Production of Tyramine in "Moromi" Mash during Soy Sauce Fermentation

[Factors Related to the Production of Histamine and Tyramine in Rice Bran Pickles]

Some rice bran pickles contain histamine (Him) and tyramine (Tym), which are nonvolatile amines, presumably produced by microorganisms during the fermentation process. When attempting to identify the histamine- and tyramine-producing bacteria from commercially available cucumber rice bran pickles containing Him and Tym, it was identified histamine-producing bacteria were found to be Raoultella ornithinolytica, and tyramine-producing bacteria were Lactobacillus curvatus. When those bacteria were cultured in media containing rice bran (the raw material for rice bran pickles), Him and Tym were produced. However, it was suggested that Him and Tym were not necessarily produced by the presence or absence of amine-producing bacteria, but rather, their production was affected by the amount of precursor amino acids and other bacteria that were present during rice bran pickles production.

[Content and Origin of Nonvolatile Amines in Various Commercial Pickles]

The content of nonvolatile amines (putrescine, cadaverine, histamine, tyramine, and spermidine) in commercial pickles and their raw materials was determined in order to investigate the origin of these amines and to evaluate possible health risks. The nonvolatile amine content varied depending on the type of pickle; histamine and tyramine contents were relatively high, namely, 6.0-264 and 2.0-369 _μg/g, respectively, especially in soybean paste pickles and moromi pickles. Amines derived from raw materials were detected in soy sauce pickles, soybean paste pickles, and moromi pickles. However, the raw materials/vegetables of rice bran pickles, sake lees pickles, and malt pickles did not contain these amines, and so the amines in these pickles might have been produced by microorganisms during the fermentation process. Judging from the measured amine content of pickles, the potential health risk is estimated to be low.

Selective inhibitors of monoamine oxidase type B and the "cheese effect"

Potentiation of the cardiovascular and other effects of dietary tyramine by monoamine oxidase (MAO) inhibitors (cheese effect) has been a major limitation to clinical use of these drugs. The discovery that MAO exists in two distinct isoforms, MAO-A and MAO-B, together with the development of selective inhibitors of each isoform, enabled the understanding that selective inhibition of MAO-A, or inhibition of both isoforms, will cause cheese effect, but selective inhibition of MAO-B can be elicited without dangerous pressor reaction. This development has permitted the introduction of selective MAO-B inhibitors to clinical medicine for treatment of Parkinson's disease. This review describes the basic mechanisms involved in cheese effect, as well as providing information on tyramine levels in a variety of foodstuff, and surveys clinical information from tyramine pressor testing with the selective MAO-B inhibitors, selegiline and rasagiline.