Ionizing radiation applications for food preservationeffects of gamma and e-beam irradiation on physical and chemical parameters of chestnut fruits

Resumen

[EN]In Mediterranean countries chestnut fruits represent an important food product with a high economic relevance in local economy. The production of European chestnut (Castanea sativa Mill.) varieties in E.U. countries represents more than 100 kton, with an income for the producers of several million of euros, value that increases along the market chain. These fruits are also exported to other countries that, due to international phytosanitary laws, impose the absence of insects. Until recently, the method used for chestnuts post-harvest disinfestation was chemical fumigation that is environment aggressive and toxic for the operators. Following the request for an urgent alternative for the agro-industry, that process and export these fruits, and considering that irradiation is a more environment friendly technology that could be used as an alternative, gamma and electron beam irradiation were tested and validated as a possible alternative. Food irradiation is already an industrial technology used for several items, nevertheless, its effects in specific food matrices should be studied and validated. Previous studies of irradiation effects in chestnuts were performed mainly in Asian varieties but in a limited number of parameters. In this research, a detailed study of the impact of gamma and electron-beam irradiation effects (dosis 0.25, 0.5, 1, 3, 6 kGy) on physical, chemical and antioxidant parameters of European chestnut fruits of Castanea sativa varieties (Cota, Judia and Longal from Portugal; and two varieties from Turkey and Italy), stored up to 60 days was performed. The physical parameters evaluated were the drying rate, colour and texture; chemical analyses included determination of the nutritional profile, dry matter, ash, proteins, carbohydrates, total energy, fatty acids, sugars, organic acids, tocopherols and triacylglycerols composition; the antioxidant properties were evaluated through free radicals scavenging activity, reducing power and inhibition of lipid peroxidation inhibition, as also determination of total phenolics and flavonoids. The effects on non-irradiated and gamma or electron-beam irradiated chestnuts were compared, as well as their interaction with storage time. Both types of irradiation showed to represent a suitable solution for chestnuts post-harvest treatment. With no exception, the storage time caused higher changes in physical, antioxidant and nutritional/chemical profiles than both irradiation types, confirming that this technology, at the applied doses, did not affected chestnut fruits quality. Qualitative changes were detected in the structure of certain fatty acid molecules, without affecting its total content. These results were described for the first time highlighting these parameters as possible indicators of irradiation processing. In fact, the main differences found in irradiated samples were related with storage time or different assayed cultivars. It was also analysed the irradiation feasibility and the economic impact of electron beam processing in chestnut fruits, considering that this technology could have more acceptance than gamma irradiation. This work addressed different areas of research focusing on a technological solution of a problem proposed by the agro-industry, bringing innovation to a traditional food product. Independently of the irradiation source, chestnut variety or geographical origin, gamma and electron beam irradiation is an environmental friendly alternative technology for chestnut post-harvest treatments that can substitute the chemical fumigation also presenting a positive contribute in the economy of fruit producers.