other uses for TDS meter?

[brewstergalVT]

I just got a TDS meter along with my countertop RO system. Checked out the TDS meter on my tap water and distilled water but on the packaging one of the applications listed is for food and beverage testing. So this has me wondering if one can test finished beer for TDS. If so, can you share your experience? I understand TDS doesn't give any specifics but I'm wondering if anyone has used a TDS meter for anything besides water?

 

[Vale71]

So this has me wondering if one can test finished beer for TDS.

Of course you can, but all you'll get is a (very high) meaningless number that will be completely useless.

 

[brewstergalVT]

Of course you can, but all you'll get is a (very high) meaningless number that will be completely useless.

OK, thanks. I wanted to know if it would damage the TDS meter to use it to test beer as I've not used one before.

As far as useless and meaningless, I have one more question: can you explain why it's meaningless and useless? Is that because of the reactions that happen in the boil and in fermentation causing unpredictable changes in minerals in the finished beer? Carbonation? Or something else? Why would the numbers be so high?

I wanted to see if testing two beers brewed the same but with different water will yield different TDS, say a pilsner with RO and another with high temporary hardness (but not boiled and racked off the sediment) would show a significant TDS difference in the finished beer. I'm not concerned with the actual number but if there is a significant difference. I'm thinking some of what I detect (and don't like in many beers) is either a result of high minerals or high alkalinity and I'm wondering if that can be verified with a TDS meter. Sounds like the answer is no but now I want to know why.

Maybe this question should be posted elsewhere (but I haven't found a sensory evaluation specific category), if so let me know.

 

[Konadog]

Well, it only measures "Total Dissolved Solids" but it doesn't tell you "What" dissolved solids, so you really have no information to use.

 

[brewstergalVT]

Yes, I understand that it doesn't tell you 'what' but that's not my question.

 

[Vale71]

The numbers are high because malt brings a lot of dissolved solids into the mash, much more than what you started with in the water. The number is meaningless because, as others have said, it doesn't tell you what is actually in the beer. So if comparing two beers you get a reading of 900ppm for beer N.1 and 1000ppm for beer N.2 it just doesn't tell you anything about the differences between the two beers, you'll be just as clueless as you would be without the measurements.
You don't have to worry about the instrument being damaged though, unlike PH meters TDS meters have sturdy and durable probes.

 

[brewstergalVT]

Good to know the probes are sturdy. Thanks!

I don't understand enough about conductivity and TDS obviously. I know there is a lot going on in the mash but in finished beer what is it that causes the TDS number to be so high? Is it the alcohol? Dextrins and residual sugars? Does carbonation play a role? If so, why? I thought TDS was basically a total of all the minerals (or dissolved solids) in a given liquid measured somehow via conductivity so I wouldn't think alcohol or sugars would play a role but all I have to work with are question marks so I really have nothing but guesses.

I'll play around but would love it if someone could explain the specifics of why to me.

 

[MaxStout]

You have your own RO system, but if you ever do buy bottled water from the store or in those big jugs, it's helpful to know if they added any "minerals to taste." The meter won't tell you what the minerals are, but you'll know if it's more than just RO. Also, for those who buy bulk water from the store--some of those water dispensers might be dodgy. No idea how often they replace filters, but I wouldn't bet on the water being up to par.

That added minerals thing is just marketing. Pure RO without it tastes great.

 

[ajdelange]

Yes, there are lots of used for them. One is to check the concentration of brines which is great if you need to know the concentration of brines. Another use for the homebrewer could be in checking the strength of calcium chloride solutions. There is at least passing mention of this in the sticky on calcium chloride solutions here.

 

[twd000]

I use my TDS meter to test the solution in my hydroponic Tower Garden

 

[brewstergalVT]

I'm still wondering what it is with beer that wouldn't cause a TDS reading to be significantly different with 2 beers if one beer was brewed with straight RO and the other brewed with high minerals and high alkalinity, and all other factors the same. Assuming there is a taste difference, why wouldn't there be a difference in the TDS reading in the finished beers? What am I missing?

 

[Silver_Is_Money]

I'm still wondering what it is with beer that wouldn't cause a TDS reading to be significantly different with 2 beers if one beer was brewed with straight RO and the other brewed with high minerals and high alkalinity, and all other factors the same. Assuming there is a taste difference, why wouldn't there be a difference in the TDS reading in the finished beers? What am I missing?

I'm willing to guess that the ppm TDS value of beer is so high that water mineralization and alkalinity will be dwarfed by it. But that's only a guess. I've never stuck my TDS meter into beer.

 

[brewstergalVT]

My guess too but I was figuring someone had science to back up our guess. And I know carbonation could give an inaccurate reading but assuming flat beer it just gives me more questions: what is the mineral content of a beer brewed with say RO water? What happens in the mash, boil and fermentation in regards to TDS? It would be great to know.

 

[Vale71]

Assuming there is a taste difference, why wouldn't there be a difference in the TDS reading in the finished beers? What am I missing?

TDS stands for Total Dissolved Solids. It is actually a misnomer as all it measures is conductivity and through that it measures the density of charges in water, which in itself is a very good insulator. The charges in water will mostly come from dissolved solids that have a ionic bond that will be broken by water, leaving the unbound ions to go happily swimming around and, as a side effect, increasing the liquid's conductivity. As a result of this a TDS meter will not measure compound that do not break into ions when they go into solution (so much for Total!) such as: alchohol, dextrins, melanoidins, proteins, hop oils, etc. etc. In short, all those compounds that actually give a beer most of its characteristics such as color, ABV, mouthfeel, taste, aroma. Because of this it is perfectly possible to have two completely different beers such as a light lager and a stout to have the same conductivity and thus display the same value on a TDS meter.

 

[brewstergalVT]

Thank you for the details, got it!

 

[ajdelange]

I think it very unlikely that any two beers (unless from the same batch) would have the same conductivity. Hydrogen ion content is related to pH - a change of 0.3 unit doubles or halves it and thus would change conductivity. Also the liquor is not the only source of mineral ions in beer. The grains contribute large amounts. Some proteins have ionized side groups and thus may contribute to conductivity (but not, I think, much because of their low mobility). Isomerized hops are more soluble than unisomerized because the acids are ionized (have lost their protons). Thus, theoretically, a more bitter beer would have higher conductivity but again I expect the hop ions to be of low mobility.

Now untangling any of this in a way that would make conductivity useful as a beer QC metric is likely impossible. One exception might be that beers made in ostensibly the same way from ostensibly the same materials ought to have similar conductivity.

 

[Vale71]

I think it very unlikely that any two beers (unless from the same batch) would have the same conductivity.

My point was that since conductivity is just the result of the density of dissolved charges, regardless of what substances actually carry those charges, it is perfectly possible for two beers that are worlds apart from a sensory standpoint to end up having the same (by same meaning of course very close) TDS readings by mere chance. As such this measurement really tells us nothing at all about a beer's qualities and characteristics.

 

[ajdelange]

It is very unlikely that two people will have the same Bertillon measurements. But they sometimes, if rarely, do. Hence the Bertillon system has been relegated to history. Much the same with conductivity as a potential QC parameter. Were there any merit in it ASBC or EBC would have adopted it.