The purpose of this study was to evaluate changes in the quality characteristics of mackerel fish fillet under freezing storage conditions. The changes in product quality were determined by measuring pH, volatile basic nitrogen (VBN); thiobarbituric acid (TBA), lightness (L*), redness (a*), yellowness (b*) values, shearing force, and microbiological evaluation (Total Plate Count, TPC) during 21 days of storage at −20, −5, and −1 o C, and their shelf-lives were established. TPC as an effective quality indicator was used to estimate the shelf-life via linear regression analysis. The TPC increased steadily with increasing storage periods at every temperature (p<0.05) and showed a significant relationship with temperature at −1 o C (r=0.949), −5 o C (r=0.919), and −20 o C (r=0.905). Therefore, based on TPC, the shelf life of the mackerel fillet was noted to be 32 days when stored at −1 o C, more than 51 days when stored at −5 o C, and about 2 months when stored at −20 o C.

This study was conducted to establish roasting conditions for optimization of Citri Unshii Pericarpium antioxidant activity using response surface methodology (RSM). A central composite design was applied to investigate the effects of two independent variables, namely roasting temperature (40∼100°C; X1) and roasting time (5∼15 min; X2), on responses such as electron donating ability (Y1), total phenolic content (Y2), total flavonoid content (Y3), and hydroxyl radical scavenging activity (Y4). The maximum electron donating ability was 72.38% at a roasting temperature of 71.12°C and roasting time of 9.39 min. The maximum total phenolic content was 10.76 mg tannic acid equivalents/g at a roasting temperature of 69.71°C and roasting time of 8.39 min. The maximum total flavonoid content was 105.99 mg quercetin equivalents/100 g at 72.54°C and 8.64 min. The maximum hydroxyl radical scavenging activity was 60.33% at 68.97°C and 9.84 min. Based on the superimposition of three dimensional RSM with respect to electron donating ability, total phenolic content, total flavonoid content, and hydroxyl radical scavenging activity under various conditions, optimum conditions were established as follows: roasting temperature of 70.90°C and roasting time of 9.03 min.Key words: Citri Unshii Pericarpium, roasting conditions, antioxidant activity, response surface methodology, optimization