A novel strategy for improving drying efficiency and quality of cream mushroom soup based on microwave pre-gelatinization and infrared freeze-drying

Abstract The present study was carried out to achieve a more efficient dehydration process along with low undesirable quality decrease for cream mushroom soup (CMS) by combining microwave pre-gelatinization (MPG) with infrared freeze-drying (IRFD). Wheat flour was gelatinized using a microwave heating unit for different times, and was used in CMS formulations. Freeze drying (FD) was carried out using conventional as well as IRFD and drying time, energy consumption and product quality characteristics (flavor, viscosity of rehydrate juice; moisture absorption and crystallinity of dried soup solid) of CMS were studied. Compared to FD, IRFD reduced the drying time and energy consumption by 23.81% and 28.43%, respectively. The microwave pre-gelatinization of wheat flour and subsequent use in IRFD, while in comparing with single infrared freeze drying, did not affect drying time and energy consumption; however, it significantly improved the flavor and viscosity of soup upon rehydration, and reduced the tendency to retrogradation. The microwave pre-gelatinization time of 120 s at 8 W/g energy level was found to be the most suitable condition for microwave pre-gelatinization of wheat flour. Industrial relevance Undesirable decrease of viscosity in starch containing soup and high energy consumption of traditional freeze-drying limit the large-scale industrial production of freeze-dried starch containing product. Therefore, inhibiting viscosity reduction and reducing production cost are the crucial steps for industrial production of freeze-dried cream mushroom soup. Microwave pre-gelatinization and infrared freeze-drying have made outstanding contributions on improving starch stability and reducing drying energy consumption, respectively, which caters to the preferences of industrial production and can be used in industrial production of freeze-dried instant cream mushroom soup.