Effect of wounding intensity and methyl jasmonate pretreatment on phenolic compounds and antioxidant capacity of fresh-cut pitaya fruit
Xiao-an Li (Nanjing Agricultural University)Fan Gao (Nanjing Agricultural University)Qing-hong Long (Nanjing Agricultural University)Chen Chen (Nanjing Agricultural University)Peng Jin (Nanjing Agricultural University)Yong-hua Zheng (Nanjing Agricultural University)
The effect of different degrees of wounding stress and a pre-cutting methyl jasmonate (MeJA) treatment on phenolic compounds and antioxidant capacity of fresh-cut pitaya fruits during 4 days of storage at 15 degrees C was investigated. For the wounding intensity study, pitaya fruit were cut into slice (1cm thickness), half-slice(1/2 section from a slice of 1cm thickness) and quarter-slice(1/4 section from a slice of 1cm thickness) to generate different wounding intensities, with the intact pitaya fruits without any wounding as the control. For MeJA pretreatment study, intact pitaya fruits were first treated with 0, 1, 10 or 100µmol/L of MeJA and then cut into quarter-slice. Total soluble phenolics (TSP), antioxidant capacity (AOX) and phenylalanine ammonia-lyase (PAL) activity in all fresh-cut produce increased significantly during storage compared with whole pitaya fruits. This enhancement in TSP, AOX and PAL activity increased with wounding intensity. Increases in reactive oxygen species (ROS) production was also observed in all fresh-cut pitaya fruit. Pre-cutting treatment with 100µmol/L of MeJA further promoted the increase in TSP, AOX, PAL activity and ROS production in quarter-sliced pitaya fruit. These results demonstrated that increasing wounding intensity and pre-cutting MeJA treatment can improve the biosynthesis of phenolics compounds and enhance the antioxidant capacity of fresh-cut pitayas. ROS may play a key role as signaling molecules in wounding-induced biosynthesis of phenolic compounds in fresh-cut pitaya fruits.