[in Japanese]

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One of the requirements for food packaging is barrier property. Especially, in order to prevent oxidation degradation, many gas-barrier films have been developed. Gas-barrier property depends on “macromolecular glass-transition point”, “crystallinity”, “free volume” and “cohesive energy density”. On the other hand, aroma retention-ability does not correspond directly to gas-barrier property. In terms of aroma retention ability, “affinity” between penetrated aroma-component and packaging film is important.
Then, as the aroma retention-ability provided by packaging film depends on environment and content ingredient, it is necessary to select the suitable barrier film considering its exact performance.

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Reuse of PET bottles reduces PET resin usage and waste, and contributes to decrease of greenhouse gas emission. However, PET bottles tend to absorb smelly and dirty matters into the surface of PET resin unlike glass bottles, and it is hard to remove them completely by washing. DLC coating has possibility to prevent absorption of substances into PET resin surfaces. Therefore, we have recently developed a technique for forming an intermediate layer between DLC layer and PET bottle surface, which enables to withstands repeated washing cycles without exfoliation. Various evaluation tests for reuseability of improved DLC coated bottles were carried out and the results indicated DLC coated PET bottles have potential for reuse.

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Quantitative evaluation of the aroma barrier of plastic materials was very important for designing the packages of aroma-sensitive contents. The aroma permeability testing was designed with a diffusion cell and dynamic headspace analysis with GC/MS of the lower permeant concentration side of the cell. Cyclohexane, 2-propanol and ethyl acetate with high saturation vapor pressures were used as the permeants analogous to the aroma components such as limonene, 1-butanol and ethyl butyrate respectively. The aroma permeability was measured of the film samples of PGA, PET, NyMXD6 and EVOH. The result showed PGA provided the lowest permeability of all the 3 permeants under both conditions of 0% RH and 100% RH, which fact suggested that PGA is a most suitable barrier material for packaging of aroma-sensitive products.

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MAP（Modified Atmosphere Packaging）is a method that keeps fruit and vegetables freshness through the adjustment of gas concentration in bags by maintaining an adequate balance between their respiration and the gas permeability of the bags. The bags‘Partial seal packaging’are sealed partially with fused part and non-fused part by sealing roller. Chinese chives were packaged by partial seal packaging. The concentration of oxygen and carbon dioxide in the bag after storage under 20℃ for 5 days was about 5 and 11%, respectively. Sugar and ascorbic acid contents of Chinese chives retained high, and the occurrence of yellow leaves and decayed leaves were markedly suppressed in this condition. The freshness retained when the partial seal packaging were used during summer distribution test.

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