Glass amylopectin

Figure 8.6 Variation in glass transition temperature of starch (DSC data) as a function of water content 1, 2 and 4 correspond to gelatinized potato, rice and wheat starch 3 and 5 correspond to amorphous amylopectin and granular wheat starch, respectively. Inset shows the DSC traces of native wheat starch at...

The glass transition of amylopectin measured by DSC, DMTA and NMR. Carbohydr. Polym., 18, 77-88. 

It is well known that every starch processing method is facilitated by the presence of water. Water depresses the melting point of amylopectin crystallites and lowers starch melt viscosity. Native potato starch contains about 18% water when stored at ambient atmosphere (room humidity about 55%). If one does not add more than about 10% water the melt-processed starch will solidify when cooling down. If more water is added to the starch, its glass transition falls below room temperature (Zeleznak Moseney, 1987). The moulding then exhibits a rubbery state and solidifies later when the excess water evaporates. 

Orford, P.D., Parker, R., Ring, S.G., and Smith, A.C. Effect of water as a diluent on the glass-transition behavior of malto-oligosaccharides, amylose and amylopectin, Int. J. Biol. Macromol., 11, 91,1989. 

Schematic of range of glass transition data for low moisture cereal foods and their major components (starch, amylopectin, gluten).

Kalichevsky M.T., Blanshard J.M.V., The effect of fructose and water on the glass transition of amylopectin, Carbohydr. 

MT Kalichevsky, EM Jaroszkiewicz, JMV Blanshard. A study of the glass transition of amylopectin-sugar mixtures. Polymer 34 346-358, 1993. 

Kahchevsky MT, Jaroszkiewicz EM, Ablett S, Blanshard JMV, Lillford PJ (1992) The glass transition of amylopectin measured by DSC, DMTA and NMR. Catbohydr Polym 18 77-88 Kalogeras IM (2011) A novel approach for analyzing glass-transition temperamre vs. composition patterns application to pharmaceutical compound 4- polymer systems. Eur J Pharm Sci 42 470-483... 

Increases in amylopectin crystallinity underlies part of the phenomenon known as bread staling (10). However, it has been recently shown that a rise in the glass transition temperature of the gluten, probably due to moisture migration, is more important (14-16). 

Earlier measurements on the moist transitions of extracted hemicelluloses were made by differential scanning calorimetry (DSC) (4). This enables the glass transition to be studied from a thermodynamic point of view, but information relevant for mechanical considerations such as the effect of load frequency is lacking. Some measurements in temperature scans in dynamic mechanical tests have been performed on carbohydrates such as amylopectin (13-15). The problem with such measurements on moist samples is the evaporation of water at the high temperatures. To avoid such problems, a technique for humidity scans... 

Corn high in amylopectin, a starch which is used in the paper industry and as a coating or sizing in the fabrication of woven fiber glass. 

---