Acta Vet. Brno 2009, 78: 679-684
Impact of Heat Treatment on the Freezing Points of Cow and Goat Milk
The aim of this study was to monitor the impact of heat treatment variables on the freezing point of cow and goat milk. The freezing point (FP) was established in 30 bulk tank samples of goat milk and in 30 bulk tank samples of cow milk which were subject to laboratory heat treatment at temperatures of 72 °C (A), 85 °C (B), 95 °C (C), with the same exposition times of 20 s. Freezing point measurements of raw and heat-treated milk were carried out in compliance with the Standard CTS 57 0538 by a thermistor cryoscope. The FP of raw cow milk increased with heat treatment from the initial values of -0.5252 ± 0.0114 °C (O) by 0.0023 °C (A), 0.0034 °C (B) and 0.0051°C (C). Changes in FP values of goat milk were detected, from its initial value of –0.5530 ± 0.0086 °C there was an increase in the FP depending on the mode of heat treatment due to pasteurization by an average of 0.0028 °C (A), 0.0036 °C (B) and 0.0054 °C (C). The dynamics of the changes were similar both in goat and cow milk. Freezing point values in cow and goat milk differed (P ⪬ 0.01) when compared to the freezing point of untreated milk after the individual interventions as well as when compared between each other. An increase in the heat treatment temperature of cow and goat milk causes an increase in the freezing point (a shift towards zero). These results can be used in practice for checking the raw material in dairy industry.
