Study presents the variation in free amino acids (FAAs) and total AAs in rice at different milling degrees. Two rice cultivars; Pachchaperumal and Bg 406 were subjected to three (4%, 7%, 12%) degrees of milling, and the variations in AA composition of milled rice and resulting bran were studied. Milling caused significant (p < .05) reduction (5.7%–40.0%) of AAs in rice. Milling accounted for an increase in density of FAAs with sweet and sour taste in rice while reducing FAAs with bitter taste. Parboiling unequivocally aided the retention of AAs in rice upon milling. A variety-specific distribution of AAs was observed inside the rice grain. Despite the reduction in AAs upon milling, the nutrient density, which is the ratio between the essential to nonessential AAs was not reduced in rice. Rice bran contained nutritional gamma amino butyric acid (GABA) (19.6%–29.1%) and essential AAs (35.7%–38.8%).

Novelty impact statement

Milling is a post harvesting technique used in the production of rice that improves the physical properties of rice, which are desired by the consumers that include whiteness, translucency and sensory properties as well as the storage stability. The amino acid content in rice is significantly reduced with the increase in milling degree. However, milling increases the ratio between the sum of FAAs with sweet and sour taste to, sum of free amino acids with bitter taste, which could be attributed to one of the factors leading to the enhanced sensory quality observed with the well-milled rice. Parboiling enables the retention of nutritionally and functionally important amino acids that include essential amino acids and gamma amino butyric acid (GABA) during the milling process.