Application of combining ozone and UV-C sterilizations in the artificial drying of persimmon fruits

Abstract

China has a large market for dried persimmon fruits, but mold and sulfur dioxide (SO2) residue have become serious potential consumer health risks. To reduce these risks, the adopted ozone and/or UV-C sterilization methods were applied; however, these methods had low effectiveness due to lack of sterilization condition optimization based on the drying process. In this study, bacteria and fungi strains were identified and optimal ozone and/or UV-C conditions were selected by treating predominant strains. Results show that Curtobacterium, Luteibacter, Rhodotorula, Penicillium, and Aspergillus were the predominant microorganisms in the whole artificial drying process, and drying at 36 and 72 h were found to effectively influence the quantity of microorganism contamination. Comparing the mortalities of microorganism revealed that the sterilization of combining ozone with UV-C was superior to the individual utilization of ozone or UV-C. Moreover, the physic-chemical results of the dried persimmon fruits suggested that this non-thermal sterilization could alleviate astringency, but hadn't significant effects on other properties, including color, moisture content, water activity, and protopectin. Therefore, these optimal conditions could potentially enhance the production of dried persimmon fruits.