Nitrogen solubility of extruded cereal grains

Abstract

Six whole-grain cereals and quinoa were examined to determine extrusion processing effects on nitrogen solubility. Eight extrusion conditions were applied and effects of cereal variety, extrusion temperature, revolutions per minutes (rpm) and feed moisture on nitrogen solubility were observed. Nitrogen solubility was determined spectrophotometrically. Extrusion conditions resulting in least overall mean percent nitrogen solubility across all cereals studied were observed to be 15% feed moisture, 100°C/150°C product temperature and 100 rpm. A consistent pattern was observed across all cereals with regard to extrusion combination: 25% feed moisture, 100°/150°C product temperature and 150 rpm, resulting in the most favorable overall mean percent nitrogen solubility profile. Extruded rye and quinoa exhibited improved nitrogen solubility over unprocessed counterparts at extrusion conditions of 25% feed moisture, 100°C/150°C product temperature and 150 rpm. Unprocessed corn, millet and low tannin sorghum remained more highly soluble than extruded counterparts, indicating a loss in protein functionality after extrusion. Extrusion, in general, improved nitrogen solubility of wheat. High tannin sorghum was particularly insoluble in both the unprocessed and extruded states. © 1993 Academic Press. All rights reserved.