Effect of Roasting Methods and Microwave-Assisted Extraction on the Bioactive Compounds of Date Seeds

Abstract

In this study, phenolic compounds were extracted from unroasted and roasted date seeds by microwave-assisted (300, 450, 600, and 800W) method, and their changes were investigated.  TPC values ranged from 6628.89 to 9763.29 mg GAE/100 g dry weight. DPPH inhibition values ranged from 44.78% to 58.17%, with the highest antioxidant activity observed in the traditional roasting samples extracted at 800 W for 2 min. Generally, unroasted samples gave higher TPC results than traditional and microwave roasting. On the other hand, traditional roasting samples gave higher antioxidant activity results. HPLC analysis showed that rutin was the predominant phenolic compound in unroasted date seeds. Gallic acid and 3,4-dihydroxybenzoic acid became detectable after roasting and reached their highest concentrations in traditional roasting samples. PCA, as a multivariate analysis, was a successful method for the classification of the unroasted, traditional roasting, and microwave-roasting samples based on TPC and antioxidant activity.