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RESEARCH PRODUCT

BIOPOLYMERS USED AS EDIBLE COATING TO LIMIT WATER TRANSFER, COLOUR DEGRADATION AND AROMA COMPOUND 2-PENTANONE LOST IN MEXICAN FRUITS

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Low preservation of typical fruits in countries with warm weather represents a limitation to export. A recently proposed method to increase shelf-life of fresh guava, is the application of biopolymers as edible coatings. This research involves the use of biopolymers of microbial origin obtained with low cost nutrients, to prepare edible coatings applied on mexican guava and apricot. Dextrans obtained by fermentation with Leuconostoc mesenteroides isolated from a typical mexican beverage named pulque (cactus juice fermented). Dextrans were purified by precipitation with methanol and dispersed in purified water. This procedure was repeated 3 times to eliminate carbohydrates others than dextrans. The functional properties of dextrans were compared with four highly purified biopolymers: xanthan gum, potato starch, sodium alginate, carboxymethylcellulose and tragacanthin. Dextran production gave 30% of transformation sugar-dextran in a liquid medium. Dextrans showed better properties as gas barrier compared to the other polymers. However, coatings based on dextran showed poor water retention on fruits at room temperature. The best efficiency of dextrans resulted when coated fruits was preserved at 4°C, by increasing guava quality characteristics (size, color, aroma, water content). Results have shown differences on functional properties among the biopolymers studied. Dextrans could be a good option to preserve fresh fruit, if water retention is not the main purpose. A combination of biopolymers (multi-layer coating) or their application in a emulsified way could improve their performances.