The riboflavin content has been estimated by the microbiological method in a number of beers of different types. The level of riboflavin has been followed in various stages of the brewing process by the same method and it has been found that:—(1) There is possibly a small loss of riboflavin during mashing. (2) There is no loss of riboflavin during boiling with hops. (3) There is an increase in Riboflavin of over 100 per cent. during top fermentation. This production of riboflavin by yeast is a property of many strains of S. cerevisiae. (4) The determination of riboflavin in malt has been investigated, and acid extraction has been shown to lead to high results.
Section I. Contains the results obtained.
Section II. Is experimental and contains: (1) A description of the methods employed. (2) Experiments on the effect of hop resins on the microbiological method as applied to beer. (3) Experiments on the estimation of riboflavin in malt.
Copper is determined in the residue obtained after wet oxidation of beer or brewing materials as described in a previous paper (this Journal, 1951, 363). When the residue is treated with sodium diethyldithiocarbamate, a compound is formed which is soluble in carbon tetrachloride giving a yellow solution. The yellow colour of this solution may be matched by glass slides in a Lovibond tintometer or evaluated in a photoelectric colorimeter. The copper is determined by reference to standard curves.
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