Extrusion process of maize grits used for nixtamalization.

The aim of the paper was to seek optimum conditions of extrusion cooking and follow-up processing to produce high-quality tortillas with good sensory properties. Sixteen samples of maize flour were prepared by extrusion with and without alkaline treatment. The extrudate diameters depended primarily on the moisture content of the premix and the temperature in the extruder. Alkaline treatment with calcium hydroxide [Ca(OH)2] had a strong effect on water absorption index (WAI), water solubility index (WSI), pH, and colour of the extrudates. Besides, WAI was influenced by the moisture of the premix and by the temperature in the second zone of the extruder. Soluble dietary fibre (SDF) in the samples with the addition of Ca(OH)2 increased more than in the samples without alkaline treatment. In addition, a higher screw speed influenced SDF. The texture of the tortillas was very dependent on the addition of Ca(OH)2, on the moisture of the premix and the temperature in the second zone of the extruder. [ABSTRACT FROM AUTHOR]