QUANTIFICATION OF THE RATIO OF WHEY POWDER TO MILK POWDER USING SPECTROSCOPY IN ALKALI

A spectroscopic determination is presented for the quantification of w hey powder in milk powder. This method is based on differences in tyro sine to tryptophan ratio for caseins and whey proteins and can also be used to calculate milk proteins to whey proteins in milk products. Wh ereas at neutral pH the zero-order spectra of tryptophan and tyrosine overlap, at alkalic pH the spectrum of tyrosine shifts towards the red and the absorbance at the maximum is duplicated as a result of the io nization of tyrosine. Due to the better resolution between both spectr a, a method could be developed based on the zero-order or first order spectra.