A COMPARATIVE EVALUATION OF INTEGRITY AND COLOUR PRESERVATION OF SLICED APPLES PROTECTED BY CHITOSAN AND ZEIN EDIBLE COATINGS
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Asociación Iberoamericana de Tecnología Postcosecha, S.C.
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Chitosan (chitin deacetylated derivate) and zein (storage proteins of maize) are promising materials for use as protective edible coatings on several fruits and, in particular, for post-harvest conservation, increasing self-life of intact fruits. In the present study, two basic coating formulations, one based on chitosan (hydrophilic) and one based on zein (hydrophobic), reported as efficient in covering intact apples, were evaluated on sliced samples. Chitosan gel was prepared in a concentration of 2.0 gL-1 dissolved in 1 % acetic acid aqueous solution and the zein formulation with 4.0 % (w/w) with 0.25 % wt of oleic acid as plasticiser dissolved in 70 % ethanol aqueous solution. Sliced apples (cv. Gala) were separately coated and evaluated with respect to mass loss, firmness and colour alteration when storage at room temperature. The results show that both formulations have some positive action in preserving mass and firmness, with better results to zein-coated samples. Nevertheless, both coatings introduce significant variations on mesocarp colour and may accelerate the surface's browning instead of inhibiting it, not being indicated for use as protection on processed apples. Increasing in coating thickness and the association of antioxidant agents are discussed.
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