| A dry process, using hot air jets to cook tempered corn for dry masa flour production, was developed and evaluated. The new process required less energy and water than the method (nixtamalization) presently used. The effect of water availability and temperature, 20, 30 and 40$spcirc$C, on tempering time was assessed. Corn was tempered with 100, 85, or 70% of the water necessary to raise its moisture to 30% and agitated for 12 hr. The remaining tempering water (15% or 30%) was added and agitated for about 2 hr. The tempered corn was cooked at 204$spcirc$C for 2.75, 2.33, or 1.08 min; or 232$spcirc$C for 1.75, 1.33 or 1.08 min; or 260$spcirc$C for 1.5, 1.16, or 0.83 min, and ground with a Wiley mill using a screen plate with 6 mm diameter perforations. The ground corn was hammermilled to produce coarse and fine flours. Particle size distribution (PSD), moisture content, water absorption, and pH of the experimental flours, and masa and tortillas made from them were evaluated. The shortest tempering time was 3 hr for a temperature of 40$spcirc$C when excess water was used. Coarse flours had larger PSD when the percent of water added at the beginning of tempering was increased (70, 85, 100%), and/or the cooking temperatures were higher (except for short cooking times), but fine flours were not affected. Fine flours had higher water absorption capacity, shorter mixing times, and produced better masa and tortilla quality than coarse flours.;In general, higher cooking temperatures rendered better masa and tortilla quality than lower temperatures. Samples cooked at 232$spcirc$C for 1.75 or 1.33 min, or 260$spcirc$C for 1.5 or 1.33 min produced flours with different degrees of starch gelatinization and water absorption capacity. Nevertheless, they produced about the same good masa and tortilla quality when processed using pilot plant equipment. Samples cooked at 204$spcirc$C for 2.16 min, 232$spcirc$C for 1.08 min or 260$spcirc$C for 0.83 min did not produce cohesive masas. Dry cook flours needed more starch gelatinization and water absorption capacity to produce masas with characteristics similar to commercial flours. |
