Effects of different ultrasonic enhancement methods on the quality characteristics of dried lotus root in heat pumps

Abstract

Objective: This study aimed to explore the effect of different ultrasonic enhancement methods on the quality characteristics of dried lotus root in heat pumps. Methods: The effects of US, CU, and USOD on the drying characteristics, appearance color, microstructure, texture characteristics, nutritional quality and antioxidant characteristics of the lotus root heat pump during the drying process were investigated. Ultrasonic (US), direct contact ultrasound (CU), USOD and heat pump drying (HPD) were treated in series and parallel. The coefficient of variation method was used to comprehensively evaluate the quality of lotus root dried by different ultrasonic enhancement methods. Results: US, CU and USOD treatments had positive effects on the HPD speed of lotus roots. The brightness (L*), polysaccharide content, and hydroxyl radical scavenging rate of lotus root obtained by USOD-HPD were the best, which were 77.98, 51.68 mg/g, and 45.94%, respectively. US-HPD treatment can better retain the content of flavonoids and vitamin C in lotus root. HPD lotus root had the highest polyphenol content and DPPH radical scavenging. The comprehensive evaluation results of the coefficient of variation method showed that the USOD-HPD lotus root had the best quality. Conclusion: The combined drying method of USOD-HPD can effectively improve the quality of lotus root.

Keywords

• lotus root
• ultrasound
• pretreatment
• drying