Development of edible films from protein of brewer's spent grain: Effect of pH and protein concentration on physical, mechanical and barrier properties of films

Brewer's spent grain (BSG) is the protein-rich agro-industrial waste generated from breweries. In this study, the protein extracted from BSG was used in the development of edible film. BSG protein films plasticized with glycerol were developed at varying pH and protein concentrations. The effect of pH and protein concentration on the physical properties of films were studied. Film's properties were significantly affected by pH and protein concentration. High pH favors the increase in the protein film's solubility, with increased tensile strength, elongation at break, and puncture strength. The tensile strength of the films was in the range of 0.71 to 1.44 MPa. The film's solubility increased by increasing pH, whereas swelling capacity, water activity, and water vapor permeability (WVP) decreased. Increased concentrations of protein in films resulted in enhanced moisture content, mechanical properties, and water activity. The transparency values of films were increased by increasing pH and decreased by increasing the protein concentration.