Improvement of the in vitro protein digestibility of amaranth grain through optimization of the malting process

In recent decades, amaranth grain has been extensively studied for its remarkable nutritional profile and agricultural characteristics, e.g., having a short cultivation period and being drought resistance. Despite possessing a high nutritional quality, amaranth also contains several anti-nutrient compounds that can decrease the bioavailability of its nutrients, especially its protein content. Malting/germination can be employed as an appropriate pre-treatment to improve the nutritional properties of native cereal grains. Therefore, in the present study, the effects of malting including its two important design factors, duration (24, 36 and 48 h) and temperature (22, 26, and 30 °C), on the in vitro protein digestibility and anti-nutrient compounds of amaranth grain were investigated and optimized. The germinated seeds yielded higher protein content (14.86 g/100 g db) and digestion (83.58%) when compared to the native grains, 13.76 g/100 g db and 76.03%, respectively. Significant decreases in phytic acid (30%) and oxalate (38%) and increase in tannin content (47%) were observed. Both germination duration and temperature were found to be significant factors on the measured properties. Over the selected range of variables, it was found that germinating amaranth for 48 h at 28 °C provides the maximum protein digestibility. Finally, correlations between the anti-nutrient content and protein digestibility were observed.