Abstract
Sucrose (C12H22O11) is a nonreducing disaccharide comprising of one glucose ring (C6H12O6) and one fructose ring (C6H12O6) bridged through a C–O–C linkage. The physical properties of aqueous sucrose solutions have been intensively investigated over a long period of time. The temperature vs concentration (d in wt%) phase diagram of the sucrose-water system reveals a stable unsaturated liquid region with concentration below 60%, a metastable supercooled region between 60 and 95%, and a glass region above 95% at room temperature. Temperature studies of viscosity indicate that the sucrose-water system can be classified into a fragile glass former. Sugars as glass-forming materials have attracted some attention during the last two decades. The technological and biological importance of the glass transition in sugars, as a food, is now widely recognized, and intensive research activities are being directed towards understanding the glass transition in various sugar-water systems utilizing various experimental techniques. The acoustic properties of glass-forming liquids have been one of the important subjects of Brillouin light scattering (BLS) since the late 1960s. BLS studies on glucose solutions and trehalose solutions have been performed to determine the glass transition temperature TG. However, the acoustic dispersion of sugar solutions has not yet been fully investigated. We examined the acoustic dispersion of sucrose solutions by means of BLS as a function of d up to 79% at 23 C. Unsaturated solutions below d 60% can be prepared at 23 C by dissolving granulated sugar into pure water. For metastable 70 and 79% solutions, granulated sugar was solved into water at 50 and 80 C, and then cooled to 23 C. The sucrose concentration was determined using a conventional refractometer. BLS spectra were probed using the 488 nm line (1⁄4 0) from an Arþ laser in a single cavity mode with an output power of 15mW. Backscattered BLS spectra were obtained using a (3þ 3)-pass tandem Fabry– Perot interferometer. The depolarized BLS component is more than two orders of magnitude weaker than the polarized component. Figure 1 shows the development of the BLS spectrum normalized by spectrum accumulation time as a function of d of up to 70%. Strong modification of the BLS spectrum through viscoelastic coupling between the sound wave and a relaxation mode can be clearly seen above d 1⁄4 40%. The observed BLS spectrum Oðq; !Þ can be written as
Published Version
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