Thiamin is available to the food and feed industries as thiamin-Cl-HCl (79% thiamin) or thiamin-NO3 (81% thiamin). These compounds are stable up to 100°C and are readily soluble in water. One international unit of thiamin activity is equivalent to 3 mg of crystalline thiamin-HCl. Because it contains a free amino group, heat processing can rapidly destroy thiamin bioactivity via the Maillard reaction. Likewise, any processing procedure that involves alkaline treatment leads to loss of thiamin activity. The thiamin contained in feed ingredients is present largely in phosphorylated forms, either as proteinphosphate complexes or as thiamin mono-, di-, or triphosphates. Some raw ingredients (e.g., fish) contain thiaminases, which can destroy thiamin in diets to which it is added. Whereas thiaminases are of particular concern in the nutrition of cats and fur-bearing animals, they are of little consequence in food-animal production. Fish and meat meals have essentially no bioavailable thiamin activity, primarily due to high-temperature processing of these products.
Pelleting results in some loss of thiamin activity, as does premix storage in the presence of minerals. About 48 and 95% retention of thiamin activity occurs when thiamin is stored in the form of the HCl and NO3, respectively, in a premix for 21 days at 40°C and 85% relative humidity. In a complete feed stored under similar conditions, thiamin-HCl retains only 21% of its activity, whereas thiamin-NO3 retains 97% of its activity. Thus, the mononitrate form of thiamin would seem to be the more stable form when storage in hot environments is anticipated.
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