Lipid and Secondary Metabolite Profile Changes During Cold Storage of Dongzao (Ziziphus jujuba Mill. cv. Dongzao): Responses to Postharvest Treatments and Implications for Marketability

Dongzao (Ziziphus jujuba Mill. cv. Dongzao) is a popular fresh-eating cultivar with a short shelf life at room temperature. As Dongzao acreage increases in the United States, extending the fresh-fruit supply window is important for commercial production. A preliminary study showed that Dongzao fruit began developing mold after approximately 5 weeks of cold storage. Therefore, a subsequent study evaluated the effects of an ethylene absorbent and two fungicides, Scholar and Mentor, on fruit quality, decay, and metabolomic changes during extended cold storage at 0 ± 0.5 °C. Compared with untreated fruit, the ethylene absorbent did not extend storage life or reduce decay, with more than 30% stem-end rot observed by week 6, suggesting that ethylene removal had limited effects on Dongzao storage deterioration. Both fungicides substantially reduced decay, but Scholar was more effective, with no stem-end rot detected after 9 weeks of storage. Heatmap and principal component analyses further showed that Scholar-treated fruit after 9 weeks clustered with fruit stored for 6 weeks, suggesting that Scholar treatment was associated with delayed metabolic changes accompanying advanced storage deterioration. Cold storage induced extensive lipid remodeling, with substantial increases in lipid metabolites, particularly lysophosphatidylcholines, lysophosphatidylethanolamines, and free fatty acids, indicating pronounced changes in membrane lipid metabolism under prolonged low-temperature storage. Cold storage also broadly altered secondary metabolism, including flavonoids, phenolic acids, alkaloids, and terpenoids. Although cold storage was the primary driver of metabolomic changes, Scholar treatment was associated with distinct alterations in flavonoid and terpenoid profiles after 9 weeks of storage. Together, the results demonstrate that Scholar treatment can substantially extend the cold-storage life of Dongzao fruit and suggest that delayed decay and senescence are accompanied by distinct metabolic changes during prolonged storage. To our knowledge, this is the first study of Dongzao cold storage conducted in the United States and the first to characterize untargeted metabolomic changes in Dongzao during extended cold storage, providing a foundation for future research on Dongzao cold storage.