Postharvest application of brassica meal-derived allyl-isothiocyanate to kiwifruit: effect on fruit quality, nutraceutical parameters and physiological response

The use of natural compounds to preserve fruit quality and develop high value functional products deserves attention especially in the growing industry of processing and packaging ready-to-eat fresh-cut fruit. In this work, potential mechanisms underlying the effects of postharvest biofumigation with brassica meal-derived allyl-isothiocyanate on the physiological responses and quality of 'Hayward' kiwifruits were studied. Fruits were treated with 0.15 mg L^-1 of allyl-isothiocyanate vapours for 5 h and then stored in controlled atmosphere (2% O₂, 4.5% CO₂) at 0 °C and 95% relative humidity, maintaining an ethylene concentration <0.02 μL L^-1. The short- and long-term effects of allyl-isothiocyanate on fruit quality traits, nutraceutical attributes, glutathione content, antiradical capacity and the activity of antioxidant enzymes were investigated. The treatment did not influence the overall fruit quality after 120 days of storage, but interestingly it enhanced the ascorbic acid, polyphenols and flavan-3-ol content, improving the antioxidant potential of kiwifruit. The short-term effect of allyl-isothiocyanate was evidenced by an increase of superoxide dismutase activity and of oxidative glutathione redox state, which were restored 24 h after the treatment. The expression levels of genes involved in detoxification functions, ethylene, ascorbate and phenylpropanoid biosynthesis, were also significantly affected upon allyl-isothiocyanate application. These results suggest that allyl-isothiocyanate treatment probably triggered an initial oxidative burst, followed by an induction of protective mechanisms, which finally increased the nutraceutical and technological value of treated kiwifruits.