The freezing point of raw and heat treated sheep milk and its variation during lactation
2013
Janstova, B., University of Veterinary and Pharmaceutical Sciences, Brno (Czech Republic). Dept. of Meat Hygiene and Technology | Navratilova, P., University of Veterinary and Pharmaceutical Sciences, Brno (Czech Republic). Dept. of Meat Hygiene and Technology | Kralova, M., University of Veterinary and Pharmaceutical Sciences, Brno (Czech Republic). Dept. of Meat Hygiene and Technology | Vorlova, L., University of Veterinary and Pharmaceutical Sciences, Brno (Czech Republic). Dept. of Meat Hygiene and Technology
The freezing point of milk is an important indicator of the adulteration of the milk with water, but heat treatment may also affect its value. The aim of this study was determine freezing point of raw and heat treated sheep milk and its variation during lactation. The freezing point was determined in 42 bulk tank raw sheep milk samples and 42 pasteurized milk samples collected during lactation of sheep at one ecofarm in Moravian Walachia (Valassko in the Czech Republic). The freezing point was determined in accordance with the standard CSN 57 0538 using a thermistor cryoscope. The average freezing point of raw milk was -0.617 +/- 0.052 deg C, with a range from -0.560 to -0.875 deg C. The freezing point was lower in the first months of lactation and increased at the end of lactation. The freezing point correlated (r = 0.8967) with the content of total non-fat solids. The average freezing point of sheep milk pasteurized at 65 deg C for 30 min was -0.614 +/- 0.053 deg C, with a range from -0.564 to -0.702 deg C. The median of freezing point differences between raw and pasteurized milk was 0.004 deg C. Our study extends data about physico-chemical properties of sheep milk and registers for the first time specific changes in the freezing point value of sheep milk by heating.
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