Abstract:

Flesh leatheriness is a major problem during cold storage of loquat fruits. In order to identify the optimal maturity level of loquat fruits for cold storage so as to retard flesh leatheriness and extend the storage life of loquat fruits, Jiefangzhong loquat (Eriobotrya japonica Lindl. cv. Jiefangzhong) fruits with 70%, 80% or 90% maturity levels were selected as the experimental subjects to measure the changes of quality indexes and lignification related enzyme activities of loquat fruits stored at 4 ℃. Results showed that loquat fruits higher maturity level exhibited more severe lignification. When loquat fruits were stored for 35 d, there was no significant difference in lignin content between loquat fruits at 70% maturity and those at 80% maturity (P ＞ 0.05). The total sugar and total soluble solids content of loquat fruits at 80% maturity was significantly higher than those at 70% or 90% maturity (P ＜ 0.05). There were no significant differences in titrable acid (TA) content and cinnamyl alcohol dehydrogenase (CAD, EC 1. 1. 1. 195.), polyamine oxidase (PAO, EC 1.4.3.6.), peroxidase (POD, EC 1.11.1.7.), 4- coumarate coenzyme A ligase (4CL, EC 6. 2. 1. 12.) activities of refrigerated loquat fruits with different maturity. Significantly higher phenylalanine ammonia lyase (PAL, EC 4.1.3.5.) activity was observed fruits with 90% maturity than those with 70% or 80% maturity (P ＜ 0.05). A significant positive correlation was found between PAL activity and lignin content (r = 0.89). In conclusion, PAL activity is closely associated with lignification of loquat fruits during cold storage and the optimal maturity level of loquat fruits for storage at 4 ℃ is 80%.

Key words: loquat, lignification, maturity, phenylalanine ammonia lyase (PAL)