As a method to measure freshness of fish, the determination of volatile basic nitrogen in flesh is adapted in many cases.
The author examined a method usually employed in preparing the sample for the determination to see if it is really efficient for the purpose. The following results were obtained.
The sample solution to be used for the determination has been prepared by adding acidic protein precipitants to a fish flesh. When the sample was kept in store under certain conditions, the amount of volatile basic nitrogen increased in it.
The increase of volatile basic nitrogen may be attributed to the presence of precipitated substances. Because no increase are observed in the sample solutions which have been filtered and stored in a cold place.