Gamma and electron beam irradiation as an alternative for postharvest treatment: a case study with chestnuts

Chestnut fruits are an important food commodity in the Northeast region of "Trás-osMontes", representing an income of approximately 17 M€ and being Porn1gal one of the: world's biggest producer. Due to environmental concerns a broad spectrum fumigant, methyl bromide, was banned in 20 I 0 by the European Union. Since then, no adequate postharvest treatment has been implemented, fostering research on suitable alteratives. Our research group has been testing gamma and electron beam irradiation as an alternative postharvest treatment for chestnuts. On a first attempt to evaluate the influence of irradiation, various doses were tested (0, 0.5, I, 3 and 6 kGy) along different storage times (0, 30 and 60 days). The effects were assessed in the most important chemical parameters, namely nutritional, antioxidant, sugar, fatty acid, tocopherol, organic acid and triacylglyccrol profiles, in which, all seemed to be altered to a greater extent by storage time than by the different doses. Another important conclusion was the validation of I kGy as the optimal dose for chestnuts conservation. This conclusion sustained the venture to extend the study to four varieties (Longal, Judia, Cotaand Palummina) with a fixed dose of I kGy for both gamma radiation and electron beam. The results were processed through principal component analysis and confined that both gamma (1) and electron beam (2) irradiation showed high potential to be used as postharvest conservation technology. The most marked differences were found between the four different cultivars, especially Cola and Palummina, while non-irradiated and irradiated chestnuts proved to have very similar profiles in all the assayed parameters, with irradiation having an attenuating effect.