COMPARATIVE STUDIES ON FREE RADICAL SCAVENGING CAPACITIES AND TOTAL PHENOLIC CONTENTS OF WHOLE AND DEHULLED ADLAY (COIX LACRYMA-JOBI VAR. MA-YUEN ) AS AFFECTED BY THERMAL PROCESSING METHODS

Abstract

Substantial researches have been performed to support the beneficial effects of adlay; however, there were limited studies on the effects of processing methods on these claimed benefits. This study investigated the effects of roasting, boiling, and steaming on the total phenolic contents (TPCs) and radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging properties of both whole and dehulled adlay. Whole adlay demonstrated higher TPC and better DPPH radical scavenging activities than dehulled adlay. Different processing methods significantly changed the content and activity of antioxidants of both whole and dehulled adlay. All processed adlay samples exhibited significant (P < 0.05) differences in TPC and antioxidant activities as compared with the respective raw adlay sample. The thermal processed adlay samples still contained substantial amounts of antioxidants. Roasting is considered to be the best processing methods, which increased TPC and radical DPPH scavenging activities of both whole and dehulled adlay. PRACTICAL APPLICATIONS This research would have practical applications in providing value-added food products or nutraceuticals derived from hull and dehulled adlay. Presented information will guide home-cooking practice as well as food industry to retain more health benefit components through selecting optimum cooking methods. The results indicate that thermal processing remarkably affected phenolic contents of adlay and significantly changed the antioxidant capacities of adlay. In addition, dehulled adlay lost lot of phenolics and antioxidants, roasting significantly increase phenolics and antioxidant capacities of adlay. Therefore, to increase bioavailability of active components from adlay and gain more health promoting effects, the roasting method may be a good processing method.