Comparison of the influence of citric acid and acetic acid as simulant for acidic food on the release of alloy constituents from stainless steel AISI 201

Abstract

To ensure the safety of metals and alloys intended for food contact, a new European test protocol (CoE protocol) using citric acid as a food simulant was published in 2013. This study investigated the influence of citric acid and exposure conditions on the metal release from an austenitic manganese stainless steel (AISI 201). Exposures in 5g/L citric acid resulted in significantly lower metal releases compared with specific release limits set by the CoE protocol. 5g/L (0.3vol%) citric acid was more aggressive than 3vol% acetic acid (Italian protocol) due to higher metal complexation. Studies on abraded surfaces revealed that most metals were released during the first 0.5h of exposure due to surface passivation. Surface abrasion, increased temperature (40–100°C), increased surface area to solution volume ratio (0.25–2cm2/mL) and increased citric acid concentration (0–21g/L) all resulted in increased released metal quantities.