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Quantitative Determination of Alpha and Beta Lactose in dried Milk and Dried Whey

Cornell University, Ithaca, New York

ABSTRACT

1. A method is described for the determination of the amounts of alpha and beta lactose in dried milk and whey, and also of the total amount of anhydrous lactose in these products.
   
2. A clear, colorless extract of the product is obtained quickly, using an alcoholic solution of Hg Cl₂ as protein precipitant, and norrit as a decolorizing agent. The nitrate is polarized as soon as possible and again after standing. The relative amounts of alpha and beta lactose are computed from the change in optical rotation. Total lactose is calculated from the final (equilibrium) rotation and sample weight.
   
3. Alpha and beta lactose gave satisfactory results when analyzed by this method, as did also dried milk and whey, alone and with additions of alpha and beta lactose.
   
4. The composition of the lactose in dried whey was shown to range from 90 per cent beta to 95 per cent alpha, on the anhydrous basis.
   
5. Norrit adsorbs lactose from aqueous solution, the alpha form being adsorbed preferentially. Lactose is eluted from the norrit by 10 to 20 per cent alcohol.