Saponin

A powdery resin that covers quinoa seeds, which must be rinsed off before the seeds can be used. If the seeds are not rinsed properly, the resin will produce a bitter flavor that can be very unpleasant. Quinoa sold in the United States (including imported quinoa) is washed and well processed, so the saponin usually is not an issue; however, it is still a good idea to give the seeds a quick rinse before cooking.

To cleanse unprocessed quinoa, wash the seeds in a large bowl containing cold water. Rub the seeds briefly in the water to loosen the resin; then strain the quinoa (the strainer should be made of a fine mesh because the seeds are so small). To finish the process, the strainer should be positioned under cold running water, rinsing the quinoa until the water runs clear.