Improvement of set yogurt shelf life and quality by protective edible layers incorporated with Lactobacillus plantarum

Abstract

In this study, layers were designed to protect yogurt using sourdough powder, wheat flour, and gelatin incorporated with Lactobacillus plantarum. The antimicrobial and antifungal (against Aspergillus terreus) characteristics of designed layers were investigated in vitro. After yogurt preparation, designed layers were placed on the surface of samples and stored at 4°C for 21 days. The physical and microbial properties and susceptibility to the growth of A. terreus in samples were assessed. For sensory evaluation, samples mixed with layers and yogurt without layers were evaluated. The in vitro antimicrobial and antifungal results indicated that the bacterial gelatin layer had the largest inhibitory zone, and the bacterial sourdough layer had the maximum inhibition growth against A. trreus. The viability of L. plantarum in the sourdough layer remained more than 106 CFU/g after two weeks on the yogurt. The designed layers could reduce the syneresis and pH of yogurt during storage in all cases. The sourdough and wheat flour layers could prevent fungal growth for at least 7 days. The taste of yogurt mixed with the bacterial wheat flour layer received the highest score, while the taste of the yogurt that had been protected with the sourdough layer was better than other samples.