Abstract
Protein films were made from whey protein, soy protein and egg white protein to determine film water vapor permeability (WVP) and appearance. The optimum pH to form whey protein (WP), soy protein (SP) and egg white protein (EWP)-based films was 6.5-7.5, 7.0-7.4 and 12, respectively. To increase film moisture barrier, WP and SP solutions were heated for 30 min at 90°C and EWP solutions at 45°C followed by the addition of glycerol as plasticizer at 25-35% content (dry weight basis). Protein films were dried at either 70 or 80°C for 2-3 hours. Glycerol content (GC), protein type and drying temperature influenced film WVP. Increasing the GC improves protein molecules movement and increases permeability; while increasing drying temperature causes protein denaturation, which induces tight networks and reduces film permeability. EWP films imparted the highest WVP followed by SP and WP films, respectively. All films showed transparency and the gradient of yellowish appearance depended on protein type and drying temperature. WP coating application on oranges reduced weight loss and respiration rates. These results indicate that different protein types can be formed to provide different properties for coating application on fruit and vegetables. Protein edible coatings have potential to extend shelf-life of fruit and vegetables.
Published Version
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