Effect of oleic acid–beeswax mixtures on mechanical, optical and water barrier properties of soy protein isolate based films

Soy protein isolate (SPI) based films are effective barriers to oxygen, lipids and aroma compounds but they provide yellowish films and are not effective water vapour barriers. Different ratios of lipid mixtures (oleic acid and beeswax at different ratios) were incorporated into the SPI based films to improve their properties. Oleic acid, pure or mixed with beeswax, had a plasticizing effect on the films and also reduced water vapour permeability regardless of the lipid ratio and the BW percentage in the lipid mixture. When the protein–lipid ratio was 1:0.25 and beeswax percentage in the lipid mixture ranged between 30 and 50, gloss values were the closest to those of the control film made with only SPI, and are consequently the most highly recommended, although they maintain yellowness.