고주파 해동이 동결 어류의 물리화학적 특성에 미치는 영향

Abstract

Freezing is one of the most important preservation technologies, especially for marine fishes because of their high susceptibility to spoilage. Thawing is a common and essential part of frozen fishery products for processing as food material. But inappropriate thawing process affects the texture and taste of fish muscle. Radio frequency thawing (RFT) is a new technology that provides uniform thawing to the entire part of the frozen product using frictional heat by rotation-vibration motion among the molecules. The movement of the energy is provided by the electro-magnetic wave in a conductor. This is known as a high speed and high quality thawing method comparing to conventional natural thawing (NT). But there is very limited research work has been done for using RFT to apply in frozen fish processing. The objective of this study was to measure and evaluate the advantage and quality parameters of RFT compared with NT on commonly consumed marine fishery products in Korea namely: Spanish mackerel (Scomberomorus niphonius), mackerel (Scomber japonicus), Alaska pollock (Gadus chalcogramus, formerly Theragra chalcogramma), croceine croaker (Larimichthys crocea) and squid (Doryteuthis bleekeri). Different physico-chemical and biological parameters such as temperature change, water holding capacity, drip loss, extractive-nitrogen, viable cell count, coliform count, acid value and peroxide value of RFT and NT treated samples were measured. Thawing time at appropriate temperature was 2 ~ 3 hours in RFT where as it was 24 hours in NT. Expressible drip loss was 2.25 ± 1.06% and 4.42 ± 1.80% by RFT and NT respectively. RFT showed higher values of extractive-nitrogen content of 392.16 ± 42.10 mg/100 g than NT of 315.30 ± 42.07 mg/100 g. Viable cell and coli form were counted 102 CFU/g to 104 CFU/g and 102 CFU/g in case of RFT whereas the values were 103 CFU/g to 105 CFU/g and 104 CFU/g in case of NT products. The acid value and peroxide values were found 7.89 ± 4.78 mg KOH/g and 14.04 ± 3.71 meq/kg, 9.86 ± 4.52 mg KOH/g and 27.87 ± 5.56 meq/kg for RFT and NT respectively. This result demonstrated higher thawing quality of RFT than NT. So, RFT is expected to play a major role in thawing frozen fish for high quality fishery products development.