Thiamin hydrochloride is a colorless crystal that is freely soluble in water (1g per ml), whereas the mononitrate salt is only sparingly soluble (27 mg per ml).
Thiamin hydrochloride is relatively stable to air if protected from light and humidity. Thiamin mononitrate is fairly stable to air if protected from light and is less sensitive to humidity than thiamin hydrochloride. The mononitrate salt is typically more stable than the hydrochloride salt under similar conditions.
Thiamin salts are usually stable in dry multivitamin premixes that contain no added choline or trace elements but are rapidly destroyed under alkaline conditions or in the presence of sulphide.
The thiamin-destroying enzyme thiaminase is present in certain raw fish, shellfish, rice polishings, Indian mustard seed, mung bean (green gram) and linseed (Liener, 1980). Thiaminase has long been recognized in some raw fish preparations and is more commonly found in freshwater fish than in marine fish. Fish species that contain thiaminase, as well as some that do not, were reviewed by the National Research Council (NRC, 1983). Thiamin is destroyed only after contact with the thiaminase over time (Ishihara and Yasuda, 1974). Heating to 83°C for at least five minutes or ensiling thiaminase-containing raw fish reduces thiaminase activity (Greig and Gnaedinger, 1971; Anglesea and Jackson, 1985).
Thiaminase has been suggested as the causative agent identified in Cyuga, or M74, syndrome in the Great Lakes, the Finger Lakes of New York and in the Baltic Sea (Fisher et al., 1996, 1998; Amcoff et al., 1998; Fitzsimons and Brown, 1988; Fynn-Aikins et al., 1998; Hornung et al., 1998; Ji et al., 1998). Low maternal thiamin status was shown to affect larval survival (Fisher et al., 1996; Fitzsimons and Brown, 1988; Ji et al., 1998).
