Amorphous food

Levine, H. 2002. Introduction Progress in amorphous food and pharmaceutical systems. In Amorphous Food and Pharmaceutical Systems (H. Levine, ed.). Royal Society of Chemistry, Cambridge, UK. 

Lievonen, S.M. and Roos, Y.H. 2002a. Nonenzymatic browning in amorphous food models Effect of glass transition and water. J. Food Sci. 67, 2100-2106. 

The water present in foods may act as a plasticizer. Plasticizers increase plasticity and flexibility of food polymers as a result of weakening of the intermolecular forces existing between molecules. Increasing water content decreases Tg. Roos and Karel (1991a) studied the plasticizing effect of water on thermal behavior and crystallization of amorphous food models. They found that dried foods containing sugars behave like amorphous materials, and that small amounts of water decrease Tg to room temperature with... 

Roos, Y.H. 1993. Water activity and physical state effects on amorphous food stability. J. Food Process Preserv. 16 433-447... 

Roos, Y., and M. Karel. 1991d. Plasticizing effect of water on thermal behaviour and crystallization of amorphous food models. J. Food Sci. 56 38-43. 

Carbohydrates and proteins are typical hydrophilic components of concentrated food systems. These components tend to form amorphous, noncrystalline structures at low water contents (White et al. 1966 Slade et al. 1991 Roos 1995). Well-known food processes resulting in glass formation by amorphous or partially amorphous food components include baking, extrusion, dehydration and freezing (Roos 1995). In these processes, removal of water as part of the manufacturing process results in the formation of a noncrystalline, amorphous state, which is extremely sensitive to water and may show various time-dependent changes causing loss of quality and reduced shelf life. 

A second-order transition is defined as one in which the second derivatives of G and g with respect to temperature exhibit discontinuities at the transition temperature. Although glass-transition of amorphous foods has the properties of a second-order transition, there are no well-defined second-order transitions in foods (Roos, 1998). 

Shalaev, E.Y. Zografi, G. The concept of structure in amorphous solids from the perspective of the pharmaceutical sciences. In Amorphous Food and Pharmaceutical Systems Levine, H., Ed. The Royal Society of Chemistry London, UK, 2002 11-30. 

Lechuga-Ballesteros D, Miller DP, Zhang J. Residual water in amorphous solids, measurement and effects on stability. In Levine H, ed. Progress in Amorphous Food and Pharmaceutical Systems. London The Royal Society of Chemistry, 2002 275-316. 

Shalaev E and Zografi G. The Concept Of Structure in Amorphous Solids From the Perspective of the Pharmaceutical Sciences. In Amorphous Food and Pharmaceutical Systems. Cambridge The Royal Society of Chemistry 2002. 11-30. 

Increased moisture can allow greater solubility of amorphous food components. In an intermediate moisture food, it is very likely that some... 

Crank, J. The Mathematics of Diffusion, 2nd Ed., Clarendon Press, Oxford, 1975. Gordon, M. and Taylor, J.S. Ideal copolymers and second order transitions in synthetic rubbers. I. Non-crystalline polymers, /. Appl. Chem., 2, 493,1952. Karel, M., Anglea, S., Buera, M.P., Karmas, R., Levi, G., Roos, Y. et al. Stability related transitions of amorphous foods, 246. pp. 249,1994. 

Three amorphous food model systems consisting of lactose, trehalose, and lactose/trehalose (1 1) as matrix materials, and L-lysine and D-xylose (1 1, 5% w/w) as reactants were prepared by freeze-drying. Aliquots (1 g) of the powdered freeze-dried model materials were transferred into 20-ml glass vials, which were stored in desiccators over four relative vapor pressures (RVP) of 33.2,44.1,54.5, and 65.6%. Triplicate samples were removed at 10- to 24-h intervals depending on the RVP, and the extent of browning was determined spectrophotometrically at 280 and 420 nm. 

Karel, M., Anglea, S., Buera, R, Karmas, R., Levi, G., and Roos, Y. Stability related transitions of amorphous foods, Thermochim. Acta, 246, 249, 1994. 

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