The Effect of Irradiation on the Natural Volatile Compounds of Dried Mint and the Migration of Chemicals from the Packaging Materials

Dried vegetables such as mint are usually prepackaged irradiated to prevent the post contamination and reduce the microbial population. This process might affect the type and the amount of natural volatile essential oils of the product and also some ions,free radicals and low molecular weight volatile compounds might be released from the packaging materials due to radiolysis reactions migrated into the package and might be adsorbed onto product.
Dried mints, the mixtures of two species (spearmint, peppermint) were packaged in pouch of three layers of polypropylene film and were irradiated at 8, 1 and 15 KGy. The changes in the natural volatile compounds of the product and those that were released from packaging and were isolated by distillation-extraction technique were analyzed using gas chromatography equipped with flame ionization detector.
59 different compounds were identified which might be classified into the following groups: a) the essential oils which were completely destroyed at three different doses (Sabinene, 7-myrcene). b) The essential oils which their concentration were increased by increasing the irradiation dose (Trans sabinene hydrate, cis-jasmone). c) The essential oils which were safe in the lower doses but partially lost at 15KGy. d) Chemical volatile compounds from polymeric packaging material which migrated into the package (tert butyl benzene).
The results indicated that essential oils from spearmint were more sensitive to irradiation than peppermint. To save the functional quality and also safety of prepackagedirradiated dried mint, processing dose may not exceed from 8KGy and more resistant mint species such as peppermint should be packaged in polymeric materials with lower sensibility to irradiation, i.e. polyethylene terephthalate.