Dynamic changes of non-volatile compounds and evaluation on umami during infrared assisted spouted bed drying of shiitake mushrooms

The present study was carried out to report the dynamic changes of non-volatile components and the evaluation on umami of shiitake mushrooms during infrared assisted spouted bed drying (IRSBD) under different temperatures (45, 50, 55, and 60 °C) and airflow speeds (7.0, 7.5, 8.0, and 8.5 m/s). In addition, the drying characteristics and dried product rehydration ratio of shiitake mushrooms were also analyzed. Results demonstrated that compared with airflow speeds, drying temperature has a more significant effect on the drying characteristics of shiitake mushroom during IRSBD. Of all the drying process, the contents of flavor nucleotides, organic acids (tartaric acid, malic acid, succinic acid and citric acid), free amino acids (Asp, Glu and Ser) and equivalent umami concentration (EUC) value of Shiitake mushrooms are constantly increasing. The contents of soluble sugar and free amino acids such as polyol, acetic acid and fumaric acid increased significantly in the early and middle stage of drying, while decreased in the late stage of drying. The increase of temperature and airflow speed have a positive effect on retaining the flavor components of dried products. The condition of IRSBD with 55 °C and 8.0–8.5 m/s airflow speed is suitable for the dehydration process of Shiitake mushrooms to maintain better dried samples structure and yield high quality dried products with rich flavor in industry.