Polyphenolics and antioxidant capacity of white and blue corns processed into tortillas and chips

White and blue corns of Mexican and American origins were lime-cooked to obtain nixtamals with optimal moisture (48-50%) for tortillas and chips. Blue kernels had less bulk density, softer endosperm and, consequently, required less cooking time than the white kernels. The optimum cooking regime for the white kernels was 100 degrees C for 20 min, while the optimum for both pigmented genotypes was 90 degrees C for 0 min (until the lime-cooking solution reached 90 degrees C). Doughs, tortillas, and chips were characterized by total soluble phenolics (TSP), anthocyanins (ACN), and antioxidant capacity (AOX). A dough acidification procedure using fumaric acid (pH 5.2) was assessed as a means to improve TSP, ACN, and AOX retention. The Mexican blue corn had higher AOX (16%) than the American blue genotype, although the latter had a threefold higher TSP content (12.1 g/kg, dwb). Mexican and American blue corns had higher AOX capacity (29.6 and 25.6 micromolar trolox equivalents TE/g dwb), respectively, than the white corn (17.4 micromolar TE/g). White corns did not have detectable amounts of ACN, while blue Mexican and American kernels contained 342 and 261 mg/kg. Lime cooking had the greatest negative impact on the stability of TSP, ACN, and AOX. However, the acidification reduced ACN, TSP, and AOX losses by 8-23, 3-14, and 4-15%, respectively. Similar ACN losses were observed for both types of blue kernels when processed into nixtamal/dough (47%); however, ACN losses in tortillas and chips manufactured from the American blue genotype were higher (63 and 81%, respectively) than those of Mexican blue corn products (54 and 75%). ACN losses were highly correlated to TSP (r = 0.91) and AOX capacity losses (r = 0.94).