Abstract

We evaluated the effect of gamma irradiation doses (0, 125, 250, and 500 Gy) in control of psychrotrophic bacteria in different strains of Agaricus bisporus (ABI-07/06, ABI-05/03, and PB-1) during storage, cultivated in composts based on oat straw (Avena sativa) and Brachiaria spp. The experimental design was completely randomized in a factorial scheme 4 ´ 2 ´ 3 (irradiation doses ´ composts ´ strains), with 24 treatments, each consisting of 2 replicates, totaling 48 experimental units (samples of mushrooms). The mushrooms collected from all culture conditions were packaged in plastic polypropylene with 200 g each and subjected to Cobalt-60 irradiator, type Gammacell 220, and dose rate 0.740 kGy h^–1, according to the treatments. Subsequently, the control (nonirradiated) and other treatments were maintained at 4 ± 1°C and 90% relative humidity (RH) in a climatic chamber to perform the microbiological analysis of mushrooms on the 1st and 14th day of storage.According to the results, it was found that the highest mean colony psychotrophic count, after 14 days of storage, was observed in strain ABI-07/06 [1.30 × 10⁸ g^-1 most probable number (MPN)] in nonirradiated mushrooms, coming from Brachiaria grass-based compost, and this same strain under the same storage conditions, coming from the same type of compost that underwent a dose of 500 Gy, obtained a significant reduction in mean colonies of psychrotrophic bacteria (2.25 × 10⁴ g^–1 MPN). Thus, the irradiation doses tested favored reducing the number of colonies of psychrotrophic bacteria, regardless of the type of compound and strain of A. bisporus.

Key words: Champignon, shelf life, postharvest, mushrooms.