Effect of drying on the total phenols content and antioxidant activity of bananas from cvs. Musa nana and Musa cavendishii

Bananas and plantains are today grown in every humid tropical region and constitute the 4th largest fruit crop of the world. The fruit peel turns from deep green to yellow or red while the flesh varies from ivory-white to yellow or salmon-yellow. The pulp may be firm, astringent, even gummy when unripe, turning tender, slippery or starchy when ripe. The flavor may be mild and sweet or subacid with a distinct apple tone. Bananas of cultivars Musa nana (MN) and Musa cavendishii ( MC) were subject to drying for comparison of their properties with the corresponding fresh fruits, namely convective air drying and lyofilization in a freeze-drier. All samples, for fresh and dried bananas, were obtained by crushing the product, having taken a mass of 5 g. Subsequently, 6 successive extractions were performed for each sample ( three with methanol and three with acetone solution (40% v/v)), lasting one hour each, done with the aid of an ultrasonic bath. For each extract it was determined phenolic content by Folin-Ciocalteu reagent, and the antioxidant capacity was estimated using the ABTS assays. The results allowed concluding that both types of banana studied present quite similar results in what concerns the total phenolic compounds present. Furthermore, it was observed that air drying decreased total phenols content relatively to the fresh bananas, when expressed as dry matter basis, for both temperatures tested (50 degrees c and 70 degrees C). Also lyophilisation decreased the phenolic content, but in a lesser extent when compared to air drying.