*2.5. pH Values*

Table 3 compared the pH values of packaged and unpackaged strawberries. The pH values of unpackaged strawberries increased significantly with the increase of storage time. The pH values of unpackaged strawberries reached to 3.99 ± 0.29 after six days. Han et al. demonstrated that the pH values of fruit are related to the fruit senescence [29]. A possible explanation for this might be the utilization of organic acids of fruit during respiration [30]. The pH difference between day 2 and day 4 was not statistically significant for all packaged groups. Martinez–Ferrer et al. considered that might be the low conversion rate of organic acids during respiration [30]. The pH values of strawberries packaged with PVA/CH-2, PVA/CH-2.5 and PVA/CH-3 were significantly different than the pH values of strawberries packaged with the PVA sample at day 6. The findings of the current study are consistent with those of Cong et al., who found that CH coating containing natamycin slowed the changes in pH values of Hami melons [31]. At six days, the pH values of fruits packaged with PVA/CH-2.5 was 3.65 ± 0.16, and the change was minimum (3.41 ± 0.08 for one day). A possible explanation for this might be that relatively small changes of O2 and CO2 levels resulted in slight changes of the pH values for strawberries [32].

**Table 3.** pH analysis of strawberries treated with different films during storage.


Notes: Values with the same letter are not statistically different, according to Duncan's Multiple Range Test at *p* < 0.05; a, b, means with the same letter in the same column are not significant different (*p* > 0.05).
