In the manufacture of jelly and candy and in the canning of fruit, the recrystallization of sugar is undesirable. Sucrose readily recrystallizes from a solution, but invert sugar has a much greater tendency to remain in solution. The hydrolysis reaction has several practical applications. This 1:1 mixture is referred to as invert sugar because it rotates plane-polarized light in the opposite direction than sucrose. The hydrolysis of sucrose in dilute acid or through the action of the enzyme sucrase (also known as invertase) gives an equimolar mixture of glucose and fructose. Therefore, sucrose is a nonreducing sugar. In addition, sucrose does not undergo reactions that are typical of aldehydes and ketones.

Thus, sucrose is incapable of mutarotation and exists in only one form both in the solid state and in solution. As long as the sucrose molecule remains intact, neither monosaccharide “uncyclizes” to form an open-chain structure. This linkage gives sucrose certain properties that are quite different from those of maltose and lactose. The incidence of galactosemia in the United States is 1 in every 65,000 newborn babies. As a child with galactosemia grows older, he or she usually develops an alternate pathway for metabolizing galactose, so the need to restrict milk is not permanent. If galactosemia is recognized in early infancy, its effects can be prevented by the exclusion of milk and all other sources of galactose from the diet. The disease may result in impaired liver function, cataracts, mental retardation, and even death. An infant with galactosemia experiences a lack of appetite, weight loss, diarrhea, and jaundice. Consequently, the blood galactose level is markedly elevated, and galactose is found in the urine. Galactosemia is a condition in which one of the enzymes needed to convert galactose to glucose is missing. These are taken orally with dairy foods-or may be added to them directly-to assist in their digestion. The most common treatment for lactose intolerance, however, is the use of lactase preparations (e.g., Lactaid), which are available in liquid and tablet form at drugstores and grocery stores. Cooking or fermenting milk causes at least partial hydrolysis of the lactose, so some people with lactose intolerance are still able to enjoy cheese, yogurt, or cooked foods containing milk. Alternatively, many food stores now carry special brands of milk that have been pretreated with lactase to hydrolyze the lactose. The symptoms disappear if milk or other sources of lactose are excluded from the diet or consumed only sparingly. The buildup of water and bacterial decay products leads to abdominal distention, cramps, and diarrhea, which are symptoms of the condition. At the same time, intestinal bacteria may act on the lactose to produce organic acids and gases. In people with lactose intolerance, some of the unhydrolyzed lactose passes into the colon, where it tends to draw water from the interstitial fluid into the intestinal lumen by osmosis. Up to 20% of the US population suffers some degree of lactose intolerance. For some people the inability to synthesize sufficient enzyme increases with age. As a result, many adults experience a reduction in the ability to hydrolyze lactose to galactose and glucose in their small intestine. Infants and small children have one form of the enzyme lactase in their small intestines and can digest the sugar easily however, adults usually have a less active form of the enzyme, and about 70% of the world’s adult population has some deficiency in its production. Lactose makes up about 40% of an infant’s diet during the first year of life. To Your Health: Lactose Intolerance and Galactosemia Whether it occurs in the body or a glass beaker, the hydrolysis of maltose produces two molecules of D-glucose. The same reactions can be carried out in the laboratory with dilute acid as a catalyst, although in that case the rate is much slower, and high temperatures are required. In the body, such hydrolysis reactions are catalyzed by enzymes such as maltase. Therefore, an ingested disaccharide must first be broken down by hydrolysis into its two constituent monosaccharide units.

The human body is unable to metabolize maltose or any other disaccharide directly from the diet because the molecules are too large to pass through the cell membranes of the intestinal wall. Maltose is about 30% as sweet as sucrose. In the manufacture of beer, maltose is liberated by the action of malt (germinating barley) on starch for this reason, it is often referred to as malt sugar. It is formed most often by the partial hydrolysis of starch and glycogen. Maltose occurs to a limited extent in sprouting grain.

Anomeric carbon definition