Determination of the antimicrobial effect of edible coatings containing williopsis saturnus var saturnus against yeast and mold growth onthe surface of kashar cheese

Keywords:kashar cheese, edible film,Williopsis saturnus var.saturnus One of the most important problems of kashar producers in milk industry is the mold spoilage on the surface.Vacuum packing has partial solution to this problem because of rough structure of kashar surface.Williopsis saturnus var. saturnus yeast killer yeast has been reported to have an antagonistic effect on mold and yeast reproduction in many scientific studies.In this project, W. saturnus var. saturnus yeast culture was applied directly or with whey protein based edible coatings on cheese to prevent mold growht.The reason for the use of the yeast cultivar with edible coating is to produce edible coatings that exhibit antifungal effects by encapsulating yeast. In our study, 50 g of cheese samples were coated with edible films based on whey protein with or without W. saturnus var.saturnus or yeast without coating at a concentration of 6.9 log cfu/g. After drying, they were packed in vacuum and without vacuum packages and stored at 4°C for 56 days. The number of W. saturnus, lactic acid bacteria, mold and yeast counts were observed throughout the storage period. Chemical analysis, weight lost, water activity, color and pH of kashar cheese samples were also observed. The results showed that during the 56 days of the storage period; the count of Lactic Streptococcus and Lactobacillus spp. were supported or inhibited by coating application with yeast, respectively; however, the number W. saturnus var. saturnus yeast was increased by 1-2 log cfu /g. Application of W. saturnus var. saturnus slightly decreased the growth of other yeasts and molds on the cheese samples. The chemical properties and color of all cheese samples did not change with coating and yeast application (p>0.05). Treatment of coating containing W. saturnusantagonist yeast did not cause a significant change on pH and water activity value (p> 0.05). Increase in dry matter cntent of the the samples coated with W. saturnus is less than that in control samples. The sensory characteristics of cheeses coated with different coating solutions were statistically similar (p> 0.05). In a conclusion, application of whey protein coating containing W. saturnus var. saturnus on the cheese samples have a significant potential to inhibit mold and yeast growth during shelf life.