Influence of microwave vacuum drying on glass transition temperature, gelatinization temperature, physical and chemical qualities of lotus seeds

This study investigated the effects of microwave power density on effective moisture diffusion coefficient (D-eff), glass transition temperature (T-g), gelatinization temperature (T-P), physical and chemical qualities of lotus seeds during microwave vacuum drying. D-eff increased by 42% and 127% at 15 W/g and 20 W/g, respectively, when compared with 10 W/g. Tp was negatively correlated with the relaxation times of T-21 and T-22, while T-g, was negatively correlated with the relative areas A(22). The rates of change of color were observed to be divided roughly into two periods, consisting of a rapid change caused by enzymatic browning and a slow change caused by non-enzymatic browning. An equation is provided to illustrate the relationship of k(1) and k(2) of Peleg's model depending on power density during rehydration kinetics. The samples at 20 Wig exhibited the higher content of amino acid (540.19 mg/100 g d.b.) while lower starch (17.53 g/100 g d.b.). (C) 2017 Elsevier Ltd. All rights reserved.