Abrasive Dehulling of Quinoa (Chenopodium quinoa): Effect on Saponin Content as Determined by an Adapted Hemolytic Assay

Abstract

A hemolytic method was optimized and standardized against a commercial saponin preparation to provide a sensitive assay of the saponin content of quinoa. Increasing the extraction temperature and time (beyond 1 hr) and storage (30 C) of ground quinoa flour decreased the hemolytic activity of a crude extract of the grain. For 17 cultivars of quinoa, saponin content ranged from 0.14 to 0.73%, the 1,000-seed weight from 1.99 to 5.08 g, and abrasive hardness index from 40.3 to 80.3 sec. The 1,000-seed weight correlated significantly with both saponin content (r = 0.72, P less than 0.01) and the abrasive hardness index (r = 0.79, P less than 0.01) indicating that larger seeds contained more saponin and were harder. Abrasive dehulling to a flour extraction ranging from 85.2 to 98.8% reduced the saponin content to a low level. Generally, the higher the initial saponin content of the cultivar, the greater the loss of bran required during dehulling. Concentrations of oil and protein were similar in dehulled (flour extraction greater than 90%) and whole grain, whereas ash content was reduced slightly by dehulling. Cultivars with a low level of saponin provide optimum yields with abrasive dehulling.