AOAC Final Action Methods in 2018

Figure 2016.15B. Separation of protein MW size standard.

(i)  Determination of casein region .—For SMP, set casein integration start time just before the β-casein peak (about 3.1 min after the peak of the 10 kDa IS). For infant formulas, identify β-casein peak according to SMP eGram and set casein integration start time just before this peak. For all samples, set the end time at the valley between the end of the κ-casein peak and the Ig H and BSA peak (about 7.0 min after the 10 kDa IS). ( j ) If using 32 Karat software fromBeckman, the data processing steps are described in the Appendix [ J. AOAC Int . 101 , 1566(2018) https://doi.org/10.5740/jaoacint.18-0057].

between the end of casein and the peak of immunoglobulin heavy chain (Ig H) and bovine serum albumin (BSA) should be no more than 25% of the height of the IS in the sample. (h)  Integration of the electropherograms (eGrams) .—Integrate eGrams of both SMP (Figure 2016.15C ) and infant formulas (Figure 2016.15D ) by setting baseline from 0.4 min before IS peak to the valley between the end of the κ-casein peak and the peak of Ig H and BSA (no negative peaks should be generated by the integration); perform a manual integration from the peak of Ig H and BSA to the end of the last peak in the eGrams (integrate all peaks after the Ig H and BSA peak).

High MWWhey

LowMWWhey

Casein

Figure 2016.15C. eGram of skimmilk powder.

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