where ka is the antioxidant activity constant (h1
), t is the drying
time (h), and xa is the ratio of the antioxidant activity. Parameter
ka of Eq. (9) was determined by a linear least squares method using
the measured ratio of the antioxidant activity. Table 5 shows the
coefficient ka for each drying temperature. Fig. 9 shows the changes
in the antioxidant activity ratios during hot air and vacuum drying.
These results agreed with the calculated results (RMSE = 0.290–
1.018), and the ratio of antioxidant activity can be explained using
Eq. (9) (see Table 5).