In lactose production the remaining product after separation of the lactose crystals, usually by decanting (see page 279), is called mother liquor. As it usually contains 1/3 protein, 1/3 lactose solution/crystals, and 1/3 salts, it is difficult to dry, as the salts and lactose make it very hygroscopic, and deposits in the chamber are therefore normally seen.

It is, however, possible to apply the same technique as earlier described, introducing warm air at 60ºC tangentially into the drying chamber, whereby the mentioned problems can be minimized. The integrated fluid bed dryers will also be advantageous for this product. Fats of various types can also be added to the mother liquor prior to the drying. Cooling of the powder is then performed in a Vibro-Fluidizer into which cold air is applied. Dried mother liquor is used as stock food and is specially suited for animals that cannot utilize the lactose such as poultry.

Special attention should however be paid to the high salt content, which may lead to troublesome digestion for some animals. Another thing is the absence of the aminoacid Methionine which is only present in whey proteins in a limited amount. Synthetic Methionine (or fishmeal or soy proteins) should be added.