Determination method of oligopeptides and free amino acids in fish meal

The tannic acid was selected as the precipitant of peptide in fish meal.The contents of protein and free amino acids in the filtrate of fish meal are determined by the Kjeldahe method and formaldehyde-titration method respectively, then calculate the contents of oligopeptides.The results showed that this method was convenient in operation and suitable for application in the determination of oligopeptides and free amino acids in large fish meal samples and the results were good in determination of oligopeptides and free amino acids in fishmeal by using this method.