The Incorporation of Oleic Acid and Anthocyanin in Gelatin Film for Bekasam pH Monitoring

Abstract

This study was aimed to develop and investigate the characteristics of the gelatin film with oleic acid (OA) and anthocyanin extract incorporation and its application for Bekasam pH monitoring. Anthocyanin was extracted from red cabbage (RC), sweet potato (SP), black bean coat seed (BB), and purple rice (CR) and then tested for pH sensitivity. Anthocyanin from SP was selected as showed the highest pH sensitivity. Gelatin film was incorporated with 20% of anthocyanin extract and 50% OA then characterized in comparison with control, and film with only OA or anthocyanin extract. The film with OA and anthocyanin extract incorporation was selected for application as the color changes can be observed clearly at pH 2-11. Red color was present on the film added with anthocyanin extract from SP. OA incorporation significantly decreased the elongation of the film, while it is on the contrary for anthocyanin extract incorporation. Both OA and anthocyanin extract incorporation decreased thickness, moisture content, and tensile strength of the film significantly (p<0.05). Additionally, there was a reduction trend of water vapor permeability for gelatin film incorporated with OA and anthocyanin. However, this reduction was insignificantly different with the control (p>0.05). The incorporation of OA provided wavier surface while anthocyanin extract incorporation enhanced the compactness and smoothness of the film, and provided smoother surface of the film. Higher enthalpy was needed for melting the film with anthocyanin extract. The film was unable to provide the color changes corresponding to the pH decrease of Bekasam during fermentation for 7 days.