Abstract: The present investigation was performed to evaluate the effect of 1.0 kGy 60Co gamma irradiation on physicochemical characteristics (color, texture and microstructure), water migration and sensory characteristics of shiitake mushrooms (Lentinus edodes) during storage at (4 ± 1) ℃ and (80 ± 5)% relative humidity. The results indicated the L* values of irradiated and non-irradiated mushrooms were 90.06 and 90.54, respectively, which decreased to 87.77 and 80.71 after 21 days of storage, indicating that the irradiation treatment delayed browning and prevented color deterioration of fresh shiitake mushrooms. The firmness of irradiated shiitake mushrooms was significantly higher than that of the non-irradiated one. Moreover, the irradiation treatment slowed down the decomposition of the reticular hyphal structure of mushrooms. Low-field nuclear magnetic resonance (LF-NMR) analysis showed that the states of water in the non-irradiated control were very unstable and the peak area for each of the three states fluctuated greatly. The T23 peak area of free water transverse relaxation time increased slightly in the early stage of storage, then decreased sharply, the T21 peak area of bound water increased first and then decreased, and the T21 peak shifted to the right in the later stage of storage, while the peak area of transverse relaxation time T21 for bound water did not change greatly. The peak area of transverse relaxation time T22 for immobile water increased initially and decreased later for both treated and untreated samples. In conclusion, the 1.0 kGy 60Co gamma irradiation treatment improved the stability of the states of water in fresh shiitake mushrooms and delayed sensory quality deterioration, maintaining the physiological characteristics well, reducing water loss and extending the shelf life.

Key words: Lentinus edodes; irradiation preservation; color; hardness; microstructure; water migration