Effect of soaking process on nutrient bio-accessibility and phytic acid content of brown rice cultivar

Abstract

Grain soaking treatment could reduce phytates improving mineral and protein bioavailability. To evaluate the effects of soaking process with lactic acid on phytates and nutrient content (Fe, Zn, and proteins) from whole rice grain, a surface response methodology with a 32 factorial experimental design was used. The independent variables were time (24, 36 and 48 h) and temperature (35, 45 and 55 C) of soaking. The results showed that soaking decreased total phosphorus (TP) in the range of 35e92.4 mg/100 g compared to 255 mg/100 g in whole rice. The losses of phytate in the grains were between 87 and 91%, the remnant phytic acid phosphorus in the grains being between 15.1 and 20.9 mg/100 g, and the most effective treatment was soaking at 45 C for 48 h. The losses of the different nutrients were high in all of the different soaking treatments, reaching 50% for Fe, more than 64% for Zn, and around 45% for proteins. Although protein digestibility and mineral dialyzability were improved, acid soaking of brown rice would not be suggested as a useful process to reduce phytates from whole rice grains, if the production of a staple food is the main objective.