Moisture Sensitivity, Optical, Mechanical and Structural Properties of Whey Protein-Based Edible Films Incorporated with Rapeseed Oil

The objective of this work is to study the eff ect of the rapeseed oil content on the physical properties of whey protein emulsion fi lms. For this purpose, whey protein fi lms with the addition of 0, 1, 2 and 3 % of rapeseed oil, and glycerol as a plasticizer were obtained by the casting method. Film-forming emulsions were evaluated and compared using light scatt ering granulometry. The Sauter mean diameters (d 32 ) of lipid droplets in fi lm-forming solutions showed an increasing trend when increasing the oil volume fractions. The inclusion of rapeseed oil enhanced the hydrophobic character of whey protein fi lms, reducing moisture content and fi lm solubility in water. All emulsifi ed fi lms showed high lightness (L*90). Parameter a* decreased and parameter b* and total colour diff erence (E) increased with the increase of the volume fractions of oil. These results were consistent with visual observations; control fi lms were transparent and those containing oil opaque. Water vapour sorption experimental data at the full range of water activity values from 0.11 to 0.93 were well described with Peleg's equation (R 2 0.99). The tensile strength, Young's modulus and elongation at break increased with the increase of rapeseed oil volume fraction, which could be explained by interactions between lipids and the protein matrix. These results revealed that rapeseed oil has enormous potential to be incorporated into whey protein to make edible fi lm or coating for some food products. The mechanical resistance decreased with the addition of the lipids, and the opacity and soluble matt er content increased.