Glass transition and caking of spray-dried lactose |
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| Authors: | Richard J. Lloyd,X. Dong Chen,& Jim B. Hargreaves |
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| Affiliation: | Milk Powder Technology Section, New Zealand Dairy Research Institute, Private Bag 11 029, Palmerston North,;Department of Chemical and Materials Engineering, The University of Auckland, Auckland, New Zealand |
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| Abstract: | Simple test methods to determine the onset temperatures of viscous flow and caking of spray-dried amorphous lactose are described. The extent of viscous flow was measured as an increase in the density of lactose plugs within a cylindrical aluminium compaction apparatus after incubation for 3h at a specified temperature. Caking was characterized by an increase in the hardness of the lactose plugs formed. The onset temperature of viscous flow decreased with increasing water activity, Aw, and corresponded to the onset temperature of glass transition, Tg1. Glass transition temperatures were determined using both differential scanning calorimetry (DSC) and nuclear magnetic resonance (NMR) spin relaxation. The results suggest that elevation of the powder temperature above Tg1 promotes viscous flow and increases the potential for caking of amorphous food powders. |
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| Keywords: | Amorphous lactose caking crystallization glass transition |
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