Optimization of anthocyanin and effects of acidulants on phytochemicals and antioxidant activities in purple waxy corn cookies

The objectives of this study were: 1) to investigate the optimal condition of purple waxy corn cookies (PWCCs) process on the maximal anthocyanin content using response surface methodology (RSM) 2) to evaluate the effects of adding organic acids of PWCCs on the total anthocyanin content (TAC), total flavoniod content (TFN), total phenolic content (TPN), 2,2’-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging ability (ABTS-RSA), ferrous chelating ability (FCA) and 3) to investigate the effects of storage temperatures of PWCCs on TAC and total plate counts (TPC). The optimum condition for maximal TAC (221.47 µg CE/g) was: 1.08% guar gum content and 24.5% water content (flour base basic). The acidification of PWCCs with four organic acids including citric acid, fumaric acid, glucono-delta-lactone (GDL) and lactic acid at 0, 1, 2, 3, 4, 5, or 6% (flour weight basis) could reduce TAC, TFN, TPN, ABTS-RSA and FCA degradations. In addition, PWCCs exhibited a significant decrease in phytochemical and antioxidant degradations as increasing of acid concentrations. However, acidified PWCC with 3% citric acid showed the highest of TAC (269.2 µg CE/g), TFN (398.9 mg QE/g), TPN (688.6 mg GE/g), ABTS-RSA (3.8 mg TE/g), and FCA (544.6 µg EDTA/g). Lightness and chroma values of PWCCs were significantly increased as acid concentrations increased meanwhile hue value was decreased. Storage condition of PWCCs at 4 oC could reduce the anthocyanin degradation and the growth of microbes higher than storage at room temperature. This study confirmed that RSM was appropriately used to maximize the anthocyanin contents in PWCCs and adding organic acids could reduce the phytochemical and antioxidant degradations as well as microbial growth.