Changes in saponins, phenolics and antioxidant activity of quinoa (Chenopodium quinoa willd) during milling process

Abstract

Quinoa seeds were milled in order to investigate the effect of the degree of milling (DOM) on the content of saponins, free and bound phenolics, and their antioxidant activity evaluated through oxygen radical absorbance capacity (ORAC) and ferric reducing power (FRAP). Results showed that saponins, responsible for a bitter taste and anti-nutritional effects, can be effectively removed from quinoa during the milling process. As the DOM increased from 0% to 27.23%, the total saponin content decreased by 41.8%, while the total phenolic and flavonoid contents decreased by 31.5% and 41.4%, respectively. The total ORAC and FRAP antioxidant activities also decreased by 39.6% and 40.7%, respectively. However, the contribution of the bound fraction to the total phenolic content changed slightly from 18.7% to 19.1% (p > 0.05). In addition, the contents of twelve phenolic compounds including both free and bound forms decreased significantly with increasing DOM. Gallic and ferulic acids were found to be the major compounds present in the free and bound forms, respectively. Therefore, low DOM (<15.89%) is recommended for acceptable sensory quality and retention of these phytochemicals during quinoa milling process.