The effects of processing on the content of amino acids and fatty acids and the release of glucose from quinoa grains were evaluated in this paper. The processes included dehulling, boiling, extrusion, heating under pressure, and baking (infrared heating). The retention rate (AR) of essential amino acids and fatty acids of dehulled and boiled quinoa was 100%. The oil content of the extruded quinoa samples of two varieties was 47.71% and 39.75% lower than the corresponding raw quinoa samples. Baking and heating under pressure had different effects on the essential amino acid content, fatty acid content, and hydrolysis rate of quinoa starch. The results indicated the different cooking methods affect the essential amino acid content, fatty acid composition, release of glucose, and nutritional quality of quinoa, and moderate processing should be adopted to fully utilize the essential amino acids, fatty acids, and starch in quinoa.

Heating under pressure treatment (HUP) is a method which can keep the complete form of quinoa grain after processing, which is beneficial to the development of subsequent products. The conditions for quinoa heating under pressure was optimized by response surface methodology to be: quinoa grains were regulated with adding 6.3% of pH 7.0 water and heated under 0.36 MPa pressure for 3–5 min, resulting in the predicted maxima of total phenolic content (TPC), Flavonoid and Saponin content were 313.21 mg GAE/100 g, 1.621 mg/g, and 16.78 mg/g and the values of OH Scavenging Rate, DPPH Scavenging Rate, ABST+ Scavenging Rate were 69.45, 91.73, and 52.38% separately. The content of flavonoid and saponin in the HUP samples were more than that in the boiled, baked, and extruded samples, which were close to that in raw quinoa sample, and meaning high retention of active phytochemicals and antioxidation activity in HUP quinoa. The hydroxyl radical scavenging rate is related to the content of polyphenol, flavonoid and saponin.

This study conducted a detailed evaluation of the nutritional value and proximate composition of milled quinoa grain at different dehulling rates with the goal of identifying a range of dehulling rates that retain the maximum level of nutrients and phytochemicals.Eleven samples of quinoa grain processed at different dehulling rates were obtained through light abrasive milling. The relationship between the dehulling rate and the nutritional composition of quinoa grain was determined. As the dehulling rate increased, the proportions of protein, fat, dietary fiber and ash decreased, whereas the proportion of starch increased. With the increase of dehulling rate, increasing amounts of protein, fat, starch, dietary fiber, saponin, flavonoids, and total phenolic were lost with the hull residue. At the dehulling rates of 8.6%, 11.72% protein, 7.57% fat, 4.72% starch, 28.9% total dietary fiber, 45.5% soluble dietary fiber, 48.58% saponin, 26.18% flavonoid, and 42.25% total phenolic were lost in dehulled quinoa grain compared with the raw quinoa grain. Optical microscope photos and scanning electron microscope (SEM) images showed that only the pericarp of quinoa was scoured when the dehulling rate was below 8.6%, and the quinoa grain retained a complete embryo. Therefore, to retain maximum nutritional and phytochemical content in the quinoa and maintain quinoa grain integrity, it is necessary to limit the dehulling rate of quinoa in the range of less than 8.6%.