Starch high amylopectin

In comparison with a pullulanase, the purified amylopullulanase displayed 3-fold higher specificity towards soluble starch and amylopectin and 7-fold higher specificity towards glycogen (12). The amylopullulanase hydrolyzed various high molecular weight starch substrates (Table II). Even the mammalian glycogen which... 

Ortega-Ojeda, F. E., Larsson, H., Eliasson, A. C. (2005). Gel formation in mixtures of hydrophobically modified potato and high amylopectin potato starch. Carbohydr. Polym., 59, 313-327. 

Fredriksson, H., Bjork, L, Andersson, R., Liljeberg, H., Silverio, J., Eliasson, A. -C., Aman, P. (2000). Studies on a-amylase degradation of retrograded starch gels from waxy maize and high-amylopectin potato. Carbohydrate Polymers, 43, 81-87. 

A starch molecule may contain up to 6000 glucose units, although this number is highly variable and can be as low as 200. Plants produce two forms of starch, amylose amylopectin, as illustrated in Figure 13.6. In amylose, the glucose units... 

NMR spectrum depends on the type of starch (amylose-to-amylopectin ratio) and is associated with the numbers of carbon atoms in the branching points and thermal glucose units. Tables X and XI present 13C spin-lattice relaxation times (Tus) and nuclear Overhauser enhancement (n.O.e) for l3C nuclei of starches of various origins. Figure 21 shows H NMR spectra of amylose and a high-amylopectin waxy sorghum starch. 

High amylopectin starch Non-gelling starch Carbohydrate Waxy maize... 

Starch is also a polysaccharide, like cellulose, but it is much less crystalline. The major component of starch is amylopectin, which is a highly branched polymer, while cellulose is strictly linear. These branches prevent amylopectin from crystallizing as well as cellulose. Starch is an excellent source of energy (or stored sugar) for plants and animals for these reasons Because it is less crystalline than cellulose it is more soluble than cellulose, and the branched structure also means there are more end groups at which enzymes can start chewing the polymer apart. 

The enzymatic activity of isoamylase is determined by measuring the rate of hydrolysis of high-amylopectin starch and is expressed in isoamylase units (lAU). The isoamylase enzyme preparations contain at least 1.25 x 10 lAU/g and have the following composition total organic solids (TOS), approximately 4% water, approximately 58% maltose and glucose, approximately 37% and glycerol fatty acids, approximately 0.1%. 

These two peaks are pointed as Gr and Mir and are correlated with the G and Mi peak in the gelatinization phenomenon. Gr and Mir are mainly due to amylopectin, which, after the gelatinization process, can rebuild its structure under appropriate time-temperature conditions giving rise to new thermal transitions close to the original ones [34], Gr and Mir are detectable both in normal starches and in waxy (high amylopectin content) starches (in this case Gr and Mir are more pronounced) [34,35]. 

The polysaccharide starch contains glucose units joined by 1,4-a-glycosidic bonds. Amylose is an unbranched form of starch, whereas amylopectin is highly branched. Glycogen, found in animals, is more highly branched than amylopectin and has a higher molecular weight. 

The long linear chain structure of amylose is reflected in the film-forming properties of its acetate. Films prepared from acetylated whole starch and amylopectin are quite brittle, whereas those from butanol-precipitated amylose are similar to films from high-grade cellulose acetates (94)-... 

The other main form of plant starch is amylopectin, which has a molar mass as high as 150,000,000 g/mol (Fig. 22.13). It has the same a(l 4) bonds as amylose, but it also has branches designated o (l 6). As a result of its high molar mass and its branches, amylopectin is insoluble in water. 

The majority of native starches are mixtures of amylose and amylopectin, two homopolysaccharides composed of a-D-gluco-pyranose molecules in Cj conformation. Amylose and amylopectin usually occur in a weight ratio of 1 3. In some varieties of cereals (maize, barley and rice) and other plants (potatoes), either amylose (starches of high amylose content or amylostarches) or amylopectin (starches high in amylopectin or waxy starches) predominate. 

---