A new approach on the sample preparation of powdered dairy products

Malvern Panalytical has developed a novel approach for the reliable and consistent preparation of pressed powdered dairy samples. This approach minimizes heterogeneities, providing a truly representative sample and immobilizes the fat content allowing a unified pressing process, producing stable and consistent pressed pellets for a wide range of samples. This solution is valuable in a large number of industries including dairy product manufacturers, ingredient and food manufacturers, suppliers, analytical and research labs.

Background

The analysis of pressed powdered dairy samples (whole and skimmed milk powder, milk protein, whey powder, cheese powder, infant formulas, etc.) by XRF spectrometry faces two major challenges: the inherent small-scale heterogeneity from many of those materials and the high fat content that may be present.

For some products,  like  infant  formula,  a high  degree  of  small-scale  heterogeneity may be caused  by  the  manufacturing process,  namely  the  mixing  of  skimmed milk powder with different oils/fats and mineral premixes. Additionally, if  samples with a high fat content (> 10%) are to be pressed into pellets,  they  cannot  be subjected to pressures larger than 2-4 ton, otherwise the fat  will  be  extruded  out  of the sample, differentially mobilizing elements within the pellet and making an accurate and reproducible measurement impossible.

On  the  other  hand, some samples with very low fat content may need  higher pressures to form stable pellets. The use of different pelletizing pressures for a same application may render unpredictable analytical errors, especially with such low-density samples.

Malvern Panalytical has developed a novel approach for the reliable and consistent preparation of pressed powdered dairy samples. This approach minimizes heterogeneities, providing a truly representative sample and immobilizes the fat content allowing a unified pressing process, producing stable and consistent pressed  pellets  for  a  wide  range  of  samples. This solution is valuable in a large number  of  industries   including dairy product manufacturers, ingredient  and food manufacturers, suppliers, analytical and research labs.

Materials and methods

In this study, commercially available infant formula with 26 % fat was firstly combined with PANblend-1 before being homogenized in a mixer-mill (Retsch™ MM400). Samples  were  prepared  using  4.5  g   of infant  formula  with  0.5  g  of  PANblend-1 and homogenized for 90 s at 20 Hz, using a 25 ml ZrO2 vessel and one  20  mm  ZrO2 mixing ball. The homogenized powders were then pressed into 35 mm  diameter pellets using a manually operated hydraulic press applying 100 kN of force for 30 s.

Ten pellets of infant formula were prepared according  to  this   procedure.   For comparison,  ten  pressed  pellets   of   the same   infant   formula   were   prepared without PANblend-1 and without homogenization, by pressing them into 35 mm tablets using a manually operated hydraulic press employing a force of 30 kN for 30 s. Elemental analysis was performed with an Epsilon 4 benchtop EDXRF spectrometer using the same measurement conditions and time for both sets of samples.

Results

One of the major  advantages  of  the  method  demonstrated  here  is the outstanding increase in the  sample  preparation  repeatability  of  the  results,  the  consequence  of  a   thorough   sample homogenization and immobilization of fat during pressing.

In Table 1, those  results  can  be  observed  for  a  commercial  sample of infant formula with high fat content prepared with the new methodology  and  using  the  PANblend-1   additive.   Comparison results are obtained from standard preparation without homogenization and low-pressure pressing.

All measured elements in the samples prepared with PANblend-1 presented a smaller spread of the results, as indicated by lower standard deviation (SD) values. The sample preparation repeatability for calcium showed an impressive 8.2 times improvement in relation to a standard preparation. The spread on the chlorine results improved by 6.3 times, potassium by almost 4 times, phosphorus and sulfur both by more  than  2  times.  Notice that absolute concentration values are slightly different between the two sets of samples due to the dilution effect.

Table 1. Sample preparation repeatability results for a commercial sample of infant formula (26 % fat) and improvement factors when using the PANblend-1 method

table1.PNG

Conclusion

It was demonstrated that a new methodology  of sample preparation for dairy powders provides unparalleled sample preparation repeatability, contributing to more  accurate  analytical results. A total analytical solution for  the  dairy  industry  can  be provided by Malvern Panalytical, including a customized approach to sample preparation and all the expertise required for optimal analysis.

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