Starch Molecules

Given the size of the starch molecule, starch was classified as a complex carbohydrate, which chemically it is. Nutritionally, starch, particularly potato starch, is broken down into glucose fairly quickly. If the gluten molecule is regarded as a giant construction set the body has the key to break down the links between the individual molecules. However, while 

The non-break down of physically inaccessible starch explains why wheat is ground into flour in the first place. This may also explain the claims that modern flour with its very small particle size is less healthy than the sort of flour produced by ancient wind and water mills. The resistant nature of ungelatinised starch also explains why starch-based foods were baked in the first place. 

Resistant starch will serve as primary source of substrate for colonic microflora and may have important physiological benefits. On this basis resistant starch can be classified as a dietary fibre. The Association of Official Agricultural Chemists (AOAC) method of determining dietary fibre will measure some resistant starch as dietary fibre. 

Chemically, both varieties of starch are polymers of glucose with the a-D-glucose units in the 4Ci conformation. The glucose units are linked -(1 - 4)- in both amylose and amylopectin but in amylopectin roughly one residue in twenty is linked -(1 - 6)-, which forms branch points. The proportion of branch points varies, depending on the source of the amylopectin. 

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The Turing mechanism requires that the diffusion coefficients of the activator and inlribitor be sufficiently different but the diffusion coefficients of small molecules in solution differ very little. The chemical Turing patterns seen in the CIMA reaction used starch as an indicator for iodine. The starch indicator complexes with iodide which is the activator species in the reaction. As a result, the complexing reaction with the immobilized starch molecules must be accounted for in the mechanism and leads to the possibility of Turing pattern fonnation even if the diffusion coefficients of the activator and inlribitor species are the same 62. 

Cationic starches show decreased gelatinization temperature range and increased hot paste viscosity. Pastes remain clear and fluid even at room temperatures and show no tendency to retrograde. This stabiUty is due to Coulombic repulsion between positively charged starch molecules in dispersion. 

When you eat starchy foods, they are broken down into glucose by enzymes. The process starts in your mouth with the enzyme amylase found in saliva. This explains why, if you chew a piece of bread long enough, it starts to taste sweet The breakdown of starch molecules continues in other parts of the digestive system. Within 1 to 4 hours after eating, all the starch in food is converted into glucose. 

Starch molecules have many exposed O—bonds, so this phosphorylation reaction results in multiple phosphate groups attached to each starch molecule. The remaining —OH group on each phosphate can condense with an O— H bond on another starch molecule. This cross-linking of starch chains gives the desired thick consistency of puddings and pies. 

One bodily function that relies on acids and bases is the process of digestion. During digestion, food is broken down into small molecules that the body can use. Digestion begins in the mouth when food comes into contact with an enzyme called amylase found in the saliva. Enzymes are the body s catalysts. They speed up chemical reactions that would otherwise be too slow to be useful to the body. Amylase breaks down starch molecules and converts them into sugars. 

Results and Discussion. Of the 12 samples of starch graft copolymer synthesized, half were hydrolyzed to anionic polyelectrolytes. Synthesis data on these 6 samples are given in Table 2. These particular samples were chosen for hydrolysis because the samples can be intercompared to see the effect of synthesis variables on ultimate product properties. Samples 5, 8, and 11 have the same mole ratio of cerium ion to starch backbone, N, in their reaction mixture. Samples 7, 8, and 9 all have the same refctable mass per starch molecule,... 

Saliva begins the process of chemical digestion with salivary amylase. This enzyme splits starch molecules into fragments. Specifically, polysaccharides, or starches, are broken down into maltose, a disaccharide consisting of two glucose molecules. Salivary amylase may account for up to 75% of starch digestion before it is denatured by gastric acid in the stomach. 

These concepts have to be correlated with the inherent helical form of the starch molecule, and attempts which have been made to determine the orientation of the portions of the molecules in the crystallites will be dealt with later (in the Section on x-ray diffraction studies—see p. 376). In this connection, the work on the orientation of synthetic crystalline polymers into spherulites containing helically arranged molecules23 may be important. 

Starch liquefaction, 10 287-288 Starch molecule, techniques for characterizing, 20 562 Starch phosphates, 4 724t Starch sodium phosphate monoesters, 4 721... 

One of the difficulties of using starch as a surface size is that when surface-sized papers are recycled, the starch is readily solubilised into the aqueous system where it contributes to the nutritional pollution load of the effluent. This can be controlled to a large extent by introducing cationic groups into the starch molecule which bind strongly to the anionic cellulose in a similar manner to starches used as dry strength agents (Chapter 7). 

Starch-containing plants Another potential ethanol feedstock is starch. Starch molecules are made up of long chains of glucose molecules. Hence, starch-containing materials can also be fermented after the starch molecules have been broken down into simple glucose molecules. Examples of starchy materials commonly used around the world for ethanol production include cereal grains, potatoes, sweet potatoes and cassava. Typical cereal grains commonly used for ethanol production in the EET are rye and wheat. 

Calorimetric investigations of hydrous metal oxide suspensions are more scarce. A study of starch adsorption on hematite revealed that the adsorption process became less exothermic as surface coverage increased (25). This was attributed to a rearrangement of starch molecules to less favorable configurations. 

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