Identification of the species of origin of cooked fish by isoelectric focusing

Some proteins in fish are relatively heat-stable. They can be extracted with water and separated by isoelectric focusing to produce a band pattern that is unique to a species, even after it has been cooked. Major changes occur to this pattern in the first few minutes of cooking, but other, species-specific, changes have been observed to occur over longer cooking times. Using a range of cooked standards, it has been possible to identify the species of origin of fish from retailers of fish and chips.