Author Topic: Yeast Starter Pitch Going Nuts  (Read 2030 times)

RPIScotty

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Re: Yeast Starter Pitch Going Nuts
« Reply #15 on: April 27, 2016, 01:25:09 AM »
I was thinking the respiration cycle is roughly 72 hours and my yeast needed all the oxygen it could get during that period.  Anyway, just me thinking out load.

There is no true respiration cycle with brewing yeast cultures because they are Crabtree positive.  All reproduction is fermentative.  What the yeast cells do is shunt O2 and a percentage of the carbon in the wort to the respiratory metabolic pathway for the biosynthesis of ergosterol and unsaturated fatty acids.  The yeast culture in the photo shown above is a Yorkshire square strain (NCYC 1333) that has an O2 demand that is so high that it cannot be fully met with pure O2 saturated wort.  Very high O2 demand is characteristic of Yorkshire strains, which is why they aerate actively fermenting wort with a shower head looking device known as a fish tail in Yorkshire breweries.  You can see a fish tail in action in this video: https://youtu.be/KJmLNj14C_w?t=12s

Yorkshire would be Sam Smiths?

Offline Saccharomyces

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Re: Yeast Starter Pitch Going Nuts
« Reply #16 on: April 27, 2016, 01:31:33 AM »
Good point. If a 3-piece airlock is used then one would be safe.  But, is there not a chance, prior to fermentation producing positive pressure, that if one uses an S-shaped airlock a temperature drop in the wort could lead to negative pressure suckback of air/dust from outside the fermenter into the wort?

Believe it or not, contamination via the airlock will not happen because the temperature drop does not create enough suction to draw dust into the fermentation vessel.  Louis Pasteur demonstrated this principle when he debunked the theory of spontaneous generation in 1859 using what is known today as Pasteur flask.  A Pasteur flask is flask with an S-shaped neck that is not unlike an S-shaped airlock.  Here's a webpage that outlines Pasteur's experiment: http://faculty.sdmiramar.edu/dtrubovitz/micro/history/Pasteur.html

I shot the photo shown below a couple of years ago to demonstrate how blank slants can be prepared in a home kitchen.  The slants were removed from the pressure cooker when they molten hot and laid at an angle with their caps loose to cool.  The temperature drop that the slants experienced was much greater and rapid than the temperature drop that a fermentation vessel experiences.  Yet, some of the slants shown in the photo were 18 months old when I subcultured the last of the cultures.  Not one of the blank slants or the cultures that were grown on the slants exhibited signs of contamination.



« Last Edit: April 28, 2016, 01:39:26 AM by Saccharomyces »

Offline Saccharomyces

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Re: Yeast Starter Pitch Going Nuts
« Reply #17 on: April 27, 2016, 01:43:44 AM »
Yorkshire would be Sam Smiths?

Samuel Smith is one of many historical Yorkshire breweries. Theaktson's is in North Yorkshire.  The Exchange Brewery (formerly Tennant's Brewery) in Sheffield, South Yorkshire was a major Yorkshire Brewery.  The yeast culture known as Ringwood in the United States was originally sourced from a Yorkshire Brewery known as Webster's Brewery in Halifax, West Riding of Yorkshire, which is why all of the Peter Austin designed/Alan Pugsley-installed breweries use a fish tail to aerate beer on the second day.  Peter Austin acquired Ringwood from the Hull Brewery, in East Yorkshire, which acquired the culture from Webster's Brewery.  Timothy Taylor is also a Yorkshire Brewery.  Timothy Taylor is the source of Wyeast 1469.

Offline JT

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Re: Yeast Starter Pitch Going Nuts
« Reply #18 on: April 27, 2016, 04:15:55 AM »
Good to see you back!

Offline dilluh98

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Re: Yeast Starter Pitch Going Nuts
« Reply #19 on: April 27, 2016, 05:47:51 PM »
Good to see you back!

I second that.  :)