Hydrolyzed Yeast

Hydrolyzed yeast is yeast whose cells and proteins have been broken down into smaller pieces, and it is used in small amounts in cat food. Tufts veterinary nutritionists describe cats as carnivores with special nutrient needs, so yeast plays a minor part next to animal protein. We found no FDA restriction on it in pet food. If your cat has a food allergy or medical condition, ask your veterinarian.

Source: sites.tufts.edu

Hydrolyzed yeast is added mostly for flavor. Breaking yeast down releases savory compounds that give food a taste close to broth. It also brings B vitamins, some protein and a fiber called beta-glucan. Makers sometimes use it as a palatability booster in dry food.

Hydrolyzed means the ingredient was broken down with water, usually with the help of enzymes or acid. Large proteins are split into smaller peptides and amino acids. That makes the ingredient taste stronger and dissolve more easily. The same word appears in hydrolyzed protein diets, where the goal is pieces small enough that the immune system does not recognize them.

They are close but not identical. Hydrolyzed yeast usually means the whole yeast was broken down, cell walls and all. Yeast extract is the soluble part left after the cell walls are separated and removed. Both add a savory flavor, and both have their own pages on Pettings.

Pettings gives hydrolyzed yeast 3 out of 5 and lists it as a yeast ingredient. It appears on 5 of the 149 dry cat foods we list. It usually appears low on the ingredient list. Each food's page shows how it scores overall.