Changes in Texture and Flavor of Dehydrated Shiitake Mushroom during Rehydration

This study was conducted in order to explore the changes in the texture and flavor of dried shiitake mushroom during rehydration. Dried shiitake mushroom was rehydrated at different constant temperatures (40 and 100 ℃) for up to 180 min. An electronic tongue, headspace solid phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS) and laser scanning confocal microscopy (LSCM) were used to analyze the texture and flavor characteristics of shiitake mushroom during the rehydration process. The results showed that both rehydration temperature and time had significant effects on the texture, volatile flavor and taste of rehydrated mushroom. At 40 ℃, the rehydration ratio almost reached equilibrium after 30 min, and the umami intensity was the second highest, but the water retention capacity decreased compared with all other groups. The hardness and chewiness of the 40 ℃/30 min group were moderate, whereas the elasticity was the highest. The browning index of cap was the second highest, while the browning index of gills was not significantly different from that of any other group. Microscopic observation showed that the mycelium was unfolded and the shear force was moderate. In addition, the antioxidant activity of mushroom rehydrated at 40 ℃ was higher than that of mushroom rehydrated at 100 ℃, the loss of soluble protein was less, and the content of free amino acids was higher and reached its maximum after 30 min. Furthermore, the characteristic flavor substances, mainly sulfur compounds and ketones, were well retained after rehydration at 40 ℃, but decreased seriously at 100 ℃. In conclusion, the texture and flavor of shiitake mushroom changed significantly during the rehydration process, and rehydration at 40 ℃ for 30 min resulted in better quality of shiitake mushroom.