Effect of combination of ultraviolet light and hydrogen peroxide on inactivation of Escherichia coli O157:H7, native microbial loads, and quality of button mushrooms.

摘要

Mushrooms are prone to microbial spoilage and browning during growing and processing. Ultraviolet light (254 nm, UV-C) has been used as an alternative technology to chemical sanitizers for food products. Hydrogen peroxide (H₂O₂) is classified as generally recognized as safe for use in foods as a bleaching and antimicrobial agent, and could control the bacterial blotch and browning of mushrooms. This study investigated the effects of water wash (control), 3% H₂O₂ wash, 0.45 kJ m-2 UV-C, and combination of H₂O₂ and UV-C (H₂O₂ + UV) on microbial loads and product quality of mushrooms during storage for 14 days at 4 degrees C. Additionally, the inactivation of Escherichia coli O157:H7 inoculated on mushrooms was determined. Results showed that water wash, H₂O₂, UV-C and H₂O₂ + UV resulted in 0.44, 0.77, 0.85, and 0.87 logs CFU g-1 reduction of E. coli O157:H7, respectively. Hydrogen peroxide, UV-C and the combination reduced total aerobic plate counts on the surface of mushrooms by 0.2-1.4 logs CFU g-1 compared to the control, while there was no significant difference among the three treatments during storage. After storage, UV-C treated mushrooms had similar L* and a* values as the control while H₂O₂ and H₂O₂ + UV-C treated mushrooms had higher L* (lighter) and lower a* (less brown) values than the control. Compared to water wash, all the treatments inhibited lesion development on the mushroom surface on day 14. The combination of H₂O₂ and UV achieved the best overall dual control of lesion and browning. There was no significant difference in ascorbic acid and total phenolic content among the treatments. Overall our results suggested that H₂O₂ + UV reduced microbial loads, and extended storage life by reducing lesion development without causing deterioration in nutritional quality of button mushrooms. Therefore, when properly utilized, H₂O₂ + UV could potentially be used for maintaining postharvest quality while marginally reducing populations of E. coli O157:H7 and background microflora