If quinoa is not described as “pre-washed” when purchased, you must rinse it thoroughly before cooking. It contains naturally occurring saponin, which protects the seed in nature. If consumed it can have some uncomfortable side effects.
To rinse well, place it in a cheesecloth-lined fine sieve. Rinse and drain 2 to 3 times, changing the cheesecloth after each time. Let drain thoroughly before cooking.