Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.

Messages - nyakavt

Pages: 1 [2] 3 4 ... 8
Yeast and Fermentation / Re: Predicting yeast cell counts
« on: June 18, 2010, 12:52:37 PM »
The mr. malty calc has a limit to the amount of growth that it will recommend with one starter, that happens to be 6 yeast packages worth.  So if it would take over 6 of your 20% viable packages to ferment the batch (6*20=120 billion cells), it jumps up to a new minimum.  This isn't particularly useful since most of us don't have two or more identical old yeast packages lying around. 

The other limit the mr. malty calc places is a minimum starter size of 1L.  This is the generally accepted minimum for significant new cell growth in a WL or Wyeast package. 

For old smack packs or a small amount of slurry, doing a mult-step starter is what you want.  It will ensure that you have a timely fermentation at each step to minimize the risk of other microbial infection, as well as reduce greatly the required amount of wort needed to get to your final cell count.  The wort usage is reduced with a multi-step starter because there is a starter pitching rate that results in the maximum amount of growth, above which the growth rate declines.  For example, if your starter pitch rate is 100 billion cells/L on a stir plate, there will be 130 billion new cells grown per liter of starter wort.  If your pitch rate is 12.5 billion cells/L, the new growth will be only 57 billion cells/L.  You can see a plot of the mr. malty stir plate tab, the x-axis is the starter pitching rate and the y-axis is the starter growth rate:

You should size each step to remain within the 100-12.5 billion cells/L pitching rate, to ensure timely fermentation and always have the minimum number of cells needed for adequate growth.  The closer you stay to the high side of that pitching rate, the more efficient your wort usage will be, at least with a stir plate.  You can use the formula on the chart in a spreadsheet to estimate the growth from each step size, and don't forget to add the starting cell count to get the total after each step.  So for example if you have 20 billion cells and pitch at 100 billion cells/L, that's a 200 mL starter * 130 billion new cells/L = 26 billion + 20 billion (starting count) = 46 billion after step one.  Keeping the same rate for step 2, 46 billion cells into a 460 mL starter * 130 billion new cells/L = 60 billion + 46 billion starting = 106 billion after step 2.  You'll have to play with the starter sizes to keep the minimum pitch rate and not grow too many cells for what you need.

An alternate method for doing the math above is to have the calculator do it for you.  Input your recipe parameters and yeast viability and adjust the volume down until it recommends only 1 yeast package in the starter (remember the smallest it will recommend is 1L, so this is not the most wort-efficient sized starter).  The 'cells needed' result is the final cell count in this starter.  Next input this number into the viability field and adjust the recipe volume again until you reach either the desired recipe volume or the next step size to keep to 1 yeast package in the starter.  You can repeat until your final recipe volume is reached.  As your viability exceeds 100%, you need to be cautious that your pitching rate does not exceed 100 billion cells/L (e.g. if the 'cells needed' in a previous step is 150 billion, make sure you make at least a 1.5L starter in the next step.  You may need to adjust the intermediate starter sizes to make sure this is the case).

Kegging and Bottling / Re: Beer Gun vs. CP Filler
« on: June 17, 2010, 06:19:50 PM »
Kai, what's the longest you've kept unpurged tap-filled bottles, and what temperature were they stored?  How long did it take for oxidation to show up, if it has yet?  I'm considering this method to free up keg space since I don't have a special filler, and it will probably be the higher alcohol beers that require 6-12 months of aging. 

All Grain Brewing / Re: The Ideal Batch Sparge
« on: June 10, 2010, 06:09:33 PM »
I know this is a bit late, but I thought about running sizes and batch sparging a bit and came up with an analogy that makes sense to me.  Imagine that you have a kettle that always leaves 1 gallon behind when drained.  

That's exactly how I have modeled batch sparging on various occasions.


Yep, I've found your model to very accurately predict the into-kettle efficiency when all the starch is converted prior to the first runoff.  Since I got my refractometer inconsistencies sorted, my 3 most recent calculated efficiencies were within 1% of observed efficiency.  It's a very useful tool for recipe formulation and for seeing how much efficiency decline to expect when brewing bigger batches but collecting the same amount of wort.

All Grain Brewing / Re: The Ideal Batch Sparge
« on: June 10, 2010, 05:18:49 PM »
I know this is a bit late, but I thought about running sizes and batch sparging a bit and came up with an analogy that makes sense to me.  Imagine that you have a kettle that always leaves 1 gallon behind when drained.  So if you have 200 'points' of sugar and dilute it to make 5 gallons of wort, that's a 1.040 wort.  If the kettle is drained as much as possible, 1 gallon of 1.040 wort will be left behind, or 40 points out of a possible 200 (20%).  This is analagous to a no-sparge. 

Next collect the same amount of wort in two steps, first by collecting 3 gallons then collecting 1.  For the first runnings the wort will be 1.050 gravity, leaving 1 gallon behind.  Adding 1 more gallon of water will dilute the wort to 1.025, again leaving 1 gallon behind when drained.  So here you leave behind 25 points out of a possible 200, or 12.5%.  This is a single sparge with unequal runnings.

Finally, collect the same amount of wort in two equal steps.  This is done by a 3 gallon wort which is drained, followed by adding 2 gallons and again drained.  The first draining leaves 67 points behind, which is diluted to 1.022 by the second addition, and again leaving 1 gallon behind.  Here you leave behind 22 points, or 11%.  This is a single sparge with equal runnings.   

You can see the difference between equal and unequal runnings (1.5%) is relatively small even for a large difference in runoff sizes.  The size of the 'dead space' at the bottom of the kettle can be represented in your MT by the amount of wort absorbed by the grain and any dead space, easily measured on your next batch.

Yeast and Fermentation / Re: Vexed by Acetaldehyde/Esters
« on: June 02, 2010, 12:52:41 PM »
I had an acetylaldehyde problem with a Helles 2 years ago and with a German Pils this year.  The Helles sat at 50F for 4 weeks and had a strong green apple flavor after 2 weeks in the bottle, so I left them at room temperature and they cleaned up nicely after 2 more weeks.  The German Pils had a more mild green apple that was fermented for 2 weeks cold and raised up to 70F for 1 week.  The green apple mostly dissipated, but it was still there in trace amounts.  It could have used a longer warm conditioning rest. 

The common thread on both of these beers was that they were each the first pitch of the lager yeast, none of the subsequent batches brewed with the yeast showed an acetylaldehyde problem (even light styles like Dortmunder or Bohemian Pils, or another Helles).  I think you're more likely to find it in lighter styles and when yeast health is not optimal, maybe certain strains are more prone to producing it.  I have only noticed this in lagers.

Do you rehydrate the dry yeast, and is it within the expiration date?  As others suggested a warm conditioning period will help clean it up as this byproduct needs to be consumed by the yeast, it will not otherwise age out.  I've also heard of making a small starter (1 pint) with dry yeast and pitching that into the beer to clean up diacetyl and acetylaldehyde, but haven't tried it.

Equipment and Software / Re: ATC Refractometers
« on: May 30, 2010, 04:11:01 PM »

Thanks for testing some of the theories. I assume you did not do a test where you kept the hop sample on the prisim w/o closing it immediately to see if we need to concern about evaporation.

No I forgot about this one, it will have to wait for next week.

I think stratification of run-off depends on how you collect the wort. If you have a hose that reaches all the way down to the bottom of the kettle you may get sufficient mixing action.

That's how it was, the hose was under the liquid level so I imagine it was stirring up the first runnings evenly well with the second.

Equipment and Software / Re: ATC Refractometers
« on: May 30, 2010, 05:20:19 AM »
Yeesh, long day.  Ok here are the other measurements for this brew session.

First I took a pre-boil gravity by drawing a sample from the boiling wort with a syringe.  This time I put a drop on the lens and closed it almost immediately, probably 1/2 a second lapse (this is by far faster than I've ever done it before).  This reading was 9.3 brix.  I then placed that syringe in the freezer until it was chilled and it read 9.2 brix, again inside the instrument resolution.  So it appears that quickly closing the lens will get you very close to a chilled sample.  I also took and chilled a sample before the wort got to a boil which came in at 9.1 brix, but the wort boiled for a short amount of time before I could get to it so this is not directly comparable.  Still, very close.

The final test of the day was the top-bottom measurement.  After chilling and whirlpool the kettle was allowed to rest for 20 minutes.  Then I took a sample from the top of the wort and ran 1/2 liter into the fermenter and took a sample from that, effectively the bottom of the wort.  Here the top sample read 9.9 brix and the bottom read 9.8.  Oddly the bottom was the lower reading, but again this is inside the instrument resolution so it's probably just drift. 

So this demonstrates to me that on a wort of this gravity, stratification is not a concern, and quickly covering the lens gets you close enough to a sealed container reading.  I am going to continue testing on my next few batches to see if the trend holds.  In the long run, I will still prefer to chill the sample prior to reading, at least of boiling wort, to preserve the instrument as long as possible.

Equipment and Software / Re: ATC Refractometers
« on: May 30, 2010, 12:57:38 AM »
Update on this, I'm brewing a scottish 70/- with kettle caramelization, so I was in the unique position to leave the wort sitting for a long time before firing the main burner.  The kettle sat still for about 2 hours with 25 liters of runnings, it was not stirred or disturbed other than running wort into the kettle.  After the wait (wort temp was ~125 F), I took a 5 mL sample in a 10 mL syringe, then stirred the kettle well for a minute (you could see the settled protein change the color of the wort) and take another sample from the same spot.  I then put both syringes in the freezer until it had chilled to approx. room temp, about 5 minutes.  I wiped down the outside o the syringes with a dry paper towel and shook them well.   Then I discarded the first 2 mL of sample to avoid any potential contamination by condensate on the outside of the syringe.  The unstirred sample read 6.7 Brix, and the stirred measured 6.8 brix.  This difference is within the resolution of the instrument (0.2 brix).  I did know which one I was sampling, so there is a potential for 'researcher bias' in interpreting the readings.   

This is only one observation and the wort is very low gravity, so it may not show stratification as well as another wort.  But the difference here is not enough to account for the difference I'm seeing when taking a warm sample.

Equipment and Software / Re: ATC Refractometers
« on: May 29, 2010, 05:46:32 PM »
This is a forum to discuss differences in home brewing techniques and methodology, and to learn more about the principles of brewing science.  This discussion is proof of that.

Please don't take my post as an attempt to keep you from voicing your opinion, that's how we get the best discussions.

Nyakavt, my reason is simple:  IMO, there is no need to take a HIGH TEMP sample during the boil, so I don’t.  Your statement that I don’t “verify any of my measurements” is misleading.  I calibrate my instruments and use them appropriately—therefore I have high confidence in their results.  If I use the instruments outside of normal operating conditions, I temper/adjust my interpretation of the results accordingly.  IMO, the cover plate on my refractometer is my “sealed container” [see additional discussion below].  OTOH, given the observations of others who do this, if you’re taking a larger sample from boiling wort, you’ll need a larger container and should seal it while it chills to minimize any evaporation.

The purpose of a sample in boiling wort is to ensure that the sugar is evenly mixed throughout, and to be able to adjust the boil time to reach your target gravity.  To me making the beer that I set out to make is important so that I do not need to adjust the bitterness if I am 5 or 10 points off.  The other catch on my system is that I do not have a good way to measure volume post boil, since I use an immersion chiller which distorts the reading on the depth gauge after it goes in and I don't want to worry about sanitizing it.  Volume in the fermenter is no good either since I leave a 1/2 gallon or so behind in the kettle, so even though I would be calculating my 'true' efficiency, I'm more interested in the yield I got from the grains since the number is not dependent on the trub volume in the kettle because of varying amounts of grain or hops.

It's not that I'm trying to hit a specific number for my efficiency, but I want to hit the target gravity for the recipe and this is the best way I know to do it.  The 'verifying your measurements' comment is referring to the fact that you claim quickly closing the lid on the refractometer is 'good enough' for a sealed container, but you have no direct evidence to support this claim.  Every time I've tried this (that I can remember) the number was higher than expected.  In order to know that the 'warm' measurement you are taking is accurate, you need to compare it to some known accurate value, which can be done by comparing a pre-boil and post-boil (and cooled) gravity measurement with accurate volumes for each.

I certainly agree with you that it seems unlikely that a few seconds of exposure to air is enough to cause the change in gravity I am seeing, but nevertheless I cannot just ignore the discrepancy because it seems unlikely.  The surface area to volume ratio of the sample would be much higher than in a normal case of evaporation, whose surface area is only on top of the column of liquid.  It could be a combination of things going on, I really don't know.

My highest temp sample (<170F) is done at lautering to make sure I remain >3 Brix (> 1.012 SG), and not to calculate efficiency.  For purposes of estimating the SG of final runnings, I’m comfortable with a “fuzzier” result or ballpark number.

I can agree with this, since the number is inconsequential to reaching your target gravity, and any inaccuracy would put you on the safer side of avoiding the 3P mark.

Anyway, I'll be brewing today and will keep in mind some of the points you raised richardt.  Unfortunately it's a low gravity beer so the effects of stratification, if they exist, will be harder to detect.  Either way this does not solve the issue of inaccuracies at warm temperatures, and in my process I do have a need for them to hit the target gravity.

Equipment and Software / Re: ATC Refractometers
« on: May 28, 2010, 02:32:13 PM »
Richardt, from your last post it sounds like you don't take any measurements at elevated temperatures that are subsequently verified by a cooled post boil sample, or a mash gravity reading that is verified against the laboratory yield of the mash.  So if you do not verify any of your measurements, why are you arguing that you don't need to cool the sample in a sealed container???

Equipment and Software / Re: ATC Refractometers
« on: May 27, 2010, 01:08:40 PM »
Richardt, have you noticed your refractometer readings to be consistent with post-boil volume corrected gravity when taken with a drop of boiling liquid placed directly on the lens?  Like I said, every time I've done this the gravity was higher than anticipated, sometimes to the point that the pre-boil gravity was greater than or equal to the post boil gravity (impossible!).  What can I do differently in sample taking to eliminate the issue, it's done with boiling wort in the center of the kettle? 

If you are saying that my chilled samples are inaccurate due to stratification, and the chilled sample is consistent with the post boil (and batch cooled) wort, then you are also saying that the post-boil sample is inaccurate by the same amount.  This is hard to believe, especially considering the height of the kettle vs. the height of a 5 mL sample (a sample taken at the top of a 24" kettle should be much lower than one taken at the top of a 1/2" column of wort).  Clearly more experimentation is needed since I don't have a good enough understanding of the fundamentals going on here.

Equipment and Software / Re: ATC Refractometers
« on: May 24, 2010, 07:12:15 PM »
There's no need to worry about evaporation

This has not been my experience.  I use the refractometer for lots of things on the hot side, including pre-boil OG measurements and mash gravity measurements.  The reading would be way too high (pre boil gravity > post boil gravity, or mash gravity much greater than predicted) with just a drop on the lens compared with a cooled hydrometer sample, and also when pouring a bit onto an open dish to cool before sampling.  Then a couple of times I took a hydrometer sample to chill in the freezer and checked with the refractometer right away and after chilling - the hot sample was 2 Brix higher.  I also could not get any consistency when taking two readings in a row.

For the last dozen or so batches I've switched to cooling the sample in an airtight container, either a small screw top test tube or a 10 mL syringe.  The results have been much more consistent to each other, as well as matching the hydrometer sample and the predicted mash gravity.  There could be other factors at work here (like stratification of sugar concentration in the MT or kettle) that affected my readings, but I've seen enough to convince myself that this evaporation is a real concern and must be addressed, even with small samples that are quickly covered.

I have been storing in a closet that fluctuates between 65 and 75F for the past three years or so, for lack of a cooler place or fridge space.  Any delicate hop character is gone or severely diminished within 2-3 weeks, I've noticed this on several APAs and IPAs.  Next is the oxidation, which starts take hold after 4-6 months.  Weirdly a schwarzbier that has been in there over a year still tastes fine to me, but my Maibock and traditional bock are both heavily oxidized.  After about 10 months the maibock became completely undrinkable due to autolysis, and the traditional bock is approaching that threshold at 6-8 months (all bottle conditioned).  I've also got a southern englsh brown in there that tasted fine last time I had it, about a year old, it seems that anything with some roast holds up better.

So I guess for peak freshness you've got about 3 months at these temperatures, and probably double that for less than peak but still enjoyable for your average beer.  Roast character seems to extend that time significantly, and I imagine high gravity stuff will keep better as well.  Hoppy beers, IMO, do not taste nearly as good after just a short amount of time stored warm, so keep these cold if possible.  They are still nearly as bitter after a month, but the wonderful hop aroma and flavor is a mere shadow of what it was fresh.  Finally, I suggest that you try to minimize the amount of yeast that gets into the bottle (cold crash first), this can wind up giving you some autolysis flavors way down the line, especially if the beer is particularly light or you've let in a lot of yeast.

All Grain Brewing / Re: Brewing at Twice Strength then Dilluting
« on: May 06, 2010, 05:25:04 PM »
Efficiency is the other concern, especially if you batch sparge.  Expect at least a 15-20% drop if you go from a 10 lb to 20 lb grist (batch sparging), all else being equal and collecting the same amount of wort.

Boy, I sure haven't seen anything like that.  Maybe 5, sometimes 10 points.

From Kai's site:

According to the mathematical model of batch sparging, the efficiency is dependent on the amount of grain used, pre-boil volume, absorbtion ratio, dead space, number of sparges, and relative runoff sizes, provided all other variables are well controlled and 100% conversion is achieved.  If only the amount of grain is being changed, then the model says there will be an 17% difference between the two for a 6.5 gallon (temp adjusted) pre boil, at least if my calculation is correct.  I have found this model to be a bit on the high side of estimated efficiency, I usually get a few points less than predicted.

Personally I've only done a couple of *really* big beers, so I'm not the person to look to for verification of theory.  On the last one efficiency went from a normal 80% down to 65% IIRC, collecting 7 gallons preboil with 23 pounds of grain.  Denny, I seem to remember you saying that you usually have a bigger preboil when you do the barleywine?  Far be it from me to question a brewer that has brewed a *lot* more batches, it's just hard for me to wrap my head around only a 5% efficiency reduction when going from 10 to 20 lbs of grain, all else being equal  ???

All Grain Brewing / Re: Brewing at Twice Strength then Dilluting
« on: May 06, 2010, 02:41:26 PM »
There's a guy at our tailgate that does this with extract,

Know your lot for next season yet?  We had three homebrewers bring about 10 different varieties to the Spring Game tailgate weekend before last.  That sort of thing needs to be expanded upon.

Lot 4, we usually bring one keg each.  Where are you guys?

Pages: 1 [2] 3 4 ... 8