New Brewing Research Conclusions....

Physics, chemistry and biology of brewing. The causes and the effects.

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Postby Mesa Maltworks » Mon Nov 27, 2006 1:16 pm

Larry;


Q: 1. Do you recommend 1.3 - 1.4 qts/# regardless of the method of mashing?

Other than for decoction (you can read my take on that archaic technique elsewhere) this ratio is optimal for hydrolysis which is very important in maximizing saccarification of the grist.


Q: 2. Are there any implications to the 20 minute mash using RIMS or HERMS or is it independent of mashing equipment?

It is dependant of mashing equipment in so far as the geometry of the vessel and the ability to vorlauf to clarity. If you use a "Gott" cooler which is tall and deep, the conversion rest time would have to be lengthened due to the mash bed depth. If you use a regular, rectangular cooler, the mash bed depth is greatly thinner and therefore reduces the amount of time required for conversion somewhat. That is what I mean when mentioning "vessel geometry".

I am not, nor is the pro brewing community, a fan of RIMS or HERMS however. It certainly works but can be and often is to the detriment of wort quality. This is why you never see this technique applied in professional brewing. The idea is to gently extract from the grist while minimizing the water and grain contact time only as long as is required for conversion. Unfortunately by continuously pumping hot liquor and runnings this goal is not achieved and can lead to the extraction of lipids and tannins. There is also the issue of "wort stress" which is created by the pumping action which tends to fracture the grain particles and can include the forced addition of oxygen into the recirculation loop and therefore into the pre-wort.


Q: Yeast Question:

1. Prowler 13 asked about using a stir plate. In reference to your answer could you not use a filter in your stopper while continuously stirring on the plate or is this not as sanitary as filter manufactures would lead us to believe?

If you mean using a sterile air filter stuffed into the bung (like the laboratory sterile air filters used in-line for aquarium pump wort aeration), yes you can put those in he bung. It has been a while since I read Prowler's post, but I believe that may have been in regard to using the woven plastic plugs that are really meant to cap STILL solutions, not ones being constantly stirred. I fear that using those while the starter is on a stir plate may be problematic because there is a high potential that along the way some air from the room will be drawn in. These types of "plugs" are not rated for sterile (.45 micron or less) filtration. From looking at them I would guess that they are in the 25 micron area or greater. When there is fermentation taking place in the vessel that is capped with one of these there would be no air ingress but rather CO2 would be pusing outward. Under those circumstances that would work great. But remember that when preparing starters the goal is REPRODUCTION, not fermentation. If your starters produce much krausen, there is fermentation taking place. When the yeast are in reproduction phase they produce very little CO2... this is why greater protection is required.

Q: 2. I typically get yeast slurry from a local brewpub. Should this be pitched as is with no wort aeration?


I am going to make some assumtions here... 1) you don't know the cell count, 2) you don't know the cell vitality/viability ratio and 3) you just filled a container until it was full of trub. (all of these would be normal for most brewpub yeast donations) So, that leads to the end assumption that you most likely received a very large pitch volume for a typical 5 or 10 gallon homebrew batch. Hopefully the viable/vital cell proportion was equally large and the slurry was mostly just yeast, not proteins/vegetal matter from the primary fermentation... that is what I meant by that I hoped the brewer did a trub dump during very early fermentation.

So... the answer would be based on how soon the trub was collected after fermentation had been completed at the pub and whether the beer had been "crashed" following fermentation. If you got the trub from an active fermentation (hopefully the brewer had dumped the trub from the fermenter after fermentation had begun!) The yeast would have been ready to go, no aeration required. If the yeast was harvested directly after fermentation had ceased while the beer was still at fermentation temperature, it probably still would have been OK to pitch and let it fly. Now... if the beer was crash cooled or step cooled after fermentation (very common at breweries with conical fermenters) you would need to prepare a starter with a low gravity starter solution and aerate (with sterile filtered air, not O2!) over night. This is to kick the yeast out of dormancy and start them back into the reproductive phase. Once this occurs you can pitch them in un-oxygenated wort.

Always remember... IT IS THE YEAST THAT NEEDS OXYGEN, NOT THE WORT. The oxygen uptake phase of yeast rarely exceeds 20 minutes and the volume of yeast to wort in a fermenter is disproportionately high. Aerating a full volume wort is not necessary if you properly aerated the starter. In the professional brewing world wort is oxygenated in line for only a short period for this reason. It is impractical to try to aerate a 15 bbl. pitch! Besides, in a new professional pitch, the cell volume and vitality is known and is guaranteed to be appropriate for the beer gravity and volume into which it is being pitched (assuming the brewer ordered it correctly). This is why it is required to introduce the O2 into the wort, sort of why you would do the same with pub harvested yeast that was crash or step cooled... they are dormant.


Hope this was of help!
Make your next beer (or spirit) a local one!!!!

Eric Watson
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Cayman Islands
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Postby steinbierz » Wed Nov 29, 2006 6:15 pm

Eric,

I'm pretty blown away with the detail of your answers...thanks for taking the time to fully explain.

I am certainly appreciative of my local brewer providing me and another brewing buddy with yeast but it kind of struck a nerve that I hadn't asked enough questions about the yeast. I am a pretty anal brewer but I accepted the yeast on faith alone. The brewer is a great guy and I trust that he would not intentionally give us bad product but it would also be educational for us to query him as to what it was that we were actually getting.

Regarding RIMS/HERMS...I am well aware of the debate (if you have one you swear by it, if you don't your a !@#$ fool for wasting your money on one). I made excellent extract beer way back when and in fact took a Best of Show with an extract APA. I moved up to all-graining in a Gott cooler mash tun, on to a gravity tower system with a Sanke mash tun, modified it to a direct-fired RIMS, and now to a HERMS. All along I have made the changes because, having an engineering background, I love to tinker with stuff. I have as much fun out in my brewery trying to figure out what little gadget (or big gadget) to make next as I do brewing sometimes. However, I have said all along that it isn't the equipment, its the brewer (and the ingredients, process, etc.). However, your comments may make me rethink how long I actually recirculate but I will still use the HERMS for temperature control...and dammit, the beer tastes great! ;)

Once again, thanks for the very informative post.
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More yeast questions.

Postby firstchair » Wed Dec 06, 2006 12:21 pm

I have never entered into one of these discussions before so I hope I'm doing right. Just some quick question

1. Does it make sense to add some yeast nutrient and energizer to our 5 Plato starters just to make sure the yeast has enough nutrient?

2. Would you change any part of the procedure to accommodate big beers?

3. How would you change the process to accommodate meads?

4. I'm planning to brew an 15 gallon batch of 18 Plato foreign style stout (Dragon knockoff). I was planning to brew a 5 gallon batch of 10 plato English southern brown and pitching the dregs. Would you recommend this and what should I do to maximize the yeast health of the dregs?
Thanks for all your help
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Attenuation

Postby jctull » Sat Dec 30, 2006 6:07 pm

Eric,

I am intrigued by your recommendations. In particular, I would like to know your thoughts on the effect of high-temperature mashing on attenuation. My knowledge suggests that the enzymatic activity of a 158F mash would favor a less fermentable wort that will retain higher sugars post-ferment.

My research on the topic today pulled up this paper:
http://www.asbcnet.org/journal/pdfs/200 ... 3-0185.pdf
(They appeared to have secured their website.)

It is worth noting that they authors found considerable differences in levels of FAN, attenuation, various sugar levels, and other variables with different mash-in regimes. Specifically, "the mash-in temperature that attained the highest level of fermentability (AAL) and fermentable sugar production was 65
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