Control of Natural Microbial Flora and Listeria monocytogenes in Vacuum-Packaged Trout at 4 and 10° C Using Irradiation

Abstract

The effect of gamma irradiation on the natural microflora of whole salted vacuum-packaged trout at 4 and 10 degrees C was studied. In addition, the effectiveness of gamma irradiation in controlling Listeria monocytogenes inoculated into trout was investigated. Irradiation at doses of 0.5 and 2 kGy affected populations of bacteria, namely, Pseudomonas spp., Brochothrix thermosfacta, lactic acid bacteria, H2S-producing bacteria typical of Shewanella putrefaciens, and Enterobacteriaceae, at both 4 and 10 degrees C. This effect was more pronounced at the higher dose (2 kGy) and the lower temperature (4 degrees C). Pseudomonads, H2S-producing bacteria typical of S. putrefaciens, and Enterobacteriaceae showed higher sensitivity to gamma irradiation than did the rest of the microbial species. Sensory evaluation did not show a good correlation with bacterial populations. On the basis of sensory odor scores, a shelf life of 28 days (2 kGy, 4 degrees C) was obtained for salted vacuum-packaged freshwater trout, compared with a shelf life of 7 days for the unirradiated sample. Under the same conditions, the growth of L. monocytogenes inoculated into the samples was suppressed by 2 log cycles after irradiation (2 kGy) and storage for up to 18 days at 4 degrees C.

Effect of Chilling on Microbiological, Biochemical and Sensory Attributes of Whole Aquacultured Rainbow Trout (Oncorhynchus mykiss Walbaum, 1792)

“…[36]. These values obtained in this study are close to the values reported earlier for aquacultured fresh trout from Spain [37,41], Greece [38,39] and U.K [40]. It is widely accepted that the initial microbial load of fresh water varies depending on water conditions and temperature.…”

Effects of Vacuum-packaging on the Microbiological, Chemical, Textural and Sensory Changes of the Solar Rack Dried Sardines During Chill Storage

“…This was in agreement with the works on temperate marine fish (Drosinos et al, 1997;Koutsoumanis and Nychas, 1999) and temperate fresh water fish work of Savvaidis et al (2002) where S. aureus count was 1.2 log 10 CFU gG 1 . All samples registered a 0.2 log reduction counts on the day of sensory rejections which were all within the prescribed limits for fresh dried fish recommended by ICMSF (1986).…”

Effects of ionizing radiation and modified atmosphere packaging on the shelf life of aqua-cultured sea bass (Dicentrarchus labrax)

“…Besides traditional methods involving rapid chilling and ice storage, MAP (Debevere and Boskou 1996;Masniyom et al 2002;Fagan et al 2004) and ionizing radiation treatment (Savvaidis et al 2002) have been used in food preservation giving significant results. MAP treatment improves the food shelf life by means of the use of different gases in the internal atmosphere of the food package: in fact, suitable gas mixtures can retard the microbiological growth (Banks et al 1980;Gibson and Davis 1995) in the fish by creating environmental conditions unfavorable to the microbial growth.…”