Biodegradable Films and Edible Coatings Based on Whey Protein Isolate for Extending the Shelf Life of Commercial Strawberries

This study aimed to create a unique WPI film formulation that would help maintain strawberry quality. Therefore, an edible coating from WPI was developed, and its physical, mechanical, and rheological characteristics were analysed. WPI is a biopolymer residue with attractive barrier characteristics, biodegradability, and neutral taste that can be used as an edible coating on fragile fruits such as strawberries. Key innovations from this research include a comprehensive evaluation of whey as the sole polymeric component in edible coatings for strawberries, assessing its standalone protective potential; improvement of film formulation based on whey proportion; and an inferred shelf-life extension of whey-coated strawberries aligned with commercial acceptability standards, bridging the gap between research and practical application. This study showed that increasing protein proportion reduced the film's solubility from 47.6% to 22.4%, thus enhancing its water resistance by up to 2-fold. Still, the film became tensile stiffer and more elastic modulus at 50% RH than at 70% RH. The filmogenic solution's viscosity enhanced from 2.25 at 25 °C to 4.19 Pa.sⁿ at 4 °C, indicating homogeneous coating of the fruit surface at room temperature and its adhesion at storage temperature. During cold storage, WPI coating reduced the mass loss of strawberries from a range of 5.83-16.71% in the control to a range of 2.56-13.22%, thus decreasing the mass loss by up to 2-fold compared to uncoated fruit from the control treatment, which resulted in better visual quality and a 33% extension of the shelf life of commercial strawberries. Overall, WPI films and coatings have the potential to offer a sustainable and effective protective layer for highly perishable and delicate fruits, extending shelf life and, consequently, reducing waste. Together, these properties can revolutionise the fresh produce industry to enhance global supply chain efficiency.