Arun Kota’s group at Colorado State University recently published its work on edible superhydrophobic coatings targeting applications in food packaging. The group uses U.S. Food and Drug Administration (FDA)-approved beeswax and carnauba wax in place of the traditionally used fluorocarbons, which are classified as "emerging contaminants" by the FDA, as well as more generally used inedible coating materials like silicones and polyethylene. The researchers emulsified the waxes in acetone, and spray-coated the resulting emulsion onto various surfaces, including polystyrene cups. The group demonstrated the efficacy of their coatings by pouring a variety of aqueous liquids, "including Lipton green tea, Gatorade, pancake syrup, Coca-Cola, orange juice, milk and coffee," from the cups without leaving any noticeable liquid. Moreover, the group has shown both minimal leaching (maximum coating concentration due to leaching is 0.04 mg per mL) and toxicity (coatings are nontoxic to cells at a concentration four times greater than the maximum concentration due to leaching) of its coatings, though the edible nature would render any leaching non-problematic.

In spite of the promise of these superhydrophobic coatings in food packaging, there are many issues that will delay successful commercialization. First, the paper noted issues with the mechanical durability of the coatings. On its own, improving the durability of the coatings would be a difficult, time-consuming task; however, improving the robustness while maintaining the edible nature could prove to be an insurmountable challenge, since this edible quality limits the list of possible additives to improve mechanical properties.

Moreover, the nontoxic coating space does have players much further along in the development process. Most prominently involved with nontoxic superhydrophobic coatings is LiquiGlide, with multiple patents for "self-lubricating surfaces for food packaging and food processing equipment." LiquiGlide’s technologies can also utilize carnauba wax or beeswax, among a host of other bio-based additives, for its superhydrophobic surfaces. For barrier coatings in general, TopChim produces polystyrene malemide nanoparticles loaded with vegetable oils. Similar to the coatings developed by the CSU group, TopChim's products comply with FDA regulations for direct contact with food. If the coating technology developed by the CSU group is to ever have commercial success, it must distinguish itself as an edible coating – not just a nontoxic coating – that can also compete on cost and durability with incumbents without noticeably altering the food it contacts. Readers are encouraged to monitor the progress of the Kota Group as they work to develop more durable coatings. Moreover, those interested in leveraging their industry expertise to translate an early lab-stage coating technology to a commercial setting are encouraged to engage.

Gihan Hewage is a Research Associate on the Bio-based Materials and Chemicals Intelligence team at Lux Research, which provides strategic advice and on-going intelligence for emerging technologies. For more information, visit Lux Research.