DIFFERENTIATING FEATURES FOR EVALUATING H EAT-TREATMENT OF MILK - ASPECTS CONCERNING EQUIPMENT AND PROCESS ENGINEERING

For thermal treatment of milk samples temperature-time combinations in the range between 62-140 degrees C, as well as equivalent holding tim es extended up to some minutes were applied. This was possible by use of a discontinuously operating autoclave and a continuous pilot heatin g plant equipped with exchangeable holders. In the range studied all l egally admitted heating processes can be incorporated. An equivalent h olding time (time of treatment) was calculated by considering the proc ess-inherent heating up and cooling phases. It comprises, besides the thermally induced conversion of a chemical reaction at constant temper ature (heating temperature, process temperature) only during the holdi ng phase also the conversions during the heating up and cooling phases . As a basis for calculating the equivalent treatment time the sterili zation value F-0 was used. For a number of chemical reactions, e.g. re arrangement of 1-methyladenosine and furosine formation, it has been s hown that in computing the equivalent holding time the size of the z-v alue selected is of almost no importance for the determination of the reaction velocity constants and, hence, also the kinetic parameters (z -value). The general applicability of this method - also as regards ot her heat-induced chemical reactions -needs, however, further clarifica tion.