Validation of modified milk reference sample in terms of its suitability for infra-red analysis calibration via evaluation of physical properties
Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis
HANUŠ, O., GENČUROVÁ, V., KOPEC, T., YONG, T., JANŮ, L.: Validation of modifi ed milk reference sample in terms of its suitability for infra-red analysis calibration via evaluation of physical properties. Acta univ. agric. et silvic. Mendel. Brun., 2010, LVIII, No. 2, pp. 101-110 Routine milk analyses using the effi cient 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
... 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 eff ects. Cow milk samples (MSs) were diluted (4/1) using distilled water, NaCl solution and a solution with specifi c composition (SC; because of disturbance in the balance of the milk matrix (NaCl 1.145; KCl 0.849; K 2 HPO 4 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 modifi ed) 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 (K 2 HPO 4 , 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 modifi cations diff ered (P < 0.001) from original MSs. The procedure is applicable for balance of interference eff ects of milk matrix because of relevant calibration. milk, interference eff ect, composition, milk freezing point, osmolality, electrical conductivity Address doc. Ing. Oto Hanuš, Ph.D.