The effects of processing conditions and maize varieties on physicochemical characteristics of tortilla chips

摘要

The effects of alkaline-cooking and grinding processes, different types of mutant maizes, and deep fat frying processing on physico-chemical characteristics of tortilla chips were studied. The characteristics of masa and tortilla chips were significantly affected by different alkaline-cooking and grinding conditions. Over-cooking of the corns increased the extent of starch gelatinization and resulted in sticky masa with reduced particle size. Tortilla chips prepared from over-cooked masa had increased oil absorption. Finer grinding of nixtamal reduced particle size and released more free starch granules into the masa. Oil absorption of tortilla chips was increased with finer grinding of nixtamals regardless of alkaline-cooking levels.;Endosperm mutant maizes with different amylose/amylopectin ratio significantly affected the nixtamalization process, masa properties, and tortilla chip characteristics. Waxy maize produced masa with proper handling properties when nixtamals had 49-51% moisture. However, tortillas prepared from waxy corn became sticky during and after baking. Tortillas prepared from waxy corn expanded during frying and absorbed more oil compared to chips prepared from normal maize. Mutant maizes with higher amylose content produced less cohesive masa. This was caused by insufficient dispersion of amylopectin in the masa and retrogradation of amylose molecules after cooking. Tortilla chips prepared from high amylose mutants had a darker color than control chips.;Tortilla chips had puffed or bubbly structure which consisted of large and small air cells distributed thoroughly inside of the chips. In general, small air cells were found near the outer surfaces, while large voids and cracks were located in the middle of tortilla chips. Most starch granules inside of the tortilla chips were completely gelatinized and lost their integrity, while those at the outer surfaces retained their integrity. Most frying oil was absorbed into tortilla chips by covering the surfaces and filling the air cells and internal voids by capillary action, rather than bound chemically to endosperm components, e.g. starches.;More than 90% of starches in tortilla chips were gelatinized after deep fat frying. However, some starches in tortilla chips became less soluble, expandable, or dispersible, as evidenced by Rapid Visco-Analyzer, high performance size-exclusion chromatography, and solubility in dimethyl sulfoxide. Thus, chemical modification of starches, similar to cross-linked starches, occurred during deep fat frying. The processing of corn into tortilla chips caused starch to gelatinize, anneal (during steeping), and cross-link (during baking and frying). This information could enhance the organoleptic characteristics of tortilla chips.