Want to brew my first iipa

[Seven]

Anyone who believes that yeast cells need dissolved oxygen should read the "Olive Oil" paper (http://www.brewcrazy.com/hull-olive-oil-thesis.pdf).

As I stated earlier, yeast cells do not respire in the presence of glucose concentrations above the Crabtree threshold; however, they will switch into respirative reproduction mode after consuming all of the available glucose and all of the sugars that they can reduce to glucose if dissolved oxygen remains in solution. The phenomenon is known as diauxic shift. During diauxic shift yeast cells use ethanol as their carbon source. Diauxic shift is one of the reasons why we do not want to aerate green beer.

www.ncbi.nlm.nih.gov/pmc/articles/PMC3133784/

"The preferred source of carbon and energy for yeast cells is glucose. When yeast cells are grown in liquid cultures, they metabolize glucose predominantly by glycolysis, releasing ethanol in the medium. When glucose becomes limiting, the cells enter diauxic shift characterized by decreased growth rate and by switching metabolism from glycolysis to aerobic utilization of ethanol. "

The shift from anaerobic glycolysis (fermentation) to aerobic utilization of ethanol as a carbon source is why using pure O2 without a dissolved O2 meter is like playing Russian roulette with one's beer.

Just out of curiosity, how many high gravity batches have you brewed using the olive oil method and what were the results?

 

[CryoEng]

Me. About 20 brews.

I let the wort run down the inside of the carboy, then add a small drop of olive oil.

I also pitch enough yeast.

I get good final gravity and the beers have turned out nice.

From any tech info I can find, there's no good oxygenation of the wort at any time of the process.

Cheers!

 

[Yooper]

Some of the info IlIkebeer and I are referring to comes from the new(ish) book, "Yeast" by Chris White and Jamil Zainasheff.

It's a great read, and I recommend it to all brewers.

One of the things I read last night talked about olive oil vs oxygen and that while the FG was the same, the esters and sterols produced were not. I don't have the book in front of me right now, but I do believe that the jist was that the flavor of a traditionally oxygenated wort was preferable, at last in the succeeding generations.

I will agree that oxygen vs no oxygen would be generally preferable- but I really don't know if at a homebrew level with no dissolved oxygen meter that I could tell the difference between 8 ppm of 02 vs 10 ppm. And the graph linked to above states no differences in FG. Of course, things like esters are important to the final flavor of the beer and perhaps there would be slightly less esters with 10 ppm.

For me, I make most of my beers under 1.075 most of the time. Splashing/shaking/venturi devices work great for me and I get a huge foamy head on my wort before pitching. I also pitch the proper amount of yeast at the proper temperature and ferment at the proper temperature. It's a combination of all these things that combine to make a great beer, and so I would say that an 02 system would be cool to have, but for me it would be another thing to sanitize and mess around with. My March pumps send my wort at a high velocity into the fermenter, so I haven't worried much at all about underoxygenation.

 

[CryoEng]

It's a combination of all these things that combine to make a great beer...

Agreed.

Yeah, most of my brews start under 1.070.

I know I'd never detect the difference in the esters and sterols from either method.

Using an extra 1/4 ounce of different hops for 5 more minutes, or mashing 3 degrees cooler/warmer or adding 4 ounces too much crystal, etc., etc., etc., will have greater noticeable impact. To me anyway.

I (and most home brewers) simply can't control the process well enough. We're in the small numbers (batch size) statistics and the variables are many. Some are strong.

I just figure I'll give the little buggers their fat and not even think/worry about O2. So far, no complaints from them.

Cheers!

 

[thisisbeer]

I have read somewhere about Sierra Nevada using the olive oil method. That really discouraged home brewers from using it. They said with the small amount they used in full commercial batches would be hard to duplicate on a home brew scale. Even a drop would be using to much by a large amount and that it could negatively effect the beer. I need to dig that up somewhere....

But if it works there are no issues. I have never tried the oil method. I am curious about it.

 

[EarlyAmateurZymurgist]

Just out of curiosity, how many high gravity batches have you brewed using the olive oil method and what were the results?

Using olive oil at the level that I brew these days is impractical because the amount needed is so small that it would be difficult to measure (I currently brew 1 to 3-gallon batches).

The point that I was trying to make is that yeast cells do not respire in the presence of glucose levels higher than the Crabtree threshold (which all beer worts exceed). The reason yeast cells need oxygen at the beginning of fermentation is for sterol and unsaturated fatty acid (UFA) biosynthesis. If the yeast culture pitched into one's wort has adequate stores of these compounds and the number cells pitched is large enough that maximum cell density is only a couple of generations away from the mother cells, then dissolved oxygen requirements drop radically (the reason why properly pitched dry yeast does not require aeration). If we supply sterols and UFAs directly to the yeast, the need to aerate goes away. This information is backed up by peer-reviewed science, as well as by an experiment that was performed at White Labs (http://www.whitelabs.com/blog/olive-oil-vs-aeration-experiment).

We need to remember that fermentation is an anaerobic process (known formally as anaerobic glycolysis). All cell reproduction in normal and high gravity worts is anaerobic. The ability of a yeast culture to reach terminal gravity in a high gravity wort is a function of the sterol and UFA reserves found in the mother cells and how close to maximum cell density a culture is when pitched. The mother cells share their sterol and UFA reserves with all of their offspring. As sterols and UFA reserves fall, yeast cell membranes become less permeable. In essence, yeast cells do not stop fermenting because there is not enough dissolved oxygen. Yeast cells stop fermenting because they can no longer pass nutrients and waste products through their cell walls. It's the same reason why yeast cells stop fermenting above a certain alcohol level. However, in that case, the cells lose their ability to pass nutrients and waste products through their cell walls because they become dehydrated due to the fact that ethanol is highly hygroscopic.

Needing to aerate wort with pure oxygen in order to reach terminal gravity is a sign that one is pitching too little yeast. The oxygen that is not taken up by the mother cells is taken up by the daughter cells in order to support greater numbers of divisions. I do not have attenuation problems. I have over-attenuation problems because I pitch a large number of healthy cells into my beers. Most of my beers run 7%+ ABV, which isn't exactly low gravity beer. Other than the miniscule amount of oxygen that my wort picks up while draining from my kettle into one of my primary fermentation vessels, I do not aerate my wort at all. All I do is pitch a yeast culture that was grown under aerobic conditions; therefore, the culture is very healthy going into the primary.

I have included a few yeast-related photos from my brewery for those who may believe that I am here to troll HBT. The reason why I came to this forum in the first place is because it appears to be epicenter of the yeast rinsing movement on the Internet. Those who have read my postings know I how I feel about the voodoo-laden process of rinsing yeast with boiled tap water.


My Current Culture Collection (none of the cultures are Wyeast or White Labs cultures)

Cultures that I Isolated (Plated) from Brewery Sources

The culture tube with "HAR" on the Parafilm in the photo shown above is Harpoon's yeast culture. The "GEN:1" on some of slants denotes that a slant was inoculated directly from a plated cultured (I am in the process of rebuilding my bank after a long hiatus from the hobby). The number to right of the colon is incremented every time I subculture a slant to another blank slant (i.e., the next subculture will be GEN:2). This number is not a yeast generation number. It is a culture generation number. Each slant was inoculated with one or more yeast colonies from a plate, each of which was the offspring of a single yeast cell.

Culture Collection Cultures

The cultures shown above were acquired from major research-oriented culture collections. These yeast cultures originally cost between $71.00 and $300.00 each. None are available from Wyeast, White Labs, or any other commercial yeast source. I like to purchase cultures from collections on solid media (i.e., plates or slants). However, some collections only supply yeast in lyophilized form in glass ampules. A lyophilized culture looks like a white spec of dust.

A Plated Yeast Culture

The plate shown above contains Scottish and Newcastle's Tyneside culture. The well-isolated round colonies are all each the offspring of a single yeast cell; therefore, they are single-cell isolates. Single-cell isolates are also known as pure cultures (Emil Hansen pioneered single-cell isolation at Carlsberg Laboratory). I streaked this plate a few days ago. Only well-isolated colonies that exhibit good morphology will be used to inoculate slants using aseptic transfer technique (one colony per slant for this culture).

40ml Sterile Starters

The container shown above contains 100ml media bottles that each contain 40mls of absolutely sterile wort. The 40mls of media in each bottle was autoclaved in the bottle. I use these bottles when propagating a yeast culture from a slant. Using absolutely sterile wort to propagate yeast from a slant allows me to start a culture using only a loopful or two of yeast without fear of infection.

A 40ml Sterile Starter

The bubbles in the starter shown above are from moving it. The media is 100% sterile because it was autoclaved for 15 minutes at temperature and pressure levels necessary to achieve sterilization. The stripes on the autoclave tape shown below indicate that these levels were achieved inside of my pressure cooker. This piece of autoclave tape basically looked like plain old masking tape before the media bottles were placed into my pressure cooker (it was attached to one of the bottles).

In closing, while most brewers use yeast to brew, brewing is something that I do to get to play with yeast. Playing with brewer's yeast is what kept me heavily engaged in the hobby for the decade spanning early 1993 through early 2003, and it's what brought me back to the hobby after a ten and a half year hiatus.

 

[norsk]

I must be the luckiest person in the world. 90% of my beers are north of 1.090, rarely use O2, prefer filling one bucket from another bucket times 4 for aeration, and the beer always comes out great...

 

[Soldevi]

EarlyAmateurZymurgist,

That is impressive. You say that you don't aerate at all, do you pitch your yeast according to the well known calculators? Or do you pitch at a higher amount?
1.25m/ml or greater?

 

[g-star]

I too would also be interested to hear what your pitch rate is EAZ.

You present a lot of sound theory, but I wonder how much of this (sufficient sterol production via areobically grown starters) is observed in practice for the average homebrewer. I would also like to know at what concentration O2 becomes detrimental (as you indicated in post #25) for the home and professional brewers around the world who follow this well-established practice.

It would seem that if the commonly accepted 8-12ppm concentration of O2 prior to pitching would be good practice to ensure sufficient sterol production, if that concentration is below the threshold for "the shift from anaerobic glycolysis (fermentation) to aerobic utilization of ethanol as a carbon source".

Thanks.

 

[EarlyAmateurZymurgist]

You say that you don't aerate at all, do you pitch your yeast according to the well known calculators? Or do you pitch at a higher amount?
1.25m/ml or greater?

Based on my current yeast propagation method, I would estimate that I pitch around 1.1m very active cells per milliliter per degree Plato for ales. One would basically have to pitch a fresh vial of White Labs yeast per gallon in order to achieve that pitching rate with a 17.5P (1.072) wort. Pitching a single vial of White Labs yeast into five gallons of 12P (1.048) wort equates to less than 0.5m cells per milliliter per degree Plato, and 0.3m cells per milliliter per degree Plato with a 17.5P wort (and that's being very generous with the cell count in a White Labs vial). The pitching rates that the on-line calculators give are based on 0.75 million cells per milliliter per degree Plato for ales.

 

[EarlyAmateurZymurgist]

You present a lot of sound theory, but I wonder how much of this (sufficient sterol production via areobically grown starters) is observed in practice for the average homebrewer. I would also like to know at what concentration O2 becomes detrimental (as you indicated in post #25) for the home and professional brewers around the world who follow this well-established practice.

It would seem that if the commonly accepted 8-12ppm concentration of O2 prior to pitching would be good practice to ensure sufficient sterol production, if that concentration is below the threshold for "the shift from anaerobic glycolysis (fermentation) to aerobic utilization of ethanol as a carbon source".

The problem stems from not knowing how much, if any, oxygen remains in solution after glucose and all sugars that can be reduced to glucose have been metabolized by the yeast culture. If excess O2 was not a problem for breweries, then funding for research into ways to eliminate aeration would dry up. The New Belgium study forced a lot of brewing scientists to reassess what they knew about oxygen requirements.

Everything that I know about brewing yeast is the result of scratching a personal itch. In the early days, being able to culture yeast was simply a means to an end because the dried yeast cultures that were available at the time were hit and miss (anyone remember the old Red Star beer yeast?), and Wyeast offered only a handful of cultures that were often difficult to obtain (White Labs did not exist). I was driven to research the effects of excessive O2 on beer flavor because my beers were tasting funky at the end of fermentation when I was using pure O2. Every beer that I oxygenated with pure O2 had a note in the finish that tasted like oxidized alcohol. At first, I thought that I was picking up an infection. However, the plates that I made from affected beer looked no different than those that were made from non-affected beer. The only difference was that I used pure O2 to aerate the affected beer. This discovery forced me to study the affects of diauxic shift. It was while studying diauxic shift that I made the decision to switch from aerating my wort to aerating/agitating my starters and pitching a large mass of cells at high krausen.

With that said, the only way for a brewer to know if he/she is over oxygenating his/her wort is to take dissolved O2 and gravity measurements throughout the fermentation. If there is O2 in solution after the gravity has bottomed out, then a brewer is over aerating his/her wort. I have been saving to purchase a lab-grade stereoscopic microscope to replace the one that I sold back in 2004 as well as few other things that I need for my brewery (Christmas isn't the best time of year to attempt to save money). However, I plan to purchase a dissolved O2 meter after I get these purchases out of the way. I want to know for certain if the oxidized flavors that I was tasting while using pure O2 were simply the result of oxidative chemical reactions that occurred while high-levels of dissolved oxygen were in contact with the wort, diauxic shift, or something entirely different.

As I stated earlier, many amateur brewers underpitch, which increases the need the for dissolved oxygen because the culture has to go through one or more additional divisions in order to reach maximum cell density (the cells that they pitch may not be in top shape as well). The most frequently used pitching calculators on the Internet are based on a pitching rate of 0.75 million cells per milliliter for ales, which is a low pitching rate. Pitching a single White Labs vial directly into five gallons of wort with a gravity of 1.048 or higher is underpitching by at least 50%.

In the end, what matters is if a brewer is happy with his/her results. My method works very well for me. However, I have complete control over my yeast cultures (or at least as much control as mother nature will allow). The average amateur brewer has no desire to go through what I do to use yeast.