Moisture and freezing of amaranth grains and their thermal expansion capacity

Abstract

The objective of this work was to evaluate the influence of moisture content, storage temperature, and moment of hydration of amaranth (Amaranthus cruentus L.) grains on their expansion capacity, as well to compare the chemical compositions of raw and popped grain. The attributes mean weight diameter, volume of expansion, density, yield, amount of non popped grains and residence time of BRS Alegria grains were evaluated according to three grain moisture contents (9.5, 11.5 and 13.5%), two forms of storage, environment temperature (±28°C) and freezing (-18°C), and two different stages of hydration, before and after freezing. A metal plate was heated to 215°C to pop the grains. Frozen grains with 13.5% moisture content had higher average diameter and volume expansion, lower density and residence time. The grain moisture content of 13.5% produced the highest yields and grain expansions. The storage at -18°C provided larger and lighter popping than the environmental one. Popping presented reduced protein and insoluble fibers and increased lipid and soluble fiber in relation to the raw grain. Frozen grains at -18ºC and hydration at 13.5% moisture, favors the popping of amaranth, and results in higher quality of the popped grains.