Effect of exogenous melatonin treatment onAspergillusdecay, aflatoxin B1 accumulation and nutritional quality of fresh “Akbari” pistachio fruit

Abstract

This study aimed to investigate the mechanisms activated by melatonin treatment for attenuating Aspergillus decay, suppressing aflatoxin B1 (AB1) accumulation, and preserving nutritional quality in fresh pistachio fruits during storage at 25°C for 18 days. At 6-day intervals, samples from each of three replications were selected, and subjected to biochemical analysis. Our results showed that fresh pistachio fruits treated with 1,000 µM melatonin and inoculated with Aspergillus flavus, exhibited lower Aspergillus decay accompanied by lower endogenous AB1 accumulation. Melatonin treated fruit also showed lower H2O2 and malondialdehyde accumulation during storage. Furthermore, higher linolenic acid accumulation accompanied by higher phenols and flavonoids accumulation as well as superior DPPH scavenging capacity in fresh pistachio fruits treated with 1,000 µM melatonin, could be ascribed to lower lipoxygenase and higher phenylalanine ammonia-lyase enzymes activity, respectively, during storage. Besides, melatonin applying at 1,000 µM suppressed spore germination and germ tube elongation in A. flavus. Practical applications Aflatoxin B1 (AB1) accumulation as carcinogenic mycotoxin in pistachio fruits during Aspergillus flavus infection have been considered as a risk for human health. Since ROS generating from kernels could be responsible for triggering A. flavus growth and AB1 biosynthesis. Therefore, alleviating oxidative stress by melatonin treatment not only could be operative for attenuating fungal decay and decreasing AB1 accumulation but also could be favorable for maintaining the quality of fresh pistachio fruits.