Enumeration of Coliform Bacteria in Light Salted Fish Brines

For the enumeration of the coliform bacteria present in light salted fish brines, the most probable number (MPN) procedure has been applied. Results have shown that lactose fermentation is inhibited when the inoculation of brine aliquots into plain lactose broth produces a final NaCl concentration higher than 3%. Thus erroneous low counts are obtained. It was found that this inhibitory effect could be obviated by diluting commercial fish brines with an equal volume of sterile distilled water before inoculation. The total number of coliform bacteria was determined in a number of brine samples collected at three different fish processing plants. The recommended dilution has resulted in an average 40-fold increase in total counts. All the samples collected contained significant numbers of coliform bacteria indicative of faecal contamination.