Protein hydrolysate

A protein hydrolysate is a protein broken into smaller fragments, peptides, by enzymatic hydrolysis, used in pet food mainly to reduce the risk of an allergic reaction. The immune system often recognises a whole protein, so breaking it into small enough fragments lowers the chance it triggers a reaction. Hydrolysates are central to veterinary [elimination diets](/glossary/elimination-diet) for animals suspected of food allergy or intolerance. The degree of hydrolysis matters: smaller fragments mean lower theoretical allergenic potential, though never zero, and a reaction can still occur in some sensitised animals (FEDIAF). These foods call for supervised use, usually on veterinary advice, since they also serve as a diagnostic tool during a trial. A hydrolysate differs from a novel protein such as [horse](/glossary/horse) or [venison](/glossary/venison-deer): it acts on protein size rather than on novelty of source. Palatability can be reduced because hydrolysis alters taste, and the cost is higher than a standard food. Of note, in the European Union these products fall under dietetic foods intended for particular nutritional purposes (Regulation (EU) 2020/354). The marker: a hydrolysate works by shrinking the protein the immune system can recognise, and it is one of the two main strategies (with novel proteins) behind managing a [food allergy versus food intolerance](/glossary/food-allergy-vs-food-intolerance), often within [inflammatory bowel disease](/glossary/ibd-inflammatory-bowel-disease) workups.

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