According to a Prescouter (Evanston, Ill., USA) article published as an online monthly feature for Sept. 2018, among the various kinds of plastic packaging, plastic cling film is one of the most widely used today. Moving towards eco-friendly packages, new innovations in cling film packaging are shaping the future of food packaging.

Silk fibroin is a protein that has been used in adhesive, edible food sensors. It is similar to collagen and consists of hydrophobic blocks interspersed with acidic, hydrophilic regions. The nature of silk fibroin gives it unique characteristics, such as polymorphism, hydrophobicity, and conformability. These characteristics have enabled scientists at Tufts University to develop a water-based suspension that self-assembles on the surface of foods that have been dipped into the suspension. This makes it possible for perishable foods such as apples, tomatoes, bananas, and strawberries to be well preserved. The silk fibroin thin film reduces dehydration and gas diffusivity, hence contributing to extended shelf life. The study also found that thicker silk fibroin coatings on the surface of food led to lower oxygen permeability and carbon dioxide production, resulting in firmer food.

Scientists at the Georgia Institute of Technology School of Chemical and Biomolecular Engineering have found a unique way to combine the two most abundant biopolymers, cellulose and chitin, to form edible films for food packaging. The film is made by spraying multiple layers of chitin from the shells of crabs and cellulose from trees in alternation to form a flexible film comparable to PET (polyethylene terephthalate) packaging. For years, chitin has been known to have great commercial potential, and indeed, its application versatility has been a big challenge. During the development of the packaging film, researchers found that chitin nanofibers are positively charged, whereas cellulose nanofibers are negatively charged. These properties formed a good film when used in alternating layers.

Unlike plastic films, crab shells and tree fiber films are crystalline in nature. This makes it difficult for the penetration of gas molecules. In the study, crab shells and tree fiber films were found to reduced oxygen penetration by 73%. Though more research needs to be conducted to improve the film’s ability to reduce water vapor permeability, the study suggests that the film could provide suitable packaging for foods with uneven or delicate surfaces.

Wheat gluten films have been found to have better mechanical properties when the gluten concentration is 12.5% and the pH is 5. In a recent study that focused on improving the barrier and mechanical properties of gluten films, scientists researched the effects of flaxseed gum, oligomeric procyanidins, and lauric acid on the water vapor permeability, mechanical properties, and peroxide value of the film. Gluten films incorporated with these substances were found to be more dense, uniform, and hydrophobic. These improved gluten films were used in packaging salt, oil, vegetables, and seasonings.

In another study, scientists incorporated a bacteriocin-like substance to gluten films made with triticale flour to effectively reduce Listeria counts in food.

The main constraint to producing biodegradable films is their production cost. However, mango peels and antioxidant extracts from seed kernels have proven to be effective in reducing gas permeability and increasing shelf life, and this innovation comes at a lower cost compared to other cling film innovations for food packaging. Researchers found that edible films made from mango peels show good barrier properties, with relatively lower water vapor permeability. In addition, the application of seed kernel extracts conferred increased antioxidant and polyphenol activity to the food. Further, peaches coated with a solution of mango peel, mango seed kernel extract, and glycerol were observed to have 64% less ethylene production, 29% less carbon dioxide production, and 39% less oxygen consumption.

The use of mango waste during the production of edible films and coatings helps to reduce the harmful effects of food waste on our climate while providing a cheaper means of producing bioactive edible films for food packaging.

Recent studies have shown great potential in providing workable solutions to reducing the use of plastic films for packaging food. Some of these offer added benefits, such as greater antioxidant activity, reduced microbial activity, and other bioactive enhancements. Moving forward, it will become critical for all stakeholders in the food packaging industry to take the appropriate steps toward adopting the best biobased plastic film packaging methodologies into their product lines.