Effect of Home-Cooking Methods on Phenolic Composition and Antioxidant Activity of Sweetpotato (Ipomoea batatas (L.) Lam.) Cultivars Grown in Egypt

Ateea A. Bellail1, Omayma E. Shaltout, Mohammed M. Youssef, Ahmed M. A. El Gamal

ABSTRACT

Four sweetpotato (Ipomoea batatas (L.) Lam.) cultivars grown in Alexandria, Egypt, including Monofya 6, Monofya 66, Abeeis, and Beauregard were cooked using four different home-cooking methods (boiling, baking, microwaving, and deep-frying). The antioxidant contents (total phenolics by Folin-Denis, and individual phenolic acids by HPLC) as well as the antioxidant activity determined by reducing power(RP),2,2-diphenyl-1-picrylhydrazyl(DPPH),and 2,2’-azinobis(3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS) were measured in this study. Results indicated that total phenolic contents of raw flesh tissue by Folin-Denis ranged from 0.53 to 0.87 mg chlorogenic acid equivalent (mg ChAE)/g dry weight basis (dw). The RP ranged between 0.1 and 0.25 mg ChAE/g dw, DPPH and ABTS radical scavenging activities varied from 1.10 to 1.72 and 0.85 to 1.51 μmol trolox equivalent (TE)/g dw, respectively. Thermal processing significantly (P ≤ 0.05) increased the total phenolic content, as well as individual phenolic acids and antioxidant capacity of all the cultivars under study. In this respect, deep-frying exhibited the highest increment among the four processing methods. The most abundant

Standards of chlorogenic acid, caffeic acid and three isomers (4,5- dicaffeoylquinic acid (diCQA),
3,5-diCQA, and 3,4- diCQA) of isochlorogenic acid (Purity > 98%) were purchased from Chengdu
Biopurify Phytochemicals Ltd., Chengdu, Sichuan, China