Abstract:

Dynamic changes in fruit qualities and related enzyme activities of pitaya (Hylocereus undatus) stored at 15 or
5 ℃ for 50 d were studied. The results showed that the contents of total soluble sugar, titratable acid, vitamin C, protein in
pulp and red pigment in peel stored at 15 ℃ decreased during the whole storage period. During 5 ℃ storage, however, these
parameters showed significantly reduced losses. Amylase activity in pulp stored at 15 ℃ was higher than in pulp stored at
5 ℃. The activities of polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) in peel increased with storage
time at both temperatures and resulted in browning at the end of storage. The peaks of activity of peroxidase (POD) and
superoxide dismutase (SOD) were delayed and catalase (CAT) activity in peel was kept at a higher level when stored at 5 ℃,
which suppressed the increase in malondialdehyde (MDA) content compared with fruits stored at 15 ℃. Therefore, lower
temperature storage at 5 ℃ retarded fruit senescence and prolonged the storage life of pitaya by 20 days.

Key words: pitaya, low temperature storage, quality, senescence, enzyme activity