Development and characterization of an instant tortilla flour from sorghum and maize by infra-red cooking (micronizing) and extrusion cooking

Abstract

The pH, density, water absorption index, color, viscosity, particle size, and chemical composition of nine, U.S. and Mexican, nixtamalized, instant maize (NIM) flours, measured in 1983 were different (p = 0.05) from those measured in 1982. However, the properties of U.S. NIM flours were less variable between years than those of Mexican NIM flours. Highly acceptable tortillas were made from Mexican and U.S. flours having a uniform particle size distribution ((TURN)35% flour on each U.S. sieve Nos. 60, 70, and 80), a peak viscosity of 300 (+OR-) 50 B.U., a pH around 7.2, a white to a semiyellow color (L = 82.0, b = 12.0), and a water absorption index of 1.3 g water/g dry flour. Masa from these flours was cohesive (non-sticky) and could be easily shaped in commercial tortilla equipment. The properties outlined were coined as quality criteria and they were used to develop experimental micronizing and extrusion processes for sorghum or maize. Micronizing, a dry heat process, bypassed the long steeping and drying stages found in the traditional alkaline method (nixtamalization) and the milling and drying operations of extrusion-cooking. Nixtamalization and extrusion-cooking were more heat and time intensive processes than micronizing. This could lead to substantial savings in energy by micronizing grain sorghum for tortillas. Micronized sorghum flours were whiter, had higher water absorption indices (higher yields of tortillas), had better aroma, and the masas were more cohesive than those from extruded flours. Extruded tortillas were less acceptable than micronized or nixtamalized tortillas because of a brownish color and the lack of a alkaline aroma which were improved by extruding a sorghum meal with a coarser particle size. A firm basis to select and manufacture an instant, tortilla flour from sorghum or maize was established. Micronized or extruded sorghum could be used in the preparation of tortillas either alone or blended with an NIM flour. Sorghums have economic and agronomic advantages over maize in certain regions, and it may be an alternative to replace maize, provided an adequate milling technique and the optimum cooking conditions are used.