Sign in to follow this  
Followers 0
TacTicToe

Wort aeration is bad?!

6 posts in this topic

So I came across this tidbit from David Heath, not sure if any of you have heard or seen this. Apparently researchers have concluded that aerating your wort prior to pitching your yeast is bad. Check out the video and let me know what you think of this. If you think about it, it makes sense. 

 

Starts around 1:50 if you don't want to see the whole video. 

 

https://www.youtube.com/watch?v=JInakA5L864

 

Share this post


Link to post
Share on other sites

yeast need o2 at the start of fermentation for reproduction.  pitch enough and the yeast will just start eating because their numbers are high enough to do the job. pitch enough yeast and you dont need aeration. true enough i would think.

 

rehydration IS actually un-necessary with modern dry yeast... IF you pitch enough. you will likely get some osmotic shock pitching directly into wort if the wort is significantly high in gravity. cell walls are fragile on rehydration. rehydration gives the yeast a leg up on getting started quicker but again... not necessary. they will get going when they choose to. i often get activity starting in under 4 hours when rehydrating. sometimes on direct pitch, it takes 12 hrs. not a huge difference.

 

after rehydrating in water you only stir to mix. you arent aerating the yeast in the water. you aerate the COOL wort , then pitch.  stirring makes getting as many cells into the wort as possible easier. well mixed yeast = no clumping.

 

aeration of wort on the home scale does no harm prior to pitching. hotside aeration is also largely  a myth. consider large scale breweries like the colt45 plant that used to be in baltimore. huge amounts of wort flow through pipes into fermentation chambers the size of rooms and surely splash like mad until the thing is full. no harm on the big scale means no harm on the small.

 

i'm no expert but it is my understanding that the lifecycle of yeast in wort is something like this:  the cells are given food then freeze dried. the cells take up a store of nutrient before going dormant. they are then packaged. on hitting liquid they purge the contents of their cells and begin flushing with whatever liquid they are immersed in. they then take stock of the food around them and their numbers. if sufficient cells exist they skip budding and start eating.  if cell numbers are weak they start budding. budding requires o2. if you rehydrate in water, they purge and fill the cells with....water.  sg = 1.00.   drop them in wort with a sg of 1.07 and it's a bit of a shock. cells tear. you get some die off.

 

the cells then begin the budding cycle if needed and carry on. i wonder who was doing this 'research'? back in the 40s and 50s research demonstrated that cigs were actually healthy! they relaxed people. they inspired cool and calm focus etc. because you were relaxed you would live forever and be rich and happy! yay! the research was conducted by the labs sponsored by the cigarette industry.

 

again i am no scientist but in my personal observation, every single batch i have ever done of wort has been with healthy , happy yeast no matter what i did to them.. as long as i did not pitch them into really really hot wort or really really cold. i can stir, not stir, feed, not feed, hydrate, not hydrate... and if there is food and sanitation i get good results. i sometimes rehydrate.  i sometimes feed them nutrient boosts. i sometimes underpitch...sometimes over. i always have aerated my wort before pitching... and each batch has worked just fine. as for wild yeast 'getting a head start' and overpopulating the desired yeast? really? you are probably more likely to get lacto bacter transferred from your hands to the tool you stir with or even just airborn.  pitch enough healthy yeast and give them every advantage you can and they will kill wild yeast or other invaders. 

 

i could be wrong but ive only had one batch turn out bad and that was operator error... not because i aerated my wort before pitching/.

Share this post


Link to post
Share on other sites

Only one way to check this out.  Brew two identical batches side by side and only aerate one of them.  Then when both batches are ready to drink, do a blind triangle test with tasters to see which beer is preferred and if they are able to pick out the different beer.

 

I am still going to aerate.

Share this post


Link to post
Share on other sites

In a commercial brewery, they introduce oxygen into the flow of cooled wort into the fermenter.  And of course they ensure that they have the proper number of live yeast cells for fermentation.

kedogn and MRB Tim like this

Share this post


Link to post
Share on other sites
16 hours ago, BDawg62 said:

Only one way to check this out.  Brew two identical batches side by side and only aerate one of them.  Then when both batches are ready to drink, do a blind triangle test with tasters to see which beer is preferred and if they are able to pick out the different beer.

 

I am still going to aerate.

 

 

the problem with 'which batch is preferred' is it is unscientific.. entirely subjective.  better why? better to whom? how many are you surveying? the only real way to see a valuable result would be under a microscope.  do two identical batches. one with and one without aeration prior to pitching. then you would need to do a viable cell count on both batches and somehow get the numbers equal or close. the environment, temp, etc must be identical.  pitch the yeast. when fermentation starts to present signs of starting, you would then have to collect a number of samples from both batches at varying depths and locations in the fermenter just to be fair. then you would examine the yeast cells under a microscope to check viability and health.

 

how does a healthy yeast cell look compared to a sick or sugar bloated one? i dunno.  you cant even go by how aggressive the fermentation is. us04 is typically a monster. it eats like a pig and makes a huge krausen quickly for me. i usually have to worry about lid blow offs.... and sometimes it acts like a saison yeast and politely munches , taking its time.  i have an english bitter going now with us04. i pitched at 70f and brought temp down to 62f. it took off in under 12 hrs but the krausen is only an inch. it is burping out co2 at a 'normal' (for me) rate. it is in short behaving like a polite eater. it's doing its job.  does this mean that it is unhealthy because it isnt blowing off the lid like many of my other us04 batches do? no. 

 

in my experience i have noticed one indicator of unhappy or distressed yeast. they tend to make stinks. if you toss ale yeast into wine or mead must (equiv of wort), fructose and sucrose dont have much nutritional value. the yeast will complain by making really nasty sulfur smells. some wine yeasts do this too. also wine must usually is higher in gravity than beer wort. a direct pitch of ale yeast  would probably kill a large number of cells. stressed cells reproduce poorly sometimes. you probably get crappy yeast babies so to speak... which could make weird smells too.  even this is subjective because some yeasts naturally produce sulfur smells even when they are happy like certain wheat beer strains and lagers.

Brian N. likes this

Share this post


Link to post
Share on other sites

There is a lot of biochemistry going on when you pitch. Yeast are not "obligate" anaerobes and will gladly use an aerobic pathway (oxygen) to gain more energy from the maltose. As oxygen levels decrease in the wort (higher yeast cell count) they will rely upon an anaerobic, less efficient pathway that produces ethanol as a waste product. Other pathways, using different enzymes, can lead to sulfur compounds. Nearly forty years ago in grad school, I knew more, but in theory aeration of the wort gets the little guys going faster. 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0