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!

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