Abstract In this research, we aimed to evaluate the effects of various medicinal and aromatic plant aqueous extracts on physicochemical, rheological, sensorial properties of probiotic yogurts and the viability of yogurt bacteria and probiotic bacteria during the storage period. On the 28 day of storage, the maximum Bifidobacterium longum and Lacticaseibacillus casei counts were determined in thyme containing yogurt and mint and basil containing yogurt, respectively. On the 1st day of storage, the most favoured yogurt was garlic containing sample while on the 14th day, the control sample was the most favoured one. Hardness values were not showed statistically difference for all sample (p>0.05). Especially the garlic and mint yogurt samples were more liked in terms of sensory properties. Consequently, aqueous extracts of some plants such as garlic, basil and thyme have successfully used in probiotic yogurt production and all yogurt samples containing plants have the enough probiotic counts to show therapeutic effect on human health.

Abstract This research aimed to examine the probiotic viability of bacteria, rheological and sensorial properties in synbiotic ice creams produced from goat’s milk combined with probiotic culture and prebiotics. Tagatose, Litesse ultra and polydextrose (as prebiotics) were used in ice cream production and mixtures and these mixtures were inoculated with Bifidobacterium bifidum, Lactobacillus paracasei and Bifidobacterium longum combined culture. Frozen raspberry fruits, commercial raspberry and blackberry fruit purees were used as taste flavor enhancers in synbiotic ice cream. Four different ice cream types were produced including control sample. Probiotic bacteria viability, apparent viscosity, hardness and sensory properties were examined during the 120-day- storage. It was determined that frozen fruit and fruit purees addition and using prebiotics significantly affected the Lactobacillus paracasei and Bifidobacterium spp. viability and color, appearance, flavor, taste and overall sensory scores of the synbiotic goat’s milk ice creams (P < 0.05). Synbiotic ice cream samples maintained their probiotic properties during storage and were generally well appreciated in terms of sensory properties.

Abstract 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 (10µg), ampicillin (25µg), bacitracin (10µg), clindamycin (2µg), clindamycin (10µg), erythromycin (10µg), erythromycin (15µg), gentamicin (10µg), gentamicin (120µg), nalidixic acid (30µ), neomycin (10µg), novobiocin (5µg), oxacillin (1µg), penicillin (10units), streptomycin (25µg), streptomycin (300µg), tetracycline (30µg) and vancomycin (30µg). 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 (1μg) and nalidixic acid (30μg). Indeed, the highest antibiotic susceptibility was seen with antibiotics such as ampicillin (25μg), clindamycin (10μg) and erythromycin (15μg).

In this research, the probiotic Streptococcus thermophilus was inoculated into milk as co-culture to produce probiotic cheese. The effects of using Streptococcus thermophilus with other probiotic bacteria on cheese composition, and microbiological viability during 28 days of storage were investigated. Sensorial properties were determined only at 1st and 28th days of storage. The results showed that the use of Streptococcus thermophilus as co-culture in probiotic cheese production did not affect negatively the cheese components. Fat and dry matter properties of cheese weren't influenced by added probiotic bacteria. However, different level of pH, salt and lactic acid were detected. All probiotic bacteria were present in high levels throughout storage of cheeses, above 7 Log cfu.g- 1, threshold required for probiotic activity. Sensory panel showed that the highest average sensory evaluation points were recorded in cheeses made with Streptococcus thermophilus plus Lactobacillus casei, whereas other probiotic bacteria combinations had been affected less in regard to taste or appearance.

Dairy products that contain probiotic bacteria are those that are produced with various fermentation methods, especially lactic acid fermentation, by using starter cultures and those that have various textures and aromas. Fermented dairy products are popular due to their differences in taste and their favourable physiological effects. Today, fermented dairy beverages in general are produced locally by using traditional methods. Recently, due to the increased demand for natural nutrients and probiotic products, fermented dairy beverages have reached a different position and are considered to have an important impact on human health and nutrition. In this article, probiotic bacteria and functional dairy products that are produced by using probiotic bacteria are discussed.