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Brews & Views Bulletin Board Service * Brews and Views Archive 2007 * Archive through January 09, 2007 * ARRRGH....Stuck Fermentation < Previous Next >

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Matt B
Junior Member
Username: Mattb

Post Number: 30
Registered: 02-2005
Posted From: 208.61.22.246
Posted on Tuesday, December 12, 2006 - 03:58 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Fellow Homebrewers,

I seek your collective wisdom here. I will preface this by saying that I had previously told myself that I would avoid ever putting this subject up as myself. In four years of homebrewing, 60+ batches, never had this problem. In fact, having just moved to Georgia, with new water and trying dry yeast for the first time starting this summer, my attenuation has been at new levels. But...

A few weeks ago I had a two brew night, putting a couple new things into practice. First, I cranked the gap on my mill (Crankandstein GCM-3D) down one click to .040" to check the effect on efficiency (by the way, negligable). For the first batch I was brewing a 10 gallon recipe of oatmeal stout. I brewed one last year as an experiement and it turned out phenomenal. Here were the first cracks in scheme appeared, and I realized that I had less oatmeal than I expected. I substituted some base malt and roasted barley and ended up with a grain bill as such approximately (though my notes aren't perfect, Promash figured an OG of 1.045, though that seems low in hindsight):

14.0 lbs English Pale Malt
3.5 lbs roasted barley
2.0 lbs chocolate malt
1.5 lbs oatmeal

I'll leave aside the hop bill, suffice to say there was some unexpected substitutions, and I ended up with about 40 IBU. I have been batch sparging with great luck all summer, and did so again with this batch, at my normal 1.25 qts per lb. Strike temp was at 150 F (+ or - 2 degrees) according to my old dial thermometer and my new electronic thermometer, both calibrated prior to brewing. In the brewing liquor I used 5.2 and a couple teaspoons of gypsum. Since the temp was a little low, I applied heat and stirred the dickens out of it until I was at 154 plus or minus a degree throughout the mash in about 10 minutes time, making sure that it didn't keep going beyond that level. So far, so good though with the mash, left it for another 50 min.

On the first batch sparge, it got a little stuck and didn't fully drain. Ran the second batch and as it drained I kept cutting it to get it to open up. This may have hurt my effenciency a bit, but oh well. Boil for 60 minutes, cool and drain to fermenters, both at 1.045.

In one, I pitched 10 oz of S-04 slurry, and in the other 10 oz of Nottingham slurry, thinking this would get them both going strong. I then shook the crap out of them to aerate. After 24 hrs a very slow start, so I pitched an a sachet of Nottingham in the fermenter with S-04, and a sachet of S-33 in the fermenter with Nottingham. I was less worried about the end flavor than just making sure I had a strong fermentation at that point.

On a side note, the second batch that night was a Belgian tripel, following the same process, which started at 1.085. Fermentation in the tripel takes off strong. Both batches in the closet to do their thing. After a week I check gravity 1.030 in the stout fermenters, and 1.025 in the tripel. Then I realize that the recent cold weather had hit, and dropped the temp in the closet to 62 from 70. So I rouse the yeast in both batches and put them in a warmer closet to hope for the best.

Another week, the tripel is down to 1.016, but the stout is not changed a bit. I rack the stout into fresh fermentors on top of a packet of champagne yeast and yeast nutrient in an effort to restart. Another week and nothing. At all.

At this point, I am searching for answers, and I decide to brew another 5 gallons of 1.045 wort to blend. This does three things in my mind:
- I figure if I blend at peak fermentation activity, it will help kickstart the other fermentations.
- It allows me to add in the level of oatmeal I was looking for in the original recipe.
- It gives me five extra gallons to provide to someone I owe five gallons to.

This seems like a good plan, so with 6 lbs of pale malt, 2 lbs of flaked oats, and 40 IBU of NB and EKG, I make another 5 gallons of 1.045 wort. This time the wort starts a little high at about 160 F, but quickly stirring the crap out of it brings it down to about 153 in about 10 minutes. Rest for an additional 50 minutes, sparge, boil, cool, drain and pitch with a fresh packet of S-33.

After about 6 hours it appears to be off to a quick start, checking at 8 PM last night. This morning before leaving for work at 5 AM, it looks like it will soon be going strong. Then when I get home tonight, disappointment hits, and there is no sign whatever of fermentation activity, and it is also at 1.030. WTF? Fermentation temp at a constant 70 F.

Now I am bewildered. I don't know if S-33 just sucks, as this my first time using it. I don't know if it was the mash schedule, or the oats or what. I have used oatmeal in the past with stellar results, so I don't think it was that. OGs were spot on. The strike temp issues were nothing that I hadn't dealt with in the past. I am currently focusing on RDWHAHB to the best of my ability. Still this is frustrating.

Any help is appreciated. What am I missing?

Thanks,

Matt
 

Graham Cox
Advanced Member
Username: T2driver

Post Number: 799
Registered: 11-2004
Posted From: 68.32.253.156
Posted on Tuesday, December 12, 2006 - 06:05 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Hey Matt,

By my cipherin' you've got over 26% highly roasted grains there. I'm no water chemist or mash chemist, but I am guessing that despite your use of 5.2, all that highly roasted grain may have acidified your mash to the point where you may have had conversion problems. I will offer a related hypothesis that your wort may have been overly acidified, making it difficult for the yeast to do their thing.

I seem to recall reading that most dry yeast sources do not recommend repitching. You did, but you did not mention the age of your slurry, and perhaps both of those could have been a factor initially. Though you pitched a lot of dried yeast to try to get it going, I have not had good luck pitching dried yeast into a stuck ferment.

Your kraeusening plan with the extra 5 gallons sounded like a good one. I too am at a loss as to why that didn't work, as some variant of that is what I might have suggested.

All I can figure is that the high level of dark roasted malts gave you a lot of unfermentables and a highly acidified mash and/or wort. Given the multiple, and reasonable, steps you've taken up to this point, it sounds like you may be at the point where you might consider a little amylase enzyme (dangerous - I speak from experience here) or Beano (no experience) to get your FG lower.

(As an aside, I just purchased a couple of hundred pH strips to test my own mash, as I've had some efficiency problems of my own that I can attribute to nothing other than a possible pH problem. We'll find out tomorrow.)
 

Tony Legge
Member
Username: Boo_boo

Post Number: 218
Registered: 05-2005
Posted From: 142.163.83.24
Posted on Tuesday, December 12, 2006 - 10:27 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

S-04 is usually a fast fermenter and if you pitched that in your stout it should have brought your sg down fast. I think a combo of a lot of unfermentables in the roast grain and the possibility of your thermometer being off, mashing higher than you would want could be a possible cause.

I usually add my roast grains to the mash with about 15 minutes left to give my base grains time to convert at the ph I'm used to getting (5.3) in my mash.
 

Doug Pescatore
Senior Member
Username: Doug_p

Post Number: 2034
Registered: 10-2002
Posted From: 141.232.1.1
Posted on Tuesday, December 12, 2006 - 12:56 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Look to the wort. With the variety of yeasts you have thrown at this sucker with no positive result I have to conclude that your fermentation is not stuck, it is done and you have unknowingly created a relatively unfermentable wort.

-Doug
 

Fredrik
Senior Member
Username: Fredrik

Post Number: 3504
Registered: 03-2003
Posted From: 62.20.8.114
Posted on Tuesday, December 12, 2006 - 01:04 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I think Graham may be onto something.

I don't know how much the acidity of roasted barley differs from other roasted black malts but just plugging your grainbill (10% chocoalte and 16% roasted black) into my pH model (using my default values) and even if I used my own high alkaline water, the model suggests that the mash pH might be as low as 4.5.

Even set aside this, the dark grains themselves provides unfermentables. I never tried such a thing but just playing with the numbers in my pH and fermentability sheets stuck at 1.030 seems to be in the realm of possibilites dut to this.

If the dark malt acids have any impact on the yeast I don't know. But in general, weak acids that can diffuse into the cell requires the cell to spend more energy on maintaining the cytosolic pH. But I'm not sure if this is a factor in this case though. Probalby not.

/Fredrik
 

Bill Pierce
Moderator
Username: Billpierce

Post Number: 6035
Registered: 01-2002
Posted From: 24.57.224.220
Posted on Tuesday, December 12, 2006 - 01:47 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Graham is spot on in my opinion. You used a lot of acidic roast grains with limited fermentability and therefore took a double hit in terms of lowering both the efficiency and attenuation. A mash pH below 5.2 inhibits the enzymes, and the dark grains produce a relatively high percentage of unfermentable dextrins. I realize you were seeking a lot of roast character and body, but I think you overdid it. Myself, I would limit the roast barley to about 15 percent of the grain bill.
 

Matt B
Junior Member
Username: Mattb

Post Number: 31
Registered: 02-2005
Posted From: 150.226.95.18
Posted on Tuesday, December 12, 2006 - 02:38 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I have suspected that Graham's solution was the answer until the recovery batch stalled out as well. It just seemed like too many dark grains in hindsight. However, the recovery batch was only made up of pale malt and oats, and it stalled out at the same gravity without the temperature hit of the previous batches, under what were apparently optimal conditions (well aerated, 70F, quick start).

I won't be using that much dark grain again for sure. However, despite the hit on efficiency, I still hit my target at 1.045 on the initial batch due to the extra grain at the outset.

If I do use the dreaded Beano, how much are we talking for five gallons? Or, if I add yet another reliable yeast variety after blending, is there a good option?

Thanks,

Matt
 

Dan Listermann
Senior Member
Username: Listermann

Post Number: 3778
Registered: 03-2004
Posted From: 216.23.59.245
Posted on Tuesday, December 12, 2006 - 02:50 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

That is the trouble with Beano, you never know how much to use, how long it will cause the beer to ferment or what gravity it will stop at. It is something that should only be used as a last resort. I would only put a few tablets in and expect to wait for months for it to stop.

Have you tried yeast energizer? It worked for me one time.

Dan

--This space is STILL being left intentionally blank.-


 

Doug Pescatore
Senior Member
Username: Doug_p

Post Number: 2035
Registered: 10-2002
Posted From: 141.232.1.1
Posted on Tuesday, December 12, 2006 - 03:07 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Go get a couple of pounds of DME and mix it up with hot water until you get it about as thick as honey. Stir it into the fermenter (no need to aerate you have enough yeast in there) and let it ferment. Most DMEs are realtively fermentable. The DME will be fermented and you will get alcohol which will reduce your final gravity. You can even go the route of adding simple sugars. Either way you will end up with the desired amount of alcohol in the beer and liley a lot more body than you expected but a lot of body is not a bad thing sometimes.

-Doug
 

Fredrik
Senior Member
Username: Fredrik

Post Number: 3505
Registered: 03-2003
Posted From: 62.20.8.114
Posted on Tuesday, December 12, 2006 - 03:25 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

> However, the recovery batch was only made up of
> pale malt and oats, and it stalled out at the
> same gravity without the temperature hit of the
> previous batches, under what were apparently
> optimal conditions (well aerated, 70F, quick
> start).

I missed this on the first readthrough.
Makes it more weird.

About your two first attempts, it seems the yeast health is unknown? ie how old was the slurrys? etc.

But then you fail again with a new pack of S-33 which is weird.

Perhaps something else in your wort is making your yeast poop out?

Any chance your oatmeal or something else is contaminated with something that? any weird additives? was this the same oatmeal source you used before? What other stuff did you add? any other magic ingredients or treatments?

/Fredrik
 

Matt B
Junior Member
Username: Mattb

Post Number: 32
Registered: 02-2005
Posted From: 150.226.95.18
Posted on Tuesday, December 12, 2006 - 04:31 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Fredrik,

Good questions. The slurries were about one month old, but usually I don't worry about that. I know that there are some on this board who do, but I have always had very good results even after more than three months. In fact I used another slurry that was two weeks older of US-56 in the previous batch with great results, stored in the same area.

Reviewing my post, I see that I didn't mention that I normally add about a teaspoon of yeast nutrient to the boil per five gallons. This time I was trying the Wyeast brand, and on the recovery batch, I used the Crosby and Baker brand, which has worked well in the past.

As far as the oatmeal, Quaker Oats went into the original batch, which was the same as I had used successfully in the past. However, suspecting that this may be part of the problem, I used organic rolled oats for the recovery batch. So hopefully they should have nothing unnatural.

Does this make the question more difficult? I am almost nervous to brew again, as I have two big lagers in mind next, and I don't want them to stall out, as the grain bill is nearly twice that of this stout.

thanks,

Matt
 

Belly Buster Bob
Senior Member
Username: Canman

Post Number: 2676
Registered: 02-2003
Posted From: 74.119.173.225
Posted on Wednesday, December 13, 2006 - 01:58 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

have you checked your hydrometer??? had to ask
Bellybuster Bob
www.bellybuster.netfirms.com
 

Matt B
Junior Member
Username: Mattb

Post Number: 33
Registered: 02-2005
Posted From: 72.145.228.96
Posted on Wednesday, December 13, 2006 - 03:33 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Thought of the hydrometer too. It gave me good initial readings on each batch mentioned above, including the tripel, at seemed to calibrate out in water. Still racking my brain. Thanks.

Matt
 

Doug Pescatore
Senior Member
Username: Doug_p

Post Number: 2036
Registered: 10-2002
Posted From: 141.232.1.1
Posted on Wednesday, December 13, 2006 - 01:22 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Matt,
I believe that your issue has little to do with the yeast except that they are starving for sugars. Pull a sample and put it in a clear glass jar and then add a table spoon or more of sugar. If fermentation kicks off your yeast is fine and there is an issue with the fermentability of your wort. If no fermentation kicks off then there is an issue with your yeast. You can even do this in your hydrometer jar with the hydrometer in it just in case you do not catch the signs of fermentation. The sample wil read 1.030 and then will go higher after you add the table sugar and will then be somewhere below 1.030 after the table sugar is fermented.

Good luck.

-Doug
 

Dan Listermann
Senior Member
Username: Listermann

Post Number: 3781
Registered: 03-2004
Posted From: 216.23.59.245
Posted on Wednesday, December 13, 2006 - 01:35 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

A cool test Doug!

Dan

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Fredrik
Senior Member
Username: Fredrik

Post Number: 3507
Registered: 03-2003
Posted From: 62.20.8.114
Posted on Wednesday, December 13, 2006 - 01:59 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I think that's an interesting test worth making, but still I would not I would feel assured to blame it all on the wort only if there is signs of fermentation with simple sugars, because with a stuck ferment, the yeast isn't dead. It's just too weak to utilise the sugars left.

My main reason is that it's alot easier for yeast to utilise the sugars that are taken up by non-energy requiring transports, glucose and sucrose, than it is to utilise maltose, and maltotriose in particular.

glucose and sucrose need only to activate some enzymes, and then glucose can more of less pass into the cell membrane by fascilitate diffusion.

Maltose and maltotriose needs to me pumped into the cell via an energy requiring pump. Of the energy the cell can get out of one maltose molecule, it has to spend an amount corresponding to 25% of this energy into just transporting the maltose into the cell.

A maltose molecule can yield (ignoring any maintenance) 4 ATP by fermentation. And the cost to get the molecule into the cell is 1 ATP per molecule. So 25% energy is lost in transport, as compare to sucrose of glucose.

I can imagine one test that for certain determine what is the case, and that is a reducing sugar reading. If you have alot of fermentable sugar in there, the reducing sugar reading will be *significantly* higher that if it is just dextrins.

What you need is for example a glucose oxidase based blood sugar meter, this is sensitive to maltose and maltotriose as well. Many other blood sugar meters are of no use. I got one on these and I've had alot of fun with it. There are some fine-print issues with calibration, but I have tested it on both wort and beer and it gives very sensible results. To make the conclusion of wether you have fermentables or not, these marginal issues should not stop you.

I bet you can buy these meters cheap. I think I payed maybe $40 for mine and it came with 10 or 20 strips. One strip per test. They you can by extra strips when you are out of them. If you are a diabetic I guess you get it for free, or cheaper on subscription. but I had to buy one separately.

this is the model i use

http://www.everydaymedical.com/index.asp?PageAction=VIEWPROD&ProdID=155

If you want to play, that is a great gift for yourself on xmas :-)

You should also be able o sense a difference in sweetness, but that might be difficuly to grade without some references.

You could always prepare a 1.030 dextrin solution and compare the sweetness.

/Fredrik
 

Doug Pescatore
Senior Member
Username: Doug_p

Post Number: 2037
Registered: 10-2002
Posted From: 141.232.1.1
Posted on Wednesday, December 13, 2006 - 02:23 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Okay, put a couple of table spoons of freakin DME in the sample...whatever.

You have dropped all sorts of dry yeast which require no starter and no propagation to ferment a standard gravity beer (1.050 - 5 gallon batch per packet) plus a nice sized jar of yeast slurry and then on top of that a packet of champagne yeast. All of these dried yeasts are prepared with all of teh nutrients and such to make them almost bullet proof.

I have never bought the BS about stressed and such yeast and the easily digestable vs. simple sugars stuff. So if it takes some energy to ferment the maltose wouldn't the simple sugar sort of jump start the process by providing the yeast cells all of this free and easy energy? It all looks good on paper but in the end I have had many batches that were pitched with less than perfect yeast preparation (in the early days down right yeast abuse) and still had them finish the job. It may have taken them longer but they got the job done.

The point is that Matt is way off where he should be with his FG, he has thrown the kitchen sink of yeast at the wort, and now he is left racking his brain trying to figure out what happened. Without trying to narrow down the root cause of his problem (the yeast or the wort) he will never get beyond racking his brain.

-Doug
 

Dan Listermann
Senior Member
Username: Listermann

Post Number: 3783
Registered: 03-2004
Posted From: 216.23.59.245
Posted on Wednesday, December 13, 2006 - 02:34 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

"Without trying to narrow down the root cause of his problem (the yeast or the wort) he will never get beyond racking his brain. "

I gave up trying to do that. I could never get the hose in far enough to keep the siphon going.

Dan

--This space is STILL being left intentionally blank.-


 

Fredrik
Senior Member
Username: Fredrik

Post Number: 3508
Registered: 03-2003
Posted From: 62.20.8.114
Posted on Wednesday, December 13, 2006 - 03:09 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Doug, I agree completely with you that at this point wort problems seems the most likely thing after all.

I was just adding another point, BS or not. I didn't mean to pick on your suggestion, it's still a good test.

About the "stressed yeast BS", I guess we simply disagree. But alot of this is well studied. The theoretical expectation of 25% energy loss in growth on maltose vs glucose is experimenteally verified as a reduced growth yield - you get a higher growth yield on glucose than on maltose. An for sure there are general maintenance costs. At some point the maintenance costs are not covered by the energy production and if that is so, i think it makes excellent sense that the yeast poops. It's like a big company that is not going so well, why shut down the company when there are still a few people that would buy their products? Maybe the cost of running the company and paying the workers exceed the amount they make. So they shut down.

Stress and maintenance can and have been measured in several experiments by compared sugar consumption and growth yield. And it's a generally accepted fact not only for yeasts but also for bacteria that there is a energy balance, where some of the gained energy is "lost" to maintenance, instead of growth. And during a batch fermentation where the stress factors accumulate, it seems plausible to me that first of all growth slows and fementation slows (it takes longer time), but it could also be that it halts prematurely.

In either case a stuck ferment at 1.030 is certainly off chart, unless there is some stuff in the wort that doesn't belong there.

/Fredrik
 

Matt B
Junior Member
Username: Mattb

Post Number: 34
Registered: 02-2005
Posted From: 150.226.95.18
Posted on Wednesday, December 13, 2006 - 04:54 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Doug, I am definitely going to try the test tonight after work. I can see issues for consumption in the future if I can't get the small portion I planned on bottling to carbonate without additional effort.

As far as racking brains goes, the complex proteins and fatty matter may just be the nutrient lift the yeast need! Fredrik may know better on the scientific aspects of that problem. Though I would hope that the relatively higher level of fatty "stuff" in oats would help that out.

What should have been an simple, quick, and easy-drinkin' stout has made me leary of my whole process.
 

ELK
Senior Member
Username: Elkski

Post Number: 1729
Registered: 01-2003
Posted From: 71.195.244.40
Posted on Tuesday, December 26, 2006 - 03:49 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Well, you cant leave us hanging like this... What has transpired? I feel like I was reading a book and the last chapter was ripped out.
Rip them lips!
 

Matt B
Junior Member
Username: Mattb

Post Number: 35
Registered: 02-2005
Posted From: 208.61.23.121
Posted on Thursday, December 28, 2006 - 03:17 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Sorry, I just got back from Disneyworld, so I am checking now. I can tell you thus far that I have determined a few things:

1) I tried Doug's test with a small sample pulled and simple sugar added. It wasn't immediate or spectacular, but there was fermentation activity after about 24-30 hours. This told me that it was likely a fermentability issue.

2) I rechecked the calibration of my thermometers. (I have currently three main brewing ones, but my wife is in public health, and I have about a dozen around the house, truly I have no faith in any of them now. If any of you own a restaurant, just wait for the ding on not getting you meat dishes up to temp.) All continued to check out at 32 F. HOWEVER, after reading the other thermometer thread, I checked at boiling, and then watched them go down together after I turned off the heat. Two were four and five degrees off (reading 216 and 217) at boiling. I can only assume for my initial batch that I didn't leave it at the low 150 range long enough to convert.

So then I resorted to Beano drops. MTF.
 

Matt B
Junior Member
Username: Mattb

Post Number: 36
Registered: 02-2005
Posted From: 208.61.23.121
Posted on Thursday, December 28, 2006 - 04:09 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

To wrap it up, after 10 days with Beano, I am down to 1.017 for all 15 gallons, with it still showing faint signs of fermentation activity. I have made arrangements to send back two of the faulty thermometers, I will be doing double or triple decoction mashes for my last two batches of the year it order to avoid some of the potential problems here, so I am not quite as worried about it. "We're in business," ugly, but sufficient.

Does anyone have a good link to a quality, lab verifiable, accurate thermometer?

Thanks for everyone's input.

Matt
 

Dan Listermann
Senior Member
Username: Listermann

Post Number: 3870
Registered: 03-2004
Posted From: 65.29.220.144
Posted on Thursday, December 28, 2006 - 04:15 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

If you stick with the same thermometer and adjust batches for fermentability, you don't have to worry much about accuracy. Consistancy is what you really want.

Dan

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dhacker
Advanced Member
Username: Dhacker

Post Number: 705
Registered: 11-2002
Posted From: 68.221.130.197
Posted on Thursday, December 28, 2006 - 12:49 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

After all the recent talk about non-reliable thermometers, I've used a little Iodophor after mashing my last several batches just to be sure of conversion.
 

Fredrik
Senior Member
Username: Fredrik

Post Number: 3538
Registered: 03-2003
Posted From: 62.20.8.114
Posted on Thursday, December 28, 2006 - 01:27 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I think an iodine test is poor insurance against unreliable thermometers since a negative starch test really doesn't say much at all about fermentability.

For example a maltodextrin solution gives negative result, but has very low fermentability.

What you would rather need is a measure of how much reducing sugar you've got in there. I've tried to estimate the fermentability of DME with reducing sugar tests, and it's easy to get in the ballpark, but it's not accurate enough to nail individual gravity points, unless you can resolve the sugar profile and ratios between fermentables. If this is know you can be accurate. But this varies a little.

/Fredrik
 

dhacker
Advanced Member
Username: Dhacker

Post Number: 706
Registered: 11-2002
Posted From: 68.221.130.197
Posted on Thursday, December 28, 2006 - 01:39 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I agree with you Fredrik that you can't hang your hat on the iodine test, but for the level of equipment most homebrewers have at their disposal not to mention the time to do lab quality tests, it is a cheap and dirty method of detecting if a serious conversion flaw exists. It MAY have been enough to help Matt avoid is problem. . plus it takes about 2 seconds, and cost about 2 cents!
 

ELK
Senior Member
Username: Elkski

Post Number: 1731
Registered: 01-2003
Posted From: 71.195.244.40
Posted on Thursday, December 28, 2006 - 03:18 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

The dang thermometer thingy again...
You would think in this day where for 2.88$ at Walmart you can buy a magnetic refrigerator photo holder that has 3 batteries, a speaker, a microphone and will record and playback 5 seconds of audio that some company could make an accurate cooking thermometer!!
And while were wishing make the probe and cable waterproof, dishwasher approved, and accurate to +/- .5 F. Good for the oven, smoker, roast, or MT

By the way record you beer fridge menu and stick one above each tap on the door.
Rip them lips!