117 Chemical Determination of Thiamine in Cereal Products

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Methods Type: Generic Methods
Key data
Number: 117
Analyte: Thiamine (Chemical Determination)
Matrix: Cereal Products
Year of Approval: 1972
Scope: The following method is applicable to cereals and flour as well as to cereal and starch products.
Principle: In order to free the thiamine from the natural ester and protein bonds, the material to be examined is digested with sulphuric acid and subsequently treated with a phosphatase preparation. In order to exclude foreign fluorescing material the thiamine is separated from the extract by adsorption. The thiochrome resulting from oxidation with potassium ferricyanide in alkaline solution is extracted with isobutyl alcohol. The intensity of the blue fluorescence of the isobutyl alcohol extract is compared with that of the standard solution. The intensity of fluorescence is measured photoelectrically and fluorescence value of a blank test is subtracted from that of the sample extract.

Definition

The method serves for the determination of total thiamine and can be used as a reference method. The actual process of measurement is based on the thiochrome method for free thiamine. Phosphoric acid esters and other bonds with thiamine are broken down during the course of extraction and enzymic break down of the material being examined.

 

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