PROLONGING THE SHELF LIFE OF APPLES BY MODIFIED ATMOSPHERE PACKAGING

摘要

The storage life of several agricultural products can be extended by use of controlled atmosphere (CA) storage. The basic principle of CA storage involves active control of concentration of oxygen (O_2) and carbon dioxide (CO_2), besides controlling the temperature. Recommended optimal gas concentrations are reported to be 2-3% (minimum 1%) O_2 and 2% (also maximum 2%) CO_2 (Exama et al., 1993). Kader and coauthors (1989) report higher tolerances for CO_2 concentartions ranging between 2-5%, depending on the variety and storage time. In the Netherlands the recommended gas concentrations for 'Elstar' apples are 1.5% O_2 and 2.0% CO_2. Under these conditions 'Elstar' apples are stored in commercial storage rooms for up to 9 months (Evelo and boerrigter, 1994). In modified atmosphere packaging (MAP) the same principles as in CA storage are used to enhance shelf life. However, the microatmosphere inside the package around the product is not actively controlled, while the O_2 and CO_2 concentrations are obtained by a combination of the respiratory process of the produce and transport of these gases through the packaging film. The CA storage technique is very expensive and not economically feasible for storing apples in Finland. MAP is a cheaper solution for prolonging the shelf life of apples. However, since it is not possible to control gas concentrations actively in MAP applications, shelf life is shorter than in CA applications. The quality and shelf-life of new apple varieties and the possibilities of MAP for enhancing the shelf life of apples were studied in a joint research project between VTT, Agricultural Research Center (MTT), and apple growers during 19J98-2001. The results of the experiments of the 1999 season are discussed here. The aim of the MAP experiments was to find a novel, economically viable packaging solution for prolonging the shelf life of apples up to 4-5 months.