Freshness Analysis of Raw Laver (Pyropia yenzoensis) Conserved under Supercooling Conditions

Abstract

Freezing raw laver is unsuitable for the laver industry due to process characteristics and economic problems. Therefore, this study attempted to investigate supercooled storage to extend the storage period without freezing, rather than refrigeration. To compare and analyze the storage ability of supercooling, the experiment was performed under refrigeration (5 °C), constant supercooling (CS, −2 °C), stepwise supercooling (SS, −2 °C), and freezing (−18 °C) conditions for 15 days, and the physicochemical changes according to the treatment and period were investigated. All SS samples, which were designed for stable supercooling, were kept in a supercooled state for 15 days. Two samples among the twelve total subjected to CS were frozen. At 9 days, the drip losses of the CS and SS samples were 6.32% and 6.48%, respectively, which was two times lower than that of refrigeration and three times lower than that of the frozen samples. The VBN of the refrigerated samples was 108.33 mg/100 g at 6 days, which exceeded the decomposition criterion. Simultaneously, the VBN of the other treatments was under the decomposition criterion of 30 mg/100 g. However, the VBN of both supercooling samples at 15 days increased to higher than the decomposition criterion. Regarding appearance, the refrigerated samples showed tissue destruction at 9 days, but tissue destruction of the CS and CC samples was observed at 15 days, and tissue destruction of the frozen samples was not observed until 15 days. Consequently, supercooling did not maintain quality for longer periods than freezing, but it did extend the shelf life more than refrigeration, and effectively preserved the quality for a short period.