Improvement of the quality of parboiled rice by using anti-browning agents during parboiling process

Abstract

Browning occurs in parboiled rice as a result of the Maillard reaction that negatively affects consumers' acceptability. The aim of this study was to evaluate the ability of gallic acid, glycine, reduced glutathione and l-cysteine at 0.1, 0.5, 1.0 and 2.0% levels to inhibit browning reactions during the parboiling of rice. Gallic acid and l-cysteine did not exhibit browning inhibition effect at the studied levels. On the other hand, glycine and the higher concentrations of reduced glutathione (1.0 and 2.0%) were able to promote a whiter color and a low free 5-hydroxymethyl-2-furaldehyde content (HMF). The highest level of 2.0% for glycine and reduced glutathione favored protein extractability and a weaker protein-starch matrix, roughly increasing the broken grains percentage. Cooking time changed just for reduced glutathione-treated rice, as a result of their weaker protein-starch matrix and the greater ability of the grains to soften during cooking.

Keywords: Glycine-treated rice; Maillard reaction; Parboiled rice; Reduced glutathione; Rice whiteness.