Food Microbiology

The mold growth leading physical, chemical and sensory changing in food products and carrying health risks with toxin production is a main problem in the food industry. In our study, as an alternative solution, bioactive materials were developed by incorporating Williopsis saturnus var. saturnus at different concentrations (0; 3.2; 6.8 and 8.8 cfu/cm2) into whey protein concentrate (WPC) based edible films. Viability of W. saturnus var. saturnus in the films was investigated during the time of the storage. Moreover, the antifungal activity of the films incorporated with W. saturnus var. saturnus was also tested against Penicillium expansum and Aspergillus niger. The effect of the antagonist yeast occurrence in the film on physical properties and microstructural properties of the films were analyzed. The optical properties and the mechanical properties of the film samples were also observed by SEM and Instron, respectively. The results showed that bioactive WPC films containing 8.8 log cfu/cm2 W. saturnus var. saturnus were able to maintain more than 60% of the initial antagonist yeast population. In addition, the films incorporated with the antagonist yeasts reduced mycelium growth of P. expansum and A. niger on the medium by more than 29% and 19% at pH 4.5, respectively. Incorporation of more than 3.2 log cfu/cm2 antagonist yeasts significantly increased water vapor permeability of the films (P<0.05). Increased population of the yeasts also significantly increased percent water solubility of the films (P<0.05). Moreover, the distribution of the antagonistic yeasts in the films presented homogenous microstructure at SEM. Increasing concentration of the killer yeasts in the films presented a significant tendency to greenness and yellowness as well as lightness values (P<0.05). The concentrations more than 3.2 log cfu/cm2 of killer yeast population in the films significantly increased tensile strength but decreased percent elongation at break (P<0.05).