Short-Time High-Oxygen Pre-Treatment Delays Lignification of Loquat (Eriobotrya japonica Lindl.) During Low-Temperature Storage

Lignification often occurs during low-temperature storage in loquat fruit, leading to increased firmness and lignin content, water loss, and changes in flavor. As induced stress factors, short-time high-oxygen pre-treatment (SHOP) can initiate resistant metabolism and regulate the physicochemical qualities during fresh fruit storage. However, the effect of SHOP on the lignification and quality of loquat has been reported less. In the present study, loquat fruit was immersed in oxygen concentrations of 70%, 80%, and 90% for 30 min before being stored at 4 ± 1 °C. The results showed that the 80% SHOP samples had lower lignin accumulation and firmness, showing reductions of 23.1% and 21.1% compared to the control at 50 days. These effects were associated with the inhibition of the activities of lignin synthesis-related enzymes, including phenylalanine ammonia-lyase (PAL), 4-coumarate-CoA ligase (4CL), cinnamyl alcohol dehydrogenase (CAD), and peroxidase (POD). Meanwhile, 80% SHOP improved the antioxidant enzyme system and maintained the structural integrity of the cells. Furthermore, SHOP retained the color and suppressed decay and weight loss and the decline in the soluble solids content (SSC) and titratable acidity (TA). As a convenient and cheap physical approach, SHOP is a promising technology for delaying lignification by regulating lignin synthesis in loquat storage.