The Mechanism of Ultrasonic Enhanced Drying Based on the Degradation of Cell Wall Polysaccharides and Changes in Water Status of Blueberry
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Abstract:
To enhance the drying rate and quality of blueberries, this study investigated the effects of different ultrasonic durations (10 min, 20 min, and 30 min) on the texture, cell wall structure, pectin and cellulase activity, cell wall polysaccharide content, moisture status, and drying characteristics and quality of blueberries. The results indicated that the hardness values of blueberries treated with ultrasound for 20 min and 30 min significantly decreased, with the cell walls becoming wrinkled and loose. The activities of pectin and cellulase were markedly reduced. Ultrasonic pretreatment facilitated the conversion of chelated and Na2CO3-soluble pectin into water-soluble pectin, increasing the water-soluble pectin content by 12.64% to 34.36%. Furthermore, ultrasonic pretreatment increased the mobility of free water in blueberries, promoting moisture migration outward. Compared to the control group, ultrasonic pretreatment significantly reduced the mid-infrared drying time of blueberries (by 10.90% to 27.24%) and improved the retention of phenolic substances and antioxidant capacity. The drying time for blueberries treated with ultrasound for 20 min was the shortest (22.7 h), with a higher retention rate of phenolics and stronger antioxidant capacity, making it the optimal ultrasonic pretreatment condition. This study provides a theoretical basis for improving the drying quality of blueberries.
