A counterintuitive fact about stevia extract

Choosing the right ste­via extract is like choos­ing clothes for a long jour­ney. Which should you bring? There are dif­fer­ent vari­eties to choose from, with dif­fer­ent char­ac­ter­is­tics and degrees of sweet­ness. And there is no such thing as a pure ste­via extract. All come with a mix of dif­fer­ent ste­vi­ol gly­co­sides. Therefore, you must think through which ste­via extract to choose, and how pure it must be.

Purity or concentration?

We have a lin­guis­tic prob­lem when talk­ing about ste­via extract. We often talk about the ‘puri­ty’ of a ste­via extract, when we real­ly mean the amount of a cer­tain ste­vi­ol gly­co­side in that extract.

Take, for exam­ple, our own Navia 60, which con­sists of 60 per cent of the ste­vi­ol gly­co­side Reb A. Often, it is said to have 60 per cent puri­ty. That doesn’t mean there is 40 per cent dirt, but rather 40 per cent of oth­er ste­vi­ol glycosides.

Perhaps ‘con­cen­tra­tion’ is a more appro­pri­ate term. The puri­ty of Reb A is always one hun­dred per cent inde­pen­dent of its concentration.

Therefore, let’s use con­cen­tra­tion in this article.

The higher the better?

But why should we talk about con­cen­tra­tion? Is it important?

One may think that the high­er the con­cen­tra­tion, the bet­ter. And by all means. Sometimes it may very well be the case – but not always.

We start from the beginning.

Glycoside bonds

The mol­e­cule of any ste­vi­ol gly­co­side con­sists of sev­er­al glu­cose moi­eties linked by gly­co­side bonds to a sin­gle ste­vi­ol moi­ety, act­ing as a back­bone. The num­ber of glu­cose moi­eties deter­mines its char­ac­ter­is­tics, e.g. its sweet­ness, bit­ter­ness, amount of liquorice off-taste and length of aftertaste.

Sweet, sweeter, sweetest

Some ste­vi­ol gly­co­sides are more pleas­ing than oth­ers. Reb A, with its great sweet­ness, will always be more pop­u­lar than ste­vio­side – its more bit­ter-tast­ing pre­de­ces­sor. And then we have Reb M, which has almost a sug­ar­like taste, thanks to six glu­cose moi­eties. But Reb M is not always prefer­able, strange as it may sound. It is not just the sweet­ness that mat­ter when it comes to ste­vi­ol gly­co­sides. Its taste must also fit the desired flavour pro­file of a product.

So what to do, if you have a prod­uct with very par­tic­u­lar taste require­ments, and you want to sweet­en it with ste­vi­ol glycosides?

The solu­tion is to use ste­via extract with not too high con­cen­tra­tion. That’s right!

High concentration isn’t always preferably

If you have read the arti­cle Masking off-taste – a bal­anc­ing act, then you know that mix­ing ste­vi­ol gly­co­sides is one of many ways to mask unwant­ed off-taste. That’s why a ste­via extract with a low con­cen­tra­tion of Reb A (let’s say 50 or 60 per cent) can be bet­ter than one with high con­cen­tra­tion (for instance 98 per cent).

In the dawn of refin­ing ste­vi­ol gly­co­sides, this coun­ter­in­tu­itive result emanat­ed as an unex­pect­ed bonus of attempts to keep the cost down.

Genesis

Let’s go back to the time before ste­vi­ol gly­co­sides became approved in the EU.

Stevia plants from that time did not con­tain much Reb A. But there was an abun­dance of ste­vio­side, which has a quite bit­ter and not so pleas­ant taste. So using ste­via extract with nat­ur­al pro­por­tions of ste­vi­ol gly­co­sides gave prod­ucts a notice­able bit­ter and liquorice-like off-taste. Understandably, these prod­ucts got a luke­warm reception.

Were ste­vi­ol gly­co­sides real­ly the future?

A lower concentration

Fortunately, ste­via plants have been cul­ti­vat­ed to give more Reb A. But their leaves still con­tain most ste­vio­side (5–10 %), fol­lowed by Reb A (2–4 %) and minor quan­ti­ties of the oth­er ste­vi­ol gly­co­sides (includ­ing the attrac­tive Reb M, which con­sti­tutes less than 0.1 % of the dry weight of leaves). But now there was at least more of Reb A avail­able, but its price tag was still quite hefty.

The solu­tion to the prob­lem, that Reb A is expen­sive and that ste­vio­side is less flat­ter­ing to the taste, became ste­via extracts with a low­er con­cen­tra­tion of Reb A.

The surprising result

To everyone’s sur­prise, the ste­via extract with less Reb A did taste quite well. In fact, many peo­ple thought appli­ca­tions with a low­er con­cen­tra­tion of Reb A tast­ed even bet­ter than appli­ca­tions with Reb A alone. It seemed that syn­er­gis­tic effects arose when the var­i­ous ste­vi­ol gly­co­sides were allowed to meet.

And here we are today.

A real-life example

For many food and bev­er­age pro­duc­ers, the goal isn’t to remove sug­ar alto­geth­er but reduce as much as pos­si­ble with­out a neg­a­tive effect on taste.

With that goal, a soft drink com­pa­ny reduced the added sug­ar in a lemon and lime drink with 50 per cent with a ste­via extract with a high con­cen­tra­tion of Reb A.

When they lat­er replaced the ste­via extract with anoth­er with a low­er con­cen­tra­tion of Reb A, they could reduce the added sug­ar even more – to only 25 per cent.

The yoghurt evaluation

Another proof of that ste­via extract with low­er con­cen­tra­tion of Reb A can be bet­ter than a ste­via extract with high con­cen­tra­tion is found in a patent appli­ca­tion as an inter­est­ing exper­i­ment with yoghurt.

The set­up is simple.

We have sam­ples of yoghurt num­bered one through six. The first four has a small amount of added sug­ar, and the last two has no sug­ar added.

In the first sam­ple, Reb A was used with a 97% con­cen­tra­tion. Unsurprisingly, the test par­tic­i­pants said that the yoghurt tast­ed bitter.

The sec­ond sam­ple con­tained Reb A and Reb B. The par­tic­i­pants report­ed it tast­ed bet­ter but not as good as it could taste; they clear­ly felt a lin­ger­ing aftertaste.

The third sam­ple con­tained Reb A, Reb B and Reb D. Now, both the bit­ter­ness and the after­taste disappeared.

The fourth sam­ple con­tained Reb B and Reb D, but not Reb A. The sweet­ness was still present, even though it came a lit­tle late. But the par­tic­i­pants report­ed a sen­sa­tion of a dry, puck­er­ing mouth­feel like that caused by the tan­nins in unripe fruits. A taste sen­sa­tion called astrin­gency.

The fifth sam­ple con­tained the same amount of Reb A and Reb B as the third sam­ple, but less of Reb D. In com­par­i­son, this reduced the acid­i­ty and the sweet aftertaste.

The sixth and last solu­tion con­tained the same amount Reb A, Reb B and Reb D as the third sam­ple, but also var­i­ous flavour enhancers and the nat­ur­al sweet­en­er thau­matin. This was the best solu­tion, accord­ing to the test panel.

The win­ning for­mu­la was per­ceived as round in taste and sweet­ness with­out an unpleas­ant lin­ger­ing, had bal­anced acid­i­ty and very lit­tle bit­ter stiffness.

A helping hand

The yoghurt-test is a telling one. Not just in how to use ste­vi­ol gly­co­sides. It also says a lot about what it takes to suc­ceed in sug­ar reduc­tion. It’s not easy. But we hap­pi­ly help you, both with ste­vi­ol gly­co­sides and pro­fes­sion­al ser­vices. We also have ready­made solu­tions. So don’t hes­i­tate to con­tact us.