Ethylene Permeability of Commercial Plastic Films and its Effect on Quality Stability of Broccoli during Storage

Ethylene permeability of commercial plastic films, including three kinds of low density polyethylene films (LDPE) mixed with porous minerals (Ohya-ishi etc.), a kind of polystyrene film mixed with porous mineral, ethylene vinylacetate copolymer film (EVA) and multi layer films contained nylon, was determined at 20 and 30°C by both simple pouch method and Lyssy method, using LDPE (30μm) and LDPE (50μm) as control. Nitrogen, oxygen and carbon dioxide permeabilities of the same films were also determined by Lyssy method. Simple pouch method for ethylene was performed to measure periodically ethylene concentration in the film pouchs by gas chromatography. And then quality stability of broccoli packaged individually in the films tested was investigated during storage of one week at 20°C. Simple pouch method gave almost same level of ethylene permeability obtained by Lyssy method, indicating this method is useful and rapid. EVA, LDPE (30μm) and a kind of LDPE mixed with porous mineral had relatively high ethylene permeability. A typical LDPE mixed with porous mineral (Ohya-ishi) was almost same ethylene permeability with LDPE (50μm). The broccoli packaged in the high ethylene permeability films gave low off-flavor score and relative high overall score by sensory evaluation, comparing with other samples. From these results, the relation between ethylene permeability of commercial plastic films and quality stability of broccoli was discussed as effect of other gas permeability.