[Sterilization values for ultrahigh heating of milk]

Since the beginning of the 1920's the sterilization value F0 (F-value), which depends on the destruction of spores of Clostridium botulinum, has been used for evaluating the microbiological efficiency of sterilization processes. In 1980 milk-specific F-values based on the chemical changes of the content of milk ingredients were used to evaluate the UHT process for the first time. All ingredients of milk, which follow a linear reduction- or formation-curve in a half-logarithm temperature-time-diagram as a result of UHT-heat treatment, could be used to calculate the various different F-values. Systematic investigations for numerous milk ingredients have shown that this is indeed the case. Because the destruction curves for microorganism are steeper than those for chemical reactions of milk ingredients, it is possible to optimize UHT-processes in respect of necessary microbiological destruction and minimum change of the product. The basics for calculating sterilization values and for evaluating the dimension of microbiological destruction and chemical change of milk ingredients will be discussed in this review.