No abstract

This study aimed to investigate the growth and enterotoxin production of Staphylococcus aureus during the ripening and storage of Iranian ultra-filtered white cheese (IUFWC). According to the results, the addition of starter culture had significant inhibitory effects on the growth and enterotoxin production of S. aureus. Moreover, prolong survival and enterotoxin production were observed in the samples with the highest inoculum (5 log CFU/g) of S. aureus. It was concluded that proper activity of the starter culture together with the refrigeration storage of IUFWC was the key element in inhibiting the growth and enterotoxin production of S. aureus.

While brewing probiotic beer using Saccharomyces cerevisiae var. boulardii, we noticed the yeast potentially makes biofilm in glass bottles as the bottles get hazy. In this study, S. cerevisiae var. boulardii CNCM I-745 was used as a starter culture to produce probiotic beer. We studied the biofilm parameters combined with FLO11 mRNA expression and used light and scanning electron microscopy to document biofilm formation and structure. Our results revealed that ageing the beer and maturing from a sugar-rich to a sugar-limited beer, along with the stress factors from the brewing process (pH reduction and produced metabolites), led to an increase in biofilm mass; however, the viable count remained relatively stable (approximately 7.1 log10 cells/mL). Biofilm S. boulardii cells showed significantly higher FLO11 mRNA expression in the exponential and stationary phase compared to the planktonic cells. This study, therefore, provides evidence that S. cerevisiae var. boulardii makes biofilm on glass surfaces during beer bottle ageing. The impact of complications caused by formed biofilms on returnable bottles emphasizes the significance of this study.

Background: Escherichia coli O157:H7 is one of the most common causes of contamination in Lighvan cheese processing. Using from natural antimicrobial essential oils is applied method to decrease the rate of microbial contamination of dairy products. The present investigation was done to study the antimicrobial effects of Z. multiflora and O. basilicum essential oils on survival of E. coli O157:H7 during ripening of traditional Lighvan cheese. Methods: Leaves of the Z. multiflora and O. basilicum plants were subjected to the Clevenger apparatus. Concentrations of 0, 100 and 200 ppm of the Z. multiflora and 0, 50 and 100 ppm of O. basilicum essential oils and also 103 and 105 cfu/ml numbers of E. coli O157:H7 were used. The numbers of the E. coli O157:H7 bacteria were analyzed during the days 0, 30, 60 and 90 of the ripening period. Results: Z. multiflora and O. basilicum essential oils had considerable antimicrobial effects against E. coli O157:H7. Using the essential oils caused decrease in the numbers of E. coli O157:H7 bacteria in 90th days of ripening (P <0.05). Using from Z. multiflora at concentration of 200 ppm can reduce the survival of E. coli O157:H7 in Lighvan cheese. Conclusion: Using Z. multiflora and O. basilicum essential oils as good antimicrobial agents can reduce the risk of foodborne bacteria and especially E. coli O157:H7 in food products.