COLOR AND NUTRACEUTICAL CHARACTERISTICS OF NATIVE MAIZE (Zea mays L.) TORTILLAS PREPARED WITH DIFFERENT DOSES OF ALKALI AND REFRIGERATED

Nixtamalization of maize grain with anthocyanins causes considerable loss (50-75 %) of these compounds in its transformation process to tortillas. Little information exists on the effect of different alkaline pH of tortilla during storage in refrigeration. The aim of this study was to determine the effect of different alkali concentrations during nixtamalization on color, phenolic variables and antioxidant capacity (AC) of tortillas made with maize kernels with anthocyanins and stored in refrigeration. A purple blue grain maize variety (AZM) and a cherry red grain maize variety (RC) were used. Alkali concentrations were 0.5, 0.7, 1.0 and 1.5 %, and tortilla storage times were 1, 6 and 12 days. Phenolic variables included total anthocyanin content (TAC) and total soluble phenols (TSF). Antioxidant capacity (AC) was measured with the ABTS [2,2 & PRIME;-azinobis (3-ethylbenzothiazoline-6-sulfonic acid)] and FRAP (ferric reducing antioxidant power) methods. The effect of alkali on the color of tortilla was different according to the color of the grain. The AZM maize tortilla intensified its blue color when the alkali was increased to 1.0 %; in higher concentrations a yellowish tone predominated, while in RC, the pink color prevailed up to the concentration of 0.7 %; higher concentrations induced a yellowish tone. At the end of storage, the AZM tortilla lost between 61 and 76.8 % of its initial CAT, while in the RC tortilla the losses varied between 23 and 45.5 %, depending on the dose of alkali used. The CA of the tortillas was preserved during storage when low concentrations of alkali were used. The effect of the amount of alkali during nixtamalization of the grain on the color, CAT, FST and CA differs according to the color of the grain, and influences the stability of anthocyanins during the storage of tortillas.