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Abstract  

The DSC curve of freeze-dried amorphous sucrose shows the glass transition, the crystallization and the melting (just before decomposition) of the sample. Sucrose crystallization occurs below 100°C: this phenomenon can therefore be observed with the microcalorimeter Setaram Micro-DSC used in the scanning mode. Mixtures of amorphous and crystalline sucrose in known proportions were used to calibrate the instrument. Low level amorphism (down to about 0.5%) could be detected and quantitatively evaluated on the basis of the crystallization enthalpies determined. The calibration curve obtained can be applied to determine the degree of amorphism in milled sucrose. A simple gravimetric method, based on the desorption of water induced by recrystallization of the amorphous layer can be used to obtain similar data more rapidly. This simple method is particularly useful for controlling the amorphism on line during a process, and is also briefly described.

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The purpose of this study was to measure the effect of co-lyophilized polymers on the crystallization of amorphous sucrose, and to test for a possible relationship between the ability of an additive to raise theT g of a sucrose-additive mixture, relative to theT g of pure sucrose, and its ability to inhibit crystallization. Differential scanning calorimetry was used to measure the glass transition temperature,T g, the non-isothermal crystallization temperature,T c, and the induction time for crystallization,Q, of sucrose in the presence of co-lyophilized Ficoll or poly(vinylpyrrolidone) (PVP). The effect of these polymers on the crystallization of sucrose was significant as demonstrated by a marked increase inT c, and in the induction time (Q) in the presence of relatively small amounts (1–10%) of additive. Surprisingly, small amounts of polymeric additive had no effect on theT g of sucrose, although at higher concentrations, theT g increased proportionally. Thus, it appears that the inhibition of sucrose crystallization by the additition of small amounts of a higher-T g component cannot be attributed solely to changes in molecular mobility associated with an increase inT g.

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Abstract  

The relaxation map of highly concentrated sucrose water mixtures was built using mechanical and impedance spectroscopies. Data of - and -relaxation processes obtained with both techniques complete calorimetric and rheological measurements. The temperature evolutions of the relaxations were extrapolated using the measured data and the equations commonly used to describe the relaxations: Arrhenius and WLF behaviours for respectively the - and -relaxations. The temperature/frequency domain when and processes merge for 99% sucrose solution is discussed with respect to scenery proposed in the literature.

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SBA-15 silicas containing sucrose

Chemical, structural, and thermal studies

Journal of Thermal Analysis and Calorimetry
Authors:
M. Barczak
,
M. Oszust-Cieniuch
,
P. Borowski
,
Z. Fekner
, and
E. Zięba

either extraction with ethanol and acid or calcination at elevated temperatures. One of the scientific applications of SBA-15 silicas is their use as hard templates for the synthesis of ordered mesoporous carbons (i.e., CMK-3, CMK-5). Sucrose is

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Dynamic and sub-ambient thermal transition relationships in water–sucrose solutions

Differential scanning calorimetry and neutron scattering analysis

Journal of Thermal Analysis and Calorimetry
Authors:
D. Champion
,
C. Loupiac
,
D. Russo
,
D. Simatos
, and
J. M. Zanotti

structural and functional alterations of these systems. The ability of sugars to preserve biomolecules during freezing has been recognized for years. The disaccharides most often described in literature for this aim are sucrose, maltose, and trehalose. This

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connection with the addition of such prebiotics to food products ( Picazo et al., 2019 ). FOS can be thought of as low molecular weight, non-viscous, water-soluble dietary fibers. Short-chain FOS can be produced by enzymatic synthesis from sucrose using

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Abstract  

Using a micro-calorimetrical DSC we have compared the acid-catalyzed inversion of sucrose in homogeneous and heterogeneous systems. Acetic acid was chosen as catalyst for homogeneous system, and several carboxylic cationites were used as heterogeneous catalysts. The kinetic apparent parameters (A, E, k ap) for all the systems were calculated from DSC data with Friedmann’s method and catalytic constant, k323 cat, was further inferred. We found that the specific catalyst efficiency, q cat, in heterogeneous system is over 5000 times higher than in case of homogeneous ones. The activity of heterogeneous carboxylic systems is still about 30 times larger than those of a strong mineral acid in homogeneous catalysis. The results indicate the high efficiency of heterogeneous systems for soft acid catalysis of the sucrose hydrolysis.

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Abstract  

40% w/w sucrose/water solutions were analyzed by Modulated Differential Scanning Calorimetry [1] in the sub-ambient temperature region. At these temperatures, the solutions exhibit a complex, two-step thermal event. The lower-temperature event is believed to be the glass transition of the amorphous sucrose phase. The nature of the higher-temperature event is the subject of controversy. This event has been shown to have distinct second-order characteristics, and as such is believed to be a second T g. Others feel that this event is the onset of melting. The temperature region between these events contains a devitrification exotherm. Through the use of MDSC, both in scanning and stepwise quasi-isothermal modes, improved sensitivity and resolution of MDSC provides new insight into the nature of these transitions.

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Abstract  

The influence of the reaction conditions upon the sucrose acid hydrolysis to glucose/fructose equimolecular mixture was investigated, in heterogeneous and homogeneous system, by means of DSC method. The recorded DSC signal was used to evaluate the kinetic parameters and the afferent catalytic constant, k cat 323 values. In homogeneous conditions the used catalyst was acetic acid while in heterogeneous systems a series of carboxylic resins was used as catalysts. The results show a dependence of the kinetic parameters on homogeneous/heterogeneous catalyst nature and on resins experimental properties (cross-linking degree, granulation, porous nature of polymeric matrix, swelling time).

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Abstract  

This work describes the experimental determination of sucrose hydrolysis kinetics using a heterogeneous catalyst. We used an Amberlite IR-120 strong acidic cation-exchange resin. The experiments were performed under previously determined optimal process conditions: sucrose mass concentration, γ S = 50 g L−1, catalyst mass concentration, γ C = 180 g L−1, rotational frequency of the stirrer f m  = 180 min−1, and temperature ϑ = 79 °C. The parameters of the supposed kinetic model were determined using experimental data. The kinetics of sucrose hydrolysis over Amberlite IR-120 has not been reported to date. Therefore, we could not directly compare the calculated values of kinetic parameters with those from the literature. However, the calculated values are within the range of values determined by other types of catalysts. Furthermore, we investigated the influence of catalyst mass concentration γ C on the reaction rate constant k′.

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