A Multilayered Edible Coating to Extend Produce Shelf Life

The reduction of food waste plays a pivotal role in increasing the robustness of the global food system by positively affecting food security while mitigating environmental impact. For fruits and vegetables, the Food and Agriculture Organization of the United Nations (FAO) estimated a 50% waste of crops during the food supply chain [1], predominantly concentrated in the postharvest, distribution, and end user consumption stages and mostly caused by the premature spoilage of perishable crops. Of growing interest is the waste of fresh-cut produce (FCP), (i.e., edible portions of fruits and vegetables cut in smaller pieces after removal of inedible parts) [2] the production of which is constantly increasing, and thus brings challenges in terms of quality retention, shelf-life preservation, and food safety [3]. In fact, the increased metabolism of the wound tissue results in a shorter shelf-life due to water loss, softening, browning, and biotic spoilage [4]. In this context, packaging with tuned oxygen and water barrier properties is largely used to decelerate spoilage, however, it can immoderately increase the cost and the environmental impact. To solve this problem, edible coatings have been studied as a method to preserve FCP freshness and reduce nonbiodegradable plastic packaging waste [5]. In this work, silk fibroin (SF) and poly(vinyl alcohol) (PVOH) were coupled to develop a new edible coating material with enhanced mechanical and gas barrier properties [6]. SF and PVOH water suspensions were mixed at different ratios to form multilayered membranes that, after a phase separation, assembled on the surface of fresh-cut produce upon dip coating. The effects of the mixing ratio on transparency, mechanical properties, water vapor, and oxygen permeability of the films were investigated. Higher PVOH fractions corresponded to an increased ductility (increased elongation at break and decreased Young’s modulus), which is essential for a food packaging material. A coating with SF:PVOH weight ratio 1:1 presented the minimum water vapor permeability and was selected to perform perishable food preservation studies. Weight loss and color changes of coated fresh-cut apples over 14 days of storage at 4 °C were significantly lower than those of uncoated controls. The addition of ascorbic acid to the coating material was also investigated to obtain an active food coating with antioxidant properties. The obtained results demonstrated the ability of SF:PVOH blends to assemble into bilayered edible coatings that extend the shelf life of fresh-cut produce.<br/><br/><br/>[1] FAO (2011). Global Food Losses and Food Waste. Food and Agriculture Organization of the United Nations (FAO).<br/>[2] Allende, Ana, Francisco A. Tomás-Barberán, and María I. Gil. "Minimal processing for healthy traditional foods." Trends in Food Science & Technology 17.9 (2006): 513-519.<br/>[3] Olivas, G. I., and G. V. Barbosa-Cánovas. "Edible coatings for fresh-cut fruits." Critical reviews in food science and nutrition 45.7-8 (2005): 657-670.<br/>[4] Mehyar, G. F., and J. H. Han. "Active Packaging for Fresh-Cut Fruits and Vegetables." Modified atmosphere packaging for fresh-cut fruits and vegetables (2011): 267.<br/>[5] Ruggeri, Elisabetta, et al. "Edible Biopolymers for Food Preservation." Sustainable Food Packaging Technology (2021): 57-105.<br/>[6] Ruggeri, Elisabetta, et al. "A multilayered edible coating to extend produce shelf life." ACS Sustainable Chemistry & Engineering 8.38 (2020): 14312-14321.