Application of Edible Protein Coating Agents in the Preservation of Citrus reticulata “Hong Mei Ren”
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Abstract:
A soy protein isolate (SPI) coating agent, whey protein isolate (WPI) coating agent, and SPI-WPI composite coating agent were used to preserve the Citrus reticulata variety “Hong Mei Ren.” In addition, a control group (CK) with no treatment was established for comparison and evaluation of preservation performance. The microscopic morphology of the peel was observed, and the storage quality of the fruit was measured. The results showed that the decay indices and weight loss rates of the three treatment groups were lower than those of the CK group. After 14 days of storage, the decay index of the CK group was 6.66%, and that of the SPI group was 3.33%. There was no decay in the WPI and SPI-WPI groups. After storage for more than 35 days, the decay index of the CK group exceeded 20%, and the mass loss rate reached 16.15%. These values were significantly higher than those of the treatment groups. Changes in the total soluble solid (TSS) value and titratable acid (TA) content in the treatment groups lagged behind those in the CK group by 1~2 weeks. After 14 days of storage, the TSS values in the treatment groups increased by 0.77%~1.70%, whereas the TSS value of the CK group no longer increased. After storage for 21 days, the TA content of the CK group reached a minimum of 6.29 g/L, whereas the TA values of the treatment groups were 8.48, 8.03, and 8.79 g/L, respectively, significantly higher than those in the CK group. Changes in the vitamin C, total phenolic, and flavonoid contents in the treatment groups were lower than those in the CK group. Scanning electron microscopy imaging revealed that the protein coating agents formed smooth and dense films on the fruit surface, covering the pores on the cuticle, and thereby enhancing gloss while slowing metabolism. The storage period of the C. reticulata variety “Hong Mei Ren” can be prolonged by protein coating agents to enhance the storage tolerance of the fruit. WPI and SPI show good preservation effects in early and late storage stages, respectively, whereas the performance of SPI-WPI was intermediate.
