Effects of packaging methods and materials on quality of prepared crisp grass carp (Ctenopharyngodon idellus C. et V) fillets during cold storage

Abstract: Crisp grass carp (Ctenopharyngodon idellus C. et V) is a grass carp fed with broad bean as the sole food, but it is very different from ordinary grass carp and famous for its unique taste (more compact and crisper than ordinary grass carp). However, the shelf life of the products is limited due to the high protein content. The study was to investigate the effects of packaging methods and packaging materials on the quality of prepared crisp grass carp fillets, which were marinated in the water extract from Perilla leaf during the storage at 4 ℃. The results showed that the total bacteria count grew the fastest in prepared crisp grass carp with air-conditioned packaging (AP), whereas the lowest count of total bacteria was found in the sample with modified atmosphere packaging (MAP) during chilled storage at 4 ℃. On the 15th day during the storage, the average of total bacteria count of the fillets with MAP reached 5.61 log CFU/g, which didn’t exceed the limitation at the end of the shelf life of aquatic products, while the total bacteria counts of the fillets with other 2 packaging methods, i.e. vaccum packaging (VP) and AP exceeded that limitation. At the end of the storage, the drip loss rate, TVB-N (total volatile basic - nitrogen) value and TBA (thiobarbituric acid) value of the prepared crisp grass carp fillets packaged with MAP were lower than that with VP and AP. For these samples packaged with MAP and PVC (polyvinyl chloride) taken as the material, the drip loss rate reached 5.07% on the 15th day. At the same time, the TVB-N value reached 13.91 mg/100 mg, which was less than the secondary freshness in national standard. The preservation life of prepared crisp grass carp fillets was more than 15 d with MAP during chilled storage at 4 ℃. In addition, TBA values of the fillets with MAP were lower than that with VP and AP by 16.40% and 46.46%, respectively. During the whole storage, the texture of samples with MAP decreased more slowly than that with VP and AP. Moreover, the hardness of prepared crisp grass carp fillets with MAP at the end of storage was 26.41% and 27.08% higher than that of the other 2 groups, respectively. For sensory evaluation, the sensory scores of fillets were not significantly different between MAP and VP. However, the average scores of MAP and VP were about 2.00 higher than that with AP. For packaging materials, the differences of the quality among them were very significant. The differences of hardness, drip loss rate, TBA value and sensory score between different packaging materials were significant during chilled storage at 4 ℃. More importantly, packaging material is one of the most important factors affecting the quality of prepared crisp grass carp fillets, and the prepared crisp grass carp packaged with the NY/EVOH/PET composites possessing high barrier properties had the best freshness. In summary, this paper provides the reference for the application of MAP and the material with high barrier properties in the preservation of prepared crisp grass carp fillets. MAP and the material with high barrier properties are more conducive to keeping the quality of prepared crisp grass carp fillets during chilled storage at 4 ℃.