Process Optimization and QualityEvaluation of Gwamegi fromPacific Saury (Cololabis saira) using Response Surface Methodology

Abstract

Drying- freezing process and quality evaluation of Gwamegi from Pacific Saury was optimized by using response surface methodology. A fractional 3-level-3-factor experimental design which consisted of 15 experimental treatments and three replicates at the center points, was adopted to see the effect of such independent variables as drying cycles (4-12 numbers), drying temperature (5-15 °C) and drying time (3-5 hours) on the responses of moisture content (%), weight loss (%), volatile basic nitrogen (mg/100g) and trimethyl amine. Data were analyzed using SAS statistical software and a second-order polynomial models were obtained for predicting the response. Also, the 3-dimensional graphs were drawn with Maple 8 software. From regression analyses, the coefficient of regressions (R2) for moisture content, weight loss, VBN and TMA were 0.9519, 0.8578, 0.9691 and 0.8230 respectively, showing that moisture content and VBN fits better in a model. The minimum and maximum values of moisture content, weight loss, VBN and TMA ranged from 27.73 ± 0.39% to 50.45 ± 0.64%, 22.98 ± 0.94% to 52.49±0.58%, 6.3 ± 0 to 16.8 ± 1.98 mg/100g and 40 ± 3.67 to 117.85± 3.34 respectively. The optimal drying conditions are temperature of 15.6 °C, time of 5.1 hours and drying cycles of number 12. Drying temperature has the most significant effect followed by drying cycle and drying time. These results provide us with the basic information required to control qualities of Gwamegi and other dried fish and fishery products.