whereas those containing Yarrowia lipolitica exhibited the lowest ethanol content.
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    Production of set-type yoghurt using Enterococcus faecium and Enterococcus durans strains with probiotic potential as starter adjuncts
    Akpinar, A; Saygili, D; Yerlikaya, O
    The study investigated the potential use of Enterococcus faecium and E.durans strains as adjunct cultures in the production of set-type probiotic yoghurt. There were significant changes and differences in the pH, titratable acidity, textural properties and microbiological properties of the products containing adjunct culture during the storage period (P < 0.05), whereas there were no statistically significant differences between the sensory properties (P > 0.05). In conclusion, the use of Enterococcus species that have known probiotic properties as the adjunct culture in yoghurt production can also positively affect the physical, chemical and rheological properties in addition to its positive effects to the functional properties by increasing the viable probiotic bacterial counts.
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    Incorporation of Propionibacterium shermanii subsp. freudenreichii in probiotic dairy drink production: physicochemical, rheological, microbiological and sensorial properties
    Yerlikaya, O; Akpinar, A; Saygili, D; Karagozlu, N
    The aim of this study was to investigate the use of Propionibacterium shermanii subsp. freudenreichii as a combined culture with Lactobacillus acidophilus (AP), Bifidobacterium animalis subsp. lactis (BP), Lactobacillus casei (CP) and Lactobacillus rhamnosus (RP) in probiotic dairy drink production. Although Propionibacterium spp. is used for many purposes including biopreservative and adjunct culture, in this study, probiotic dairy drinks containing P. freudenreichii were evaluated in terms of their physicochemical, rheological, microbiological and sensory properties. The results of the study showed that P. freudenreichii can also be suitable for the production of probiotic drinks and that there are no adverse effects on the product characteristics.
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    Evaluation of antimicrobial activity and antibiotic susceptibility profiles of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus strains isolated from commercial starter cultures
    Yerlikaya, O; Saygili, D; Akpinar, A
    This research investigated the antimicrobial activity and antibiotic susceptibilities of nine Lactobacillus delbrueckii subsp. bulgaricus strains and nine Streptococcus thermophilus strains isolated from commercial yoghurt cultures. The antimicrobial activities of overnight culture strains against Bacillus cereus CECT 131, Bacillus subtilis ATCC 6633, Campylobacter jejuni NCTC 11351, Candida albicans ATCC 14053, Enterobacter aerogenes ATCC 13048, Escherichia coli ATCC 25922, Listeria monocytogenes ATCC 7644, Pseudomonas aeruginosa ATCC 9027, Salmonella typhimurium ATCC 14028 and Staphylococcus aureus ATCC 12600 were investigated using the disc diffusion method. The antibiotic resistance/susceptibility profiles of the strains were determined using antibiotic discs, which included ampicillin (10?g), ampicillin (25?g), bacitracin (10?g), clindamycin (2?g), clindamycin (10?g), erythromycin (10?g), erythromycin (15?g), gentamicin (10?g), gentamicin (120?g), nalidixic acid (30?), neomycin (10?g), novobiocin (5?g), oxacillin (1?g), penicillin (10units), streptomycin (25?g), streptomycin (300?g), tetracycline (30?g) and vancomycin (30?g). The results of the study showed that while the Streptococcus thermophilus strain SY8, Lactobacillus bulgaricus strains LY6, LY8, LY9 and LY10 showed antimicrobial activity for all test microorganisms, Streptococcus thermophilus SY5 strains showed the weakest antimicrobial effect. All the Lactobacillus bulgaricus and Streptococcus thermophilus strains were resistant to oxacillin (1?g) and nalidixic acid (30?g). Indeed, the highest antibiotic susceptibility was seen with antibiotics such as ampicillin (25?g), clindamycin (10?g) and erythromycin (15?g).
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    An application of selected enterococci using Bifidobacterium animalis subsp. lactis BB-12 in set-style probiotic yoghurt-like products
    Yerlikaya, O; Saygili, D; Akpinar, A
    The present study aimed to develop a novel dairy product by combining Bifidobacterium lactis subsp. lactis BB12 (R) with proven probiotic properties with Enterococcus faecium K67E3 and Enterococcus durans K63E1, which possess potential probiotic properties. Physicochemical, textural and viscosity properties, microbiological, and sensorial attributes of set-style probiotic yoghurt-like products were analysed during the storage at 4 degrees C for 21 days. The starter culture type had an effect (p < 0.05) on physicochemical, textural and viscosity properties of probiotic yoghurt-like products. High probiotic viability was determined in all samples except for the LD sample containing a combination of Bifidobacterium animalis subsp. lactis BB-12 (R) and Enterococcus durans K63E1. The use of starter culture combination containing Streptococcus thermophilus, Bifidobacterium animalis subsp. lactis BB-12 (R) and Enterococcus durans K63E1 (TLD) in the probiotic yoghurt-like product yielded better textural parameters, apparent viscosity, and improved sensory attributes. Although Enterococcus genera are not thought to be completely safe for use in human food so far, as a result of the research findings, it would be of interest for the dairy industry in the development of novel probiotic dairy products.
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    Microbiological aspects and challenges of whey powders - I thermoduric, thermophilic and spore-forming bacteria
    Hebishy, E; Yerlikaya, O; Mahony, J; Akpinar, A; Saygili, D
    For dairy processors, spoilage and pathogenic spore-forming bacteria are key sources of concern, not only due to their ability to remain dormant in a desiccated state in powders and to survive heat treatments, but also their ability to form biofilms in the vegetative state that lead to contamination of foods. These include members of the genera Bacillus, Geobacillus, Anoxybacillus, Brevibacillus, Paenibacillus and Clostridium, many of which are associated with food poisoning and spoilage. Here, we review the common bacterial species that form spores in whey powders and their sources and provide insights into their risks and strategies to control them.
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    Utilization of pomegranate and black grape seed by-products in yogurt production: Effects on phenolic compounds and antioxidant activity
    Çaliskanlar, S; Saygili, D; Karagzölü, N; Karagözlü, C
    The present study investigated the potential utilization of pomegranate and black grape seed by-products of the food industry in yogurt production. Specifically, we examined the effect of polyphenols on antioxidants in yogurts produced using two different starter cultures: classical yogurt culture (Lactobacillus delbrueckii subsp. bulgaricus + Streptococcus thermophilus) and yogurt culture supplemented with L. casei. Various parameters, including pH, acidity, viscosity, fat content, protein content, dry matter content, color, microbiological properties, and sensory attributes, were analyzed in the yogurt products. The present findings indicate that incorporating pomegranate and grape seed powder and using different starter cultures significantly affected the yogurt's phenolic content and antioxidant activity. Furthermore, we observed decreased phenolic content and antioxidant activity during the 21-day storage period. Interestingly, yogurts produced with pomegranate seed powder and L. casei culture exhibited higher antioxidant activity than the other samples. Importantly, none of the yogurts containing pomegranate and grape seed powders had microbial counts below 107 cfu/g for L. delbrueckii subsp. bulgaricus, S. thermophilus, and L. casei, indicating no adverse effects on probiotic properties. Sensory evaluation revealed that the yogurt product prepared with grape seed powder and a combination of yogurt culture (L. delbrueckii subsp. bulgaricus + Streptococcus thermophilus) and L. casei was particularly well-received. In conclusion, the functional properties of grape seed powder and pomegranate seed powder make them suitable natural ingredients for enhancing the antioxidant activity of yogurt. The study highlights the potential of utilizing these by-products to develop yogurt products with added health benefits. The search for consuming healthy products is increasing day by day and it is inevitable for consumers to turn to functional products with health-supporting features. The enrichment of yogurt, which is a traditional product, with pomegranate and black grape seeds with high antioxidant capacity improves both the sensory properties of the final product and increases the health-supporting quality of the final product.image
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    Microbiological aspects and challenges of dairy powders - II: Biofilm/biofouling
    Hebishy, E; Yerlikaya, O; Reen, FJ; Mahony, J; Akpinar, A; Saygili, D; Datta, N
    Biofilms generated during production of dairy/whey powders can cause contamination, spoilage and equipment failures, posing a significant challenge in the agri-food sector. Factors including temperature, protein composition, equipment structures and surface topography influence biofilm formation and resistance to cleaning and sanitation. Several species of bacteria are well adapted to these challenges, posing the most pressing concerns of dairy whey process. Despite efforts to improve cleaning-in-place strategies, bacteria persist in difficult-to-clean areas. This review provides insights into bacterial biofouling in dairy protein powders, highlighting the mechanism of biofilm formation, predominant bacterial genera, critical processing steps and strategies to manage biofilm formation during the manufacturing process. This review article aims to enhance understanding of bacterial biofouling in dairy protein powders, particularly whey powders, by examining the formation mechanism, critical processing steps, factors affecting biofilm formation and control strategies in dairy powder manufacturing. While previous reviews on general food processing and dairy biofilms have been published, this is the first specific review on whey powders. image