Packaging Technology Influence on the Shelf Life Extension of Fresh Raspberries

Raspberries have been classified as a non-climacteric fruit - they have high physiological post-harvest activity, short ripening and a senescence period. The objective of this study was to examine the possibility of shelf life extension of primocane raspberry cultivar 'Polana' by packaging in different materials. The experiments were performed in the Latvia University of Agriculture Faculty of Food Technology, Jelgava and in the Latvia State Institute of Fruit Growing, Dobele during the year 2007. Contents of ascorbic acid, anthocyanins, color in the L*a*b* measuring system, changes of moisture content and pH were analyzed during the storage period of three weeks. Oxygen and carbon dioxide dynamics in hermetic packages were analyzed by gas analyzer. The effect of packaging materials for shelf life extension was determined by using different packages: PP (polypropylene) trays inserted in pouches made from PLA (polylactic acid) films of different thickness 25 and 40 micrometer; cardboard boxes placed in PLA film pouches of different thickness 25 and 40. PP boxes manufactured with holes and cardboard boxes covered with net were used as control packaging in the experiments. The content of vitamin C rapidly increased during the first two days of storage in samples of all packaging materials but after four days ascorbic acid content started to decrease. The influence of packaging materials on the ascorbic acid content of raspberry samples was not significant. The anthocyanin content of all samples packaged in PLA material was quite stable during the whole storage time. The lowest weight losses were obtained in the PLA-40-PP sample (2.6%) although the other packaged samples did not exceed 5.2%. All samples placed in PLA (polylactic acid) film pouches by thickness 25 μm had optimal gasses composition (10 to 20% CO2 and 5 to 10% O2) for storage of primocane raspberry cultivar 'Polana'.