Cereal Chem 64:218-222   |  VIEW ARTICLE

Nutritional and Functional Characteristics of Extrusion-Cooked Amaranth Flour.

C. Mendoza M. and R. Bressani. Copyright 1987 by the American Association of Cereal Chemists, Inc. 

Two amaranth grain selections, GUA-17 (Amaranthus cruentus) and CAC-38 (A. caudatus), were processed into flours by extrusion cooking. Two samples of GUA-17 were cooked at 146 and 154 C and one sample of CAC-38 at 154 C using a Brady extruder. The nutritional value of the extruded flours was evaluated by net protein ratio (NPR) assays, and their functional properties were characterized by water absorption index, water retention, amylographic viscosity, damaged starch, and available lysine. The extruded amaranth flours contained slightly more protein and fat than the raw flours, suggesting some contamination with the soybean used to adjust the equipment for extrusion. Furthermore, the extruded flours had higher water absorption, water retention, and damaged starch than the raw samples. Peak Brabender viscosity was reached at 58 C and was higher for raw GUA-17 than for CAC-38, with a peak value of 46 C. Extrusion cooking decreased the viscosity in the extruded flours of both cultivars; however, peak values for CAC-38 were observed at 25 C and for GUA-17 at 48 and 44 C. Available lysine was not affected by extrusion cooking. The GUA-17 sample extruded at 154 C had a higher NPR (3.59) than the sample processed at 146 C (3.04), and both were higher than the raw sample (2.19). Likewise, CAC-38 processed at 154 C had an NPR of 3.30 as compared to a value of 2.35 for raw. The energy density of a drink based on the GUA-17 extruded flours was partially determined by some hydrolysis of the starch through the addition of 10% germinated amaranth grain. The drum-dried product retained its original protein quality (3.14) with higher total sugar content, higher water retention, and no change in available lysine. A food product containing 45.64% of the extruded and hydrolyzed amaranth flour with 8.72% milk and 45.64% sugar was shown to be acceptable, although some panel members objected to the viscous nature of the drink.