Aishath Naila, Steve Flint, Graham C Fletcher, Phil Bremer and Gerrit Meerdink
The aim of this work was to explore suitable methods (bacteria/enzyme) to degrade histamine as an alternative method for the control of histamine in food. Histamine degradation by bacteria was studied in trypticase soy broth containing 500 ppm of histamine at 30°C for 9 days. The bacteria studied were Lactobacillus sakei (AGR 37, AGR 46, Lb 706), Arthrobacter crystallopoietes DSM 20117 and Vergibacillus halodonitrificans Nai18. All L. sakei strains reduced histamine to about 50% while V. halodonitrificans Nai18 degraded histamine by 30%. A. crystallopoietes DSM 20117 did not degrade histamine. Diamine oxidase (DAO), however, degraded histamine (500 ppm) to an undetectable level (<0.1 ppm) in the model system (buffer). DAO was more successful than the bacteria in reducing histamine in the preliminary trials, therefore, DAO was selected for further study in a food system, the tuna soup used to manufacture Rihaakuru, a fish paste product from the Maldives, containing 1% salt at a pH of 6.0. The DAO degraded histamine in the tuna soup to an undetectable level, confirming the potential for DAO to reduce histamine during the manufacture of Rihaakuru. This enzyme may have potential to control histamine in other foods but different appropriate environmental conditions (eg levels of pH) would need to be tested to determine their effect on the activity of DAO.