Milk freezing point determination with infrared spectroscopy and thermistor cryoscopy method
Two analytical methods were used for determination of the freezing point on identical test raw milk samples. The aim of this research was to investigate possibility of usage infrared spectrometry method, with MilcoScan FT 6000 milk analyzer for determination of milk freezing point, comparing to results obtained by using a reference thermistor cryoscopy method with Cryoscope 4C3 analyzer. During period of four months, total of 320 milk samples were analyzed. Once a week milk samples were sampled at collection reservoirs from twenty milk producers. Milk freezing point was analyzed with each of investigated methods in three consecutive testing respectively repetition. The results of freezing point were recorded as higher by reference in comparison to infrared spectroscopy method. Mean difference from 1.31 to 5.28 m°C respectively 3.43 m°C was determined between results obtained with infrared spectroscopy and reference method. Mean repeatability results for both investigated methods showed slight difference, sr%=0.194 for the reference method and sr%=0.193 for the infrared spectrometry method. Statistically significant difference between the means of the obtained results with two different investigated methods (P>0.05; P>0,01) was not determined. The results indicate the conclusion that infrared spectroscopy method can be used for detecting adulteration of milk with water addition as screening method. Based upon the obtained results usage of infrared spectrometry method in determination of raw milk freezing point is recommended because it is faster and can be carried out with current analyzers used for determination of other milk quality parameters, for example analyzer MilkoScan FT 6000.
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