Preservation of salted, vacuum-packaged, refrigerated sea bream ( Sparus aurata) fillets by irradiation: microbiological, chemical and sensory attributes

Abstract

The effect of gamma irradiation (1 and 3 kGy) on the shelf-life of salted, vacuum-packaged sea bream ( Sparus aurata) fillets stored under refrigeration was studied by monitoring the microbiological, chemical and organoleptic changes occurring in fish samples. Non-irradiated, salted, vacuum-packaged fish served as control samples. Irradiation affected populations of bacteria, namely, Pseudomonas spp., H 2S-producing bacteria, Brochothrix thermosphacta, Enterobacteriaceae and lactic acid bacteria. The effect was more pronounced at the higher dose (3 kGy) applied. Of the chemical indicators of spoilage, trimethylamine (TMA) values of non-irradiated, salted sea bream increased slowly to 8.87 mg N (100 g) −1 flesh (whereas for irradiated, salted samples significantly lower values were obtained, reaching a final TMA value of 6.17 and 4.52 mg N (100 g) −1 flesh at 1 and 3 kGy, respectively (day 42). Total volatile base nitrogen values increased slowly attaining a value of 60.52 mg N (100 g) −1 for non-irradiated, salted sea bream during refrigerated storage whereas for irradiated fish, lower values of 48.13 and 37.21 mg N (100 g) −1 muscle were recorded at 1 and 3 kGy, respectively (day 42). Thiobarbituric acid values for irradiated, salted sea bream samples were higher than respective non-irradiated (salted) fish, and increased slowly until day 28 of storage reaching final values of 1.01 (non-irradiated, salted), 2.15 (1 kGy) and 3.26 mg malonaldehyde kg −1 flesh (3 kGy), respectively (day 42). Sensory evaluation (taste) showed a reasonably good correlation with bacterial populations. On the basis of sensorial evaluation, a shelf-life of 27–28 days was obtained for vacuum-packaged, salted sea bream irradiated at 1 or 3 kGy, compared to a shelf-life of 14–15 days for the non-irradiated, salted sample.