A Comparison of Result Reliability for Investigation of Milk Composition by Alternative Analytical Methods in Czech Republic

Abstract

The milk analyse result reliability is important for assurance of foodstuff chain quality. There are more direct and indirect methods for milk composition measurement (fat (F), protein (P), lactose (L) and solids non fat (SNF) content). The goal was to evaluate some reference and routine milk analytical procedures on result basis. The direct reference analyses were: F, fat content (Röse-Gottlieb method); P, crude protein content (Kjeldahl method); L, lactose (monohydrate, polarimetric method); SNF, solids non fat (gravimetric method). F, P, L and SNF were determined also by various indirect methods: -MIR (infrared (IR) technology with optical fi lters), 7 instruments in 4 labs; -MIR-FT (IR spectroscopy with Fourier's transformations), 10 in 6; -ultrasonic method (UM), 3 in 1; -analysis by the blue and red box (BRB), 1 v 1. There were used 10 reference milk samples. Coeffi cient of determination (R 2 ), correlation coeffi cient (r) and standard deviation of the mean of individual diff erences (MDsd, for n) were evaluated. All correlations (r; for all indirect and alternative methods and all milk components) were signifi cant (P ≤ 0.001). MIR and MIR-FT (conventional) methods explained considerably higher proportion of the variability in reference results than the UM and BRB methods (alternative).

An Overview of Determination of Milk Fat: Development, Quality Control Measures, and Application

“…The diffuse scattered irradiation is converted by a suitable optical device to the spectroscope detector (Machovič and Novák, 1998). In general and according to the results of other authors (Tsenkova et al, 1999;Kukačková et al, 2000;Jankovská and Šustová, 2003;Hanuš et al, 2009Hanuš et al, , 2014Mlček et al, 2016), the reliability of fat contents in raw milk (in terms of the gradual decreasing of individual differences (variability) in standard deviation value between routine and reference method results) by routine methods (in practical use under the conditions of their today technical design) is growing in the following order: IR spectroscopy with filter technology and in mid-range of spectrum = IR spectroscopy with whole spectrum and FT in mid-range of spectrum > IR spectroscopy in the near-range spectrum ≥ turbidimetric method > ultrasound method. The reliability order is also given by a growing correlation between coefficients of routine and reference results of milk fat in the same sources.…”

“…This method can be primarily applied to drinking milk (whole, semi-skimmed and skimmed milk). On the other hand, Hanuš et al (2014) described good results also with raw milk samples. The next routine method for determination of milk fat and other milk components is the ultrasound analytical procedure (Perlín, 2003).…”

“…Under the Czech Republic conditions (Hanuš et al, 2014), the proficiency testing system is based on relevant standards -CSN 57 0530 (CNI, 1973), CSN 57 0536 (CNI, 1999) and CSN EN ISO / IEC 17025 (CNI, 2005). Proficiency testing not only reveals any errors in the results, but also provides the possibility for comparison with other participants who can identify potential problems, e.g.…”

Milk Protein Analysis: an Overview of the Methods - Development and Application

“…The system of proficiency testing is based in the Czech Republic (Hanuš et al, 1998(Hanuš et al, , 2006(Hanuš et al, , 2014 to relevant standards -CSN 57 0530 (CNI, 1973), CSN 57 0536 (CNI, 1999) and CSN EN ISO / IEC 17025 (CNI, 2005). Benefits of proficiency testing are not only demonstrating non-errors and errors of the results, but also for confirming competent performance by comparison with other participants which can identify possible problems, e.g.…”

“…At solid materials there is used a mechanical spinner for homogenization; however, actual homogenization of the liquid milk sample to the correction of the optical scattering effects of the fat globules by their size unification is generally not performed. Therefore, it is possible to declare greater suitability (Lefier et al, 1996;Hanuš et al, 2009Hanuš et al, , 2014 as well as the effectiveness of flow analysers MIR (Voort et al, 1987) and MIR-FT with homogenization of samples to analyse the content of liquid milk fat and proteins.…”