Bacteriological Quality of Tuna Fish ( Thunnus thynnus ) Destined for Canning: Effect of Tuna Handling on Presence of Histidine Decarboxylase Bacteria and Histamine Level.

The present paper analyzes the bacteriological quality and histamine content of tuna fish samples destined for canning. Raw material used in the canning process was of good quality. Histamine-producing bacteria counts were only found in three samples from the last step of the canning process before sterilization. Most of the bacteria identified as histamine formers were gram negative, and nearly all of which belonged to the Enterobacteriaceae family. Morganella morganii was the most frequent and active histamine former in tuna fish destined for canning. Other powerful histamine-producing bacteria isolated during the canning operation were Klebsiella oxytoca , Klebsiella pneumoniae and some strains of Enterobacter cloacae and Enterobacter aerogenes . They all were able to produce more than 500 ppm of histamine in experimental conditions. Most of these species might be expected to be found as a result of contamination of fish during capture and subsequent unhygienic handling in the canning plant. An increase in histamine content in tuna meat was not expected through the canning process. Histamine content always was acceptable in accordance with the maximum allowable levels of histamine fixed by both the European Economic Community and Food and Drug Administration.