Bacteriological investigation of a case of red discolouration in Dutch salted summer herring

An investigation was carried out of a case of reddening in salted herring, caught in August and landed in September 1951.

Cultivation experiments were started using a fish milk medium, containing 10, 16 and 23 wt% of NaCl; incubation was carried out at 37, 30, 24 and 15°C. and both under aerobic and under anaerobic conditions.

Growth of red halophiles was observed exclusively in platings on 23 wt% NaCl. Those incubated aerobically at 37°C. showed growth after 1 month and those at 30 and 24°C. after about 2 months. No growth of red halophiles occurred at 15°C.

The brine and the gonads present in the barrel, containing red herring, and a brine and gonads sampled from a barrel of unspoiled herring, turned out to contain the same red, halophilic sarcinae.

The numbers of these sarcinae in the red and in the undiscoloured brine both were of the order of 100/ml, being about ten times the numbers found in either the discoloured or the normal tissues.

The conclusion must be drawn that the type of red discolouration of herring described here is not caused by red halophilic bacteria.