correct refractometer for sugars

[KernelCrush]

I make almost as much mead as I do beer.  Refractometers are made to measure sucrose and then we calibrate them to measure maltose for beer.  Should a refractometer be recalibrated for the fructose and glucose in a mead must?  Has anyone vere tried this to see if there is a difference?

[MaltLicker]

Total SWAG here, but I 'think' Brix refracts are ideally suited to vineyards and such where they go out and squeeze grape sugars onto refracts to time the ideal harvesting point of the grapes. 

So I'd think less/zero correction would be required since grape sugars are largely glucose and fructose. 

[brewfun]

There is no distinction between the two. Twenty brix in wine is equal to 20 brix in mead or beer. Refractometers are accurate only for pre fermentation. Attenuation is where the two beverages diverge.

You have to get out to 30 Brix to see a 0.0001 difference between the two.

Lab measurements comparing malt yield by weight to the refractive index in Brix verify this.

[KernelCrush]

It just seemed logical to me that if a sucrose refractometer had to be recalibrated maltose then it would also have to be calibrated for glucose & fructose. But I am certainly no chemist.  I checked Milwaukee website and their base model is for sucrose, they have a different model # for sucrose, and another model # for fructose.  I went to another higher end supplier (Misco) and they can pre-program the various sugar tables into one refractometer.  But I think i can live with 0.0001 error. 

[brewfun]

Wellll.... okaaaaayyy.... 

Haha! Now you're talking about something different. When you say "refractometer" to a brewer or vintner, 99% of the time they'll think hand held.

Electronic readers are a whole 'nuther kettle of fish. Some may or may not use Infra Red spectrographics to determine specific sugar content. The Milwaukee model that we were talking about in Reviews doesn't and it's analogous to a hand held. But is IS temperature sensitive, even though it says ATC. Higher temps can cause low readings.

[jomebrew]

You don't calibrate for wine or beer, sucrose or maltose.  All of the refractometers I have seen, used and researched work with wine and wort.   The only calibration is to distilled water.

[KernelCrush]

Maybe I am misunderstanding the whole concept. I often do both. I calibrate (to zero) with steam distilled water.  My refractometer is designed to measure sucrose. We apply a wort correction factor to correct for maltose...I assume this is what is being done in Beersmith when you perform the 'calibrate refactometer'.    I made a 13 Brix solution of table sugar (sucrose), honey (glucose/fructose) and DME (maltose).  At 68F the hydro readings were 1.054 for sugar and honey, but it was 1.050 for the maltose.  I was using beersmith tool to measure my last few batches of mead forgetting that it was set for maltose.

[brewfun]

@KernalCrush, Academically, you're right. Different sugars refract differently. Its physics.

What's measurable is relative changes, rather than absolute sugars. We base those relative measurements on distilled water as a 0.00 baseline. I don't want to be contentious, so what follows is just some of my thoughts and experience. I appreciate that you want to understand the difference.

In your example, did you boil the DME to remove proteins? If not, those were suspended in the solution and showed up in your reading.

Even if you did boil to coagulate proteins, there are still some left in suspension, along with trisaccharides, polysaccharides, tannins and a host of other malt components that make the difference between beers' residual post fermentation gravity and the 0.990 reading of fermented sugar and honey (grapes, too). All that crap changes refraction, too.

Table sugar and honey will have a far higher percentage of a "pure" sugar to measure. Sucrose is somewhat easy to purify, which is why it's the standard. Do the same test with a "raw" or brown sugar and I suspect your results will vary a bit.

In my previous example, I was pointing out that different sugars also refract various light wavelengths differently. So, a mixed solution can be teased apart and analyzed. This is waaaaay beyond the needs of homebrewers and all but the most "engineered" of breweries.

BeerSmith's gravity number is derived from malt analysis numbers. These are measurements of absolute levels of dissolvable solids (aka 100% efficient extract), which include things you don't want in your beer, like tannins. This is going to read higher pre-boil than post, if you were to add back the water from evaporation. BeerSmith calculates each grain or sugar source individually when predicting a reading.

The most practical example I can give you is my post boil and post chill numbers. With an all malt wort. Post boil, I might have a reading of 17 Plato. Post chill, the reading falls to ~16.8 and change. The difference? Cold break is still suspended in the post boil number, but has coagulated out in the post chill number, causing it to be lower.

[KernelCrush]

No I did not boil the DME.  I do remember though thinking 'this sure is cloudy'  ???when I measured it. 

I used the wrong term (calibrate) in the title of the original post.  I should have said 'correction factor'.

Still having a real hard time wrapping my head around it for some reason. I guess I got off track sometime after I read this
http://www.brewersfriend.com/how-to-determine-your-refractometers-wort-correction-factor/ and Kai's link in the same document.
 
Can someone define 'wort correction factor'.

[brewfun]

Can someone define 'wort correction factor'.

It's an individual number for your refractometer based on observations between a calibrated high resolution hydrometer and your refractometer.

It is: Temperature corrected hydrometer reading converted into Plato divided by your observed plato reading.

The result is the multiplier applied to your refractometer readings.

***OPINION:
Here's where it gets weird, bordering on religious, to me... The conversion relies on observations and varies widely from refractometer to refractometer. Kai notes he MULTIPLIES by 1.04, where another article cites DIVIDING by the same number. Some see as little as 1% difference; then there is your observation, KernalCrush, which is an 8% difference (1.08 factor).

So KC, when I try to get details about this I get just as confused as you. The information all agrees that its sort of a "big deal," but there's no consensus about what the deal actually is.

It seems to me that with an observable difference between sugars there would be a predictable model of variation. There isn't.

I already covered how wort differs from "purer" sugar solutions; and even with different mash techniques the malt component profile percentages don't vary as widely enough to account for the variation between authors. 

Which makes me think that what's really being done is compensating for optical differences between cheaply made prisms. Again, just my opinion.

I believe that a key to good brewing is just recording what you observe. Don't try to record what you THINK you should observe. The same is true of evaluating your beer quality.

[KernelCrush]

There are some posts by sean terrill  and aj delange on this too.  It appears to  vary depending on the wort composition (or not).  My correction varies between slightly less than 1 to 1.04 on worts tested on brew days.  I think I will go back to floating an egg. 

My original idea was that no WCF is required for meads, which is where I went wrong by using the beersmith tool for mead when it was automatically factoring in the maltose correction. 

Thank you for your responses Brewfun. Your reasoning suggests I let it go.  I just get hung up on stuff when I have nothing else to do except drink beer and think about these things, at least on the weekends.

[KernelCrush]

Its the weekend again, so

I found this Brix conversion table corrected for maltose.   It seems to agree with my 1.054 measurement.

http://beerbarons.org/images/pdf/brewingCheatSheets/refractometerBrixToSGConvertion.pdf

Going to the USDA tables for sucrose suggests 1.052 at the same 13 Brix, so both my sugar & honey measurements were off somehow.

This is from Brads Blog

"Here’s where some people get disappointed when using a refractometer.  Refractometers are calibrated to measure the amount of sugar (sucrose) in a clear sample of water.  The sugar in barley beer (maltose) is a different animal.  Therefore some adjustment needs to be made to take into account the fact that we’re measuring colored maltose and not clear sucrose.  You can’t just use the measurement you made with the refractometer."

It is also discussed in How to Brew beginning on page 265.  Its not in the online version.

I'll have to wait till next Christmas for one of these.  Til then?

http://www.amazon.com/Atago-PAL-20S-Digital-Hand-Held-Refractometer/dp/B004J4XE2E