Partially and extensively hydrolyzed
For example, Nutramigen, Pregestimil, Nutrilon Pepti Junior, Neocate.
These formulas are recommended for babies who suffer from problems in digestion and absorption or if it has been proven that they suffer from a milk protein allergy. These formulas should be used only if your doctor has recommended it for a specific cause.
In Partially hydrolyzed formulas, the protein is broken down into small parts that are easier to digest. In extensively hydrolyzed formulas, the proteins are further hydrolyzed to help the digestion. All the macronutrients are found in a partially-hydrolyzed state - amino acids, fatty acids and simple sugars at different levels of hydrolyzation depending on the specific formula. This process helps the digestion of the nutrients and makes the formula hypoallergenic (if the proteins are fully-hydrolyzed).
Nutramigen and Pregestimil differ from one another in their ingredients, including the fatty acids that are absorbed differently in the body. Pregestimil contains a special type of fat called medium-chain triglycerides (MCT) which is best for infants with a medical problem causing difficulties in the absorption of fat, while Nutramigen is more suitable for babies with an allergy to proteins. Neocate is a formula in which the proteins are found in their most hydrolyzed form (the proteins’ building blocks - amino acids) and is designed especially for babies that are allergic to cow’s milk proteins and serious problems with the digestion of proteins, that didn’t manage successfully with other formulas.
Some babies refuse to eat these formulas because of the sour taste and smell, that is a by-product of the process of hydrolyzation. In any case, it is better to use this formula only if recommended by a doctor and with follow-up.