Choice of optimal conditions for X‐ray fluorescence analysis of milk products with varying fat content

Abstract

The design of experiments was used to study sources of errors in the sample preparation and to choose optimal conditions for X‐ray fluorescence (XRF) analysis of milk products of varying fat content. The measurements were performed using the conventional wavelength‐dispersive XRF (WDXRF) and the total reflection XRF (TXRF) techniques. For WDXRF, the dried milk samples were pelletized, and the mathematical models were constructed, which described the dependence of XRF intensity on the pelletizing pressure, the pellet weight and the milk fat content. The effect of radiation time on the stability of pressed milk powder samples was also estimated. When applying TXRF, the sample preparation involved diluting milk samples with the ultrapure water, adding the internal standard (Ga) and drying of a sample aliquot on a quartz glass sample carrier. The mathematical models were designed, which described the dependence of the sample preparation error on the dilution ratio and sample aliquot pipetted on the carrier. A physical interpretation of the obtained mathematical models was proposed. Copyright © 2013 John Wiley & Sons, Ltd.

Evaluation of X-ray fluorescence spectroscopy as a method for the rapid and direct determination of sodium in cheese

“…ences between cheese types did not affect the ability of the XRF to successfully determine Na. These findings are similar to other studies looking at the effect of fat content in milk powders on the determination of several minerals using XRF (Gunicheva, 2010;Smagunova and Pashkova, 2013). Based on this result, any natural cheese type (regardless of gross composition) can be successfully analyzed using any of the 6 calibration methods created with an individual cheese type.…”

“…A layer of oil (oiling off) was observed on the sample film after the final reading and Na intensity decreased with increasing residence time in the autosampler (results not shown). Similarly, Smagunova and Pashkova (2013) found discoloration in both skim and whole milk powder-pellets and oiling off in whole milk powder-pellets after successive measurements and long measurement times (>20 min per sample; sample chamber temperature was ~38°C). Smagunova and Pashkova (2013) reported that the melting of fat contributes to scattering (enhancement of the XRF intensity) effects when measuring elements like Na due to primary and secondary radiation.…”

“…Similarly, Smagunova and Pashkova (2013) found discoloration in both skim and whole milk powder-pellets and oiling off in whole milk powder-pellets after successive measurements and long measurement times (>20 min per sample; sample chamber temperature was ~38°C). Smagunova and Pashkova (2013) reported that the melting of fat contributes to scattering (enhancement of the XRF intensity) effects when measuring elements like Na due to primary and secondary radiation. Oiling off was not observed when the experiment was repeated with a reduced-fat Cheddar cheese sample, and for this cheese type Na intensity was not affected by 10 consecutive runs (P > 0.05).…”

“…X-ray fluorescence is also a rapid, precise, nondestructive, and a potential alternative method for direct Na determination in foods (Jastrzebska et al, 2003;Pashkova, 2009;Rinaldoni et al, 2009;Smagunova and Pashkova, 2013). Several studies have used XRF for the measurement of individual elements in milk and dairy products such as infant formula powders (Chan and Palmer, 2013;Fernandes et al, 2014).…”

Analytical advances in the determination of calcium in bovine milk, dairy products and milk-based infant formulas

“…T-XRF can be successfully applied as a screening tool for chemical composition and quality control in the analysis of milk. Smagunova and Pashkova (2013) provided recommendations in sample pre-treatment of liquid milk with different fat contents (1.5-4.0%) for the analysis of minerals by T-XRF. The authors recorded an increase in the repeatability of calcium outcomes, when milk was diluted with water (to 5% total solid content) prior to the lyophilization step.…”