Methylmercaptopentane as an interaction product between packaging and food

5 Methylmercaptopentane as an interaction product between packaging and food 

A complaint of an off-odor that smelled like cat urine occurred practically simultaneously in two different cooked ham products. Both products were cooked and packed in polyamide/ionomer laminate films coming from different film manufacturers with different sources for the PA but the same source for the ionomer. One of the two cooked ham producers used two different printing inks on the same laminate and received complaints only for one of the two packages. 

The simultaneous complaint cases as well as the observed dependence on the printing ink pointed to a complex relationship for the mechanism needed to describe the formation of the off-odor (Franz et al. 1990). 

A GC study of the film for volatile components was able to confirm the fact that in both of the problem films DAA was detected (3 mg/dm2 and 9 mg/dm2) while the good film was found to contain none. At the same time mesityloxide itself was not found in any of the films. 

To confirm that structure I was in fact the cause of the off-odor, compound I was produced synthetically by a reaction of hydrogen sulfide with mesityloxide. Also the off-odor from the problem ham was first extracted with methanol and hexane and then concentrated. Subsequent study with GC showed the synthesized compound I (Fig. 13-4), whose structure was confirmed by MS, had the same FID retention time as the substance producing the off-odor at the end of the GC column identified by sniffing the ham extract. With this result the identity of the cat-like off-odor was explained, but not the mechanism of formation. 

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