Freshness indicators of defrosted fillets ofLepidocybium flavobrunneumin vacuum skin packaging/VSP packaging during cold storage

Abstract

The aim of study was to monitor chemical parameters (pH, total volatile basic nitrogen, trimethylamine, free fatty acids, peroxide value, and thiobarbituric acid assay) in the samples of defrosted fi llets of escolar (Lepidocybium fl avobrunneum) fi sh, packed in vacuum skin packaging (VSP) during 15 days of storage at +2±2 ºC. Comparison was done with fi llets packed in vacuum (control samples). The obtained results from our research showed that VSP packaging can be recommended, as it showed slightly better stability than vacuum packaging. The initial values of total volatile basic nitrogen (TVBN) content (in mg/100 g) in fi sh samples were low (vacuum 16.36±0.65; VSP 16.67±0.45) and these values did not change signifi cantly until day 9. TVBN was signifi cantly higher (P<0.05: vacuum 23.31±2.41, VSP 21.76±2.08) in samples analysed after 9 days of storage. Similar results were found during estimation of free fatty acids content. Trimethylamine (TMA) content was in the correlation with storage time in the same way as total volatile basic nitrogen content. During the experiment, the highest peroxide value expressed in meqO 2 kg -1 (vacuum 1.77±1.38; VSP2.16±0.11) and thiobarbituric acid assay content expressed in mg kg -1 (vacuum 4.20±0.43; VSP 4.10±2.61) were relatively low.Keywords: escolar fi sh, freshness, chemical changes, lipid oxidation Escolar fi sh, Lepidocybium fl avobrunneum, fi llets without skin are a regular part of seafood menu in the Czech Republic. The transportation of this fi sh to the Czech Republic may last several days (ca. 2-4 days) due to the remote areas of the catch of this fi sh (Pacifi c Ocean) and follow-up manipulations within the logistic fl ow of materials. After thawing in the Czech Republic, fi sh are fi lleted, re-vacuum packaged (consumer packages of various weights), and sold with the warning that it is a thawed product (EC, 2011). The shelf-life of this repacked product is 9 days from the date of packaging. Escolar fi sh contains very high amounts of oil and the oil composition of this species differs from most seafood due to the presence of wax esters, which are responsible for diarrheal effects on consumers (NICHOLS et al., 2001). Fish packed in vacuum are commonly sold in the Czech Republic in contrast to fi sh packaged by vacuum skin manner. Darfresh vacuum skin packaging (VSP) of fi sh is an innovative method, which also extends the shelf-life of fi sh, while offering the possibility of microwave heating of fi sh together with the packaging.The aim of this research was to evaluate freshness parameters of defrosted escolar fi sh samples during 15 days of storage at +2±2 ºC. Samples were VSP as experimental samples and vacuum packed as control samples, because escolar (Lepidocybium fl avobrunneum) fi sh can only be placed on the market in packaged form. In conformity with Regulation (EC, 2008), the fi llets of escolar fi sh are placed on the market in vacuum packaging and labelled