ULTRASONIC PORTABLE MILK ANALYZER
w w w . m i l k o t e s t e r . c o m
Appendix Freezing point determination
1. Methods for determination.
The milk analyzer determines the freezing point of each sample and the
quantity of added water. The milk analyser does not measure the
freezing point, but calculates it from the components it depends on. The
basic components in the milk are water, solids, lactose, FAT, proteins,
minerals (salts) and acids. The freezing point depends only on the
diluted in the milk components and quantity of the solvent (in the milk it
is water). The ultrasonic technology allows direct measurement of FAT,
proteins, l salts (the soluble components, only influencing the
freezing point), and the quantity of the solvent in % is determined by 100
% – total solids %, total solids = lactose % + FAT % + proteins % + salts
% + acids %.
Without understanding the meaning of the freezing point – determined or
shown from the milk analyzer added water result easily may lead to a
mistake for the value of this parameter.
2. The basic freezing point.
Milk freezes at lower temperature than water. The average freezing point
of the raw milk in the most regions is at about -0,540
С
. The average
reading for your region is called “basic” freezing point.
The freezing point of milk is a “physiological constant”. This does not
mean that it will not vary. In fact feed, breed, season, time of lactation,
climate, whether the sample is taken at the beginning, middle or end of
lactation – all these factors will have an effect on the freezing point of the
individual sample. This means that there is an average value of all these
numbers. The more samples used in obtaining this average, the more
reliable it is as a base. Or the basic freezing point is an average of
freezing points of milk, taken from many cows. When a laboratory
checks a producer, it is only comparing the average of the producer’s
cows against a larger area average.
The Health authorities establish the basic freezing point or agriculture
departments in some regions, sometimes by universities, separate dairy
producers, or their associations. Frequently, tolerances have been
established on top of a basic freezing point to allow some variations in
the milk as well as device or operator variations.
Without mentioning the basic freezing point, the Association of Official
Analytical Chemists now recommends an upper limit freezing point at -
0,525
C (2,326 standard deviations above the most recently determined
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