How Is Erythritol Made? Manufacture of a Low-Calorie Sugar Substitute

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Erythritol. In sugar alcohol, the carbonyl group is replaced by a OH group. Photo by Clara Piccirillo.

“How is erythritol made?”

To answer this question, we will briefly introduce erythritol, explaining what it is and its importance. Then we will talk about the process used at industrial level for its production, describing each step in detail.

What Is Erythritol?

Erythritol is a chemical compound belonging to the family of sugar alcohols. These are molecules which have some characteristics in common with sugars and others with alcohols. Like sugars, they have a hydroxyl group (O–H) on every carbon atom in the chain. However, they differ from the “standard” sugars because they do not have end carbonyl groups  (C=O); instead they have end hydroxyl groups, which is characteristic of alcohols.

Erythritol’s formula is shown in the picture above. It can be seen that an OH group is bonded to the first carbon atom of the molecule, instead of a carbonyl.

Why It Is Important?

Erythritol is widely used in the food industry as a sweetener. In fact it has a sweetness of about 60-70 % of that of sucrose (i.e. the normal sugar we use in everyday life). At the same time, however, erythritol is much less calorific; according to the Harvard School of Public Health, a teaspoon of erythritol contains only 0.2 calories, instead of about 4 calories for sucrose.

Fruits like grape contain erythritol. Photo by Diciu.

The main reason for this is that, due to its different chemical structure, erythritol is absorbed much less by our body and, therefore, it gives it almost no energy.

Moreover, some studies showed that erythritol could also be beneficial to our oral health, as it can inhibit plaque formation.

Where Does Erythritol Come From?

Erythritol is a naturally-occurring molecule, we can find it in fruits such as pears, water melons and grapes; it is also present in some drinks like sake and wine, and sauce such as soy sauce.

Due to its large demand, however, the erythritol we use is produced at an industrial level with a fermentation process, using maize/corn as starting material.

Glucose has a carbonyl group. Photo by Clara Piccirillo.

Conversion into Erythritol: More Than One Step

Manufacturers use maize as a source of starch in the production of erythritol; therefore, the first step is the extraction of starch from maize.

Starch is a compound formed by glucose molecules bonded to each other to form long chains. Glucose (see Figure) is one of the most common sugars in nature; it is present, for instance, in the table sugar sucrose.

With a hydrolysis process, the long chains of starch are broken down into the smaller glucose molecules.

At this point, glucose is converted into erythritol with a fermentation process.

Fermentation by a Fungus

Fermentation is a process we are all quite familiar with; probably the most common application is the production of wines from grapes, beer from cereals, and other alcoholic beverages.

From a chemical point of view, during the fermentation one or more sugars are converted into alcohol, by either bacterial strains, yeasts or combinations of both.

In the case of erythritol, a fungus, Moniliella pollinis, performs the fermentation. With this, the glucose carbonyl group is converted into a hydroxyl group and the molecule goes from 6 carbon atoms to just 4.

Purifying Erythritol

At the end of the fermentation, it is essential to “clean” the product, to eliminate all impurities and to obtain high purity erythritol.

Manufacturers accomplish this in several steps, the first one being a cleaning of the fermentation broth by passing the broth through solid material (adsorbents) which can retain some of the impurities.

Subsequently, the broth passes through filters whose pores have quite small dimensions (between 0.01 and 0.1 mm) to completely remove the fungus responsible for the fermentation.

The last step is a crystallization; the broth is cooled down to a temperature which makes erythritol precipitate from the fermentation solution. This means that erythritol becomes a solid which can be separated from the solution. This process may be repeated several times to ensure a high level of purity, generally higher than 99.5 %.

Is Industrial Erythritol Safe?

Erythritol is a compound which the Food and Drugs Administration (FDA) classified as Generally Recognized as Safe (GRAS) for the first time in 1999; in 2001 this status was confirmed. Up to the present day, there is no proven and indisputable evidence showing toxic effects associated with erythritol toxic.

Some people are concerned that industrially-produced erythritol may be “different” from the natural sugar alcohol, and hence possibly dangerous.

These fears, however, are not justified, as erythritol is the same molecule – whatever its origin may be. For our health and/or nutrition, it makes no difference whether erythritol comes from a fruit or from an industrial plant. This is true, of course, assuming that the industrial process was performed properly, implementing the existing legislation on food safety.

Sources

The Harvard School of Public Health. Carbohydrates. Accessed on January 28, 2014.

Monedero V. et al., Perspectives of engineering lactic acid bacteria for biotechnological polyol production. Appl. Microbiol. Biotechnol. (2010), 86, 1003-1015. Accessed on January 28, 2014.

Cargill. Erythritol manufacturing process. Accessed on January 28, 2014.

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