摘要：The heat stability of raw milk heated to a temperature of 140 °C was examined considering the influence of heat pretreatment on its use for UHT sterilized milk production. Heat stability was determined immersing capilary tubes (diamemter 1 mm) containig about 20 μL of milk into oil bath (140 °C) and observing the time in seconds required for its coagulation. Heat stability of examined milk samples varied from 285 to 865, the mean value being 552 sec. Heating of raw milk (63 °C/15 sec) slightly reduced heat stability, but subsequent storage (4 °C) for days caused a decrease of heal stability from 1 to 22%. Heat stability of milk heat pre-treated to the temperature at 70, 80 and 90°C for 20, 60 and 120 sec. increased from 27 to 56%. Heat lability of heat-pre-treated milk was reduced due to the storage (4°C) for one day about 11 to 19%, but it was still considerably higher than that of preliminary non heated milk. The highest heat stability after two days of storage was of pre-treated milk samples heated again after one day of storage. Heat pre-treatment of preholding had no adverse effects on heat stability of milk. It can be implemented in the UHT processing of milk in order to improve its heat stability.
