| Summary: | 碩士 === 國立屏東科技大學 === 食品科學系 === 94 === Gelatin, a hydrophilic protein, is the product from collagen through thermal denaturation. The primary sources of gelatins come from skins, bones, ligaments, and tendons of slaughtered mammals. Gelatin has been the most popular choice among gum markets due to its unique low viscosity, high elasticity, and the advantages of source and price. It has been extensively utilized in food, pharmaceutical, photographic films, and cosmetics industries. The consumers get occasional panic cause by epidemic diseases of raised animals, e.g., the mad cow disease earlier cause many cosmetics to retrieve from the market. The necessity indeed exist for the alternative sources of gelatins.
Tilapia (Tilapia mossambica Peters) has been the largest product on Taiwan aquatic farming. Tens of thousand people rely their living on the production and processing of tilapia. It has been designated as the flagship product for Taiwan fishery exports by Council of Agriculture, Taiwan in 2004. Cobia (Rachycentron canadum) is a rising star for offshore aquaculture fish farming. Fillet currently makes up the most amounts for export tilapia and cobia. There would be abundant residue of fish body after filleting which is currently underused. Therefore this study was aimed to explore the feasibility of better utilization of filleting byproducts in order to enhance the processing profit.
Gelatin was extracted from the skins of tilapia and cobia, respectively. Self-made gelatins were characterized and compared to commercially available gelatins which originated from pigskin, mammal bones (gelatine), agar, and market tilapia. All samples were subjected to physicochemical characterizations and were added to fish balls for examining the effects on the structure and texture. Viscosity measurements of thin gelatin solutions were conducted from 25 – 61 °C. The purchased tilapia gelatin exhibited a viscosity peak at 55 °C (rising temperature) and 58 °C, respectively. Pigskin gelatin showed the viscosity peaks at 52 °C and 58 °C, respectively; while gelatine registered at 52 °C and 55 °C. There were 46 °C and 49 °C for self-made tilapia skin gelatin, 49 °C and 52 °C for self-made cobia gelatin. Overall, commercially available gelatins had the denaturing temperature around 60 °C, yet less than 50 °C were general values for self-made fish gelatins. The above indicated a inferior characteristics of self-made gelatins when subjected to heat processing. With the gelatins incorporated into the fish balls, the results showed that purchased tilapia gelatin and pigskin gelatin exhibited the greatest improvement on the hardness, cohesiveness, springiness, and adhesiveness, while the self-made ones demonstrated lesser enhancement. Sensory evaluation revealed that 1.5 - 2 % of gelatin addition was the favorite products in appearance, yet 3% addition scored the lowest for appearance. 2% of gelatin addition was found to be the optimal for the flavor of fish balls, which was also the most appropriate amount for overall acceptability. Self-made cobia skin gelatin was found to be the most inferior one when compared to other gelatins by sensory evaluation.
Key words: gelatin, tilapia (Tilapia mossambica Peters), cobia (Rachycentron canadum), viscosity, gel strength, texture profile analysis
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