The effect of hot air treatment on volatile compounds in nectarine fruit and the regulation of glycosidically bound compounds by sugar

In order to investigate the impact of hot air (HA) treatment on the sugars and volatiles in postharvest nectarine fruit, nectarines were treated with HA at 40 °C for 4 h and stored at 1 °C for 35 days. Changes of sugars, free and glycosidically bound volatiles, β-glucosidase (β-Glu) activity, and the gene expression of UGT (UDP-glucosyltransferase) in nectarine fruit were determined. The results showed that compared with CK, HA treatment delayed the firmness decline of 48.01%, weight loss of 32.13%, internal browning index of 58.03%, and maintained the high commodity quality of nectarine fruit at the end of storage. HA could reduce the content of aldehydes and increase the content of esters. The bound linalool in HA increased by 171.41% compared with the CK. In addition, the results of in vitro experiments showed that glucose and sucrose systems could increase the content of free and bound linalool by up-regulating the expression of PpUGT85A2, promoted the accumulation of bound benzaldehyde and nonanal, and reduced the corresponding free volatile compounds, it showed that free aldehydes can be synthesized from soluble sugars into bound aldehydes.