Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis (Jan 2010)

Validation of modified milk reference sample in terms of its suitability for infra-red analysis calibration via evaluation of physical properties

  • Oto Hanuš,
  • Václava Genčurová,
  • Tomáš Kopec,
  • Tao Yong,
  • Libor Janů

DOI
https://doi.org/10.11118/actaun201058020101
Journal volume & issue
Vol. 58, no. 2
pp. 101 – 110

Abstract

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Routine milk analyses using the efficient indirect infra-red method are important for the milk food chain quality. The reliability of the results depends on the calibration quality. It is important to use a relevant set of reference calibration samples (RCSs). RCSs with right range of values can be prepared using various methods. This paper was aimed to balance the impacts of dilution for decrease of main components in RCSs because of minimal change of matrix interference effects. Cow milk samples (MSs) were diluted (4/1) using distilled water, NaCl solution and a solution with specific composition (SC; because of disturbance in the balance of the milk matrix (NaCl 1.145; KCl 0.849; K2HPO4 1.8463; citric acid 1.7; urea 0.3 g / l)) for reduction in main milk components. Fat (F), crude protein (CP), lactose (L), milk freezing point (MFP), osmolality (OS) and electrical conductivity (EC) were measured in all (original as well as modified) MSs. The lowest MFP and OS were in the original milk −0.5559 °C and 274.5 mOsmol/kg. The MFP was increased to −0.4369 °C and osmolality decreased to 217.83 ­mOsmol/kg by the addition of water. The MFP was decreased (−0.4903 °C) and returned to original milk value by the addition of NaCl solutin. MFP was −0.4788 °C due to SC addition. The decrease was less than for NaCl. The ability of other SC components (K2HPO4, KCl, citric acid and urea) to MFP decrease is less than for NaCl solution. EC was highest for NaCl set 4.69 mS / cm, EC for SC was 4.48 mS / cm (P < 0.001). The original MSs set showed EC 4.27 mS / cm. The SC was the nearest to original MSs in terms of total mineral composition. ECs for both modifications differed (P < 0.001) from original MSs. The procedure is applicable for balance of interference effects of milk matrix because of relevant calibration.

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