Starch, hydrolysis with acid

D-glucose, dextrose, C Hi20 . The most common hexose sugar. It is present in many plants, and is the sugar of the blood. It is a constituent of starch, cellulose, glycogen, sucrose and many glycosides, from all of which it can be obtained by hydrolysis with acids or enzymes. 

Starch has been cross-linked with epichlorohydrin (65—5.4 D-glucosyl residues per cross-linkage) by an iterative method that preserves the crystalline structure of the starch granule. The stability of the modified granules to digestion by a-amylase (measured by the loss of weight on incubation) increased with the extent of cross-linking, whereas the susceptibility to hydrolysis with acid decreased. 

Partial hydrolysis with acid is carried out at higher temperatures than the production of soluble starch, generally in 40% starch suspensions containing HCl at a concentration of 0.02-0.03 mol/1 at temperatures of 135-150 °C for 5-8 min. 

Ordinary glucose is ct-glucopyranose monohydrate m.p. 80-85°C and [ajp 4-113-4 . In solution it gives a mixture with the form with [alo 4-52-5 . It is manufactured from starch by hydrolysis with mineral acids, purification and crystallization, and is widely used in the confectionery and other food industries. It is about 70% as sweet as sucrose. 

Starch is often modified by hydrolysis with hydrochloric or sulfuric acid (93). The resulting product is resistant to syneresis, keeps food in suspension after cooking, and exhibits much greater free2e—thaw stabUity than unmodified starch. Modified starch is commonly used in baby food, fro2en prepared foods, pie fillings, meat products, and candy. 

A solution of iodine in aqueous iodide has an intense yellow to brown colour. One drop of 0.05M iodine solution imparts a perceptible pale yellow colour to 100 mL of water, so that in otherwise colourless solutions iodine can serve as its own indicator. The test is made much more sensitive by the use of a solution of starch as indicator. Starch reacts with iodine in the presence of iodide to form an intensely blue-coloured complex, which is visible at very low concentrations of iodine. The sensitivity of the colour reaction is such that a blue colour is visible when the iodine concentration is 2 x 10 " 5 M and the iodide concentration is greater than 4x 10 4M at 20 °C. The colour sensitivity decreases with increasing temperature of the solution thus at 50 °C it is about ten times less sensitive than at 25 °C. The sensitivity decreases upon the addition of solvents, such as ethanol no colour is obtained in solutions containing 50 per cent ethanol or more. It cannot be used in a strongly acid medium because hydrolysis of the starch occurs. 

Maltodextrins and corn syrup solids are produced from starch, usually corn. The starch, which is almost pure carbohydrate, is cooked or pasted to open the granule and then hydrolyzed. Products can be made by hydrolyzing with acid or enzymes or with a combination of acid and enzymes. After the desired amount of hydrolysis has occurred, the reaction is stopped, and the product is filtered to remove insoluble materials and then dried. 

Further, the hydrolysis of starch nitrate in acids containing little or no sulphuric acid does not proceed to such a large extent as is usual when starch is treated with mixtures of high sulphuric acid content. 

Base Hydrolysis. Protein digestions in basic media have proven to be no panacea. Early studies employed 4.2N sodium hydroxide and saw success with pure proteins (68). Collaborative studies (69,70) have since shown optimized recoveries of 85% for NaOH hydrolyses in complex food samples. In general, for samples rich in fats and carbohydrate, attempts to use starch or ascorbic acid as protective agents have shown little improvement in recoveries. 

Carbohydrates are classified as either simple or complex. Simple sugars, or monosaccharides, are carbohydrates such as glucose and fructose that can t be broken down into smaller molecules by hydrolysis with aqueous acid. Complex carbohydrates, or polysaccharides, are compounds such as cellulose and starch that are made of many simple sugars linked together. On hydrolysis, polysaccharides are cleaved to yield many molecules of simple sugars. 

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