Novel whey protein isolate/polyvinyl biocomposite for packaging: improvement of mechanical and water barrier properties by incorporation of nano-silica

Abstract

The current global proposal for withdrawing polymers with high resistance to degradation and from fossil sources from disposable appliances, as well as the increasing trend of cheese production and whey generation, are some of the incentives for using whey proteins to produce biodegradable packaging films. Brittleness and poor water barrier limit the application of whey protein isolate (WPI) films in the food packaging sector. The addition of polyvinyl alcohol (PVOH) to WPI film, making a blend, improves flexibility but maintains poor water barrier and tensile strength. In this work, to make WPI/PVOH blends more suitable for food packaging applications, films of WPI/PVOH were reinforced with up to 4% of colloidal nano-silica (NS) for improvement of mechanical resistance and water vapor barrier, thus producing a novel biocomposite in terms of composition. At 4% of NS, the values obtained for tensile strength and tensile modulus were 10.2 and 78.2 MPa, being suitable for food packaging application when compared to commercial polymers currently used as packaging. An expressive reduction of water sorption (17% of decrease) and water vapor permeability (40% of reduction) was observed at 4% of NS, increasing the efficiency in keeping integrity during application and leading to a material with a higher water vapor barrier. The addition of 4% of NS in WPI/PVOH films is indicated to improve tensile strength and water barrier, thus increasing its application potential as food packaging.