DETERMINATION OF ORGANIC-ACIDS AND SUGARS IN CHEESE, MILK AND WHEY BYHIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

This report details fast economical methods for extraction and quantit ation of organic acids and simple sugars using high performance liquid chromatography (HPLC). The extraction method does not require a clean up step since the HPLC columns are not susceptible to contamination b y co-extractants. The methods were used to survey Cheddar cheese-makin g trials as well as commercial cheeses. In the Cheddar cheese, the lac tic acid (11.53-13.37 mg g(-1), formic acid (0.28-0.50 mg g(-1)), citr ic acid (2.10-2.13 mg g(-1)) and acetic acid (0.14-0.15 mg g(-1)) vari ed very little between trials and between batches within the trials. A nalysis of commercial cheeses showed a range of concentrations of orga nic acids between varieties and between samples of the same variety. T he lactose content was high enough in the milk and whey from the chees e trials (39.11-46.21 mg ml(-1)) to use a refractive index detector (R I). The residual lactose concentration in Cheddar and commercial chees es was too low to be measured accurately by RI, so a different and mor e sensitive system with a pulsed amperometric detector (PAD) was used for this assay. A significant amount of lactose was found in Cottage c heese (4.31-0.00 mg g(-1); only very low residues of mono-and disaccha rides were found in the other commercial and Cheddar cheese samples. C rown Copyright (C) 1997 Published by Elsevier Science Ltd.