Peer-Reviewed Journal Details
Mandatory Fields
Barham, AS; Omar, AME; Roos, YH; Hodnett, BK
2006
August
Crystal Growth & Design
Evolution of phases and habit during the crystallization of freeze-dried lactose/salt mixtures in humid air
Published
()
Optional Fields
GLASS-TRANSITION TEMPERATURE X-RAY-DIFFRACTION SKIM MILK POWDER AMORPHOUS LACTOSE PARTICLE STRUCTURE MONOHYDRATE ADDITIVES KINETICS CRYSTAL RECRYSTALLIZATION
6
8
1975
1982
Phase compositions, transient phases, and morphology of the crystallization of freeze-dried lactose/salt mixtures in humid air were estimated by in situ X-ray diffraction analysis complemented by ex situ scanning electron microscopy, powder diffraction, and analysis of the solid state alpha/beta anomeric ratios by gas-liquid chromatography. The salts studied are calcium chloride (CaCl2), magnesium chloride (MgCl2), potassium chloride (KCl), and sodium chloride (NaCl) with lactose/salt molar ratios of 2: 1, 4: 1, and 9: 1 mol/mol. Following an induction period during which water is sorbed, crystallization is rapid and the predominant phases observed using the in situ method in freeze-dried lactose/magnesium chloride (MgCl2), sodium chloride (NaCl), and potassium chloride (KCl) are mixtures of alpha-lactose monohydrate and beta-lactose. In general, the alpha/beta ratio of the solid state as measured by gas-liquid chromatography was similar to the crystalline phase composition as measured by X-ray diffraction. A transient phase appears in lactose/KCl (4: 1 and 9: 1 mol/mol), lactose/ MgCl2 (9: 1 mol/mol), and lactose/ NaCl (9: 1 mol/mol), namely, alpha/beta mixed phase. Another transient effect observed with nearly all the lactose-salt mixtures was the observation of a subtle shift in the lattice parameters of alpha-lactose from a = 8.006 angstrom, b = 21.562 angstrom and c = 4.800 angstrom for short crystallization times to a = 7.982 angstrom, b = 21.562 angstrom, and c = 4.824 angstrom for longer times. The transient effects, namely, the observation of the alpha/beta mixed phase and the distortion in alpha-lactose monohydrate lattice parameters, are explained in terms of stresses induced during the rapid onset of crystallization.
1528-7483
10.1021/cg060214d
Grant Details