Glassy starch

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). 

Molecular Mobility in Glassy Starch Influence of Hydration and Sucrose... 

Kim, Y.J., Hagiwara, T., Kawai, K., Suzuki, T., and Takai, R. Kinetic process of enthalpy relaxation of glassy starch and effect of physical aging upon its water vapor permeability property, Carbohydr. Polym., 53, 289, 2003. 

One method of producing hard, amorphous, glassy, starch-based materials is to use an extruder. A starch-based melt at typically 30% moisture can be forced through a die to... 

Microencapsulation using extrusion is mainly described for glassy carbohydrate matrices [14-16, 28-29]. The glassy carbohydrates, such as starch and maltodextrins, are melted at elevated temperature and low water contents and are intensively mixed with the active in the extrusion barrel. Extrusion has been used for volatile and unstable flavours. The shelf life of flavour oils could be extended from several months to 5 years, compared with 1 year for spray-dried materials. The main drawbacks of the technology are the high investments costs and the formation of rather large particles (500-1,000 pm). 

Culled) food potatoes are not normally used because of their low dry matter content (glassy potatoes) and relatively small starch granules,5 which are more difficult to process. When the price of food potatoes is low due to overproduction (culled) food potatoes are sometimes processed between the starch campaigns in Europe. Reclaimed potato starch, which is starch recovered from the process waters from other potato processing industries (French fry, chip/crisp and potato puree manufacturers) is processed on a small scale in Europe and North America. 

Cooked but unexpanded thermoplastic starches (TPS) have wider applications, because of the fact that approx. 8% of water can be removed after the cooking process by devolatilization at 300 mbar, corresponding to a cooling by approx. 70 °C down to 100°C. That means that the exiting strand does not expand but yields a glassy, plastic-like pellet that can be dried in a fluidized-bed dryer. 

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