Abrasive milling of quinoa: Study on the distribution of selected nutrients and proteins within the quinoa seed kernel

There is big interest in effective fractionation of quinoa to take best advantage of the whole kernel. Knowledge is necessary of the localization of ingredients, the seed structure and its characteristics as well as an appropriate technique to yield the desired ingredients at its best. In this study, quinoa was milled successively eight times for 1 min using an abrasive disk mill. After each milling step, the polished seeds and the removed parts were analysed. With increasing milling time the protein, fat and ash content of the polished seeds decreased, whereas the concentration of glucose (mainly from starch) increased strongly. After 8 min, the remaining kernels lost about 65% of their mass, the final protein, fat and ash content was only 3.35, 1.37 and 0.33%, respectively. Evaluating the abrasive mass showed that the main part of the embryo was removed until the fourth minute of milling, where about 35% of the total kernel was removed. The optical evaluation of microscopic pictures of the dehulled seeds helped interpreting results of the chemical analysis. The detailed protein analysis for Osbourne fractions revealed a shift in the protein fractions ratio over the milling intervals, which is controversial to other reports.