STRATEGIES FOR THE EXTENSION OF THE SHELF LIFE OF READY TO EAT PRICKLY PEAR FRUITS

The prickly pear fruit (Opuntia ficus indica L. Miller) belongs to the Cactaceae family. The fruit is a berry which is composed by an epicarp and the pulp is the edible portion of the fruit. At maturation, the epicarp assumes the characteristic color of the cultivar, that can be yellow, red or white. In Italy, the prickly pear is mainly cultivated in Sicily (90% of the national production). The prickly pear fruit is very sensitive to low storage temperatures (< 5°C) which cause damages. The fruits can be successfully commercialized as a ready-to-eat product, peeled and suitably packaged. The main limit to its production is the production of off-flavours due to different factors, such as the growth of microorganism and the action of endogenous enzymes (lipid oxidation). In fact, the oxidoreductases are directly responsible for the lipid oxidation, which has influence on the production of off-flavours, and the structure and shelf-life of the fruit. The lipoxygenase (LOX) is a dioxygenase which catalyzes the oxidation of polyunsaturated fatty acids (LH) to hydroperoxides (LOOH). The aim of this work was to compare different packaging technologies to extend the shelf lifeof ready-to-eat prickly pear fruits. The LOX activity, microbial counts and gas composition were evaluated for not treated samples packed in modified atmosphere with barrier film (a), ordinary atmosphere with permeable film (b), and for samples treated either with a blanching (c) or with a blanching followed by a dipping in a citric acid solution (d), packed with permeable film in ordinary atmosphere. The pretreatment conditions are essential for the LOX activity, in particular the blanching reduced its activity by at least 30 percent especially in combination with fruit acidification and limited the microbial proliferation. As a result of suitable pretreatment and packaging operations the shelf life of ready-to-eat prickly pears can be successfully extended.