Abstract:The effects of color and crispness preservation pretreatments on frozen-thawed litchi pericarp were investigated in this study, including the effects on phenolase oxidation, cell integrity, browning, and other quality attributes. The results show that the color and shine of the litchi pretreated with 8% C6H8O7 + 0.5% Vc + 1% CaCl2 closely resemble those of fresh litchi. Compared to those of the control group, the relative electrolyte exudation rate and the juice loss rate of litchi after this pretreatment are decreased by 18.71 and 0.92%, respectively. In addition, the hardness retention rate is increased by 14.17%, while the residual enzyme activities of polyphenol oxidase and peroxidase are decreased by 158.18 and 342.14%, respectively. Meanwhile, the contents of polyphenols and anthocyanins and the antioxidant capacity retention rate increased by 9.79, 27.11, and 10.21%, respectively. Citric acid is found to be more effective in color preservation than Vc, while CaCl2 plays a critical role in maintaining crispness. Synergistic effects are noted among the three color- and crispness-preserving agents. In particular, the protective effects of Vc on cell integrity are observed only in the presence of CaCl2. The combination of 0.5% (m/V) Vc with citric acid and CaCl2 synergistically show enhanced color preservation and texture protection against enzymes. Hardness is better preserved at higher citric acid concentrations. In conclusion, pretreatment with 8% C6H8O7 + 0.5% Vc + 1% CaCl2 can be considered as a suitable solution for color and crispness preservation of frozen litchi. The results of this study can provide technical support for the preservation and processing of litchi.
