Lactose crystallization: determination of α-lactose monohydrate in spray-dried dairy products
2002
Schuck, Pierre | Dolivet, Anne
A new method was used to determine the amount of α-lactose monohydrate present in spray-dried milk products. During the manufacture of spray-dried milk products, the lactose may crystallize (a process during which the α-lactose picks up a molecule of water), while the hygroscopicity and caking properties decrease. In order to determine the degree of crystallization of α-lactose monohydrate, the water bound to the crystals (water of crystallization or hydrate water) is calculated as the difference between total moisture and free moisture or non-hydrate water. The free moisture content is determined in a drying oven at 87 or 105 oCat constant weight. The totalmoisture is determined by a newmethod using a vacuum-drying desiccator with dried zeolite powder as a function of temperature, vacuum and time. This newmethod is then compared to the Karl Fishermethod. Results on the percentage of α-lactose monohydrate are also presented for various milk, whey and lactose powders with degrees of crystallinity of α-lactose monohydrate ranging from 0 to 100%. Combining the method for total moisture content using a vacuum-drying oven, and the method for freemoisture contentmakes it easy to determine the amount of α-lactosemonohydrate in spray-dried dairy products.
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