Physicochemical Changes of Starch in Maize Tortillas During Storage at Room and Refrigeration Temperatures

Abstract

Physicochemical changes of starch and loss of texture were determined in maize tortillas during 72 h storage at room and refrigeration temperatures. Properties analyzed included apparent amylose content, content of enzyme resistant starch (RS) type III, and thermal properties determined with differential scanning calorimetry (DSC) and X-rays diffraction. In addition, tortilla firmness was assessed using an uniaxial compression test with a texture analyzer. Storage temperature did not significantly affect firming rate or starch properties, except from thermal properties. Firmness was developed mainly during the first 24 h storage, remained nearly the same during 24—48 h and slightly increased after 72 h storage. Resistant starch (RS) formation followed the same trend as development of firmness. A first order endothermic transition that can be attributed to amylopectin retrogradation was observed after 2 h storage at both temperatures. This transition shifted to higher temperatures during storage, the effect was specially evident for refrigerated tortillas. X ray diffraction patterns of stored tortillas suggested that crystallinity slightly increased during storage. Most of the loss of tortilla texture, determined as firmness, occurred during the first 24 h storage at room and refrigeration storage conditions. This loss of texture was likely due to starch retrogradation and the latter possibly increased content of resistant starch.