The effect of low-dose gamma irradiation on the yeasts of British fresh sausage

Abstract

The effect of low-dose gamma irradiation (1·5 and 3 kGy) on the yeasts of British fresh sausage was investigated. Irradiation had a significant lethal effect on yeast numbers and also affected the composition of the yeast microflora of sausages containing sulphite preservative (S) and unsulphited (US) sausages. Levels of radiation resistance differed between yeast genera. Trichosporon spp. (in particular T. cutaneum) demonstrated greatest radiation resistance, and dominated the initial microflora of both US and S samples irradiated to a dose of 3 kGy. After storage at 4°C for 7 and 14 days Trichosporon spp. were isolated from irradiated (3 kGy) US samples but not from irradiated (3 kGy) S samples. In contrast, Debaryomces spp. were greatly reduced in number by a 1·5 kGy treatment and were only isolated from unirradiated samples after storage at 4°C for 7 and 14 days. Candida spp. (in particular C. zeylanoides) constituted the major microfloral component of both types of sausage initially and persisted after an irradiation dose of 3 kGy, suggesting that they may possess an inherent resistance to irradiation (D s 3·3 kGy, D 10 sig 0·3 kGy). Of the yeast strains studied, Sporobolomyces roseus exhibited least radiation resistance. After 14 days storage at 4°C, no significant differences between the numbers of yeasts in unirradiated S samples and 1·5 kGy US samples were found indicating that low-dose irradiation may serve as an alternative treatments to sulphite preservation for sausages.