Food Microbiology

During harvest, drying, and storage process of peanut (Arachis hypogaea L.), if its water activity exceeds the critique level fungus will grow and produce secondary metabolite called aflatoxin. Aflatoxin produced by Aspergillus flavus is mycotoxin which is carcinogenic, teratogenic and hepatoxic. Many scientific studies have shown that Williopsis saturnus var. saturnus yeast as a killer yeast has antagonistic antifungal effects. In this study, effect of edible coating incorporated with Williopsis. saturnus var. saturnus on the growth of A. flavus and aflatoxin production on peanuts. Whey protein concentrate (10%) and 2% glycerol were dissolved in water and heated for 30 min. After cooling, Williopsis. saturnus var. saturnus (10 logs CFU/mL) was added into the coating solution. The roasted peanuts were coated with coating solution with and without yeast, distilled water containing yeast (10 logs CFU/mL) or water as control by spraying. The peanuts were dried at 40 ºC in an oven. Following drying, the surface of peanuts was contaminated with A. flavus (4 logs CFU/g). The contaminated peanuts were dried, packed and stored for 90 days at 25 ºC. Every other week, in the peanut samples, the number of yeast and mold, the amount of aflatoxin, TBA (thiobarbituric acid), and weight lost, and water activity were observed. The results showed that the number of Williopsis saturnus var. saturnus stayed stable for 84 days (8 logs CFU/mL) in the samples. Application of coating with and without yeast and only yeast solution reduced aflatoxin production in the peanuts samples approximately 1.7, 0.4 and 0.6 ppb comparing with control (water) during 84 days of storage, respectively. Oxidation of peanut samples were depressed about 40 and 60% by application of coating and coating containing yeast cells comparing with control at the end of storage, respectively. Both water activity and weight lost at all film groups slightly increased. Therefore, the results showed that application of edible coating with the yeast cells has potential to use in industrial base to prevent aflatoxin production in peanuts.