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Interaction of water with maltodextrins and lactose

Shah, Ajay; (2003) Interaction of water with maltodextrins and lactose. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

The effect of drying on the introduction of amorphous material was investigated using lactose as a model substance. It was found that microwave-vacuum drying of lactose monohydrate and fluid-bed drying of commercial spray-dried lactose did not introduce detectable amounts of amorphous material in to the sample. The interaction of water with maltodextrins was then investigated. It was found that the maltodextrins undergo a change in physical form from a free-flowing powder through a hard, caked material to a sticky, plasticised material on moisture sorption. It was shown that this change in physical form for the maltodextrins is due to a 'humidity caking mechanism'. Microcalorimetry is able to detect the changes in physical form through broad shoulders/peaks. It was suggested that the broad shoulders/peaks are due to differences in the heat capacity of the materials brought on by water uptake. Following exposure to 75% RH in the DVS, it was found that M150 and M200 were present in a collapsed amorphous state, whereas M040, M100, and M500 were in a non-collapsed amorphous state. Shrinkage of M200 was observed by microscopy further indicating collapse. A thermodynamic study of the maltodextrin-water interaction found that water sorption in to the maltodextrins occurs in three stages. The first stage involves water that is hydrogen bonded directly to the anhydroglucose units, with a ratio of one water molecule to two anhydroglucose units. This is followed by breaking of some of the original hydrogen bonds and sorption of further water. The final stage results from the changes in physical form occurring in line with the humidity caking mechanism. BET monolayer values were calculated for the maltodextrins. It was found that the "monolayer values" represent the amount of water that is directly bound to the anhydroglucose units. Swelling was also found to occur up to the "monolayer value".

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Interaction of water with maltodextrins and lactose
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Biological sciences; Lactose; Maltodextrins; Water
URI: https://discovery.ucl.ac.uk/id/eprint/10100820
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