A New Type of Flat Sour Spoilage of Commercial Canned Coffee

A New Type of Flat Sour Spoilage. II

Abstract

In order to confirm the role of obligate anaerobes (O. A.) in a new type of flat sour spoilage found in Japan, detailed investigations were carried out on commercial canned coffee.
Two kinds of canned coffee samples were taken from lots which had suffered from flat sour spoilage. The samples were incubated both at room temperature and at 55°C, and examined microbiologically.
No spoiled cans were found among the samples incubated at room temperature. However, forty and sixteen spoiled cans were found in the samples incubated at 55°C. The spoilage rates were 8.9% and 3.6%, respectively. The appearance, and the changes of pH, vacuum level and flavor of these samples were very similar to those of cases of O. A. flat sour spoilage.
Spore-forming obligate anaerobes, which were identical with the causative bacteria of O. A. flat sour spoilage, were isolated without delay from 27 out of 30 spoiled cans opened under aseptic conditions.
Thus, a high ratio (27/30) of successful isolation of the bacteria from the spoiled cans was achieved.