The USDA misspelled the name of this drink in their report. The correct spelling is chiilchin, not chilchen. This confused readers of their report, as they were unable to find information on the latter. Though I guess we shouldn't be surprised given the Federal government's track record with Native Americans!
What is chiilchin? It is the Navajo name given for sumac berries, which come from the staghorn sumac plant (Rhus typhina) of the Anacardiaceae family. The plant is Native to the Southwest United States. In addition to chiilchin (chil'chin and chilchin) it goes by other names including lemonade berry, three leafed sumac, squawbush, and skunk brush.
It is most often consumed in two forms - eaten as a pudding or drank as a beverage.
The English name for the pudding would be sumac berry pudding. It's an ancient recipe with a history going back further than fry bread and Navajo tacos. As a beverage, the sumac berry tea recipe is perhaps the most popular, which consists of steeping the red cones of the berries in hot water, with optional sweetener such as agave and possibly additional herbs.
The amount of antioxidants contained in a typical drink recipe is reflected in this ORAC value.
USDA Database for the Oxygen Radical Absorbance Capacity (ORAC) of Selected Foods, Release 2 - Prepared by Nutrient Data Laboratory, Beltsville Human Nutrition Research Center (BHNRC), Agricultural Research Service (ARS), U.S. Department of Agriculture (USDA) - May 2010