Ion-exchange HPLC analysis of a broad spectrum of organic acids from matured Cheddar cheese and assessment of extraction methods

An ion-exclusion HPLC technique was used to separate a total of 16 organic acids from matured Cheddar cheese. Three extraction methods, reported in th e literature for the purpose of extracting organic acids from cheese, were evaluated by determining the percentage recovery of the organic acids from the selected cheese. All three extraction methods evaluated yielded high re covery rates for all compounds analyzed. The method using 0.009 N H2SO4 gav e best recoveries for II of the 16 detected compounds while the barium hydr oxide/zinc sulphate extraction method yielded best recoveries for oxalic an d malic acids. The buffer-acetonitrile extraction method showed the highest recovery percentages for propionic, isovaleric and n-valeric acids. In add ition, the method using 0.009 N H2SO4 exhibited improved retention of minor peaks. With the exception of oxalic acid, organic acid concentrations dete rmined for the mature Cheddar cheese corresponded well with values in the l iterature. On the basis of amount of analytes separated, resolution and eas e of analysis, the 0.009 N H2SO4 extraction method and proposed ion-exchang e HPLC protocol was well suited for the quantification of a broad spectrum of major and minor organic acids from Cheddar cheese. However, rapid sample pre-treatment techniques to eliminate contaminating biochemical species, r equire investigation. (C) 1999 Canadian Institute of Food Science and Techn ology. Published by Elsevier Science Ltd. All rights reserved.