Rinse the lentils and store in a jar in a cool place for a few days, rinsing every eight hours. Source: http://www.livestrong.com/article/527529-myth-of-lentils-as-an-incomplete-protein/. Grains Grains, such as rice, oats, wheat, rye and corn, can act as complementary proteins for legumes such as lentils.They contain the cysteine and methionine that lentils lack, and lentils provide the lysine that grains do not contain enough of. Whole grains are a more nutritious option than refined grains.inse the lentils and store in a jar in a cool place for a few days, rinsing every eight hours. Source: http://www.livestrong.com/article/527529-myth-of-lentils-as-an-incomplete-protein/. Grains Grains, such as rice, oats, wheat, rye and corn, can act as complementary proteins for legumes such as lentils.