Abstract:
The effect of acetic acid vapor on mycelia growth and spore germination of Aspergillus niger, a
causal agent of fruit rot of longan, was investigated on culture medium. Fumigation with acetic acid
at 99.5% for > or = 30 min showed completely inhibition on fungal mycelia growth and spore
germination. The effect of acetic acid fumigation for 30 min to control fruit rot disease of longan cv.
Dow, which caused by Aspergillus niger, was studied. The data revealed that acetic acid fumigation
could delay fruit rot disease, but it caused pericarp browning (low L* value) and significantly
enhanced respiration rate, pericarp firmness, electrolyte leakage, and the activities of polyphenol
oxidase (PPO) and peroxidase (POD) in compared with non-fumigated treatment. Combined effects
of 99.5% acetic acid fumigation for 30 min and gamma irradiation at 400+-10 Gy on fruit rot disease
and quality oflongan fruit was studied during storage at l3 C for 28 days. The result showed that
acetic acid fumigation was able to reduce fruit rot disease of gamma irradiated longan fruit by 26-39%.
But the combined treatments of acetic acid fumigation and gamma irradiation resulted in
higher weight loss, browning of inner pericarp, and firmness of pericarp than gamma irradiated
treatment alone. However, the combined treatments did not affect on firmness of aril, aril colour
and electrolyte leakage of longan aril (pulp).