Orotic acid: a milk constituent. Enzymatic determination by means of a new microcalorimetric method

The presence of orotic acid (a precursor of nucleic acid) in milk is very important in order to ensure its nutritionalvalue and good conservation. In the literature, chromatographic, spectrophotometric and polarographic methods are reviewed. The reported values have a very wide interval range (19–664 mg l_1) and a low precision. The new method proposed in this article employs an enzymatic reaction. It has been improved on standards and then tested on milk samples. The same samples were also tested by means of a known spectrophotometric method. The new analytical method for orotic acid determination is reliable; the results are more accurate and more precise if compared with the usual methods, and it shows the same sensibility. The calorimetric analysis is faster and easier, owing to the fact that no sample treatments are required.