Preparation and Mechanical Properties of Wheat Protein Isolate Films Cross-linked with Resorcinol

Abstract

ABSTRACT: The purpose of the present work was to preparation and study of full biodegradable Eco-friendly bio-composites by using renewable resources. In this study, wheat protein isolate (WPI) films were formed by crosslinking with resorcinol through solution casting method for packaging applications. By varying the resorcinol content(10, 20, 30, 40, and 50 wt %), its effect on mechanical properties of the wheat protein isolate film was measured. Theaddition of 20% resorcinol led to an overall increase in the tensile strength from 5.2 to 18.6 MPa and modulusincrease from 780 to 1132 MPa than WPI films. The % elongation was increased from 2.8 to 9.05 when compared tounmodified WPI film. A thermal phase transition of the prepared WPI was assessed by means of DSC. FTIR isevident that the characteristic WPI spectral IR bands shifted on cross-linking with resorcinol. Key Words: Wheat protein isolate, Resorcinol, Mechanical properties, Biodegradable films 1. INTRODUCTION Petroleum-based plastics dominate today’s plastics marketbecause of their high strength, lightweight, low cost, easy pro-cessability, and good water barrier properties. Plastic materialsmay be degraded by naturally occurring microorganisms inthe environment, but the process may take about 150 years(low density polyethylene), while paper can be naturally bio-degraded in about one year [1]. Inert and non-biodegradableplastic materials account for about 30% by weight of municipalsolid wastes, but due to their low density they represent 2/3 ofthe wastes volume. There has been a growing interest for edi-ble films and coatings in recent years trying to reduce theamount of wastes, capable of protecting the food once the pri-mary packaging is open, and because of public concerns aboutenvironmental protection [2]. However, most of the syntheticpolymers are not biodegradable. Synthetic biodegradable poly-mers, such as poly(lactic acid), polycaprolactone, and poly(hydroxy butyrate) have high production costs. With theincreasing concerns of environmental pollution caused bynon-biodegradable, petroleum based plastics; increasing effortshave been made to utilize the polymeric materials derivedfrom agricultural products. Environmental concern about plastic materials is leading toand an increasing interest towards the development of eco-logical products. The use of disposable plastic materialincreases in understandable waste portion and for this reasonit is necessary to develop more recyclable and/or biodegrad-able plastics to reduce the amount of plastic waste. The recenttrend is to develop fully sustainable, biodegradable, eco-friendly and easily disposable materials. Therefore, in the pastdecades, extensive studies have been made for the potentialuse of polymeric materials derived from renewable resources,such as carbohydrate, starch and proteins [3-5]. Plant proteinsfrom soy [6,7], corn [8], why protein [9], cotton seed [10], andwheat [11], have been studied because of their abundance, lowcost, good biodegradability and sustainable properties forusage as films and plastics. Natural matrices are biodegradable,renewable and cheaper. Further, these materials are expectedto lower the usage of synthetic polymers which are non-degradable and derived from precious depleting fossil fuels. Inaddition to its use as a food ingredient, non-food applicationsof wheat protein as polymeric materials have attracted increas-ing attention in recent years. The main attractive features ofwheat protein-based plastics are that they are biodegradable,environmentally friendly, and from an abundant renewable