Abstract
As a preliminary step of the microbiological examinations of frozen fish, a study of the bacterial counts was carried out. The results obtained are reported as follows together with some additional information.
1. The deterioration in freshness was proportional to the bacterial counts at low temperature (-40°C), and the counts showed the same patterns as in the case of the pure culture. There appeared to be no connection between the putrefaction rate and the degree of the initial contamination.
2. The number of living bacteria seemed to be closely related to the level of volatile basic nitrogen (VB-N). The initial putrefaction point based upon the bacterial counts comes earlier than that based upon the level of VB-N. The putrefaction may be progressing at the time when the initial putrefaction point in terms of VB-N is detected.
3. There is positive correlation between the number of bacteria and that of coliforms in the flesh of fish. It is significant that the number of coliforms can be determined rapidly as the index of spoilage of the frozen fish.
4. Similarly, the bacterial counts in the ice glaze correlate with the number of bacteria and coliforms on the surface of the fish. This fact suggests that the frozen fish suffers from the secondary contamination.
