Effect of heat treatment and milling on the seed, flour, rheology and baking quality of some amaranth ecotypes.

Forty-five harvests corresponding to the two predominating domestic species of amaranth in Mexico were studied. The proximate analysis revealed some statistically significant differences throughout three years of observation. The Ca, P and Fe content did not vary greatly in 15 samples. No chemical differences were either manifested in the Mercado and Aztec types of A. hypochondriacus, nor in the Mexican type of A. cruentus. The latter exhibits a higher grain yield and a shorter life cycle; however, its baking quality is apparently inferior to that of the Mercado type of A. hypochondriacus. The heat treatment of the seeds (toasting, popping and cooking) affected protein and lysine contents as does in cereals and leguminous seeds although toasting in particular improves its sensory characteristics without altering digestibility and PER. Popping only improves PER. Heating at 90 or 170 degrees C for three to five minutes, at the usual seed's moisture rate of 6 to 15%, does not affect protein content and does so only slightly in the case of the fatty acids content. Amylographic and farinographic values of the starchy fractions indicate similarities to C. quinoa and differences with respect to wheat. In the case of "amaranth milk", viscosity and gelatinization temperature produced satisfactory values. The extension of amaranth cultivation in the country is hereby suggested in view of the seed's nutritional quality, and considering the behavior of whole amaranth flour and its fractions.