IS ETHANOL STABILITY OF MILK A RELIABLE TEST?

Abstract The alcoholic stability of milk is a current problem in many countries that still use the alcohol test to measure the microbiological quality of milk. Beyond microbiological acidity, many factors can also affect the alcoholic stability of milk, leading to a confounding effect in alcohol test and industrial losses. The present study aimed to evaluate the relationship between pH, bacterial count, Dornic acidity, lactose percentage and ethanol stability of milk. The samples comprised fresh raw milk from 322 dairy farms from Parana state. According to the results of the 72º ethanol test and the Dornic acidity test, the samples received the following classification: stable milk, acidic milk, or unstable milk to ethanol. There was no relationship among pH, Dornic acidity and microbiological count in samples of milk that were unstable to alcohol test. Unstable milk to ethanol has pH values ranging between 6.6-6.8 with low microbiological count (less than 105 cell.mL-1) and higher lactose percentages (up to 4.5%). As bacterial count increase, the lactose percent tends to decrease, but not necessarily together. This feature makes the alcohol test unreliable, and the use of other parameters is strongly recommended such as thermal stability, lactic acid titration, pH, and clot-on-boiling test.