UV-C Irradiation Delays the Quality Deterioration of Postharvest Shiitake Mushrooms (Lentinula edodes)

The fruiting bodies of shiitake mushrooms (Lentinula edodes) are highly susceptible to postharvest quality deterioration due to their loose tissue, high moisture, and active metabolism. Low-dose ultraviolet-C (UV-C) irradiation, a green, safe, low-cost, and efficient physical treatment especially suitable for high-moisture and metabolically active produce, offers a promising solution to this problem for the postharvest preservation of shiitake mushrooms. In this study, the effects of different doses of UV-C irradiation (2.5, 5.0, and 7.5 kJ·m−2) on the postharvest quality of shiitake mushrooms were systematically compared by measuring weight loss, respiration intensity, cap opening percentage, firmness, color (L*, a*, b*), electrolyte leakage, MDA content, antioxidant enzyme activities (SOD, CAT, POD, PAL), chitin content, chitinase activity, and the expression of LeCHI and LeCDA genes. The results showed that UV-C irradiation at 5 kJ m−2 significantly delayed the increase in weight loss (by approximately 32% at day 15 compared to control) and reduced respiration rate (by 25–35% during days 3–9) and cap opening rate (27.3% vs. 48.0% in control at day 15) while maintaining higher firmness and better color retention over the control group. Furthermore, this treatment effectively inhibited electrolyte leakage and malondialdehyde accumulation, enhanced the activities of SOD, POD, CAT, and PAL, maintained chitin content, and downregulated the expression of chitinase and cell wall degradation-related genes. Thus, 5 kJ m−2 UV-C irradiation is effective in maintaining postharvest quality and extending the storage time of shiitake mushrooms.