Application of Indicator Film from Butterfly Pea Flower Extract for Detecting Freshness of Fish Fillets

Abstract

          Color of anthocyanin extract from butterfly pea is bright and can easily be changed by pH value, so it can be used as pH indicator. The objectives of this study were to produce the freshness indicator for application with two fish fillets (pangasius dory and salmon). The indicator film was prepared by using 2 (% w/v) carboxymethyl cellulose incorporating with butterfly pea extracts at pH 4. For evaluating the efficacy of film as pH indicator by immersion test, the results found that the color of indicator film can be changed immediately after immersing films into different pH buffers (pH values of 2 to 9). At pH 2, the indicator film exhibited a pink color. When the pH value increased, its color was changed as more purple to blue shade and became a green color at pH 7. Likewise, vapor diffusion test using acetic acid and ammonia as an evaporating agent showed the great result of color change that it is a function of time. The color was increasingly changed from blue to pink, when the film was exposed with a vapor of acetic acid solution for a longer time while changed from blue to green when exposed with a vapor of ammonia. The film indicator was applied on salmon and dory fillets and stored at 4 ºC for 15 days. It was found that the color change of film indicator was depended on storage time. Its color was changed from blue to deep blue, and finally green. The result also demonstrated that the color change of film indicator was related to the quality change of fish fillet. For evaluating its feasibility to be used for commercial purpose, fish fillet labels were designed and conducted with 100 consumers. It was found that most of consumers had more correct the meaning of indicator designed using a short text than indicator designed using a symbol.