Use of a model solution for the evaluation of heat damage in milk treated in a UHT heat exchanger

Heat damage in milk can be determined by measuring either reaction products, whose formation is time-temperature dependent, or the loss of thermolabile constituents contained in raw milk. The purpose of this study was to find a relationship between heat damage in milk and the performances of a 10% sucrose solution at pH 3 used as a model solution. Heat treatments were performed on a laboratory indirect heat exchanger especially assembled. The investigation was based on the experimental determination of the time-temperature profiles in the plant, the kinetics of sucrose inversion in the model solution, and the reaction kinetics of some indices of heat damage in milk, such as the formation of lactulose and the loss of α-lactalbumin. On the basis of the percentage of noninverted sucrose remaining in the model solution, a calculation procedure is proposed for checking the performance of an ultrahigh-temperature plant with reference to heat damage and the bacteriological reduction.