Physico-chemical studies of sucrose thin films (original) (raw)
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Spectroscopic study of the structure of sucrose in the amorphous state and in aqueous solution
Carbohydrate Research, 1986
The structure of noncrystalline sucrose in the amorphous, solid state and in aqueous solution was investigated. Differences of structure of amorphous solid samples, the quenched-melt, and freeze-dried sucrose, are revealed by differential thermal analysis (d.t.a.) and from the Fourier-transform infrared (F-t.-i.r.) spectra. Factor analysis of the F.t.4.r. spectra of aqueous solutions of sucrose shows the existence of at least two forms of the sucrose molecule. Analysis of 13C-n.m.r. spectra of amorphous and crystalline sucrose reveals a sensitivity of the fructosyl moiety to the morphology of the sample.
Materials Chemistry and Physics, 2000
A survey is given on morphological modifications induced on sucrose crystals by some tailor-made additives (mono-and oligosaccharides). Special attention is paid to a critical discussion of our analysis of the structure compatibility between additive molecules and surface sites of the crystals, and further of its developments concerning incorporation of additives in the crystal lattice. Finally, it is shown as X-ray powder diagrams of sucrose crystals grown in the presence of these additives, coupled with chromatographic analysis of crystal sectors, proved to be a promising sensitive tool, chiefly to associate the different lattice spacing variations to the absorption anisotropy.
Kinetics of Sucrose Crystallization in Whey Protein Films
Journal of Agricultural and Food Chemistry, 2006
The kinetics of sucrose crystallization in whey protein isolate (WPI) films was studied at 25°C in four different relative humidity environments: 23, 33, 44, and 53%. The effects of protein matrix, crystallization inhibitors, and storage environment on the rate constants of sucrose crystallization were determined using the Avrami model of crystallization. It was found that a cross-linked, denatured whey protein (WP) matrix more effectively hindered sucrose crystallization than a protein matrix of native WP. The crystallization inhibitors tested were lactose, raffinose, modified starch (Purity 69), and polyvinylpyrrolidone (Plasdone C15). Raffinose and modified starch were determined to be the more effective inhibitors of sucrose crystallization. At lower relative humidities (23, 33, and 44%), the cross-linked protein matrix played a more important role in sucrose crystallization than the inhibitors. As relative humidity increased (53%), the crystallization inhibitors were more central to controlling sucrose crystallization in WPI films.
Journal of Pharmaceutical Sciences, 2009
The purpose of this study is to investigate protein-sugar interactions in dried protein solids as a function of sucrose level using water sorption isotherm data and secondary structure information from Fourier transform infrared (FTIR) spectroscopy. Three IgG1 fusion proteins and two cytokines were freeze-dried with sucrose at different sucrose/protein mass ratios. The water monolayer of the colyophilized sucrose/protein samples, as determined by BET analysis of water sorption data, was found to be lower than that expected based on additive contributions of pure protein and pure sucrose. This negative deviation suggests the presence of a solid-state interaction between protein and sucrose that reduces the availability of total water-binding sites. The difference in water monolayer between colyophilized and a physical mixture of protein and sucrose reached a maximum value at sucrose/protein mass ratio of 1/1 for these proteins, suggesting saturation of the protein-sugar interaction at this ratio. In addition, for four proteins studied, the normalized peak height of the major band in the FTIR spectra reached a plateau at about a 1/1 mass ratio. Therefore, it appears that there is a coupling between the preservation of protein secondary structure and the protein-sugar interaction as measured by water sorption isotherms. ß
Journal of Pharmaceutical Sciences, 2009
The purpose of this study is to investigate the impact of sucrose level on storage stability of dried proteins and thus better understand the mechanism of protein stabilization by disaccharides in lyophilized protein products. Five proteins were freeze dried with different amounts of sucrose, and protein aggregation was quantified using Size Exclusion Chromatography. Protein secondary structure was monitored by FTIR. The global mobility was studied using Thermal Activity Monitor (TAM), and fast local dynamics with a timescale of nanoseconds was characterized by neutron backscattering. The density of the protein formulations was measured with a gas pycnometer. The physical stability of the proteins increased monotonically with an increasing content of sucrose over the entire range of compositions studied. Both FTIR structure and structural relaxation time from TAM achieved maxima at about 1:1 mass ratio for most proteins studied. Therefore, protein stabilization by sugar cannot be completely explained by global dynamics and FTIR structure throughout the whole range of compositions. On the other hand, both the fast local mobility and free volume obtained from density decreased monotonically with an increased level of sucrose in the formulations, and thus the local dynamics and free volume correlate well with protein storage stability.
The solution conformation of sucrose: concentration and temperature dependence
Carbohydrate Research, 1986
i3C-N.m.r. spin-lattice relaxation measurements were used to study molecular motion in aqueous sucrose. Results show that sucrose tumbles anisotropically in solution, and that its conformation is independent of temperature and concentration. Internal rotation occurs with distinctly different rates and activation energies in the three hydroxymethyl groups. Our data are consistent with results of calculations by Bock and Lemieux6 who predicted that the conformation of aqueous sucrose is similar to the crystal conformation but with the loss of one intramolecular hydrogen-bond.
Role of water in sucrose crystallization
Carbohydrate Polymers, 1998
The rate of sucrose crystallization in supersaturated solutions is known to include at least two steps: the diffusion of sucrose from the bulk solution to the thin layer at the interface crystal/solution and the incorporation of sucrose molecules in the crystal after the release of their hydration water. Among the energy barriers encountered in the 'hurdle race' of the crystallization process, viscosity seems to be a minor hurdle and the disassociation of hydration water a major one. We will attempt to show that the dehydration of sucrose molecules prior to their incorporation into the crystal plays an important part in the crystallization process and propose to conceive the mechanism of crystal growth as mainly based on the release of water molecules and their diffusion in the bulk solution rather than a migration of sucrose from the solution to the crystal. ᭧
Journal of Pharmaceutical Sciences
The bioprotective properties of 2 disaccharides (sucrose and trehalose) were analyzed during the freezedrying (FD) process and at the end of the process, to better understand the stabilization mechanisms of proteins in the solid state. In situ Raman investigations, performed during the FD process, have revealed that sucrose was more efficient than trehalose for preserving the secondary structure of lysozyme during FD, especially during the primary drying stage. The lower bioprotective effect of trehalose was interpreted as a consequence of a stronger affinity of this disaccharide to water, responsible for a severe phase separation phenomenon during the freezing stage. Dielectric spectroscopy investigations on the freezedried state of protein formulations have shown the capabilities of trehalose assisted by residual water to reduce the molecular mobility of the vitreous matrix, suggesting that trehalose is more efficient to preserve the protein structure during long-term storage.
Influence of antioxidant structure on local molecular mobility in amorphous sucrose
Carbohydrate Research, 2014
The effect of the antioxidants gallic acid and methyl, propyl, and octyl gallate on the molecular mobility and hydrogen bond network in amorphous sucrose was studied. Solid amorphous sucrose films with and without the addition of antioxidants at a mole ratio of 1:5 (antioxidant/sucrose) were cast from solution onto quartz slides. Local molecular mobility from 0 to 70°C was measured using tryptophan amino acid as a luminescent probe dispersed in the films. Phosphorescence from the tryptophan probe provides spectroscopic characteristics-emission spectrum and lifetime-that are sensitive to changes in molecular mobility induced by the addition of antioxidants. Local molecular mobility detected by tryptophan increased in the following order: sucrose < sucrose-octyl gallate < sucrose-propyl gallate 6 sucrosemethyl gallate 6 sucrose-gallic acid. The antioxidants also modulated the activation energy for matrix motions that quench the tryptophan phosphorescence in a structure-dependent manner. IR measurements as a function of temperature indicated that hydrogen bond strength in these amorphous films followed a rank order (sucrose-methyl gallate > sucrose-gallic acid > sucrose-propyl gallate > sucrose > sucrose-octyl gallate) that was nearly the reverse of that seen in matrix mobility. Analysis of the differential effects of the antioxidants suggests that the presence of the hydroxyl benzoyl head group increased matrix molecular mobility and hydrogen bond strength while the saturated carbon chain decreased mobility and bond strength. The influence of the carboxyl group on matrix properties was comparable to that of the formyloxy group. These results indicate that the addition of specific functional ingredients such as antioxidants may significantly affect the physical properties and consequently functional properties of amorphous edible films in ways that might condition their use. The observed changes are closely related to the chemical structure of the added species.