Wheat Proteins-based Bioplastics; Synthesis, Properties, and Applications.

Abstract

Proteins have numerous non-edible and edible uses. Wheat flour contains starch and wheat proteins. Gluten protein from wheat is widely used in the food and bioplastic industry but industrially available gluten is not 100% pure. Industrially separated gluten has different associated impurities e.g., lipids, starch, carbohydrates, etc. High-temperature exposure up to 160°C required for its separation from starch, resists the free flow of starch molecules, their entrapment causes the formation of hard particles and aggregated, a pre-crosslinked network of gluten formed. Lower solubility, protein content, and water absorption capacities of bioplastics prepared from untreated industrial gluten limit applications of industrial gluten. Different methods for wheat gluten purification including mild, mechanical, and enzymatic treatments through cellulase and amylase were developed for increasing the protein content and purity of gluten. Lowry assay was performed to determine the protein content of differently treated samples. Protein content increased with an increase in purity. The protein content of enzymatically treated mild and mechanically extracted gluten was higher as compared to untreated gluten samples. Films from untreated and treated samples were prepared and free swelling capacity was evaluated through the tea bag assay. Enzymatically treated gluten samples have shown higher absorption capacities in distilled water and saline solutions. The protein solubility of samples was analyzed through size-exclusion high-performance liquid chromatography (SE-HPLC). Industrial untreated gluten samples showed lower solubilities after repeated extractions in contrast to samples that were purified through different methods and showed high solubilities. Results from the different analyses have shown that mild, mechanical, and enzymatic treatment of gluten had less aggregated and loosely bound protein networks. Biobased gluten films with improved water absorption capacities have shown good potential to be used in hygiene products as a sustainable alternative to synthetic plastics.