Can someone explain how...

[dirty_martini]

a beer can look like this in the carboy

but look like this coming out of the keg...

just so you know...its a gose. 50/50 Pils and wheat

 

[Jtd6628]

I am interested to see the comments on this thread.

 

[DregAddict]

Dirty keg? Dirty lines? Residue from last beer? All just guesses.

How is the taste? Any off flavors that you can notice, or flavors that differ greatly from earlier samples?

 

[LVBen]

Food coloring

 

[Brewmiser]

Well I did notice your brewery is in your bathroom so.......

 

[Revvy]

It's all about optics and light refraction, and yeast flocculation. Carboy are notorious for things appearing different then they really are....


Obligatory science explanation done in small print:

Refraction
In addition to reflecting light, many surfaces also refract light: rather than bouncing off the surface, some of the incident ray travels through the surface, but at a new angle. We are able to see through glass and water because much of the light striking these substances is refracted and passes right through them.
Light passing from one substance into another will almost always reflect partially, so there is still an incident ray and a reflected ray, and they both have the same angle to the normal. However, there is also a third ray, the refracted ray, which lies in the same plane as the incident and reflected rays. The angle of the refracted ray will not be the same as the angle of the incident and reflected rays. As a result, objects that we see in a different medium—a straw in a glass of water, for instance—appear distorted because the light bends when it passes from one medium to another.

The phenomenon of refraction results from light traveling at different speeds in different media. The “speed of light” constant c is really the speed of light in a vacuum: when light passes through matter, it slows down. If light travels through a substance with velocity v, then that substance has an index of refraction of n = c/v. Because light always travels slower through matter than through a vacuum, v is always less than or equal to c, so . For transparent materials, typical values of n are quite low: = 1.0, = 1.3, and = 1.6. Because it is the presence of matter that slows down light, denser materials generally have higher indices of refraction.
A light ray passing from a less dense medium into a denser medium will be refracted toward the normal, and a light ray passing from a denser medium into a less dense medium will be refracted away from the normal. For example, water is denser than air, so the light traveling out of water toward our eyes is refracted away from the normal. When we look at a straw in a glass of water, we see the straw where it would be if the light had traveled in a straight line.

Given a ray traveling from a medium with index of refraction into a medium with index of refraction , Snell’s Law governs the relationship between the angle of incidence and the angle of refraction:

Crap-all if I understand it all, but it looks cool!

 

[Beezy]

The stuff in the glass does not look like pils and wheat. My yinzer batman senses tell me it should be really lite. Looks like a Porter almost. No clue.

 

[dirty_martini]

The keg was spotless. Cleaned and sanitized pre kegging. The flavor is what it should be....tart, wheat, coriander and slightly salty. No off flavors. The beer literally looks purplish when pouring it down the drain.

As for the bathroom comment. The joys of 2 master baths. I've probably used that facility for its intended purpose maybe 5 times in the 5 years I've lived here.

This one just puzzles me. I've brewed and legged this beer before with no issues. The beer in it before was a Berliner Weisse so there wouldn't have been a dark beer to taint it anyway, even if it was dirty.

 

[ajdelange]

In the carboy there are lots of yeast cells in suspension. They scatter light back towards the eye making the beer appear light. If you shone a light through the carboy then the light would be absorbed and the beer would appear darker.

In the glass there are no (or many fewer) yeast to scatter light and so the beer appears darker.

 

[Hatchbrew]

Don't know what did it, but that's a huge swing in color. Thank you for sharing

 

[Yooper]

There only one thing I can think of besides the light refraction issue. Oxidation will darken a beer, sometimes markedly. I've seen white wines turn brown, due to oxidation, and light colored beers turn sherry colored. That would have to be a darn severe oxidation though!

 

[dirty_martini]

In the carboy there are lots of yeast cells in suspension. They scatter light back towards the eye making the beer appear light. If you shone a light through the carboy then the light would be absorbed and the beer would appear darker.

In the glass there are no (or many fewer) yeast to scatter light and so the beer appears darker.

I've poured wheat beers I've made in that glass and in actuality, are much paler in color than the carboy because there's less liquid for light to travel through. This beer should look like a straw yellow color in the glass, instead it's like a purplish brown.

 

[dirty_martini]

There only one thing I can think of besides the light refraction issue. Oxidation will darken a beer, sometimes markedly. I've seen white wines turn brown, due to oxidation, and light colored beers turn sherry colored. That would have to be a darn severe oxidation though!

I was thinking the same thing. I've seen brown chardonnays. This beer went right from carboy to keg and started carbing up. There's no sign of oxidation in the flavor either.

The carboy that I took a pic of is the split batch that's still aging (no boil Berliner). This is like some phenomenon that I can't imagine getting solved.

 

[ajdelange]

I've poured wheat beers I've made in that glass and in actuality, are much paler in color than the carboy because there's less liquid for light to travel through. This beer should look like a straw yellow color in the glass, instead it's like a purplish brown.

What you see depends on how much of the light that reaches your eye is transmitted and how much scattered. Obviously the appearance of the transmitted part depends on the amount of coloring material in the beer and the path per the Beer-Bougert-Lambert law (and the spectral composition of the entering light) whereas the scattered part depends on the number of yeast cells (and protein globs) in suspension and the direction of the impinging light (and its spectral composition). An interesting implication of the Lambert law is a shift towards red as the path lengthens. Wheat beers (mit Hefe trüben) really look their best when there is a balance of transmitted and scattered light. They almost seem to glow. A good photographer knows how to set that up. See, for example, the cover of Eric Warner's monograph in the AHA series.

Oxidation should not be a factor because no oxygen should have touched your beer.

I suppose refraction could be a factor if the Brewster angle were exceeded beyond which angle there in no transmission - all the light is reflected at the interface - but that would imply strange viewing - lighting angles.

 

[IrregularPulse]

Did you perhaps do a berry wheat in the past and forget the keg was still in there? Lines crossed? That's a weird one for sure!

 

[JoePro]

Honestly I think you switched kegs.

 

[Tiber_Brew]

Did you use sea salt or iodized salt?

Iodized salt can turn purple in the presence of acid or starch given a little bit of time. I had this happen to me with a batch of pickled eggs that I made once. I used iodized salt in my brine, and when it sat for a week or two, the contents reacted with the iodized salt to make everything in the jar purple! I guess that's why "pickling salt" is not iodized.

My guess is that you have a similar reaction happening in your beer from using iodized salt, which is reacting with the acid from your acidulated malt, or from unconverted starch in your beer. Check the packaging on your salt, and next time use pickling or sea salt for a Gose.

TB

 

[Native302]

It's the keg fairies

 

[DregAddict]

Did you use sea salt or iodized salt?

Iodized salt can turn purple in the presence of acid or starch given a little bit of time. I had this happen to me with a batch of pickled eggs that I made once. I used iodized salt in my brine, and when it sat for a week or two, the contents reacted with the iodized salt to make everything in the jar purple! I guess that's why "pickling salt" is not iodized.

My guess is that you have a similar reaction happening in your beer from using iodized salt, which is reacting with the acid from your acidulated malt, or from unconverted starch in your beer. Check the packaging on your salt, and next time use pickling or sea salt for a Gose.

TB

This makes complete sense. I wasn't familiar with the ingredients in a gose, so I hadn't thought about iodized salt. I was thinking that a reaction between starch and iodine would cause that kind of color, so maybe the OP had used iodophor to clean the keg and didn't rinse completely. But if iodized salt was used, I could definitely see the same thing happening.

 

[Clann]

Wow. I was all for "you got beer from the wrong tap" like you were pulling our collective leg but you have got to give it up to the HBT brew scientists

 

[Tiber_Brew]

This makes complete sense. I wasn't familiar with the ingredients in a gose, so I hadn't thought about iodized salt. I was thinking that a reaction between starch and iodine would cause that kind of color, so maybe the OP had used iodophor to clean the keg and didn't rinse completely. But if iodized salt was used, I could definitely see the same thing happening.

Agreed. I'm convinced that the OP used iodized salt, whether he knows it or not.

 

[IrregularPulse]

Wow. I was all for "you got beer from the wrong tap" like you were pulling our collective leg but you have got to give it up to the HBT brew scientists

Definitely! Nice work Tiber!

 

[Tiber_Brew]

Definitely! Nice work Tiber!

Glad to help.

TB

 

[ajdelange]

This makes complete sense. I wasn't familiar with the ingredients in a gose, so I hadn't thought about iodized salt. I was thinking that a reaction between starch and iodine would cause that kind of color,

It does?

First, in Switzerland where the dose in iodized salt is as heavy as it gets it's 20 ppb in the salt. At one gram of the salt per liter (I have no idea how much is used in this recipe, but 1 gram per liter strikes me as pretty salty) you'd be down another 3 orders of magnitude to 20 ppT. Even so, brewers are advised not to use iodized salt in their beers because iodine is poisonous to yeast apparently even at this level and below.

Second, if color were to form from a starch iodine reaction it would occur in the mash tun where we use iodine to test for the presence of unconverted starch. If the mash is adequately converted, the starch/iodine complex does not form and at most a faint reddish color is developed with an iodine concentration is more than a half dozen orders of magnitude greater than ppT. IOW if it were starch/iodine complex it would not wait to form until the fermenter where there is no starch to speak of.

 

[ACbrewer]

The starch /iodine making purple doesn't make sense. Isn't that the point of the mash? to turn the starch to sugars for yeast? So what starch?

If you look carefully at the index finger in the picture of the glass, you can see the color coming through is red, not anything else. There has been some definite chemical change. - which points back to something like iodine and starch, again, where would that starch come from. While longer wavelengths (red) get through liquids better, the amount of a glass is insufficent for this to be a refraction issue.

What cleaners do you use? What is the recipe?

 

[knotquiteawake]

It's the keg fairies

dang, I thought I was going to be first to mention them. My vote is the keg fairies or the beer gnomes.

 

[Tiber_Brew]

It can also happen with acid. That is how iodine was discovered (with acid).

Also, there very well could be small traces of starch in the beer from a less than 100% conversion, hence another possible explanation of why it happened gradually.

I don't know about you guys, but I think this is case closed.

TB

 

[ajdelange]

No it can't happen with acid if there isn't any iodine (ppT) and even if there is it can't be any acid. Courtois was working with sulfuric acid which is a powerful oxidizing agent under some conditions. Two things must be present for iodine color to develop from iodide: low pH and high redox state. Sulfuric acid and nitric acid provide both. Hydrochloric acid only the low pH.

Your lab assignment is to dissolve about a gram of potassium iodide in about 100 mL of water with one NaOH pellet (about 200 mg). This give a KI solution with high pH. Now add an oxidizing agent (I used H2O2). No color will be seen. Now add 28 Be HCl 0.1 ml at a time from a pipet. Where the blast of HCl hits the solution you will see the characteristic brown color of iodine but upon swirling it disappears again until such time as you have added enough to neutralize the NaOH pellet. At that time the color will persist and deepen the more acid you add. But it isn't the acid that is producing the iodine. It is the hydrogen peroxide. The acid just makes it possible for the H2O2 to work.

Part 2 is to make a strong solution of Mortons Iodized salt. Says right on the label that it's salt and potassium iodide. Repeat the steps above. Actually, you can skip the lye and just add the acid and hydrogen peroxide. You will not see any color because the amount of iodide in the salt is just too little.

So how about beer? It is acidic but it is in a reduced (you hope) state. I- cannot be oxidized to I2 (or I3-).

You can also repeat what Courtois did (be careful!!!!). Drop some concentrated sulfuric acid one drop at a time on a little KI and watch what happens. I2 vapor will be seen to rise and you will smell hydrogen sulfide proving that I- is able to reduce SO4-- all the way down to S-.

So I think the case is closed in the sense that we have proven it is not iodine and I think my scattering/transmission explanation is valid but I'd want to see the final beer in a cuvet in a spec and I'd want to see a sample of the fermenting beer centrifuged and in a cuvet in a spec before I definitely declared that explanation to be the one that pertains here.

 

[Tiber_Brew]

Your assignment is to propose an alternative explanation and prove it.

 

[ajdelange]

The alternative explanation was proposed in #14. What I would need to have to prove that explanation is in #29.