According to Impossible Foods, the main protein source in an Impossible burger is soy protein concentrate and isolate. To emulate the way real meat sizzles on a grill, the patties use sunflower and coconut oils as the fat. Impossible burgers are also made with natural flavors, water, cultured dextrose, yeast extract, soy leghemoglobin, modified food starch, methylcellulose, salt, L-tryptophan, and tocopherols, which are antioxidants. Methylcellulose and food starch help bind the patties together and allow them to be easily formed into kebabs, meatballs, meatloaves, and more. To give the patties a meaty flavor, Impossible Foods uses a molecule called heme that can be found in soy leghemoglobin, which comes from soy roots (via Impossible Foods). Impossible burgers are completely vegan and gluten-free, but they should be avoided by anyone with a soy allergy.
As far as nutrition goes, one 4-ounce Impossible burger patty has 230 calories, 12 grams of fat, 9 grams of carbohydrates, 370 milligrams of sodium, and 19 grams of protein. Each patty also contains 180 milligrams of calcium, 4.2 milligrams of iron, 700 milligrams of potassium, thiamin (vitamin B1), riboflavin (vitamin B2), niacin, zinc, phosphorus, vitamins B6 and B12, and folate.