Crystallization and X-ray diffraction of spray-dried and freeze-dried amorphous lactose

Crystallization and X-ray diffraction of spray-dried and freeze-dried amorphous lactose
February 2005
Md. Kamrul Haque and Yrj? H. RoosCorresponding, Department of Food and Nutritional Sciences, University College Cork, Cork, Ireland
Carbohydrate Research, Volume 340, Issue 2, 7 February 2005, Pages 293-301
Received 27 August 2004; revised 18 November 2004; accepted 25 November 2004. Available online 22 December 2004
You can view the abstract online. A subscription is required to view the full text or it can be purchased online.
Crystallization of spray-dried and freeze-dried amorphous lactose over different relative vapor pressures (RVP) and storage times was studied. Crystallization was observed from increasing peak intensities in X-ray diffraction patterns. Lactose was crystallized in the samples stored at RVP of 44.1% and above in both types of dehydrated powders. The rate of crystallization increased with increasing RVP and storage time. Similar crystallization behavior of both spray-dried and freeze-dried lactose was observed. Lactose crystallized as a-lactose monohydrate, anhydrous ?-lactose, and the anhydrous form of a- and ?-lactose in a molar ratio of 5:3 and 4:1 in both spray-dried and freeze-dried forms. Peak intensities of X-ray diffraction patterns for anhydrous ?-lactose were decreased, and for a-lactose monohydrate increased with increasing storage RVP and time. The crystallization data were successfully modeled using Avrami equation at RVP of 54.5% and above. The crystallization data obtained is helpful in understanding and predicting storage stability of lactose-containing food and pharmaceutical products.