Erythritol Is It Safe?

Erythritol is a new type of polyol sweetener with low calorific value, good crystallinity, good taste, low hygroscopicity, non-cariogenic, safe for diabetics, very stable to heat and acid, non-fermentable and does not cause gastrointestinal discomfort. It has the advantages of not browning or decomposing under normal food processing conditions, and is known as a “zero” calorie ingredient. It is widely found in fungi (such as seaweed and mushrooms), fruits (melons and grapes, etc.), and various fermented foods (such as wine, chewing gum, sake, soy sauce, etc.). It is also present in the tissues and body fluids of humans and animals, such as blood, semen, and urine. The distribution of erythritol in nature is shown in Table 1.

As the technology for producing erythritol by fermentation matures, production costs will be further reduced, and the application fields of erythritol will continue to expand due to its special physiological and metabolic properties and application functions.

1 Physicochemical properties and physiological and metabolic characteristics of erythritol

1.1 Physicochemical properties of erythritol [2, 3]

Erythritol is a four-carbon polyol with the chemical name 1,2,3, 4-butanetetrol and the molecular formula C₄H₁₀O. It is a symmetric molecule and occurs in the racemic form. The molecular weight is 122.12, the melting point 119°C, the boiling point 329–331°C, and the heat of solution -96.86 kJ/kg.

Erythritol is a white, shiny powder or crystal that is soluble in water. Its aqueous solution is a colorless, non-viscous liquid. Its chemical properties are similar to those of other polyhydric alcohols. It does not contain reducing aldehyde groups, is stable to heat and acids (applicable pH 2–12), and has a lower molecular weight and higher solution osmotic pressure than sorbitol, mannitol, xylitol and other sugar alcohols.

1.1.1 Sweetness characteristics

Erythritol is 70% to 80% as sweet as sucrose, with a cooling sensation in the mouth, pure sweetness, similar to sucrose, no aftertaste, and can be mixed with saccharin, aspartame and other sweeteners to mask unpleasant tastes.

1.1.2 High heat of solution

The heat of dissolution of erythritol is -96.86 kJ/kg, which is three times that of glucose. It absorbs more energy when dissolved in water, and has a cool mouthfeel when consumed.

1.1.3 Low hygroscopicity

Erythritol has good crystallinity and does not absorb moisture. It remains non-hygroscopic at a relative humidity of 90% at 20°C, and is suitable for processing chocolate candies.

1.1.4 Low solubility

Its solubility at 20°C is only 37%, which is about 50% of the solubility of sorbitol. When making highly sweet foods, it should be mixed with other sugar alcohols to prevent crystallization and maintain the stability of the food texture.

1.1.5 Strong heat and acid resistance, stable to heat and acid

Erythritol is highly heat-resistant and does not decompose even at high temperatures (160°C). It is stable to heat and acid, does not decompose, discolor or undergo the Maillard reaction, and is suitable for food processing where color is critical.

1.1.6 Low water activity and high osmotic pressure

Due to the small size of erythritol molecules, the molecular weight is only about 1/3 that of sucrose, which can greatly reduce the water activity. The water activity of a 25°C, 36% aqueous solution is 0.91; and erythritol has a high osmotic pressure. The osmotic pressure of a 20°C, 15% aqueous solution is 461.5 KPa, which is 3.2 times that of sucrose and 1.8 times that of sorbitol. This characteristic of erythritol is beneficial for improving 0℃, 15% aqueous solution osmotic pressure of 461.5 KPa, 3.2 times that of sucrose, 1.8 times that of sorbitol. This characteristic of erythritol is conducive to improving the preservative ability of food and extending the shelf life of food.

1.1.7 Freezing point depression and viscosity characteristics

Erythritol has a small molecule and a significant effect on lowering the freezing point. The freezing point of a 25℃, 30% w/w aqueous solution of erythritol is -4.1℃. Compared with other sugar alcohols, the lowering of the freezing point of erythritol is significant, while the viscosity at this time is only 3.0×10-³Pa·s.

1.2 Physiological functions and metabolic characteristics

1.2.1 Unique metabolism and low production capacity

Erythritol is easily absorbed in the small intestine, most of which enters the blood circulation, and only a small amount directly enters the large intestine to be fermented as a carbon source. Since the human body lacks the enzyme system to metabolize erythritol, the erythritol that enters the bloodstream cannot be digested and degraded, and can only be excreted from the body through the kidneys in the urine. This unique metabolic feature determines the low calorific value of erythritol.

According to literature reports[2], 80% of the erythritol that enters the body is excreted in the urine, and about 20% enters the large intestine. 50% of the erythritol that enters the large intestine is utilized by bacteria. From this, it can be seen that at most only 5% ~10% of the ingested erythritol is metabolized and used as energy by the human body provides energy for the human body. The energy value of erythritol is 836 to 1672 J/g, which is only 5% to 10% of the energy of sucrose. It is the lowest energy among all polyhydric alcohol sweeteners. According to the Japanese Ministry of Health, Labour and Welfare's method for evaluating the caloric value of sugars (Wei Xin No. 71, 1991), the caloric value of erythritol is 0. In addition, according to the “Standards for Nutrition Labeling of Foods (Draft)” published by the Japanese Ministry of Health, Labour and Welfare in October 1995, the 71) determined that the caloric value of erythritol is 0. In addition, according to the “Food Nutrition Labeling Standards (Draft)” published by the Japanese Ministry of Health and Welfare in October 1995, the caloric conversion coefficient (J/g) of erythritol is 0[4]. The caloric value (J/g) of various sugar alcohol compounds is shown in Table 2[S].

1.2.2 High tolerance, few side effects

A large number of animal and clinical experiments have proven that erythritol is safe and non-toxic, has no teratogenic toxicity, does not cause chromosomal mutations, does not affect reproduction and development, is not carcinogenic, does not stimulate tumor growth, is well tolerated by the digestive tract, has no significant effect on the metabolism of diabetic patients, and has no side effects on blood sugar control [6.7]. Since erythritol enters the body and 80% of it can be quickly absorbed in the small intestine, avoiding the side effects of diarrhea and flatulence that may be caused by substances that are not absorbed, erythritol is highly tolerated and is one of the most highly tolerated sugar alcohols. Since only a small amount enters the large intestine and 50% is excreted, very little of it remains in the intestines and causes very few side effects [8].

1.2.3 Suitability for diabetics

Since the human body lacks the enzyme system for metabolizing erythritol, most of the erythritol that enters the body is excreted in the urine. Its metabolic pathway is independent of or rarely dependent on insulin, so it has no effect on glucose metabolism. Erythritol-containing foods are safe for special consumer groups with limited sugar consumption, such as diabetics.

1.2.4 Non-cariogenic properties

Because the bacteria in the mouth, especially Streptococcus mutans, cannot use and ferment erythritol, it does not cause a decrease in the pH of the tooth surface in the mouth, resulting in plaque and tooth decay. 1.2.5 Promotes the proliferation of bifidobacteria.

Research on the utilization of erythritol by intestinal bacteria has shown that erythritol has a significant proliferative effect on bifidobacteria in the intestine.

2 Production process of erythritol

The production methods of erythritol mainly include chemical synthesis and fermentation.

2.1 Chemical synthesis of erythritol

Chemical synthesis can be achieved by reacting butene-2,1-diol with hydrogen peroxide. Butene-2,1-diol is produced by first making 2-butene-1,4-diol from acetylene and formaldehyde, and then mixing the aqueous solution with an active nickel catalyst and adding a inhibitor, ammonia. Hydrogenation is carried out at 0.5 MPa to obtain erythritol. The chemical synthesis method using starch as a raw material is to use the periodate method to generate starch aldehyde, and then oxidize and crack it to generate erythritol and other derivatives [10]. The chemical synthesis method for producing erythritol has disadvantages such as a long process, high cost, serious pollution, high requirements, and poor product safety, and cannot be compared with the fermentation method. Therefore, the most researched and applied method is the fermentation method using starch as a raw material to produce erythritol.

2.2 Microbial fermentation method for producing erythritol

The fermentation method uses starch hydrolysis to produce glucose as a raw material, which is fermented by a strain of osmotolerant yeast to produce erythritol and a small amount of by-products such as ribitol and glycerol. After separation, extraction and purification, a high-purity erythritol product is obtained, with a product yield of about 50%. Compared with chemical synthesis, it has the advantages of mild conditions, easy control, environmental friendliness, less pollution, product safety, abundant raw material sources, and low cost. It is also easier to achieve large-scale production.

Yeast can produce erythritol. This was first proposed by Binkey and Wolfrom in 1950 [11]. In 1956, Spencer et al. from Canada discovered that high-osmotic yeast can also ferment sugars to produce erythritol when studying the production of glycerol by high-osmotic yeast [12]. Subsequently, Japan, South Korea, Belgium and other countries have carried out research on the production of erythritol by fermentation. Japanese scholars isolated, screened, and induced breeding from samples such as soil, fermented foods, fruits, and pollen to obtain a high-osmotic-tolerant yeast strain Aureobasidium sp. SN-115 that produces erythritol, with a yield of 50% using glucose as the raw material [13]. Jinb et al. in South Korea screened a strain of high-osmotic-pressure-tolerant Candida sp. which can produce 141 g/L erythritol with a yield of 47% when fermented at 35 °C using glucose as the raw material [16].

Taiwanese scholars Shie et al. screened 28 erythritol-producing bacteria, of which strain 166-2 can ferment 30% glucose to produce 111.0 g/L erythritol [15]. So far, the erythritol-producing microorganisms studied have mainly been some osmotolerant yeasts isolated from beehives, honey, and pollen[3], such as Aureobasidium, Moniliella, Torula, Trichosporon, Trichosporon oides, Candida, Pichia, Torulopsis, and Trigonopsis.

The main strains currently used in industrial production of erythritol are the mutant strain of Aureobasidium sp. from Japan; Candida magnoliaeu from South Korea; and Trigonopsis variabilis, Trichosporonoides megachiliensis, Trichosporonoides, and Pichia sp. from the United States. Jiangnan University[16] and Jiangsu Institute of Microbiology[17] in China have also carried out research on the production of erythritol by fermentation, but there have been no reports of its application in production. At present, a few domestic enterprises such as Shandong Huanyu have carried out the batch production of erythritol, and a small amount of the product has been launched on the market.

Shandong Institute of Food Fermentation Industry Research and Design has been committed to the research of erythritol production technology by fermentation since 1992. After more than ten years of hard work, a strain of osmotolerant yeast was obtained by screening samples such as pollen and honey.

After natural isolation, multiple compound mutagenesis treatments, domestication and other methods, the strain's ability to tolerate high sugar has reached more than 50%. Using starch hydrolysate as the raw material, the erythritol yield can reach more than 180g/L and the conversion rate can reach more than 50%. At present, the pilot test and production test of the erythritol fermentation process technology and extraction technology have been completed, and the product purity can reach more than 99%. Preliminary research results show that the erythritol-producing bacteria obtained through breeding have stable performance, loose fermentation conditions that are easy to control, fast fermentation speed, low residual sugar in fermentation, and few fermentation by-products. They are an excellent strain for erythritol production. The entire production process and technical route determined by the research is simple and easy to implement, and is suitable for industrial production. At present, the technical conditions for large-scale industrial production of erythritol are in place.

3 Erythritol applications

3.1 Erythritol applications in the food industry

In 1990, the Japanese Food Regulations approved erythritol as a direct food ingredient. In 1997, it was approved by the US Food and Drug Administration (FDA), obtained the US FDA's GRAS (Generally Recognized as Safe) certification and was allowed to label “good for dental health”. In 1999, the Joint FAO/WHO Expert Committee on Food Additives (JECFA), a joint body of the Food and Agriculture Organization (FAO) and the World Health Organization ( WHO) ,The Joint Expert Committee on Food Additives (JECFA) approved erythritol as a food sweetener without specifying an ADI value; in 1999, the Australian and New Zealand Food Authority (AN, A) approved erythritol as an edible ingredient [6], and China also allows its use in food in the GB 2760 standard.

Erythritol, as a new functional food sweetener that is just starting to be used internationally, has a wide range of uses in the food industry due to its unique physiological and metabolic properties, such as its low hygroscopicity, low calorific value, good crystallinity, non-cariogenic properties, and suitability for diabetics. Due to its good thermal and acid stability, erythritol will hardly cause browning or decomposition under normal food processing conditions, and will not cause browning during the high-temperature boiling process of hard candy production. This has a significant impact on the quality of chocolate. The high thermal stability of erythritol allows for refining to be carried out at higher temperatures, which further promotes the formation of chocolate flavor and improves product quality. Erythritol has poor hygroscopicity, and under high humidity conditions, it is not prone to moisture absorption, even in environments with humidity above 90%. This characteristic is particularly important in the processing of foods such as chocolate and chewing gum.

Experiments have shown that when 10 g of erythritol is dissolved in 90 g of water, the temperature can drop by 4.8 °C. When 17 g of erythritol is dissolved in 100 mL of water at 22 °C, there is a cooling effect of about 6 °C. The high heat absorption of erythritol makes the product feel cool and refreshing after consumption. When 17 g of erythritol is dissolved in 100 mL of water at 22 °C, there is a cooling effect of about 6 °C. The high heat absorption of erythritol makes the product have a long-lasting refreshing and cooling feeling after consumption, which is very important for improving the quality of chewing gum, refreshing solid drinks and candy.

Erythritol has a clean sweetness and can effectively mask the aftertaste of high-intensity sweeteners such as protein sugar and stevia when used in combination with these sweeteners. Erythritol can also reduce the peculiar smell of alcohol odor, improving the taste and flavor of distilled spirits and wine. When used in vegetable juice drinks, it can effectively suppress the undesirable taste unique to vegetable drinks. When added to coffee, it can effectively suppress the astringent taste of coffee. The heat and acid resistance of erythritol means that pasteurization, high-temperature or ultra-high-temperature sterilization processes will not affect the appearance of beverages sweetened with erythritol.

3.2 The application of erythritol in the production of medicine and health products

Erythritol has very low calories and is known as a “zero” calorie sweetener, so it can be used to produce various low-calorie health foods, diet foods and drinks. Due to its special physiological metabolism mechanism and the characteristic of not affecting blood glucose levels, erythritol can be used to develop functional foods or drinks for patients with diabetes and other glucose intolerance. Erythritol is non-cariogenic and cannot be used by pathogenic bacteria such as Streptococcus mutans. Therefore, candies and special tooth cleaning products made from erythritol have a positive effect on protecting children's oral health. In the pharmaceutical industry, erythritol can be used as a flavouring agent for medicines and an excipient for tablets, which can effectively improve the taste of medicines. Recent studies have also shown that erythritol derivative dihydroxy erythritol has anti-HIV activity [10]. Nitro erythritol, which is formed by the nitration of erythritol, can be used in drugs for the treatment of cardiovascular and cerebrovascular diseases and asthma patients [2].

3.3 Erythritol applications in other industries

In the chemical industry, erythritol is used as an intermediate in organic synthesis and has broad application prospects in the synthesis of alkyd resins, polyesters, polyethers, paints, explosives, etc. In cosmetics, erythritol can partially replace glycerin. Since most microorganisms cannot use erythritol, it can prevent the deterioration of cosmetics. In addition, erythritol can be used as a raw material to synthesize some rare products, such as the production of the rare L-erythrulose from erythritol as a substrate. Rahman et al. [18] in Japan introduced the technology of producing L-erythrulose by microbial oxidation of erythritol and isomerization of L-ribose isomerase, with a yield of 18%. Then it is purified by an ion exchange column, and 1. 7g of pure L-erythritol. With the rapid development of science and technology, new uses for erythritol will continue to be developed.

The technology for producing erythritol by fermenting starch as a raw material is becoming increasingly mature. Due to the abundant raw material sources, environmentally friendly production process, high product safety, and the fact that it can be considered purely natural, this process will surely become the main technological route for producing erythritol. With the continuous improvement of production technology, the quality of the product will continue to improve, production costs will continue to decrease, and the product will have stronger market competitiveness.

References

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