Abstract
In this study a novel and smart multi-functional hydrogel (MFH) was synthesized from N, N dimethyl acrylamide (DMAAm), gelatin, citric acid (CA) and pomegranate extract (PE) for instant and easy monitoring of the color change in MFH due to changes in medium conditions such as pH and temperature. MFH was utilized as food packaging material, equipped with the developed properties. MFH was synthesized with a redox polymerization technique in film form on petri dishes. Mechanical and water resistance properties of MFH were improved by CA and N, N, methylenebisacrylamide, while PE was used to gain antimicrobial, antioxidant and anthocyanin properties. Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analyzer (TGA), Liquid Chromatography-Mass Spectroscopy (LC-MS/MS) and Scanning Electron Microscopy (SEM) instruments were utilized for characterization of MFH. FTIR revealed the existence of bonding interactions between the functional group of PE and gelatin, carbonyl groups of DMAAm and carboxylic acid groups of CA. TGA results indicate that MFH was stable up to 400 °C. Then the response of total antioxidant and anthocyanin activities leading to the color change in MFH were studied at different pH values. The color change in MFH was monitored even at very small pH changes in the medium. Moreover, antimicrobial activity and stability of MFH were investigated when it was tested in harsh environments and against Escherichia coli, Bacillus subtilis and Staphylococcus aureus on real samples of whole pasteurized milk and cheese for a 7-day period. It exhibited remarkable antimicrobial activity with pasteurized whole milk and cheese. It was concluded that MFH is a very good candidate to be used as biodegradable food packaging material.
