Effects of Processing Conditions on Nutritional Qualities of Seafood -2. Effects of Cryoprotectants on the Protein Qualities of Pollock Surimi-

해양식량자원의 가공조건별 영양적 품질평가 -2. 명태연육 단백질품질에 미치는 냉동변성방지제의 영향-

To determine the optimal level of cryoprotectant on the denaturation of pollock surimi produced in Korea, the relative cryoprotective effects of crystalline sorbitol alone and in combination with sucrose were assessed. Freeze induced protein denaturation was also studied as affected by polyphosphates and maltodextrin during frozen storage at $-25^{\circ}C$ for 16 weeks. Variables evaluated included salt extractable protein, drip loss and in vitro protein quality. The best cryoprotective effect was achieved from sucrose/sorbitol 1:1(w/w) mixture at $8\%$ with $0.2\%$ sodiumpyrophosphate and sodiumtriphosphate(1:1, w/w) in surimi by measurement of salt extractable protein and drip loss. Those cryoprotectants had little effect on surimi protein quality during frozen storage as measured by trypsin inhibitor(TI), protein digestibility and computed protein efficiency ratio(C-PER). Protein digestibility of surimi was not changed significantly by polyphosphate and maltodextrin at various levels(p<0.05), with the exception of 4 or $6\%$ sorbitol and $10\%$ sucrose alone which resulted in a higher digestibility. $8\%$ sorbitol/sucrose (5:3, w/w) treatment without polyphosphates showed the highest cryoprotective effectiveness from digestibility assay.

명태연육 냉동변성을 억제할 수 있는 냉동변성방지제의 적정량을 알아보기 위하여 crystalline sorbitol을 비롯한 세가지의 변성방지제 및 sorbitol/sucrose 혼합제제를 첨가하 여 $-25^{\circ}C$에서 16주간 저장했을 때의 단백질품질 변화를 실험하였다. $8\%$ 수준의 sucrose-sorbitol 혼합제제(1:1, w/w)를 $0.2\%$ Na-pyrophosphate/ Na-triphosphate(1:1)와 병용하였을 때 drip loss가 가장 적었으며, 염용성단백질량은 가장 많았다. 또한 혼합제제를 사용했을 때는 trypsin inhibitor량, 단백질소화율 및 단백효율비의 변화가 거의 없어 단백질품질 보전에 효과적이었으나, 냉동변성방지제를 처리하지 않았을 경우에는 단백효율비와 소화율은 급격히 떨어졌었다. Polyphosphate나 maltodextrin의 경우에는 처리 농도가 증가하여도 소화율저하 방지에는 별효과가 없었으나, $4{\sim}6\%$의 sorbitol, 또는 $10\%$수준의 sucrose는 polyphosphate를 병용하지 않아도 소화율저하는 효과적으로 막을 수 있었다. $8\%$ 수준의 sorbitol/sucrose 혼합제제(5:3, w/w)처리가 소화율 보전효과로 볼 때 냉동연육의 단백질품질저하 방지에 가장 효과적이었다.