Firmness is one of the most common physical parameters used to assess the quality of fruits (Luo et al., 2009). In the present work, firmness decreased in the control and all AITC treated fruit during the storage period. The firmness of control fruit softened rapidly in the first three days and then decreased gradually to 1.30 N by day 15, namely, about 25.1% of the initial value on day 0 (Fig. 2D). However, the firmness of fruit treated with AITC at 5 and 15 μL L−1 was 4.07 N and 4.67 N on day 15, respectively. This indicated that AITC treatment could significantly inhibit the softening of mulberry fruit (P < 0.05).
3.3. Effect of AITC treatment on CO2 and O2 content in fruit container
The gas composition in the fruit container was changed by the respiration and metabolism of mulberry fruit during storage. In the control group, the CO2 content rose significantly (P < 0.05) from an initial value of 0.03% to 4.33% and the O2 content decreased dramatically from 21.0% to 16.2% on day 15, respectively (Fig. 3). However, no significance (P > 0.05) in CO2 and O2 content was observed in all AITC treated groups during storage. Respiration was a good indicator of the metabolic rates of harvested fruits and vegetables. Respiratory intensity of mulberry fruit could be inhibited by H2S treatment (Hu et al., 2014). The results in the present work showed AITC treatment could also reduce the respiration of mulberry fruit.