Validation of modified milk reference sample in terms of its suitability for infra-red analysis calibration via evaluation of physical properties
2010
Hanus, O.,Agrovyzkum, Rapotin (Czech Republic) | Gencurova, V.,Vyzkumny Ustav pro Chov Skotu, Rapotin (Czech Republic) | Kopec, T.,Svaz Chovatelu Ceskeho Strakateho Skotu, Prague (Czech Republic) | Yong, T.,Anhui Agricultural Univ., Hefei (China). Dept. of Animal Sciences | Janu, L.,Vyzkumny Ustav pro Chov Skotu, Rapotin (Czech Republic)
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 the right range of values can be prepared using various methods. This paper was aimed to balance the impact 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)). Fat, crude protein, lactose, milk freezing point (MFP), osmolality (OS) and electrical conductivity (EC) were measured in all samples. The lowest MFP and OS were in the original milk: -0.5559 deg C and 274.5 mOsmol/kg. The MFP was increased to -0.4369 deg C and osmolality decreased to 217.83 mOsmol/kg by the addition of water. The MFP was decreased (-0.4903 deg C) and returned to original milk value by the addition of NaCl solution. MFP was -0.4788 deg 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 less than 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 less than 0.001) from original MSs. The procedure is applicable to balance the interference effects of milk matrix because of relevant calibration.
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