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What is Sorbitol?
Sorbitol is a sugar alcohol, belonging to the class polyols. It has a pleasant taste and is found in fruits, vegetables like the pears, apples, prunes and etc. sorbitol is used as an emulsifier and comprises of very less calories. In industries, glucose is reduced which means the sugar is hydrogenated to produce sorbitol. Sorbitol is an organic compound, which dissolves in water and is white in color.
History of Sorbitol
In the year 1872, from the mountain ash berries, sorbitol was initially identified. Joseph Boussingault termed the name sorbitol and extracted it. Nowadays, sorbitol is produced by reducing glucose. A starch source is the corn, which is broken into smaller compounds which is the sugar.
To form sorbitol, to the glucose molecule, hydrogen is added using a catalyst. Sorbitol has been approved by the USFDA and is used in food. Apart from US, countries like Australia, Japan and Canada are also using sorbitol after approval in drinks and food items.
Properties of Sorbitol
The formula for sorbitol is C6H14O6, which is polyol produced by hydrogenation of glucose. Both sorbitol and mannitol are sugar alcohol, having same formula, however differ as they are isomers of each other and presence of OH group on the second carbon.
Mannitol has a melting point of 166-168℃, whereas sorbitol has 94-96℃, thus differing in melting point. Both these sugar alcohol can be produced artificially, but exist naturally as well and are used as sweeteners. They have application in medicine as well. Sorbitol is used as a laxative, whereas mannitol is used as a diuretic.
A replacement of sucrose is the sorbitol, which is also sweet in taste, but less sweet than sucrose, thus having lower number of calories. Sorbitol has a lower glycemic index which is 9 when compared to sucrose which is 65.
Biological Action of Sorbitol
Sorbitol can be produced from glucose hydrogenation, where aldehyde is replaced by the hydroxyl group. The enzyme required is aldose reductase and along with NADH, which is a cofactor. The conversion of glucose to fructose, takes place through the polyol pathway, which is a two-step process, where glucose is first transformed to the polyol, sorbitol and then to fructose.
The first step is sorbitol is produced from glucose hydrogenation, where aldehyde is replaced by the hydroxyl group. The enzyme required is aldose reductase and along with NADH, which is a cofactor. In the next step, sorbitol is oxidized to fructose. In this step as well, cofactor NAD+ is required and the enzyme catalyzing the reaction is sorbitol dehydrogenase.
Such type of pathway is seen in diabetes type 2, where there is damage to the insulin dependent cell like nerves, retina and kidney. In glycolysis, sugar which is not phosphorylated by the glucokinase or hexokinase enzyme, moves to the polyol pathway where it forms fructose.
Although in diabetic conditions, when there is too much of glucose, it is reduced to sorbitol by the enzyme aldose reductase. Aa polyol pathway consumes cofactors, they aren’t much left for metabolic processes like nitric acid and glutathione production. Another problem is the presence of Reactive oxygen species, which can disrupt cells.
In very minute amount, sorbitol is found in fruits and vegetables. Artificially, it can be produced from glucose and used as a sweetener. However, small intestine absorbs sorbitol at a very slower pace.
After absorption, it enters the blood and is moved to the liver cell. hepatic polyol dehydrogenase converts sorbitol to fructose. In the colon, sorbitol which was not absorbed is moved and broken by the bacteria present over here.
Although excess amount of sorbitol will result in formation of by-products like the hydrogen gas and the organism’s number will also increase, resulting in accumulation of gas, which would result in pain, heaviness and inflammation, resulting in diarrhea, which would result in uptake of water which will be taken by the large intestine.
Sorbitol Side Effects
USFDA has approved sorbitol and can be consumed by the body, but the amount which can be taken regularly is not mentioned. However, it could pose some issue as sorbitol is not readily absorbed by the body and takes quite a huge amount of time.
People with irritable bowel syndrome, fructose or sorbitol intolerant should not consume sorbitol or its food product. As sorbitol is transformed to fructose, people who are intolerant to fructose, should not consume sorbitol as well. Excess of sorbitol can result in flatulence, body pain and diarrhea.
Importance of Sorbitol
Sorbitol is used as a substrate, to carry out test related to bacteria and for media’ with less strength it provides tonicity. Sorbitol can allure and hold water, thus used as a laxative which helps to clear the bowels. Laxative effect of sorbitol is also seen fruits like prune, which induces laxative effects and thus can be consumed orally or rectally.
Sorbitol is a sugar alcohol, thus are not broken by the bacteria present in the mouth, which would result in the formation of products, thus not decaying of tooth is seen and can be used in toothpaste, syrups and cough tablets. Although majority of bacteria cannot break sorbitol, it can be disintegrated by Streptococcus mutanscan, however it takes time, thus decaying of tooth might happen.
As sucrose is sweeter than sorbitol, thus resulting in more calories around 4 kilocalories, whereas sorbitol provides only 2.6 kilocalories. Thus, food with sorbitol, state that they are diet food or sugar free or are low calorie intake food.
Sucrose has a very high glycemic index of 65 and sorbitol has that of 9. Glycemic index of fructose is 25 and that of glucose is 100. Higher the glycemic index, more are the chances of higher glucose level, resulting in diabetes and gaining weight.
In glycolysis, when glucose is not phosphorylated it moves to the glycolysis pathway, where glucose is reduced by hydrogenation to form sorbitol and then further it form fructose by oxidation. Fructose is very vital as it carries out functions like glycation and fructolysis.
Only when there is glucose in excess, it is transformed to fructose. Sorbitol is present in fruits like apples, prunes, berries, peaches and others. Sorbitol can be manufactured chemically, which acts as a sweetener in various food items and beverages.
However, small intestine absorbs sorbitol very little and very slowly. In the colon, sorbitol which was not absorbed is moved and broken by the bacteria present over here.
Although excess amount of sorbitol will result in formation of by-products like the hydrogen gas and the organism’s number will also increase, resulting in accumulation of gas, which would result in pain, heaviness and inflammation, resulting in diarrhea.