Alginate Edible Coatings Enriched with Citral for Preservation of Fresh and Fresh-Cut Fruit

Edible coatings enriched with essential oils or their constituents have been studied for their effect on increasing fresh and fresh-cut fruit shelf-life. With this work we intend to find the effect of one main essential oil constituent (citral) incorporated in an alginate-based edible coating on the preservation of quality of Arbutus unedo L. (strawberry tree) fresh fruit and in fresh-cut apple 'Bravo de Esmolfe', a Portuguese cultivar. Harvested strawberry tree fruit and fresh-cut apple were treated with the following edible coatings: alginate 1% (w/v), alginate 2%, alginate 1% with citral 0.15% (w/v), alginate 1% with citral 0.3%, alginate 2% with citral 0.15% and alginate 2% with citral 0.3%, then stored for 28 days at 0.5 degrees C and 14 days at 4 degrees C, respectively. For apple, the color parameters (L*, C*, h degrees) were better preserved in alginate without citral and had greater changes with increased citral concentrations. The firmness was better maintained with all edible coatings than in the control. Antioxidant activity was improved with alginate 1% followed by alginate with citral 0.3%. The highest microbial spoilage reduction was achieved with alginate 2% with both citral concentrations. For strawberry tree fruit treated with alginate edible coatings at 2% with citral 0.3%, color and firmness were better preserved and microbial spoilage was reduced. The degrees Brix, weight loss and antioxidant activity were not affected. Taste panels scored the use of 0.3% citral in edible coatings more poorly, so it seems that for both commodities, alginate 2% with 0.15% citral is the most appropriate in preserving the main quality properties studied.