Gluten is a protein that occurs in wheat and related grains such as barley, rye and tricale - therefore, any food that contains wheat, wheat products or products made from related grains may contain gluten. Common gluten-containing foods include bread, pastries, pasta, soy sauce and processed or imitation meats.
Aside from wheat, grains that contain gluten include semolina, spelt, Kamut and farro. Most of these grains are either closely related to wheat or derivatives of wheat. There are many grains that do not contain gluten. These grains include amaranth, buckwheat, quinoa, corn and rice. Gluten-free versions of foods often use corn or rice flour as a substitute for wheat flour.
Though breads, crackers, baked goods and cereals are some of the most common gluten-containing foods, many foods use wheat flour or other grain flours as an added ingredient. For example, wheat flour is sometimes used as a thickening agent in soups and gravies or as a binding agent in burger patties. If a packaged food does not specify whether it is gluten-free, check the ingredients for the presence of wheat or related grains.
It is possible to make foods gluten-free by replacing the wheat ingredients with another grain. Use gluten-free flour in baking, or substitute a rice-based cereal for a wheat-based one.