Osmotic-ultrasound dehydration pretreatment improves moisture adsorption isotherms and water state of microwave-assisted vacuum fried purple-fleshed sweet potato slices

Abstract

Abstract Effect of osmotic-ultrasound dehydration pretreatment on the moisture adsorption isotherms of microwave-assisted vacuum fried purple-fleshed sweet potato (PSP) was determined at 30, 45 and 60\u2009°C and fitted with six models. Absorbed water state of microwave-assisted vacuum fried purple-fleshed sweet potato was measured by low-field nuclear magnetic resonance (LF-NMR). Results indicated that the optimized conditions of osmotic-ultrasound dehydration pretreatment were 11.21\u2009min for ultrasound time, 56.99% sucrose concentration and 74.84\u2009min for osmotic dehydration time. Moisture adsorption isotherms showed type II sigmoid shape. GAB model had the best fit evaluated by the higher values of R2 (>0.9868) and the lower values of RMSE ( \u20090.9595) and pretreated fried PSP (R2\u2009>\u20090.9845) by using LF-NMR.