Polysaccharides starch grains

In contrast to the fibrous and well-oriented polysaccharides (such as cellulose and chitin), amylose in its natural state is found only in more-or-less spherical starch granules. Amylose is the minor constituent of most starches, and is a linear polymer of a-D-(l—>4)-linked D-glucose residues. The birefringence of starch grains was already well known at the turn of the century, and the cross of isocline pattern between crossed Nicols was interpreted in terms of radially arranged crystallites. Later,... 

Carbohydrates Carbohydrates are a major source of energy for humans and are present in all foods (grains, vegetables, fruits, and milk), and vary in form from simple monosaccharides (fructose, glucose, galactose, sorbitol) to oligosaccharides (maltose, sucrose, lactose, raffinose, stachyose, ver-bascose), and more complex polysaccharides (starch, cellulose, etc.). 

This section is followed by another extensive discussion of starch, the other major commercial polysaccharide. It is amazing how much difference a simple stereochemical variation can make in the structure and properties of a macromolecule. Even more fascinating patterns are observed in native starch grains. The crystalline fibrils are arranged in a fractal-like pattern called trichites (Fig. 3.14). 

Starch, a reserve polysaccharide widely distributed in plants, is the most important carbohydrate in the human diet. In plants, starch is present in the chloroplasts in leaves, as well as in fruits, seeds, and tubers. The starch content is especially high in cereal grains (up to 75% of the dry weight), potato tubers (approximately 65%), and in other plant storage organs. 

Enzymes are also added to catalyze the hydrolysis or saccharification of starch. Malt produced by the germination of barley grain contains the enzymes that catalyze this hydrolysis. Sometimes called diastase, the enzymes are primarily a- and 6-amylase. Glucoamylase is a pure enzyme that can now be used. Both diastase and glucoamylase hydrolyze starch polysaccharide to the disaccharide, maltose. For fuel grade ethanol production, hydrolysis takes place at temperatures ranging from about 120°F to 140°F (50°C to 60°C) for about 1 hour. The final product of hydrolysis is called a wort. Solids can be filtered from the wort before continuing. 

Polysaccharides Complex carbohydrates are polysaccharides (most often polymers of glucose), which do not have a sweet taste. Starch is an example of a complex carbohydrate that is found in abundance in plants. Common sources include wheat and other grains, potatoes, dried peas and beans, and vegeta bles. 

In fermentations, the amylases are either present in or added to the polysaccharide substrate at activity levels sufficient to hydrolyze starch to maltose. Yeast does not generate the amylases, so malt (germinated grain) is relied on to augment their concentration. The importance of yeast is to produce maltase for converting maltose to glucose. 

Saccharides are present in food raw materials in quantities ranging from about 1% in meats and fish, to about 4.5% in milk, 18% in potatoes, and 15-20% in sugar beets, to about 70% in cereal grains. Polysaccharides participate in the formation of structures in plants. They are also stored in plants as starch and in muscles as glycogen. Other saccharides are dissolved in tissue fluids or perform different biological functions in free nucleotides, as components of nucleic acids, or bound to proteins and lipids. 

Starch, a food-reserve substance from plant grains, is a mixture of two polysaccharides, amylose and amylopectin (Kennedy and White 1988). Amylose is... 

Starch is a condensation polymer made up of hundreds of glucose monomers, which split out water molecules as they chemically combine. Starch is a member of the basic food group carbohydrates and is found in cereal grains and potatoes. It is also referred to as a polysaccharide, because it is a polymer of the monosaccharide glucose. Starch molecules include two types of glucose polymers, amylose and amylopectin, the latter being the major starch component in most plants, making up about three-fourths of... 

Rice endosperm cell walls have been prepared by grinding the rice flour (obtained from the milled grains) to pass through a 50-mesh sieve and then treating the flour sequentially as follows (1) with cold water and then 1 1 ethanol/ether to defat the flour, (2) with a-amylase to remove starch and isolate the water-soluble polysaccharides from the supernatant fluid,... 

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