Sweet alcohols - The Sweetening Journey (part 2 of 6)

Maltitol and erythritol are sugar alcohols, and popular replacements for sugar. But what does it mean? Are there negative effects? Let’s find out in the second of six articles in our sweet journey.

15 October 2020 •

Governments, authorities, different organisations and consumers want food and beverage producers to decrease the amounts of sugar in food and beverages. But how can you do this without sacrificing the good taste? And how do we solve all the practical problems? To find the answer we have started a journey among different sweetening options. There will be six stops in as many articles.

In our last article, we took a closer look at the problem with sugar and assessed other sugar types. They weren’t any better. In a way, dextrose and fruit sugar are even worse than regular sugar. So we continued our journey and have now arrived at sugar alcohols.

Sugar alcohols – sweet alcohols

Sugar always has an oxygen atom, hanging there by itself. By connecting a few hydrogen atoms to it you get a sugar alcohol.

In most cases, this happens through hydrogenation of sugar. This means that the sugar is exposed to hydrogen (often under pressure) in the presence of a metal (often a nickel alloy). The metal acts as a landing site where a sugar molecule and a hydrogen molecule can land before they unite and become a sugar alcohol. No part of the metal will become part of the sugar alcohol; it’s merely a catalyst.

One example is the simple sugar type xylose (also called wood sugar), which after hydrogenation becomes xylitol (also called birch sugar despite it not being a sugar type but rather a sugar alcohol).

Sugar alcohols also occur naturally. For example, there is a small amount of xylitol in strawberries, plums, cauliflower and pumpkins. But the amounts are too small to make it worthwhile extracting them.

It’s also possible to produce sugar alcohols by fermentation of sugar. It is mostly erythritol that is produced this way; by letting yeasts feast on glucose.

Sugar alcohols

From where do we get the sugar alcohols used in food and beverage?

Sorbitol (E420) is present in small amounts in stone fruits and rowanberries. It is commercially produced by hydrogenation of glucose, produced in turn from starch from potato, corn, wheat, or other starch-rich crops.

Mannitol (E421) could be extracted from almost all plants; strawberries, celery, onion, pumpkins and mushroom are particularly rich in sugar alcohols. Commercially produced mannitol is, however, often produced by hydrogenation of fructose, which in turn is produced from starch or regular sugar.

Xylitol (E967) is naturally occurring in, amongst others, plums, strawberries, cauliflower and pumpkins. But the amounts are too small to make it worthwhile extracting them. Instead, xylitol is produced by hydrogenation of xylose, which in turn is produced from plant refuse from farming.

Isomalt (E963) is not present in nature. It’s produced from regular sugar, by rearranging the atoms in the fructose part so that the sugar becomes isomaltulose and rounding off with hydrogenation which turns the fructose part to equal amounts of sorbitol and mannitol. The result is a mixture of glucose-sorbitol and glucose-mannitol.

Lactitol (E966) is produced by hydrogenation of lactose, which in turn is produced from whey, which is a by-product from cheese manufacturing.

Erythritol (E968) is a sugar alcohol of erythrose, present in some algae and fungi. Unlike other sugar alcohols, erythritol is produced through the fermentation of glucose.

Maltitol (E965) is a synthetic sugar alcohol. It is produced industrially by hydrogenating maltose.

Polyglycitol syrup (E964) is a synthetic sugar alcohol produced from glucose and maltose.

Some sugar alcohols and their sweetness relative to regular sugar, glycaemic index (GI) with white bread as a reference, energy content, cooling effect and maximum number of grams per body weight before laxative effect.
Sugar alcohol Sweetness GI Energy Cooling effect Laxative limit*
Sorbitol (E 428) 50–60 % 6 2.4 kcal/​g Strong 0.17 g/​kgbw/​day
Mannitol (E 421) 60–70 % 3 2.4 kcal/​g Strong 0.30 g/​kgbw/​day
Xylitol (E 967) 90–100 % 17 2.4 kcal/​g Strong 0.30 g/​kgbw/​day
Isomalt (E953) 50–60 % 3 2,4 kcal/​g Weak 0,30 g/​kgbw/​day
Lactitol (E 966) 30–40 % 4 2.4 kcal/​g Weak 0.34 g/​kgbw/​day
Erythritol (E 968) 60–70 % 0 0 kcal/​g Strong 0.66 g/​kgbw/​day
Maltitol (E 965) 80–90 % 49 2.4 kcal/​g None 0.30 g/​kgbw/​day
Polyglycitol syrup (E 964) 25–50 % 55 2.4 kcal/​g None 0.30 g/​kgbw/​day
Maximum daily intake per kilo body weight (kgbw) to avoid laxative effect. N.B. in the EU products with more than 10% sugar alcohols must carry the warning that excessive consumption may have a laxative effect.

Better – but not good enough

So what is the point of sugar alcohols? Well, they have a sweet taste, if not as sweet as regular sugar, but most of them have a significantly lower GI than regular sugar and contain fewer calories. In addition, they don’t cause tooth decay.

Especially erythritol stands out with no calories and practically no effect on the blood sugar level.

But there’s always a downside. Sugar alcohols have their own set of issues. First of all, they don’t taste as sweet as sugar. That’s why we need more of them to achieve the same sweetness.

And that may be a problem, as they affect our digestive system and may cause stomach-ache, flatulence and in the worst-case scenario diarrhoea. That’s why products containing ten per cent or more of sugar alcohols must carry a warning that excessive consumption may have a laxative effect.

Except for their sweetness, some sugar alcohols can have a noticeable cooling effect in the mouth. The cooling sensation is due to the fact that sugar alcohols absorb heat when dissolved in saliva.

In our next article, we will look closer at bulk sweeteners, like glucose syrup, isoglucose and invert sugar. Are they the answer?

Don’t miss the other articles in the Sweetening Journey collection!

Please, share this article if you liked it.