Identification of spinacine as the principal reaction product of γ-casein with formaldehyde in cheese

Formaldehyde is added to milk in the production of grana cheese as an antimicrobial agent. In order to study the fate of the formaldehyde, a grana cheese preparation was made using 14C-labelled formaldehyde. The 14C-activity in the cheese was found to be mainly associated with the caseins, but it was not uniformly distributed among the different fractions (α(s), β- and γ-caseins). γ-Casein, separated by electrophoresis, was the most reactive component showing the highest specific activity. In the γ-casein fractions, 99% of 14C-activity was associated with the basic amino acids. The only radioactive reaction product present in the γ-casein fraction was identified by HPTLC and by an amino acid analyser to be spinacine, a condensation product of formaldehyde and histidine. Using the same method, other unknown radioactive products, of much less relevance, were detected in the total casein hydrolysate.