Как выбрать гостиницу для кошек
14 декабря, 2021
Starch may be regarded as a long-chain polymer of glucose (i. e., many glucose molecular units are bonded in a polymeric chain similar to a condensation polymerization product [16]). As such, macromolecular starches cannot be directly fermented to ethanol via conventional fermentation technology. They must first be broken down into simpler and smaller glucose units through a chemical process called hydrolysis. In the hydrolysis step, starch feedstock is ground and mixed with water to produce a mash typically containing 15 to 20% starch. The mash is then cooked at or above its boiling point and treated subsequently with two enzyme preparations. The first enzyme hydrolyzes starch molecules to short-chain molecules, and the second enzyme hydrolyzes the short chains to glucose. The first enzyme is amylase. Amylase liberates "maltodextrin" by the liquefaction process. Such maltodextrins are not very sweet inasmuch as they contain dextrins (a group of low molecular weight carbohydrates) and oligosaccharides (a saccharide polymer containing a small number of simple sugars, monosaccharides). The dextrins and oligosaccharides are further hydrolyzed by enzymes such as pullulanase and glucoamylase in a process known as saccharification. Complete saccharification converts all the limit dextrans (complex branched polysaccharides of many glucose molecules) to glucose, maltose, and isomaltose. The mash is then cooled to 30°C, and at this point yeast is added for fermentation.