How can I remove or neutralize SO2 in my homemade yeast culture solution?

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Discussion Overview

The discussion revolves around the challenges of culturing yeast for home-brewing, specifically focusing on the presence of sulfur dioxide (SO2) as a preservative in a homemade yeast culture solution derived from wholegrain cereal. Participants explore methods to remove or neutralize SO2 while considering the implications for yeast viability and culture stability.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the necessity of SO2 in the culture medium and the purpose of culturing yeast, suggesting that professionals struggle with maintaining stable yeast cultures.
  • Another participant emphasizes the difficulty of keeping yeast cultures uncontaminated and notes that the substrate used for yeast culture is typically not the same as that used for brewing.
  • A participant shares their experience with brewing, indicating that their growth media consisted of dry malt extract, yeast sediment, and tap water, which worked well without SO2.
  • Concerns are raised about the potential impact of using alkalis to neutralize SO2 on yeast viability, with no clear suggestions provided on effective methods.
  • One participant suggests that using preservative-free grain might be a better approach for future batches.

Areas of Agreement / Disagreement

Participants express varying levels of concern regarding the use of SO2 and the challenges of culturing yeast, with no consensus on the best method to neutralize SO2 or the appropriateness of the current approach.

Contextual Notes

Participants highlight the importance of sterile techniques and the control of growth media to prevent contamination, indicating that the discussion is rooted in practical brewing experiences and challenges.

xtracx
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Hi,
recently, I've gotten interested in culturing yeast for home-brewing. To keep the costs on the down low, I've made my culture solution (broth) from wholegrain cereal (containing essentil elements & malt extract). Problem is, this 'culture' contains SO2 as a preservative and obviously all micro-0rganisms cannot survive with SO2 around.

Hence, my question is how to removeor neutralise the SO2 in my solution. If possible it should be using home-based solutions to neutralise it. I was thinking of Alkalis, but I'm not too sure on how that will affect the yeast.

Any suggestions?


Thanks
 
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I've sort of avoided this thread.

Um. Why do you have SO2 in your culture medium? And more important why are you culturing yeast?

If you can show me why you are doing what you seem to be doing maybe I can dredge up some ancient memories to help.

As an aside - professionals have trouble culturing and maintaining a genetically stable yeast culture. Not to mention invader bacteria.
 
It sounds like xtracx is interested in culturing yeast to be used for home brewing. That way I read this question, the SO2 was used as a preservative in the whole grain cereal.

jim mcnamara said:
I've sort of avoided this thread.

Um. Why do you have SO2 in your culture medium? And more important why are you culturing yeast?
 
One of my colleques had a degree from UCD in brewing - he indicted that keeping yeast cultures "truw" is very hard indeed. And, normally, the substrate you use for the yeast culture is not the product used for brewing - things need to be carefully controlled, especially in terms of keeping out wild yeasts or bacteria.

And the grain used for brewing always is cleaned first to remove bacteria, preservatives and pesticides. So all of this adds up to 'what is going on' in the first post... for me. anyway.
 
jim mcnamara said:
One of my colleques had a degree from UCD in brewing - he indicted that keeping yeast cultures "truw" is very hard indeed. And, normally, the substrate you use for the yeast culture is not the product used for brewing - things need to be carefully controlled, especially in terms of keeping out wild yeasts or bacteria.

I can believe that. When I cultured isolates of specific fungi, the medium and conditions needed to be carefully controlled to exclude contaminating organisms and maintain phytopathogenicity. If Manraj is still trying to do this empirically, perhaps can find some preservative-free grain to try on the next batch. :biggrin:
 
When I used to brew, my growth media was only dry malt extract (bought at the bewing centre), some yeast sediment left from a previous batch and tap water. The sediment were mostly yeast and the yeast extract would provide some of the vitamines and amino acid needed. The tap water would provide some minerals and the chlorine would get removed by the sterilisation step.

The yeast grew very well in the medium.

As far as contamination goes, go sterile techniques and sterility of the medium and the euqipement usually prevents a lot of problem. I`ve only had 2 batches contaminated out of the 100 batches that I`ve made.
 

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