Submitted to: Postharvest Biology and Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/1/2011
Publication Date: 2/1/2012
Citation: Guan, W., Fan, X., Yan, R. 2011. Effect of UV-C treatment on inactivation of Escherichia coli O157:H7, microbial loads, and quality of button mushrooms. Postharvest Biology and Technology. Vol.64:119-125. Interpretive Summary: Mushrooms have been consumed throughout the world for many centuries, not only for nutritional value, but also for functional purposes. However, mushrooms can be contaminated with human pathogens during growing and processing. This study was conducted to evaluate the effects of UV exposure on inactivation of E. coli O157:H7, microbial population, sensory and nutritional quality of mushrooms during cold storage. Results showed that UV radiation applied at proper doses reduced E. coli O157:H7 and microbial population by more than 90% on button mushrooms. In addition, storage life was extended without causing deterioration of nutritional quality of button mushrooms. The information would be useful for mushroom processors to use UV as a sanitization step to improve the microbial safety and to extend shelf-life of mushrooms.
Technical Abstract: This study investigated the effects of ultraviolet-C (UV-C) light applied to both sides of mushrooms on microbial loads and product quality during storage for 21 days at 4 C. Microflora populations, color, antioxidant activity, total phenolics, and ascorbic acid were measured at 1, 7, 14 and 21 days of storage. Additionally, the inactivation of Escherichia coli O157:H7 by UV-C was determined. Results showed that UV-C doses of 45 to 315 mJ/cm resulted in 0.67 to 1.13 logs CFU/g reduction of E. coli O157:H7 inoculated on mushroom cap surfaces. UV-C radiation also reduced total aerobic plate counts by 0.89-0.63 log CFU/g on the surface of mushrooms. Although mushrooms treated with UV-C had more severe browning with increasing dosage after initial treatment, the control mushrooms also browned as indicted by lower L* and higher a* values after 21 days of storage at 4 C. In addition, the UV-C treatments apparently inhibited lesion development on the mushroom surface. During the first 7 days, irradiated mushrooms had lower antioxidant activity, total phenolics, and ascorbic acid content compared to non-radiated samples. However, irradiated mushrooms reached similar amounts of these nutrients as the control after 14 days of storage at 4 C. In summary, UV-C radiation could potentially be used for sanitizing fresh button mushrooms and extending shelf-life.