Impact of different processing techniques on nutrients and antinutrients content of grain amaranth (Amaranthus albus)

Abstract

Grain amaranth (Amaranthus albus) is a pseudo cereal consumed in various parts of the world especially in Africa, India and Nepal. It has attracted increasing interest over recent decades because of its nutritional and functional properties. It can potentially play a great role in mitigating food insecurity and reducing the prevalence of malnutrition in Kenya. Maximum utilization of the nutrient potential of the grain amaranth is limited by the presence of phytates, phenols, tannins, and oxalates which are mineral chelating agents and enzyme inhibiting anti-nutrients. The effects of these anti-nutritional factors may be reduced by some processing techniques. Traditionally, amaranth grain is boiled, popped, roasted, or milled to make gruel for consumption. This study investigated the impact of dry and wet heat processing techniques on the nutrient and anti-nutrient contents of grain amaranth Amaranthus albus. The dry heating processes used included roasting(160ºC 10minutes) and popping(190ºC 15seconds) while the wet heating techniques included boiling whole grains(water: seeds, 4:1) and slurries(water: flour, 6:1. Raw grains were used as the control to determine the impact on nutrient and antinutrient

content after processing. Different processing techniques significantly (p<0.05) reduced the level of unsaturated fatty acids. Mineral contents did not change significantly (p>0.05). A pronounced reduction in the anti-nutrient content (tannins, oxalates, and phytates) was observed in the case of boiling as compared to roasting and popping. The protein digestibility of raw grain was 74.8%. The protein digestibility increased to 86.2% and 92.6% after Boiling and slurring whereas it reduced to 66.3% after roasting. Heat treated and untreated grains, had high content of lysine and arginine. Wet processing resulted to higher starch gelatinization as compared to Dry heating. Different processing techniques had different impact on nutrient and antinutrients components of grain amaranth. Key words: grain amaranth, proximate composition, antinutrients, protein digestibility, starch gelatinization