ULTRASONIC PORTABLE MILK ANALYZER
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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
