The protective effect of film metallization against oxidative deterioration and discoloration of sensitive foods

The importance of the optical properties of packaging materials is often underestimated and little attention is generally given to the shelf-life of lightsensitive food products. In this paper, the effects of the light barrier of different metallized films in delaying chemical degradative reactions, which occur in dry lasagna made with eggs and spinach, were investigated. The array of films evaluated in the experiment accounted for a large distribution of optical properties. Pouches prepared from the different films were filled with dry lasagna and stored at room temperature for about 4 months under a fluorescent light source. Sensory evaluations, CIE-L*, a*, b* colour measurements and hexanal formation were evaluated during storage. The shelf-life of lasagna packed in metallized films was 2.5 times greater than the same product packed in non-metallized films. A correlation between transmittance values of the packaging films and shelf-life reduction was obtained. Because of the fat and the pigments of lasagna and also its shape (large surface area), lasagna seems to be a good model system when studying the protective performance of packaging materials against degradative reactions that involve oxygen and are very sensitive to light exposure.