Effect of Double Freezing and Subsequent Long-Term Refrozen Storage at −23 °C on the Quality of Inshore Male Capelin (Mallotus villosus)

Abstract

Whole inshore male capelin (Mallotus villosus) were stored at −23 °C for 2 mo (C2), or 6 mo (C6) prior to thawing, beheading and eviscerating, and refreezing. Though the quality of the twice-frozen product was in both cases inferior to a once-frozen sample, it was still quite acceptable after 2 yr of refrozen storage. As expected, quality was superior in the C2 samples, but in both sets of samples taste deteriorated to a greater extent than texture. Chemical measurement of peroxide value indicated a possible development of rancidity that could not be detected by sensory analysis. Considerable lipid hydrolysis occurred, with the free fatty acids (FFA) at least doubling during storage; increases were greater in C6. In both experiments FFA production correlated with texture, taste, and with extractable protein nitrogen (EPN). Dimethylamine (DMA), trimethylamine (TMA), hypoxanthine, and EPN appeared to be good indicators of storage time and sensory quality. Key words: capelin, dimethylamine (DMA), extractable protein nitrogen (EPN), free fatty acids (FFA), hypoxanthine, peroxide value, refrozen storage, taste, texture, trimethylamine