Journal ofthe Science ofFood and AgricultureJ Sci Food Agric 85:779–784 (2005)DOI: 10.1002/jsfa.2021Shelf-life extension of vacuum-packaged seabream (Sparus aurata) fillets by combinedγ-irradiation and refrigeration: microbiological,chemical and sensory changesIrene Chouliara, Ioannis N Savvaidis, Kyriakos Riganakosand Michael G Kontominas∗Laboratory of Food Chemistry and Technology, Section of Industrial and Food Chemistry, Department of Chemistry, University of Ioannina,Ioannina 45110, GreeceAbstract: The combined effect of γ-irradiation and refrigeration on the shelf-life of vacuum-packagedsea bream (Sparus aurata) fillets was studied by monitoring the microbiological, chemical and sensorychanges ofnon-irradiated and irradiated fish samples using low-dose irradiation doses of1 and 3 kGy. Fishspecies such as sea bream and sea bass are very popular in the Mediterranean countries due to their highquality characteristics, and their preservation is a constant challenge given their extreme perishability.Irradiation (3 kGy) dramatically reduced populations of bacteria, namely, total viable counts (3 vs 7 logcfug−1) for the non-irradiated samples, Pseudomonas spp (<2 vs 7.6 log cfug−1), H2S-producing bacteriatypical of Shewanella putrefaciens (<2 vs 5.9 log cfug−1), Enterobacteriaceae (<2 vs 6.0 log cfug−1) andlactic acid bacteria (<2 vs 3.5 log cfug−1) after 10days of storage. The effect was more pronounced atthe higher dose (3 kGy). Lactic acid bacteria, Enterobacteriaceae and H2S-producing bacteria typicalof Shewanella putrefaciens showed higher sensitivity to γ-radiation than did the rest of the microbialspecies. Ofthe chemical indicators ofspoilage, Trimethylamine (TMA) values ofnon-irradiated sea breamincreased very slowly, whereas for irradiated samples significantly lower values were obtained reaching afinal value of 7.9 and 6.3 mg N per 100g muscle at 1 and 3 kGy respectively (day 42). Total volatile basicnitrogen (TVB-N) values increased slowly attaining a value of67.3 mg N per 100 g for non-irradiated seabream during refrigerated storage, whereas for irradiated fish, lower values of 52.8 and 43.1 mg N per100g muscle were recorded (day 42). Thiobarbituric acid (TBA) values for irradiated sea bream sampleswere higher than respective non-irradiated fish and increased slowly until day 21 ofstorage, reaching finalvalues of 1.1 (non-irradiated), 2.0 (1 kGy) and 2.2 mg malonaldehyde kg−1muscle (3 kGy), respectively(day 42). Sensory evaluation showed a good correlation with bacterial populations. On the basis ofoverallacceptability scores (sensory evaluation) a shelf-life of28 days (3 kGy) was obtained for vacuum-packagedsea bream, compared with a shelf-life of9–10 days for the non-irradiated sample.? 2004 Society ofChemical IndustryKeywords: shelf-life; sea bream; γ-irradiationINTRODUCTIONFish and fisheryproducts are highlyperishable foods ascompared with other food commodities. The micro-bial load of seafoods may be initially either low orhigh, increasing with storage and ultimately lead-ing to spoilage. It is well documented that themicroflora of temperate marine fish consists of cer-tain species ofpsychrotrophic Gram-negative bacteriabelongingto the genera Pseudomonas, Moraxella, Acine-tobacter, Shewanella, Flavobacterium, Vibrionaceae, aswell as Gram-positive bacteria belonging to the gen-era Clostridium, Lactobacillus and Corynebacterium.Only certain bacterial species are responsible forfish spoilage, including Pseudomonas spp and H2S-producing bacteria.1 –3Photobacterium phosphoreum, aGram-negative bacterium, was also found to dominatethe spoilage microflora offresh MA-packed cod.4Since global demand for fresh fish has increasedsignificantly over the past decade, there is an obviousneed for efficient fish preservation methods. Twotypes of fish that are very popular in Mediterraneancountries include sea bream and sea bass, marketedeither as whole or filleted products. Given that largequantities of such fish species are consumed bothdomestically and exported abroad (eg to Italy), itis very important to extend their shelf-life, which∗Correspondence to: Michael G Kontominas, Laboratory of Food Chemistry and Technology, Section of Industrial and Food Chemistry,Department of Chemistry, University of Ioannina, Ioannina 451 1 0, GreeceE-mail: mkontomi@cc.uoi.gr(Received 6 January 2003; revised version received 14 July 2004; accepted 24 September 2004)Published online 1 0 December 2004? 2004 Society ofChemical Industry. J Sci Food Agric 0022–5142/2004/$30.00779
