Carbohydrates water diffusivity

Teoh, H.M., Schmidt, SJ., Day, G.A., and Faller, J.F. 2001. Investigation of commeal components using dynamic vapor sorption and differential scanning calorimetry. J. Food Sci. 66, 434-440. Tromp, R.H., Parker, R., and Ring, S.G. 1997. Water diffusion in glasses of carbohydrates. Carbo-hydr. Res. 303, 199-205. 

Menting, L. C. Hoogstad, B. Thijssen, H. A. C. Diffusion coefficients of water and organic volatiles in carbohydrate-water systems. Journal of Food Technology 5. (2), 111-26 (1970)... 

Understanding and predicting water diffusivity in supercooled and glassy carbohydrates is of great importance in the practical applications of these mixtures, in particular to the preservation of foods and pharmaceuticals. Since the discovery more than a decade ago that water retained liquid-like heat capacity in glassy starch (Noel and Ring, 1992) several studies have shown that water is mobile in glasses of carbohydrates (van den Dries et al., 1998 van den Dries et al., 2000 Tromp et al., 1997 Hills et al., 2001 Chatakanonda et al., 2003 Kou et al., 2000 Vodovotz et al., 2000 Aldous et al., 1997) and foods (Roudaut et al., 1999). 

Nevertheless, the microscopic mechanism that allows water diffusion in these glasses has remained an unsolved puzzle. We present here a computer simulation study of the microscopic mechanisms of water diffusion in carbohydrate from the viscous liquid state up to the glass. To understand the nature of water diffusion in glassy food-like systems, we employed molecular d)mamics (MD) simulations techniques to study in detail the structure and d)mamics of a concentrated glucose solution, a simple binary... 

We present here coarse grain simulation results of two simple binary water-carbohydrate mixtures that shed light on the mechanism of water diffusion in the supercooled and glassy state, the coupling of water mobility in the glass to the sub-Tg dynamics of the matrix, and the effect of the internal modes of the saccharide on the decoupling of water motion from carbohydrate translation. 

Finally, we examine the effect of the timescale of the local degrees of freedom of the carbohydrate on the d)mamics of water by comparing the mechanism of water diffusion in the solutions of the supercooled monomer DPI and the oligomer DP12. We have studied the two mixtures of identical... 

CHI 10a] Chivrac F., Angellier-Coussy H., Guillard V., etal, How does water diffuse in starch/montmorillonite nano-biocomposite materials . Carbohydrate Polymers, 82, no. l,pp. 128-135,2010. 

At very low concentrations of water, or in foods held below the free2ing point of water, physical conditions may be such that the available water may not be free to react. Under these conditions, the water may be physically immobi1i2ed as a glassy or plastic material or it may be bound to proteins (qv) and carbohydrates (qv). The water may diffuse with difficulty and thus may inhibit the diffusion of solutes. Changes in the stmcture of carbohydrates and proteins from amorphous to crystalline forms, or the reverse, that result from water migration or diffusion, may take place only very slowly. 

Heating the diffusate in water produced an odor reminiscent of roast beef broth. The diffusate could be separated into amino acid and carbohydrate fractions by ion exchange chromatography and neither produced a meaty odor upon heating, but recombining the subfractions produced a mixture with a "beef-like" odor upon heating. 

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