Interactions between aggressive food ingredients and novel non-bisphenol A food can coatings
Research Poster Engineering 2025 Graduate ExhibitionPresentation by Stiphany Tieu
Exhibition Number 129
Abstract
Previous studies of can coatings involved a single food ingredient (salt or acid) or provided little to no explanation of the food-packaging interactions. This study uses a definitive screening design to identify the main and interaction effects of aggressive food ingredients (as identified by industry) on a legacy, BPA-based epoxy phenolic coating and a non-BPA polyester phenolic coating after 2 and 7 days of storage in food simulants at 50 °C post-retorting (121 °C, 30 min). There were 17 experimental conditions, each representing a specific combination of ingredient levels. The individual and combined effects of coating type and food simulant had a significant effect on the low-frequency impedance modulus from electrochemical impedance spectroscopy (where higher values represent greater resistance against the flow of ions through coatings) and on the glass transition temperature (Tg) measured by differential scanning calorimetry (where a higher Tg generally leads to better barrier properties by restricting the movement of molecules through the coating). Paprika oleoresin (PAP) increased coating thickness and had the largest effect on Tg, plasticizing coatings and facilitating polymer degradation by acids and salts. Interactions between PAP and acids increased surface roughness of metal substrate and decreased tin dissolution, increasing corrosion potential. The combination of NaCl and acetic acid increased Cl migration into coatings, wherein H+ readily reacts with the metal surface, disrupting the passivation layer and allowing Cl to penetrate more easily. Results from this study are useful for assessing food-packaging compatibility to inform coating choices for ingredient combinations common in canned foods.
Importance
Food can coatings serve to minimize contact between cans and their contents, which could otherwise lead to corrosion. Consumers expect canned foods to last for at least two years, but early failure through corrosion can lead to unsafe or unappealing product and food waste. Regardless of the food and processing method, BPA-based epoxy coatings perform exceptionally well to protect steel from corrosion. However, due to anticipated changes in consumer sentiment and regulatory amendments, the packaging coatings industry developed non-BPA coatings. Further study of the degradation mechanisms of these novel coatings and associated corrosion phenomena is required to extend product shelf-life and improve food safety and security.