The total content of organic acids significantly (p < 0.05)
increased from 143 to 196 mg/g dry weight during the sublimation
period in FD (Fresh, FD 1 h, FD 3 h and FD 5 h), and then (p < 0.05)
reduced to 150 and 153 mg/g during the desorption period in FD
(FD 6.5 h, FD 8 h) and the MVD period in FMVD (FMVD 5.15 h),
respectively. With the temperature of samples increasing during
the sublimation period of FD, the relevant enzymes (such as malate
dehydrogenase (MDH) and citroyl synthetase (CS)) could have
been activated, promoting the formation of organic acids in the
samples (Hirai & Ueno, 1977). In the late drying stage, the organic
acids loss could be ascribed to the occurrence of decarboxylation
due to the higher temperature of heat treatment during the
desorption period of FD and the MVD period in FMVD
(Handschumacher, 1960).