Composition and physico-chemical properties of grain flour and leaves of different amaranth accessions
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Grain amaranth is widely consumed in the world as grain and vegetable. However, there is limited information on the variation in properties of different grain amaranth accessions. The aim of this study was to determine the nutritional composition of grain amaranth flours and total carotenes of amaranth leaves from different amaranth accessions. The nutritional characteristics determined for grain included crude protein, crude fat, total carbohydrate, moisture, ash, iron, calcium. The functional properties determined included; water absorption, water solubility index, viscosity and pasting properties. For leaves total carotenoids content was determined. Sensory acceptability was determined on the porridges. Statistical analysis was carried out using Statistix 9 statistical package. The data were subjected to Analysis of Variance (ANOVA) and differences between means were determined using Tukey HSD test at 5 % (p = 0.05). The crude protein content ranged from 14.79 - 17.98%. There were significant differences (p< 0.05) in the protein content among the 35 amaranth accessions, accessions PI 633596, PI 482049, PI 477915, PI 604669, PI 558499, PI Golden, PI 477913 and PI 608661 recorded the highest protein content. The crude fat content ranged from 3.81 – 6.49 %, carbohydrate content ranged from 22.88 – 76.47 %, moisture content ranged from 9.74 – 12.84 %, ash content ranged from 1.96 – 3.19 %, calcium content ranged from 2106.2 – 4209.7 ppm and iron content ranged from 75.1 – 1455.6 ppm. There were significant differences (p<0.05) in the crude fat, carbohydrate, moisture, ash, calcium and iron in all amaranth accessions studied. The variations indicate differences in genetic factors because production of different accession was done under same conditions. The high protein content in all the accessions (14.79 – 17.98 %) indicates that amaranth is a good source of proteins. Total carotenoid content of grain amaranth leaves ranged between 20 – 47mg/100 g for all accessions. The high levels of total carotene in these accessions indicate the potential of grain amaranth leaves to prevent Vitamin A deficiency which is a public health concern in Uganda. Pasting properties results indicate significant differences (p<0.05) observed in all the accessions evaluated. For most of the accessions peak viscosity (PV) ranged between 7,916.3 cP for accession PI608018 to 1,892.3 cP for accession PI 642737. Pasting temperature (PT) ranged between 73.43°C for accession PI 553073 to 91.20°C for accession PI 642737. Peak time (PT) ranged between 4.17 minutes for accession PI 553073 to 6.97 minutes for accession PI 642737. The variation in pasting properties among accessions indicates differences in amylose content and other constituents like proteins. The high pasting temperature indicate high resistance to disintegration of starches molecules, therefore more cooking required and energy consumed.