Fig. 7 shows the changes in the residual ratio of the L-ascorbic
acid content during hot air drying. The results showed that the
AsA content decreased as the drying proceeded over time, that is,
as the moisture content decreased. Hosaka (1972) proposed that
L-ascorbic acid decomposition was a first-order reaction. An equation
and parameters determined by the reaction rate theory would
be useful in an indicator for decomposition of AsA in the kiwifruit
sample during drying process. Therefore, the empirical residual
ratio during drying was applied to the first-order reaction rate
equation (Eq. (7)):