초정수압처리 및 감마선 조사가 urease 활성에 미치는 영향

Abstract

Urease is an enzyme that catalyzes the hydrolysis of urea to carbon dioxide and ammonia. Fish loses freshness and deteriorate quickly due to the enzymatic activity by the food pathogenic microorganisms. The high water activity and high protein content of fish results in the fast growth of microorganisms, leading to undesirable changes especially fishy smell and bad odor. The presence of urea causes a fishy smell, so it is important to inhibit urease activity to maintain freshness. In this study, the urease coenzyme extracted from the Vibrio parahaemolyticus strain was purified through 65% salting out, dialysis, and Sephadex G-50 Chromatography. Analysis of the purified enzyme by SDS-PAGE confirmed the presence of a subunit with a molecular weight of about 59 kDa. The inhibitory effect of urease extracted from Vibrio parahaemolyticus strain was investigated by high hydrostatic pressure(2000, 3000, 4000 bar) and gamma irradiation (3, 7, 10, 20 kGy). In addition, physical and chemical changes of Mackerel fish related to urease were confirmed through volatile basic nitrogen(VBN), and ammonia nitrogen during storage for 20 days in the refrigerator by high hydrostatic pressure and gamma irradiation of mackerel meat. As a result, the urease activity by high hydrostatic pressure and gamma irradiation decreased as the treatment intensity increased. As for VBN, the super hydrostatic treatment significantly decreased compared to the untreated group on the 10th day, and it was confirmed that the untreated group showed a complete decay level on the 20th day of storage, while the high hydrostatic treated group significantly decreased. The results suggested that the increased rate of ammonia nitrogen in the 2000, 3000, and 4000 bar high hydrostatic treated groups decreased by 23.8%, 23.8%, and 31.0%, respectively, than the compared to untreated groups. VBN showed a significant difference from the non-irradiated group when gamma-irradiated groups on the 10th day, which showed a high value on the 20th day. The results suggested that the increased rates of ammonia nitrogen in the 3, 7, 10 and 20 kGy gamma irradiation groups decreased by 20.86%, 23.85%, 24.42% and 25.58% respectively, compared to the untreated groups. From these results, it is revealed that high hydrostatic pressure and gamma irradiation have the potential to be effectively used to reduce the activity of urease for the preservation of fish.