Rapid method for measuring extracellular water in yeast preparations.

A rapid procedure for the quantitative determination of extracellular water in bulk bakers' yeast was developed on the basis of the solute dilution principle. A reagent is prepared by synthesizing the diazonium ion of p-aminobenzoic acid and coupling it to peptone. This "azopeptone reagent" permits direct colorimetric measurement, which accounts for the rapidity and simplicity of the test. Potential errors due to osmotic effects are avoided by supplementing the reagent with saline and, more importantly, minimizing the duration of contact between reagent and cells. The new method has acceptable accuracy and precision, and may also be suitable for use with other microorganisms.