Production of gelatin from skins of red snapper (Lutjanus sanguineus (Cuv. & Val.) : Pisces)
1997
Wanwimol Klaypradit
Objectives of this study were to find out optimum conditions of gelatin production from skins of red snapper [Lutjanus sanguineus (Cuv. & Val.) : Pisces]. There were 3 steps in the experiment. The first step was preparing of raw material. In this step the optimum concentration of the sodium hydroxide, the optimum concentration of 3 acids, i.e. hydrochloric acid, sulfuric acid and phosphoric acid and the time for soaking of fish skins were studied. The concentrations of solution used were 0.1-0.4 percent (w/w) and soaking time used were 4 and 8 hours. The second step is extraction. In this step, the optimum time and temperature of extraction were studied. Temperature studied were 60, 70 and 80 deg C for 0.5, 1.0, 1.5 and 2.0 hours. The final step is drying and quality testing. The drying temperature used were 50 deg C for 18 hours. Sensory evaluations of jelly dessert made from fish gelatin were also performed. The results of this research showed that in the first step the optimum concentration for soaking fish skins to have a good swelling were 0.4 percent (w/w) NaOH for 4 hours and soaking in hydrochloric acid at a concentration of 0.4 percent (w/w) for 4 hours. In the second step the optimum condition for extraction were at 70 deg C for 90 min. The production yield was 13.25 percent (w/w) of raw material used. The properties of prepared gelatin were 113 (X 0.1 mm) of gel strength, 148 mp.viscosity, 8.71 percent moisture content, 0.41 percent ash and pH 4.67. The amino acid composition of gelatin comprised 16 amino acids. Sensory evaluation indicated the prepared dessert samples were acceptable in odor and texture but unacceptable in color and flavor.
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