KINETIC-ANALYSIS OF DIMROTH-REARRANGEMENT OF 1-METHYLADENOSINE IN MILK UNDER TEMPERATURE-TIME CONDITIONS OF STERILIZATION

During heat treatment of milk the original milk ribonucleoside 1-methy ladenosine is converted to N6-methyladenosine by Dimroth-rearrangement . In the present study milk, standardized to a fat content of 3.5% and homogenized, was heated in the sterilization section under defined te mperature-time conditions. Liquid chromatographic analyses of the milk samples have shown that Dimroth-rearrangement to N6-methyladenosine i n the sterilization section studied is subjected to a first-order reac tion. The decimal reduction times (D-values) derived from the respecti ve temperature-dependent velocity constants show that Dimroth-rearrang ement is, up to a temperature of 119 degrees C and an equivalent holdi ng time of 40.5 min, respectively temperature-time combinations not ex ceeding an F-0-value of 22 min, suited to be used for kinetic analyses . At higher temperatures and higher equivalent holding times, however, Dimroth-rearrangement is accompanied with destruction reactions, whic h is reflected in an apparently delayed reaction velocity. The process parameters determined in the sterilization section (z-value = 22.9 de grees C; Q(10)-value = 2.73) can be compared with the values obtained in UHT-experiments (z-value = 30.5 degrees C; Q(10)-value = 2.13). The results obtained confirm, thus, the suitability of the methylated nuc leosides participating in Dimroth-rearrangement to be used as chemical process parameters for heat treatment of milk.