PROTEIN BIOLOGICAL VALUE OF EXTRUDED, RAW AND TOASTED AMARANTH GRAIN

Abstract

Amaranth is a false cereal that belongs to the dicotyledonous class and Amaranthacea family. An increase in the production and consumption of amaranth, particularly in tropical regions of the World, should be considered due to its excellent nutritional value. It has the additional advantage that it can be planted as an intermediate crop between successive soybean crops. Extrusion is considered one of the best methods to maximize the nutritive value of amaranth. The objective of this study was to evaluate the protein quality of raw, toasted and extruded amaranth. Defatted amaranth flour was extruded at 150ºC and at four different moisture levels (11%, 13%, 15% and 24%). The samples were extruded through a screw of 3.55:1 compression ratio, 20:1 L/D ratio at the speed of 200 rpm in a laboratory extrusion machine. Individually housed, male Wistar rats 21 to 23 days old maintained under controlled conditions of light and temperature, were used for the protein bioassays. The protein bioassay experiments used a total of eighty rats and were done according to published AOAC methods (1995). The extruded amaranth diet at 24% moisture reached higher corrected protein efficiency ratio (corrected-PER) than all the other treatments. Each of the extruded amaranth diet reached greater net protein ratio (NPR) values than casein control and raw and toasted amaranth diets. On the other hand, the true digestibility (TD) was similar to the raw and all processed grains, extruded and toasted diet, and lesser than casein control diet. The differences between extruded and raw amaranth samples were probably due to destruction of toxic factors present in the raw grain, in combination with increasing palatability, improvement of the carbohydrate use and it was not due to the increasing protein digestibility. The results indicate that extruded amaranth contains very high quality protein.

KEY-WORDS: Extrusion; toasting; amaranth; nutritional value.