Microbial community composition during artificial frosting of dried persimmon fruits

Abstract

Spoilage caused by microbial contamination in dried persimmon fruits processed by traditional frosting often leads to considerable economic losses. Artificial frosting has recently been considered as an alternative method to reduce the risk of spoilage, however, in this study, expansion of packaging and mildew formation were still observed. The dynamics of bacteria and fungi structure in different processes were determined. Results showed that Zygosaccharomyces and Aspergillus were the predominant genera in spoiled fruits in the packaging phase. During the artificial frosting, Wickerhamomyces (15.91%) and Candida (6.82%) were the predominant gas-generated yeasts and Aspergillus (20.45%) and Penicillium (15.91%) were consistently the dominant genera causing mildew. To reduce the contamination problem, pulsed light (24 J/cm2) were adopted on Day 0 of frosting and no fungi were detected on Day 3 post-frosting, which indicated to decrease significantly the amounts of Wickerhamomyces, Candida, Aspergillus, and Penicillium. Additionally, the results of the high-throughput sequencing suggested that the proportions of these predominant microorganisms were also decreased significantly during frosting. These results showed that pulsed light treatment in the artificial technique could almost overcome the problems of packaging expansion and mildew formation.