The purpose of this research is to determine the incidence and occurrence of aflatoxin M1 (AFM1) in 104 samples of milk, white cheese, kashar and butter in Sakarya, Turkey. Followed by immunoaffinity column (IAC) purification, high performance liquid chromatography (HPLC)-fluorescence detection method was implemented to analyze the samples. Results show that 61.5% of milk, 40% of white cheese, 65.4% of kashar and 29.6% of butter contains AFM1. In 53 of samples (50.96%) are not determined AFM1. The amount of AFM1 in 51 samples (49.04%) ranges from 2.4 to 47.8 ng/L/kg. AFM1 levels do not exceed the limit set by Turkish regulations (50 ng/L/kg). However, the incidence of AFM1 contamination is a potential health risk for customers, particularly for children and infants. These results emphasize the significance of constant monitoring of AFM1 levels in milk and dairy products (MDPs) in Sakarya, Turkey.

A total of 74 lactic acid bacteria (LAB) isolates were obtained from yoghurt, cheese, raw milk, boza and whey. 36 strains were identified at species levels as Lactococcus lactis (15), Lc. garvieae (8) Lactobacillus plantarum (7), Enterococcus faecium (3), Leuconostoc citreum (2) and Lb.casei (1) by MALDI-TOF MS analysis. The strains were tested for antimicrobial properties using disc diffusion method against Listeria monocytogenes, Staphylococcus aureus, Escherichia coli O157:H7, Cronobacter sakazakii, Bacillus cereus and Salmonella Typhimurium. 18 strains from available samples showed antimicrobial activity. Formation zones were appeared from 7 mm to 19 mm against all bacteria, except B. cereus. Additionally, antibiotic susceptibility of these 18 strains were investigated and strains related to 18 LAB were found resistant despite of 72.2% rifampicin, 53.3% tetracycline and vancomycin, 27.7% to erythromycin and nitrofurantoin. In this study, we investigated antifungal effects of the strains. LAB were screened for antifungal effects by using dual agar overlay against mycotoxigenic Aspergillus candidus, Cladosporium cladosporioides, Cladosporium sphaerospermum, Mucor hiemalis, Ulocladium chartarum, Aspergillus niger and Penicillium expansum. 18 LAB isolates showed antifungal effects. As a result, Enterococcus faecium has antimicrobial and antifungal properties, and therefore, it can be used under various experimental conditions in future studies.

This study aimed to explore new probiotic yeast strains, considering that Saccharomyces cerevisiae is the only yeast used industrially. To this end, yeasts were isolated from various dairy products and their probiotic potential was investigated. All yeast strains demonstrated survival potential under simulated gastrointestinal conditions, mimicking the stomach and intestinal passage. Among the isolates, 13.04% were identified as moderate biofilm producers, 34.78% as weak biofilm producers, and 52.17% exhibited no biofilm-forming ability. Catalase enzyme production was detected in all isolates, and it was determined that their hydrophobicity varied depending on hydrocarbon interactions. In this study, the percentage of autoaggregation increased with prolonged incubation times across all strains. After 24 h, the percentage of autoaggregation exceeded 60% for all isolates. It was concluded that the coaggregation ability depended on incubation time and strain type. Most of the isolated yeasts exhibited antimicrobial activity against E. coli ATCC 25922, E. coli O157:H7, B. cereus, C. sakazakii ATCC 29544, L. monocytogenes ATCC 7644, S. aureus ATCC 25923, and S. typhimurium ATCC 140828. Furthermore, the yeast strains were resistant to all tested antibiotics. The 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity revealed that the antioxidant activity of the cells was higher than that of their intracellular extracts for all tested strains. The yeasts were initially identified using MALDI-TOF and further characterized through 18S-28S rRNA analysis. There are not many recent studies on the selection of probiotic yeasts for use in the dairy industry. Therefore, in this study we wanted to investigate some functional properties of different yeasts to be proposed as probiotic cultures in this specific sector. In particular, the antimicrobial and antioxidant properties and enzymatic activity highlighted by isolates have promising implications for food safety and health. These preliminary results provide a valuable basis for the future industrial application of probiotic yeasts in the dairy sector.

This study investigated whether the use of fermented milk with added dietary fibre in ice cream production positively affected quality characteristics, especially viability, during a shelf life of 90 days at −25 °C. For this purpose, fermented milk was prepared with cultures (yoghurt and Lacticaseibacillus rhamnosus) and dietary fibre (wheat fibre and inulin). In addition to the viable cell count, some related quality characteristics, such as the sensory, physical, chemical, and thermal properties, and energy content were also examined. Streptococcus salivarius subsp. thermophilus in all yoghurt ice creams and L. rhamnosus in ice cream with wheat fibre had the highest viability for 90 days, up to 95.95%. The best scores regarding “general acceptability” belonged to the ice cream with L. rhamnosus and inulin, with a score of 7.81 out of 9. The dietary fibre decreased overrun from around 23% to 14–18%, which was positive for the viability of the cultures. The cultures and dietary fibre decreased the melting temperature down to −1.15 °C. The caloric value of the ice creams (166–168 kcal/100 g) was lower than that of standard ice cream. Probiotic ice cream production with dietary fibre and a single L. rhamnosus culture may be preferred in terms of sensory properties, cell viability, and economic aspects.

This study aimed to evaluate the probiotic properties of Enterococcus strains isolated from Turkish traditional cheeses. Fifty-two Enterococcus spp. were taxonomically determined as follows: Enterococcus faecium (26), Enterococcus faecalis (18), Enterococcus durans (6), and Enterococcus italicus (2). The ability of isolates/strains to survive the harsh conditions (acidity and in-vitro gastric solution) of the gastrointestinal tract was established. They also showed auto-aggregation, hydrophobicity, and co-aggregation ability. Hydrophobicities of the strains were found between 0.8%–21%, 0.7%–56%, and 2%–63% for xylene, chloroform, and ethyl acetate, respectively. Autoaggregation values of the Enterococcus strains were 4%–20%, 7%–30%, and 36%–98% after 2, 4, and 24-h incubation, respectively. In this study, the Enterococcus strains tested showed co-aggregation ability with the Escherichia coli ATCC 25922, Salmonella Typhimurium ATCC 14028, and Staphylococcus aureus ATCC 25923. The results of PCR amplification revealed that only five strains possess virulence factor genes (gelE,asa1,cyl A,esp). We determined antibiotic resistance, biofilm forming abilities, and hemolytic activity for safety evaluation of strains. In this large and comprehensive study, we found that only few of Enterococcus strains have promising probiotic potential, among which E. faecalis ES1 and E. faecium EM1 showed the best probiotic properties (are the most promising probiotic candidates).