Isolation and Identification of Acidic and Neutral Carbonyl Compounds in Different Varieties of Cheese

Abstract

Acidic and neutral carbonyl compounds were isolated and identified by paper chromatographic procedures. Identification of the compounds as their 2,4 dinitrophenylhydrizone derivatives were established by the following procedures (1) comparisons of Rf values with those of known compounds and Rf values given in literature; (2) decarboxalization of beta-keto acids and chromatographic analysis of the resulting neutral carbonyl compounds and (3) the light absorption of both known and unknown compounds. In 4 individual cheeses studied there were 4 to 11 keto acids in each cheese and from 2 to 8 neutral carbonyl compounds in the different cheeses. Keto acids identified were; oxalsuccinic, oxalacetic, glyoxylic, pyruvic, alpha-ketoglutaric, acetoacetic, alpha-lactic, beta-ketoisocaproic, beta-ketocaprylic, beta-ketocapric, alpha-ketoglutaric, alpha-ketoisocaproic, alpha-ketoisocapric, alpha-ketoisocaproic, and alpha-ketophenylpyruvic. Neutral carbonyl compounds included acetaldehyde, acetone pentanone- 2, diacetyl, acetylmethylcarbonyl, and C-5, and C-7 aldehydes or ketones.