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Boiling Yeast?

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Am I able to use expired/unwanted yest as yeast nutrient? Add to the boil for 10-15 then cool wort and pitch fresh yeast as normal? Is there any benefit?

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yes. yes. yes and no.

 

old or unwanted yeast can be boiled to kill it. i start timing when it reaches a low boil and then let it cook for about 5 minutes or so. then i flame out, cover and cool.  alternatively you can add it to your boil and cook like that. you want the old yeast killed especially if you are brewing using a yeast with a desired flavor profile. you dont want any of the crud yeast surviving and potentially out-eating the good yeast.

 

wort has tons of nutrients all on its own. if the yeast are relatively fresh (and you pitch enough) and not subjected to stress like heat/cold/or very high gravity they will do just fine. adding nutrient in the form of dead cells is like serving dessert at the start of a meal. the yeast will love you for it.. but will tuck into the dead cells or other nutrient first before tucking into the wort. any  time i add nutrient be it yeast , raisins, sugar, etc...  i get a little lag time added then the yeast go nuts. so absolutely not necessary in most cases.

 

when i use tired old yeast out of necessity, or i am making something with a very high o.g. i add nutrient.   i will also add a little more toward the midpoint of a high grav fermentation. example:  making a belgian dubbel or trippel. these typically call for beet sugar additions. i do step feedings to keep the yeast from  pigging out on junk food before they start working on the wort. the staged feedings keep them active and happy, and relatively stress free.

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9 hours ago, zorak1066 said:

yes. yes. yes and no.

 

old or unwanted yeast can be boiled to kill it. i start timing when it reaches a low boil and then let it cook for about 5 minutes or so. then i flame out, cover and cool.  alternatively you can add it to your boil and cook like that. you want the old yeast killed especially if you are brewing using a yeast with a desired flavor profile. you dont want any of the crud yeast surviving and potentially out-eating the good yeast.

 

wort has tons of nutrients all on its own. if the yeast are relatively fresh (and you pitch enough) and not subjected to stress like heat/cold/or very high gravity they will do just fine. adding nutrient in the form of dead cells is like serving dessert at the start of a meal. the yeast will love you for it.. but will tuck into the dead cells or other nutrient first before tucking into the wort. any  time i add nutrient be it yeast , raisins, sugar, etc...  i get a little lag time added then the yeast go nuts. so absolutely not necessary in most cases.

 

when i use tired old yeast out of necessity, or i am making something with a very high o.g. i add nutrient.   i will also add a little more toward the midpoint of a high grav fermentation. example:  making a belgian dubbel or trippel. these typically call for beet sugar additions. i do step feedings to keep the yeast from  pigging out on junk food before they start working on the wort. the staged feedings keep them active and happy, and relatively stress free.

 

When you use tired old yeast, would it be better to make a starter?

 

Talking of yeasts, there was an interesting comment on effect of rapid temperature change on yeast from one manufacturer data sheet I read (Lallemand). On reconstituting yeast, they wanted you to do it at 85-95 deg. then cool gradually to wort temp 5 min per 10 deg, using small amounts of cool wort.. Their assertion was not that the cells got killed, but that rapid temp changes cause UNWANTED MUTATIONS, potentially causing off flavors.

 

I usually just sprinkle it onto the wort though it seems to work but I am not sure of the impact on the yeast rehydration process - and how much better my beer would be if I followed their process. 

 

***************************************************** Some Yeast Facts *****************************************************

Lallemand data sheets are interesting to me, for example they illustrate difference between the yeasts and why they behave differently.

 

Why choice of yeast affects beer sweetness and attenuation.

e.g. London which they say will not eat maltotriose sugar, leading to the sweeter beers, 

"London does not utilize the sugar maltotriose (a molecule composed of 3 glucose units). Maltotriose comprises an average of 10-15% of total sugar in all-malt worts. The result will be fuller body and residual sweetness in the beer. Be advised to adjust gravities and mash temperatures according to desired result. "

https://www.lallemandbrewing.com/en/canada/product-details/london-esb-english-style-ale-yeast/

 

(If you pick the yeast in Brewers Friend calculator it does this compensation for yeast sugar usage  for you.)

 

or Belle Saison which they say is a variety  diastaticus.

"Saccharomyces cerevisiae var. diastaticus strains are capable of utilizing some types of dextrins. Extra care should be taken to ensure proper cleaning procedures are in place to avoid any cross-contamination with other brews. "

https://www.lallemandbrewing.com/wp-content/uploads/2017/03/TDS_LALBREW_PREM_BELLESAISON_ENGLISH_DIGITAL.pdf

 

I put some by accident in a brew of Sticky Wicket stout and it was very dry tasting.

 

 

Choice of yeast affects Dry Hopping

Also they describe the different effects for dry hopping incising different yeasts. Some yeasts produce chemicals that accentuate hop flavor.

https://www.lallemandbrewing.com/wp-content/uploads/2017/03/LAL-bestpractices-Biotransformation-digital-1.pdf

 

This is a fascinating paper detailing effect of various hops and transformation of the desired flavors, and includes the use of coriander as a source of chemicals for yeast transformation  into similar flavors. Don't be put off by the chemistry speak, skim to find the conclusions (unless you are chemistry geek lol).

https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.2050-0416.2010.tb00428.x

 

 

Quote

Rehydration guidelines are quite simple and present a much lower risk of contamination than a starter, which is unnecessary when using the recommended pitch rate of dried active yeast.
Sprinkle the yeast on the surface of 10 times its weight in clean, sterilized water at 30-35°C (86-95F). Do not use wort, or distilled or reverse osmosis water, as loss in viability may result. Stir gently, leave undisturbed for 15 minutes, then stir to suspend yeast completely. Leave it to rest for 5 more minutes at 30-35°C.
Without delay, adjust the temperature to that of the wort by mixing aliquots of wort with the rehydrated yeast. Wort should be added in 5 minute intervals and taking care not to lower the temperature by more than 10°C at a time. Temperature shock of >10°C will cause formation of petite mutants leading to extended or incomplete fermentation and possible formation of undesirable flavors. Do not allow attemperation to be carried out by natural heat loss. This will take too long and could result in loss of viability or vitality.
Inoculate without delay into cooled wort in the fermenter. Belle Saison yeast has been conditioned to survive rehydration. The yeast contains an adequate reserve of carbohydrates and unsaturated fatty acids to achieve active growth. It is unnecessary to aerate wort upon first use.

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on rehydrating yeast... i vaguely recall one of our old guard stating that anything beyond a 10-15 degree difference in temp from the rehydrating solution and the current wort temp could cause thermal shock.  an unrelated point:  when im doing a really high gravity ferment like hobo wine , after rehydrating i'll temper the yeast to the gravity by adding about a teaspoon of the must, stirring... let it sit for a couple minutes.. .repeat then after a few times i'll pitch.  dont know about mutants. how would one know? ive never had really off fermentations that i can think of so if ive ever got mutant yeast cells they seem to do the same job.

 

for really old yeast? yep. a starter would be ideal...  ive got some really old pasteur red that will get a starter on my next hobo wine. it's way past best by date and the must will be high gravity.   sometimes though i just dont have the motivation to run a starter for a day or two. getting that darn stir bar to stay put sometimes drives me nutty.

 

yeast today are pretty amazing and really hardy. you can really be careless with them and they will still make good beer.

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