extremely significantp < 0.01
Under the condition of 20 °C, an extremely significant decrease in GYM-A concentration occurred at pH 5 and 7 after 8 months ( p < 0.01), of which 14.8 ± 3.7% decreased ( p < 0.05) within the first two-month period and 81.8 ± 9.3% decreased ( p < 0.01) after 8 months at pH 7, while it showed no obvious decline under the treatment of pH 3 ( p > 0.05).