Effects of delayed harvesting on quality and metabolite profiles of 'Cuixiang' kiwifruit (Actinidia spp.): insights from post-ripening at room and low temperatures

Current practices for determining fruit harvest maturity lack robust scientific standards, leading to variable postharvest quality. To address this gap, this article explores a new storage method, delayed harvesting (DH), to investigate the evolution of quality attributes and metabolites of 'Cuixiang' kiwifruit at harvest (AH), room temperature post-ripening (RTP), and low temperature post-ripening (LTP). The results indicated that titratable acid content (9.36–12.56 g/kg) increased with DH time, whereas dry matter content (21.01%–17.39%) decreased. Although DH caused a decrease in total phenols (0.94–0.79 g/kg) and ascorbic acid (1.25–0.78 g/kg) at harvest, it was beneficial in alleviating the degradation of ascorbic acid during post-ripening, and improving the antioxidant activity of LTP kiwifruit. Specifically, compared to normally harvested samples, ascorbic acid content of the samples delayed for two weeks in LTP increased by 30.01%, whilst antioxidant activity, (1,1-diphenyl-2-picryl-hydrazyl radical scavenging activity: 3.92 mmol/kg; 2,2′-azino-bis[3-ethylbenzothiazoline-6-sulfonic acid] free radical scavenging activity: 6.49 mmol/kg; and ferric reducing antioxidant power: 4.49mmol/kg) showed no significant difference. The senescence, oxidative stress, and respiratory consumption of cells during DH lead to down-regulation of amino acids, alkaloids, and lipids. The up-regulation of phenylpropanoid metabolism and the expression of genes encoding flavonoid synthesis under low temperature facilitated the accumulation of phenolic acids and flavonoids during LTP. Overall, DH has greater application advantages for maintaining the quality attributes of LTP kiwifruit. The results can provide scientific data to clarify the effects of DH on the nutritional quality of 'Cuixiang' kiwifruit, and also help to understand the metabolic pattern of important metabolites during DH.