HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Marier, J. R. Articles by Boulet, M. Search for Related Content PubMed Articles by Marier, J. R. Articles by Boulet, M.

Direct Determination of Citric Acid in Milk with an Improved Pyridine-Acetic Anhydride Method

Division of Applied Biology, National Research Council, Ottawa, Canada

ABSTRACT

The determination of citric acid with pyridine and acetic anhydride has been investigated at reaction temperatures from 17 to 60° C. The optimum proportions of pyridine, acetic anhydride, water, and acetic acid for maximum color intensity and stability are given for each temperature. The procedure has been modified to eliminate the violent nature of the reaction, even when the analysis is done at a reaction temperature of 60° C. Details of a method for the determination of 25–200 µg. of citric acid, at a reaction temperature of 32° C., are presented. In comparison with previously published methods based on the reaction, the recommended technique results in improved sensitivity, stability, and reproducibility without requiring careful timing.

The method has been successfully applied to the routine analysis of milk and milk products. Milk and serum can be analyzed directly, after suitable dilution. Corrections for the interference caused by fat in homogenized milk, and by trichloroacetic acid in T.C.A. serum, can be made easily.

Results of direct analysis of milk were from 5 to 15% higher than those for the corresponding sera and are believed to represent the true values for the citric acid content of milk.