Influence of food additives on blister formation in tinplate can of coconut milk

Blistering is one of the major issues in processed canned coconut milk that contain several food additives. The goal of this work is to investigate the effect of five different food additives, guar gum, sodium carboxymethyl cellulose (CMC), polysorbate 60 (tween 60), citric acid (C₆H₈O₇), and sodium metabisulfite (Na₂S₂O₅), on blister formation in epoxy-phenolic coated tinplate cans using electrochemical impedance spectroscopy (EIS) and surface microscopy. Cathodic stripping at −6 V (Ag/AgCl) for 30 min was applied in order to provoke blisters. The results revealed that the sterilizing process deteriorated the coating performance, however, without food additives, blisters did not form even after an applied potential. Na₂S₂O₅ and CMC were the most aggressive food additives for which blisters were observed for both non-sterilized and sterilized conditions. Na⁺ ions, together with water and oxygen in the solution, permeated through the coating initiating and accelerating the blister formation.