Determination of Antifungal Effect of Edible Coatings Containing Williopsis saturnus var. saturnus Against Yeast and Mold Growth on Kashar Cheese.

One of the most important problems of Kashar cheese producers is mold and yeast spoilage during storage. Williopsis saturnus var. saturnus killer yeast has been reported to have an antagonistic effect on mold and yeast reproduction. In this study, the antifungal effect of a whey protein concentrate (WPC) coating containing W. saturnus was investigated in Kashar cheese. WPC with or without W. saturnus (7 log CFU/g) or W. saturnus without coating was applied on the surface of Kashar cheese samples and stored at 4 °C for 56 days. Microbiological, chemical, physical and sensory properties of cheese samples were assessed. After 56 days of storage, the numbers of lactic acid bacteria were not affected by WPC containing W. saturnus; however, the population of W. saturnus increased by 1 log CFU/g. Application of W. saturnus reduced the growth of other yeasts and molds (P < 0.05). Chemical, physical and sensory properties of all coated cheeses remained unchanged. In a conclusion, use of WPC coatings containing W. saturnus can potentially minimize mold and yeast spoilage of cheese during storage.

Enhancement of bifidobacteria survival by Williopsis saturnus var. saturnus in milk.

The viability of three strains of probiotic Bifidobacterium lactis that were inoculated into UHT milk was examined with and without the presence of the yeast, Williopsis saturnus var. saturnus NCYC 22, in polypropylene tubes at 30 °C. The B. lactis viable cell count for strains HN019 and BB-12 remained above 6.0 Log cfu/ml, while strain B94 had 5.7 Log cfu/ml after six weeks of incubation in the presence of the co-inoculated yeast. Incubating the bifidus milk without added yeast under anaerobic condition did not improve the survival of B. lactis HN019, indicating that oxygen removal may not be responsible for W. saturnus NCYC 22's viability enhancing property. The addition of yeast supernatant or non-viable yeast also did not show any stabilising effects, suggesting that physical contact and/or interaction between viable W. saturnus and B. lactis plays an important role in sustaining the viability of the probiotic. W. saturnus NCYC 22 could increase the survival of B. lactis in bifidus milk under ambient temperature regardless of the initial concentration of yeast cells inoculated due to yeast growth. This study demonstrated the viability enhancing effect of viable W. saturnus NCYC 22 on B. lactis HN019, which could help towards extending the shelf-life of dairy beverages containing probiotic bifidobacteria.