EVALUATION OF A DIRECT METHOD FOR THE DETERMINATION OF TRUE PROTEIN-CONTENT IN MILK BY KJELDAHL ANALYSIS

The recent adoption by the AOAC of a direct method for determination o f protein nitrogen content of milk provides a verified technique for o btaining true protein content via a single Kjeldahl digestion and titr ation rather than requiring two digestions/titrations, as specified by the established indirect method. The direct method is not applicable when the non protein nitrogen content is required to be known. An inve stigation was undertaken to gauge the robustness of this direct method and to compare its results to those provided by the indirect method, when applied to natural and artificial milk samples comprising a wide range of fat and protein contents. The direct method provided a saving of time and materials over the indirect method and gave comparable re sults, satisfying the statistical parameters of repeatability and repr oducibility as specified by the current Australian Standard indirect m ethod.