Attenuation Issues

[BREWsmith]

My last two beers have attenuated poorly, about 60%. I've never had this issue before. Assuming my new hydrometer is accurate (with distilled water it read between 1.000 and 1.002), the only thing in common with these two batches is both used maris otter as the base malt (these were the first two batches from a newly opened bag). Both batches were mashed at around 152-154 and fermented within range for the particular yeast strains (WLP001 and WLP028). Could the problem be with the maris otter from this particular maltster? The current beer, a Scottish 80, has been in the concial for just over two weeks, should I try adding back the yeast I saved from the second dump or just leave well enough alone? Thanks for your input.

[Don]

Are you sure the yeast was done working when you dumped it from the fermenter?
You said you dumped twice what were the conditions for each?
What was the OSG, FSG & how much yeast did you use?
How old was the yeast? Condition of the yeast?



There are 2 parameters regarding attenuation, that the brewer can affect.
The first one is the limit of attenuation and the second one is the difference between the final attenuation and the limit of attenuation. The limit of attenuation is set by the wort production and the difference between the final attenuation and the limit of attenuation is set by the fermentation
wort production
saccrification rest temperature: This is the first factor that comes to mind for all grain brewers. For a single step saccrification rest, the mash temperature has a great affect on the fermentability of the resulting wort. The lower the temperature (within a given range of course) the longer the beta-amylase will be able to work and produce maltose.
mash schedule: the choice of mash schedule also affects the fermentability. Some beta amylase activity is already present during a protein rest and the time it takes to heat to the saccrification rest. Another mash schedule factor is the length of the mashing time and the time the wort spends below 175 *F . Below that temperature the alpha amylase is still active and can produce fermentable sugars, though not as effective and quickly as the beta amylase which is quickly denatured at temperatures above 156 *F .
water to grist ratio: the enzymatic activity of the amylases is affected by the thickness of the mash. Thinner mashes enhance the maltose production and therefore increase the fermentability.
grain bill composition (base malt): mashes with high diastatic power (Pilsner, Pale) will produce more fermentable worts since they contain a lager amount of beta-amylase which can produce more maltose than mashes with lower diastatic power (Munich or large amounts of unmalted grains) assuming the same saccrification rest temperature.
grain bill composition (specialty malts): crystal and roasted malts add unfermentable sugars to the wort which lowers its overall fermentability.
mash pH: the beta and alpha amylase enzymes have different optimal pH ranges (beta amylase : 5.0 - 5.5 pH; alpha amylase : 5.3 - 5.8 [Palmer 2006]) and therefore the mash pH can affect the activity balance between these enzymes. Though the effect is only marginal.

[sirgiovanni]

First have to ask about your yeast. Did you have the right size starter. Was it fresh and healthy at pitch?

Mash controlled variables of attenuation can be improved if you use Lower temps.

[BREWsmith]

I followed the regimen I always do. I did the first yeast dump several days after CO2 production stopped. This was after about 8 or 9 days after brewing. I pulled the second yeast dump about 4 days later and saved it. It was a fresh vial of WL028 in a 1 liter starter. The OG was only 1.054.

[Don]

What temperature?

[BREWsmith]

68 for this one and 65 for the previous one using fresh WLP001 with a 2 liter starter Neither were high gravity.

[BREWsmith]

The only variables different between these batches and the couple dozen before are the base malts (not the type, but rather this bag and, possibly, this maltster) and the new hydrometer I bought two brew ago. Is it scientifically possible that it could be faulty? Probably not, since I just rechecked it will distilled water and it read 1.000. Should I try repitching?

[Don]

It should of been finished in the time you let it sit, but lack of CO2 bubbles is not a sure way to know if your yeast has done all they can do. You need to check the SG for 2 or 3 days to make sure.
If the yeast was fresh (less than 1 month old) has not been stressed (exposed to high temperature during shipment) you should of had enough yeasts to do the proper job.
I personally don't think the malt makes any different in what you are seeing here.
When you mash your grains it will pull all the sugars that it can (given time, temperature, crush, ratio etc...) from the grains, that is what you have to work with.
if your grains or process have something wrong you would just start at a lower OSG number, and then finish with a lower than expected number. All the other factors I mentioned above will effect this percent.

Should I try repitching?
If you think you dumped the yeast too early, you can add it back to the fermenter without any problem (keeping all sanitized), If it then drops that would mean that you dumped the yeast before it was finished.
or
I would just let it sit a few more days then check the SG, there is still a lot of yeast in the beer (unless you crash cooled it). If it changes after a couple of days then that means it is wasn't finished yet. No change would mean that's all you are going to get given the situation.

[Don]

And are you sure the temperature did not drop below 62°F?

WLP028 Edinburgh Scottish Ale Yeast
Scotland is famous for its malty, strong ales. This yeast can reproduce complex, flavorful Scottish style ales. This yeast can be an everyday strain, similar to WLP001. Hop character is not muted with this strain, as it is with WLP002.
Attenuation: 70-75%
Flocculation: Medium
Optimum Fermentation Temperature: 65-70°F
(18-21°C)
Does not ferment well less than 62°F (17°C)
Alcohol Tolerance: Medium-High

OG FG Apparent Attenuation
1.054 1.013 75.5%
1.054 1.014 73.1%
1.054 1.015 72.2%
1.054 1.016 69.3%
1.054 1.017 67.4%
1.054 1.018 65.5%
1.054 1.019 63.6%
1.054 1.020 61.7%

[BREWsmith]

It's been in my temperature controlled fridge at 68 degrees from the get go. Besides the temperature controller, I also keep a thermometer in the fridge and check it periodically. Like I said, this is the second consecutive batch with which I've had this issue after never having had the problem before.

[Chris Norrick]

Do you want another hydrometer to check yours against?

How does the beer taste? Too sweet?

Calibrate your mash thermometer too, you never know. Mine was off 5 degrees once.

BrewSMITH: [quote]I went by the co-op today and bought another. I suspect, one will be a door prize at a future meeting. I think it tastes on the sweet side, but that may be more suggestive than reality. It would be a good idea to calibrate by mash thermometer. I'll do that this weekend.

[Michael Erwin]

The rye-p-a didn't seem overly sweet last night.

[psfred]

It is quite possible that your malt is different bag to bag. If everything else is the same, low yeast activity usually just means longer fermentation time, not higher final gravity, although if you bottle too soon (or keg too soon) it then ferments out in the container, giving you a foam bomb.

You may need to modify your mash schedule to account for the difference in mashing behavior. I would suggest 152F as a maximum initial temperature, and allowing it to drop rather than holding steady -- this will geletainize the starch properly but not kill off the beta amylase right off. Stirring the mash (or recirculating in a RIMS or similar system) will enhance enzyme activity. You can go as low as 150F for the initial mash temp, but not lower (poor gelatinization, hence starch haze).

You may also need to mash longer -- an hour at least -- since it appears you are short on enzyme activity.

Or you could toss in a pound of US six row malt to give you more enzyme activity.

I would also recommend an iodine test to determine mash state. Betadyne (povidine iodine wound prep agent) or iodine sanitizer works just fine if you cannot find any iodine/potassium idodide solution. Dip some grits out into a while ceramic dish of some sort and gently flow the iodine solution over it without stirring. You may need to dilute the betadyne stuff, it's pretty thick. The husks will turn black, so ignore that and look and the other particles. In the early stages of the mash, they will turn black or purple black due to the starch, as as mashing proceeds, become lighter and lighter. For a high terminal gravity, stop when they are reddish, for low terminal gravity continue to mash until they are very faintly colored or stay white. Toss any iodine treated grist, never put it back into the mash.

If an iodine test show that the mash never proceeds past the dark red stage, you need to add some high enzyme malt to kick things up a bit.

It is also possible the yeast is wonky, although I'd not suspect that to be the case for two separate attempts with different yeasts. Failure to use maltotriose is a common mutation.

Peter

[BM1]

I usually get higher attenuation when I step up the mash temp after dropping 2 degrees or so.example: Start 152 deg./30 min. - step back up to 152 deg. with a small infusion and rest an additional 30 min. ( efficiency increases also )
And.... Also stepping up on fermentation temp. may increase attenuation %s.Like going from the lower end of the yeast range ( gradually over a few days ) to near the upper range.

As stated by others,there may be many factors.I don't know for sure. Just my 2 cents.

[BREWsmith]

Do you want another hydrometer to check yours against?

How does the beer taste? Too sweet?

Calibrate your mash thermometer too, you never know. Mine was off 5 degrees once.

BrewSMITH:

I went by the co-op today and bought another. I suspect, one will be a door prize at a future meeting. I think it tastes on the sweet side, but that may be more suggestive than reality. It would be a good idea to calibrate by mash thermometer. I'll do that this weekend.

Thanks to all of you that responded to my query!

Surprisingly the beer to out to be a pretty satisfying session ale. As for the second new hydrometer, it measure about 2-3 points lower than the other. Although I'm still suspicious of the maris otter, I used it for an IPA last weekend. It's still in primary fermentation and I'm going to be patient.