N M OBrien and T P OConnor

Biogenic amines are non-volatile, low molecular mass aliphatic, alicyclic or heterocyclic organic bases. Typically, they originate in foods from the decarboxylation of specific amino acids. Decarboxylation can occur due to indigenous decarboxylases in foods or to decarboxylases produced by microorganisms in the food. Biogenic amines are found in a variety of foodstuffs, most commonly fish of the families Scombridae and Scombereoscidae, but also in cheese. In cheese, biogenic amines are produced by decarboxylation of amino acids during ripening. Levels produced vary as a function of ripening period and microflora. High levels of biogenic amines are most likely to be detected in cheeses heavily contaminated with spoilage microorganisms. The principal biogenic amines detected in cheese are histamine, tyramine, tryptamine, putrescine, cadaverine and phenylethylamine. The ingestion of biogenic amine-containing foods may cause adverse toxic reactions. Some of the biogenic amines have vasoactive properties (e.g. histamine, tyramine, phenylethylamine, tryptamine) while others act primarily by inhibiting histamine detoxifying enzymes, e.g. the putrefactive amines, putrescine and cadaverine.

Histamine toxicity can result in a wide variety of symptoms such as rash, urticaria, inflammation, nausea, vomiting, diarrhoea, abdominal cramping, hypotension, tingling sensations, flushing, palpitations and headache. In general, toxic symptoms are relatively mild and many patients may not attend a doctor. Thus, the exact prevalence worldwide of histamine toxicity is unclear. The prevalence of cheese-related toxicity is also unclear although several incidences have been reported in the literature. For most individuals, ingestion of even large concentrations of biogenic amines, such as histamine, does not elicit toxicity symptoms since they are rapidly converted to aldehydes by monoamine oxidase (MAO) and diamine oxidase (DAO) and then to carboxylic acids by oxidative deamination. These enzymes, present in the gastrointestinal tract, may prevent/ reduce the absorption of unmetabolised histamine into the bloodstream. However, if MAO and DAO are impaired due to a genetic defect or the presence of potentiators such as foodborne putrefactive amines (e.g. putrescine, cadaverine) or pharmacologic agents (e.g. isoniazid), adverse reactions may occur on ingestion of biogenic amines. Putrescine and cadaverine have been reported to inhibit two histamine-detoxifying enzymes, DAO and histamine N-methyltransferase (HMT). Many bacteria, especially Enterobacteriaceae [65], are capable of producing putrescine and cadaverine as they possess ornithine decarboxylase and lysine decarboxylase. Tyramine, tryptamine and phenyl-ethylamine can also act as potentiators. Tyramine is the only inhibitor present in significant quantities in cheese. The anti-tuberculosis drug isoniazid inhibits histamine-metabolising enzymes and has been reported to result in histamine poisoning in conjunction with cheese consumption. Other drugs administered as antidepressants, antihistamines and antimalarials can sometimes inhibit histamine-metabolising enzymes.

Factors influencing formation of histamine and other biogenic amines include the following.

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