Deceitful dextrose product? Not 100% dextrose?

[Iggles]

Hi,

I have brewed now about 15-20 batches and often found the carbonation to be underwhelming. As a result, I started targeting 2.8 vol CO2 rather than 2.5, to get to a level I perceive to be more appropriate. Today, I checked the package of the dextrose I use. To my surprise, they suggest to use more than 8 kg of their dextrose for every 6 kg of "Sugar" (which I assume to be table sugar). That makes no sense as the difference should be closer to 10%. The product is labeled "Dextrose", with subheading "Simple & Refined" and "100% Pure Powder Natural Sweetener" (but they never claim 100% dextrose). They sell this particular product both in grocery stores and brewstores here in Canada (original manufacturer is in Ireland and I contacted them for an explanation). If their conversion is correct for their product, it means that their product is cut, containing only 80% dextrose/fermentable sugar and this would result in 0.3-0.4 CO2 volumes undercarbonation when using the online priming calculators.

My question: is this common, that dextrose may not be 100% pure?

 

[VikeMan]

Dextrose is almost never pure, i.e. it almost always contains some water, roughly 9% for dextrose monohydrate, which leads to needing almost 10% more for carbonation (or whatever). But that's nowhere near enough water to account for the directions on your paskage.

 

[passedpawn]

Besides containing 9% water, dextrose most certainly contains an anti-caking agent such as corn starch (which is found in powdered sugar). I have no idea how much.

Coincidentally, your dextrose is likely made from corn starch. ♫ It's a mother and son reunion... ♫

 

[Iggles]

Besides containing 9% water, dextrose most certainly contains an anti-caking agent such as corn starch (which is found in powdered sugar). I have no idea how much.

Coincidentally, your dextrose is likely made from corn starch. ♫ It's a mother and son reunion... ♫

Thanks for the feedback! That's my suspicion now as well, that it contains unfermentable polysaccharides as a byproduct of its source as corn starch. But that means that any online calculator is going to be off in how much dextrose to add, for this particular product by about 20% (even when taking into account monohydrate).

 

[Iggles]

As an update, the company claims that their product is 100% fermentable and that you would need to add 20% extra by weight to get the same carbonation as table sugar. Fair enough, but that's not the same as the >33% they claim in their instructions. The 20% claim is close enough to the correct answer: 16% (for 100% glucose monohydrate)

 

[VikeMan]

As an update, the company claims that their product is 100% fermentable and that you would need to add 20% extra by weight to get the same carbonation as table sugar.

100% fermentable would mean 100% pure dextrose. No consumer level bag o' dexrtrose would be that.

 

[Iggles]

100% fermentable would mean 100% pure dextrose. No consumer level bag o' dexrtrose would be that.

Do you mean it is not 100% fermentable because any consumer-level dextrose product contains by necessity higher-order unfermentable polysaccharides, or do you mean it is not 100% fermentable because of the monohydrate part?

 

[VikeMan]

Do you mean it is not 100% fermentable because any consumer-level dextrose product contains by necessity higher-order unfermentable polysaccharides, or do you mean it is not 100% fermentable because of the monohydrate part?

I was referring to the water. (I don't think that starch or other anti-caking agents amount to much percentage-wise.) It's really hard to keep moisture out of dextrose. Anhydrous dextrose is basically a lab grade thing.

 

[passedpawn]

I was referring to the water. (I don't think that starch or other anti-caking agents amount to much percentage-wise.) It's really hard to keep moisture out of dextrose. Anhydrous dextrose is basically a lab grade thing.

I have no data on dextrose, but in powdered sugar the cornstarch addtition can be several percent.

This forum is so crazy pedantic and I do love it. Keep up the good work, pedants!

 

[dmtaylor]

Dextrose would probably be hard as a rock if not for the addition of a few percent corn starch. Be thankful for the corn starch.

 

[Chino_Brews]

@Iggles , the dextrose you get from homebrew suppliers is dextrose monohydrate, which is purified and crystallized D-dextrose and also contains one molecule of water (H2O) of crystallization. What this means is that the water is hydrogen-bound to the D-dextrose as a part of the crystallization process. Pure dextrose monohydrate is 91% fermentable sugar, and 9% water of crystallization. Water is obviously unfermentable. It is also true that dextrose monohydrate can contain an anti-caking ingredient. While anti-caking ingredient that are used can be themselves used at up to 2%, dextrose monohydrate is at least 99.5% pure, so in practice 0.5% or less of anti-caking ingredient is used (typically calcium silicate, magnesium silicate, or tricalcium phosphate) and you can ignore it as immaterial.

Ironically, dextrose monohydrate is commonly used as an anti-caking agent in certain industries.

TL;DR: RDWHAHB. Dextrose monohydrate will contain exactly as much fermentables as your priming sugar calculator says.