Deterioration in the Quality of 'Xuxiang' Kiwifruit Pulp Caused by Frozen Storage: An Integrated Analysis Based on Phenotype, Color, Antioxidant Activity, and Flavor Compounds.

Kiwifruit has attracted much attention in fruit and vegetable processing due to its high nutritional and economic value. However, there is a lack of systematic research on the effects of long-term frozen storage on the pulp quality of kiwifruit. Using kiwifruit pulp stored at -20 °C for 0, 3, 6, 9, and 12 months as the research materials, the dynamic changes in the phenotype, color, antioxidant activity, and flavor compounds were comprehensively evaluated. The results showed that frozen storage caused a significant decline in the quality of the fruit pulp. Specifically, the contents of chlorophyll and carotenoids decreased and the color deteriorated (color difference increased); the turbidity and centrifugal sedimentation rates increased, and pH and viscosity changed in different stages. Additionally, antioxidant compounds, such as vitamin C and total phenols, were significantly reduced with the extension of storage duration, and the 2,2-diphenyl-1-picrylhydrazyl (DPPH)/2,2-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) free radical scavenging ability was decreased. The content of volatile aroma compounds diminished, leading to a notable shift in the flavor profile. Correlation analysis revealed that changes in volatile substances were significantly correlated with physical, chemical, and antioxidant indicators (