Corrosion Inhibition in Aluminum Beverage Cans Using Low-Molecular-Weight Chitosan as an Anticorrosive Ingredient

High Resolution Image Download MS PowerPoint Slide Aluminum cans are widely used for single-serve beverage packaging, but corrosive components found in certain beverages (e.g., Cl – in some sports and energy drinks) can limit shelf life. Here, we report that certain forms of chitosan, a widely used food ingredient and dietary supplement, will inhibit corrosion and extend the shelf life of beverages in aluminum cans. A low-molecular-weight (500 Da) commercial chitosan preparation was determined to be a promising anticorrosive at concentrations as low as 0.5 g/L based on accelerated aging treatments of coupons followed by electrochemical impedance spectroscopy (EIS) using a high Cl – sports drink as a test beverage. In long-term pack tests, addition of the chitosan preparation to the drink prior to canning resulted in 10-fold lower dissolved aluminum (0.14 ± 0.01 vs 5.25 ± 2.63 mg/L) and an elimination of visible pinhole corrosion and leaking after eight months ( n = 3, p < 0.05, Steel’s test). Pretreatment of cans with a solution of the chitosan for 6 days at 20 °C prior to filling and seaming also decreased dissolved aluminum (1.48 ± 0.63 mg/L) after 8 months vs control (5.24 mg/L). Comparison of the corrosion inhibition of ten commercial chitosan sources in of varying molecular weights (MW) and degrees of deacetylation (DDA) indicated that certain lower-molecular-weight forms (5000 Da or less) showed anticorrosive effects, but no anticorrosive effect was observed for any of the higher-molecular-weight forms (>250 kDa) ( n = 3, p < 0.05, Steel’s test). To the authors’ knowledge, this study provides the first evidence that an approved food ingredient can extend the shelf life of a corrosive beverage in aluminum cans. The strategy potentially could be extended to other beverages or semisolid foods in metal packaging.