The optimization of gelatin extraction from chicken feet and the development of gelatin based active packaging for the shelf-life extension of fresh grapes

Abstract

Synthetic plastics are causing serious environmental and health problems due to which the concept of developing biodegradable food packaging has gained considerable attention. In this study, extraction of gelatin from chicken feet was optimized followed by characterization of gelatin. Chicken feet gelatin was used to develop biodegradable nanocomposite films by the incorporation of chitosan (CS) and zinc oxide (ZnO) nanoparticles (NPs). Gelatin nanocomposite films were used to increase the shelf-life of fresh grapes by determining the browning index, weight loss, and microbial profile of fresh grapes. A high yield (7.5%) of gelatin and Bloom strength (186 g) were obtained at optimized extraction conditions (pretreatment with 4.2% acetic acid and extraction at 66◦ C for 4.2 h). Electrophoretic analysis of gelatin revealed the presence of α (130–140 kDa) and β chains (195–200 kDa), whereas a Fourier transformed infrared (FTIR) spectrometer confirmed the presence of amide A and B and amide I, II, and III. Incorporation of ZnO NPs in a gelatin–CS matrix improved the barrier and the mechanical and the thermal properties of films. Gelatin nanocomposite films with 0.3% ZnO NPs significantly reduced the weight loss (23.88%) and the browning index (53.33%) of grapes in comparison to control treatments. The microbial count in artificially inoculated grapes wrapped in gelatin nanocomposite films remained below 4 log CFU/mL until the fifth storage day in comparison to control treatments. The gelatin from poultry byproducts such as chicken feet can serve as an efficient biopolymer to develop biodegradable food packaging to enhance the shelf-life of perishable food products.