Ultrasonic pretreatments were applied to lotus seeds at acoustic energy densities of 0.29, 0.40, and 0.51 W mL⁻¹ for 10 min. After pretreatments, lotus seeds were subjected to microwave vacuum drying (MVD). Parameters of glass transition temperature (T_g), gelatinization temperature (T_p), water state, color kinetics, and free amino acid content of microwave vacuum dried lotus seeds were determined. With increasing acoustic energy density, MVD elevated the T_g values appreciably by decreasing the content of cytoplasmic bulk water in lotus seeds tissues. The T_p had a positive relationship with the relaxation times of cytoplasmic bulk water (T₂₂), while T_g had a negative relationship with T₂₂. Color kinetics were analyzed by the divisional method during MVD due to different browning reactions, which failed to appear with ultrasonic pretreatment. Free amino acid content ranged from 517.65 to 666.13 mg/100 g dry weight at 0.51 W mL⁻¹.

In this study, ultrasonic technology was combined with microwave vacuum drying technology to explore the impacts of different coupling methods (ultrasonic pretreatment and ultrasonic coupled drying) on the structural characterisation and physicochemical properties of shiitake mushroom (Lentinus edodes) polysaccharides at different ultrasonic powers (0, 120 and 280 W), and compared with hot air drying (HAD). The results demonstrated that the monosaccharide composition of Lentinus edodes polysaccharides (LEPs) remained largely unaltered after treatment with various drying methods, although significant disparities in molar content were observed. Air ultrasound combined with microwave vacuum drying (USMVD) at 280 W ultrasound power resulted in LEPs with higher contents of total sugars (8.12 ± 0.13 g/100 g), reducing sugars (10.32 ± 0.3 mg/g) and uric acid (2.23 %) compared to those obtained from the HAD treatment. Furthermore, the combination of US280MVD drying treatment of LEPs exhibited a reduction in molecular weight and an enhancement in shear-thinning ability. The results of the study indicate that USMVD is a promising drying treatment technology.