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

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.

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!