Drying Temperature Effect on Total Phenols and Flavonoids Content, and Antioxidant Activity of Borassus aethiopum Mart Ripe Fruits’ Pulp

Abstract

We assessed the total phenols content (TPC) by Folin-Ciocalteux method, total flavonoids content (TFC), and antioxidant activity (AOA) using ABTS radical cation of Borassus aethiopum Mart ripe fruits; uniquely its pulp was considered. Fresh and dried at 40, 50, 60, 70 and 80oC pulps were analyzed, through maceration and decoction, and distilled water (DW), aqueous acetone (DW+Aceto, DW/acetone, 30/70, v/v) and aqueous methanol (DW+Meth) prepared in the same way were used. Though 80oC product extracted through decoction delivered the highest extracts of TPC with DW, DW+Aceto and DW+Meth, 654.434, 780.066 and 729.934 mg GAE/g respectively; we could not retain it as the best. Very likely, the sugars were caramelizing and the derived product had an intense brown color. Whereas, at 70oC, TPCs were 447.866, 337.334 and 327.066 mg GAE/g, respectively, by decoction and in the same above solvents order. The best extract obtained with DW was statistically different from that of DW + Aceto and DW + Meth, which were not significantly different from each other, with Duncan least squares means comparison test in a confidence interval of 99%. The corresponding TFCs and AOAs were (59.34, 68.34, and 51.66 mg QE/g) and (0.4404, 0.52088, and 0.6524 µmol TE/g). The flour has a nice chocolate color. Except 60oC, an increase of the drying temperature leaded to a rising amount of TPC. Taking each factor, the extraction mode and drying temperature were main effects for extracts (p< 0.0001). The overall regression analysis showed significant correlation coefficient between TPC and AOA, with R2=0.8394.