What is the Difference Between Sorbitol and Mannitol

The main difference between sorbitol and mannitol is that the hydroxyl group of the second carbon is coming out of the plane in the Fischer projection of sorbitol whereas the hydroxyl group of the second carbon is going behind the plane in the Fischer projection of mannitol. Furthermore, sorbitol is the isomer of mannitol. 

Sorbitol and mannitol are two types of sugar alcohols used as artificial sweeteners. Sorbitol serves as a sugar substitute while mannitol is used as a medication to reduce the pressure of the eye and as a sweetener in diabetic food.

Key Areas Covered

1. What is Sorbitol
     – Definition, Properties, Importance
2. What is Mannitol
     – Definition, Properties, Importance
3. What are the Similarities Between Sorbitol and Mannitol
     – Outline of Common Features
4. What is the Difference Between Sorbitol and Mannitol
     – Comparison of Key Differences

Key Terms

Isomer, Mannitol, Sorbitol, Sugar Substitute, Sweetness

Difference Between Sorbitol and Mannitol - Comparison Summary

What is Sorbitol

Sorbitol is the sugar alcohol less commonly known as glucitol. It frequently occurs in fruits including apples, pears, and prunes. It can be produced by the reduction of glucose, changing the aldehyde group to a hydroxyl group. Also, the enzyme responsible for converting sorbitol back to fructose is sorbitol-6-phosphate 2-dehydrogenase.

What is the Difference Between Sorbitol and Mannitol

Figure 1: Sorbitol

However, the human body metabolizes sorbitol slowly. Therefore, it becomes a sugar substitute which does not produce glucose spikes in the blood. Also, it contains a lesser amount of calories, which is good for people interested in losing their weight.

What is Mannitol

Mannitol is another sugar alcohol, which is the isomer of sorbitol. Therefore, the molecular weight and the chemical formula of both sorbitol and mannitol are similar. They only differ by the orientation of the hydroxyl group on the second carbon. Also, mannitol is used as a sugar substitute, especially in diabetic food. Our intestine absorbs mannitol poorly.

Difference Between Sorbitol and Mannitol

Figure 2: Mannitol

In addition to a sugar substitute, mannitol is used as a medication to decrease the pressure of eyes and to lower the high intracranial pressure. However, electrolyte problems and dehydration are common side effects of this medication.

Similarities Between Sorbitol and Mannitol

  • Sorbitol and mannitol are two types of sugar alcohols, which are polyols.
  • They are alternative sweeteners. Also, they are nutritive and occur in some fruits and vegetables.
  • Furthermore, the food with added sorbitol or mannitol is called sugar-free.
  • Both have the same chemical formula, which is C6H8(OH)6 and the same molecular weight, which is 17176 g/mol.
  • Also, both are white color odorless powders.
  • And, both can be produced by hydrogenating saccharides.
  • Moreover, they are derived from fructose.
  • Besides, both of them do not contain ethyl alcohol; hence, they have no intoxicating effects.
  • Additionally, their metabolism releases fewer calories.
  • Thus, their absorption to the body and metabolism occur slowly. Therefore, they have a low glycemic index (GI) and are good for diabetics.
  • Also, sugar alcohols are noncariogenic since they do not promote cavities or dental caries as sugars.
  • However, a large amount of sugar alcohols may result in gastrointestinal symptoms like gas, diarrhea (similar to a laxative), and pain.

Difference Between Sorbitol and Mannitol

Definition

Sorbitol refers to a sweet-tasting crystalline compound found in some fruit while mannitol refers to a colorless sweet-tasting crystalline alcohol which is found in many plants and is used in various foods and medical products. Thus, this is the fundamental difference between sorbitol and mannitol.

Occurrence

Moreover, sorbitol naturally occurs in corn, apples, pears, peaches, and prunes while mannitol naturally occurs in the leaves of several members of the live family.

The orientation of the Hydroxyl group on C2

The main difference between sorbitol and mannitol is that the hydroxyl group of the second carbon is coming out of the plane in the Fischer projection of sorbitol whereas the hydroxyl group of the second carbon is going behind the plane in mannitol.

Produced From

Furthermore, sorbitol is mainly produced from corn syrup while mannitol is mainly produced by hydrogenating fructose derived from starch or sucrose.

Melting Point

Also, their melting point is another difference between sorbitol and mannitol. The melting point of sorbitol is 201-208 degrees Fahrenheit while the melting point of mannitol is 327-336 degrees Fahrenheit.

Appearance

Additionally, sorbitol is slightly denser when compared to mannitol while mannitol sometimes forms granules.

Degree of Sweetness

Sorbitol is half as sweet as sugar while mannitol is 0.7 times as sweet as sugar.

Amount of Calories

Besides, calorie content is also a difference between sorbitol and mannitol. Sorbitol contains 2.6 calories per gram while mannitol contains 1.6 calories per gram.

Significance

The main use of sorbitol is as a sugar substitute while mannitol is mainly used as medication. Hence, this is another difference between sorbitol and mannitol.

Types of Food

More to this, sorbitol is used for special dietary foods including diabetic food, candies, and gum while mannitol is used in the bulking agent, chewing gums, candies, and baked food.

Conclusion

Sorbitol is a sugar substitute which releases a fewer amount of calories upon metabolism. In comparison, mannitol is another sugar substitute, especially used as a medication to lower blood pressure. Both sorbitol and mannitol are isomers with different orientations of the hydroxyl group on the second carbon. They can be used as sugar substitutes in diabetic food. However, the main difference between sorbitol and mannitol is their structure, properties, and uses.

References:

1. “Sorbitol, Mannitol, Maltitol, Xylitol and Other Sugar Alcohols in Food.” Culinarylore.com, 4 June 2018, Available Here.

Image Courtesy:

1. “D-sorbitol” By Mrgreen71 – Own work (CC BY-SA 3.0) via Commons Wikimedia  
2. “Mannitol structure” By Edgar181 – Own work (Public Domain) via Commons Wikimedia  

About the Author: Lakna

Lakna, a graduate in Molecular Biology & Biochemistry, is a Molecular Biologist and has a broad and keen interest in the discovery of nature related things

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