Effects of gamma rays on sugars composition of wild mushrooms from the Northeast of Portugal

Mushrooms are one of the most perishable products and tend to lose quality right after harvest. The short shelf-life of mushrooms (1-3 days at ambient temperature) is an impediment to the distribution and marketing of the fresh product. Despite of the immense popularity of this food in the Northeast of Portugal, one of the European regions with higher wild edible mushrooms diversity, and their increase exportation to foreign countries (particularly Spain, France and Italy), data regarding alternative technologies to increase mushrooms shelf-life are scarce. Treatment by irradiation emerges as a possible conservation technique that has been tested successfully in several food products such as mangoes, strawberries, etc., and is regulated by the European Union (EU) by Directive (EC) No 1999/2/EC. Studies evaluating the effects of ionizing radiation are available mainly in cultivated species such as Agaricus bisporus, Lentinus edodes and Pleurotus ostreatus. This study shows the effect of gamma radiation on the preservation of the nutritional composition more specifically, sugars content and profile in wild samples of Lactarius deliciosus and Macrolepiota procera from Northeast Portugal. The irradiations were performed in a experimental equipment with four 60Co sources, with a total activity of 305 TBq (8.233 kCi) in November 2011, after calibration with a standard Fricke dosimeter. Free sugars were determined immediately after irradiation, and after 4 and 8 days of storage using high performance liquid chromatography coupled to a refraction index detector (HPLC-RI). It was possible to observe maintenance of the most abundant sugars, mannitol and trehalose, and a smaller rate of decrease of sugars (mainly reducing sugars) in the irradiated samples, along storage. This is in agreement with the results reported by other authors for gamma irradiated Hypsizygus marmoreus [1] or electron beam irradiated Agaricus bisporus with low doses (0.8 and 1 kGy, respectively) [2]. Overall, irradiation could be an alternative to ensure the quality and extend the life of mushrooms, protecting their sugars composition. Acknowledgements: FCT and COMPETE/QREN/EU for research project PTDC/AGR-ALI/110062/2009; POPH-QREN and FSE for BD/76019/2011 grant to A. Fernandes and A.L. Antonio thanks to FCT grant SFRH/PROTEC/67398/2010. References: [1] Xing Z., Wang Y., Feng Z., Zhao Z., Xinghua L. (2007). Effects of 60Co-irradiation on postharvest quality and selected enzyme activities of Hypsizygus marmoreus fruit bodies. J. Agric. Food Chem., 55, 8126-8132.[2] Duan Z., Xing Z., Shao Y., Zhao X. (2010). Effect of electron-beam irradiation on postharvest quality and selected enzyme activities of the white button mushroom, Agaricus bisporus. J. Agric. Food Chem., 58, 9617–9621.