Volatile and Non‐Volatile Compounds in Retort‐Processed Green Beans Packaged in Metallic Cans Coated With Corrosion Resistant Polymers

ABSTRACT This study evaluated the effects of green beans, chlorophyll and methyl cysteine on two types of coatings for metallic cans. One can was internally coated with a polyethylene terephthalate (PET) laminate and the other coated with a polyester. These metal cans were filled, sealed and heat‐treated by retort, then stored at 40°C for up to 90 days. At selected timepoints, the can coatings were evaluated for the sorption of volatile and non‐volatile compounds. Selected‐ion flow‐tube mass spectrometry (SIFT‐MS) was used to determine the production of volatile compounds in the green beans during heat treatment and to screen for their interactions with the polymeric coatings of the cans. Gas chromatography–mass spectrometry (GC–MS) was used to identify and quantify volatile compounds that interacted with the two coatings during storage. Liquid chromatography–mass spectrometry (LC–MS) was used to tentatively identify the higher molecular weight thermal degradative products of chlorophyll and their interactions with the coatings. The results showed that methyl cysteine and chlorophyll thermally degraded during the retort process and led to the formation of various reactive sulphur and nitrogen‐containing compounds that sorbed into the coatings of these cans. The results also showed that the concentration of dimethyl disulphide increased by fivefold and 3.5‐fold in the laminate and polyester coatings, respectively. The analysis of chlorophyll determined that heat‐induced nitrogen‐containing heterocyclic compounds formed during the retort process and were found in both the green beans and in the polyester coating in the cans that were processed with green beans. These compounds led to rapid visual signs of corrosion in both packaging types when exposed to the treatment groups during 90 days of storage at 40°C.