What is the difference between the bound moisture content and the free moisture content of Milk Permeate? Why is that important to know?

Milk Permeate contains primarily crystals of α-lactose monohydrate and have a characteristic tomahawk-like shape. These crystals are very hard and brittle. Milk permeate also contains all of the mother liquor which is typically separated out of refined lactose. This mother liquor is made up of denatured casein and smaller whey proteins, vitamins and minerals. Milk Permeate produced at Idaho Milk Products is primarily comprised of α-lactose Monohydrate. In its crystalline form, each lactose molecule is associated with one molecule of water. The water is incorporated in the crystal and forms an integral part of it. It is not removed by normal drying processes. When working with formulators, it is important to understand the free and bound moisture content of any lactose crystal as it will lend to degradation by Maillard browning which in turn shortens shelf life. Free moisture is on the “surface” of the lactose crystal and is measured by drying at 100 °C for 5 hours in a convection Oven. Milk permeate typically has a free moisture content of <3.00%. Total moisture is the molecule of water picked up by the molecule of lactose during the crystallization process and is perfectly stable under suitable conditions. This is measured at 100 °C for 15 hours in a convection oven. Milk permeate typically has a bound moisture content of approximately 9.00%.