Sulfites and Brewing Yeast





First let me say thanks for participating in FOY. We may not say it enough, but it is greatly appreciated. My questions concern sulfites and brewing yeast. I started making wine before I started brewing so I am comfortable with using sulfites.

1) Do brewing yeast have the same resistance to sulfites as do commercially available wine yeasts?

-Andrew Jepeal



RESPONSE:

I have not seen any definitive work comparing the two groups of yeast to their SO2 resistance. Most yeast have a mechanism to handle some SO2. They can build up some resistance to SO2 over a period of time. I have seen some spoilage yeast such as Zygosaccharomyces grow in 1000 ppm SO2. This was in a grape juice storage at room temperature waiting to be concentrated. In the range of 30 to 100 ppm SO2, that is usually associated with the wine industry, the SO2 is usually lethal to the bacteria and inhibitory to the yeast. If it is inhibitory long enough it can become lethal.

The effectivenes of SO2 is directly related to the pH. SO2 at 3.0 pH is 10X as effective as it is at 4.0 pH. It is the molacular SO2 that counts.

For your interest there are some strains of yeast that produce up to 100 ppm SO2.

Dr. Clayton Cone

 

There appears to be some differing opinions in the brewing world if sulfite solution is effective in sanitizing brewing equipment. I normally make a solution using 12.5 grams of Pot. Meta. in 1 liter of water. Any comments on the effectiveness of this solution in sanitizing equipment? Specifically;

2) Would any brewing yeast be able to survive in a solution this strong?
3) Would any spoilage organisms you're aware of be able to?

 

RESPONSE:

12.5 grams Pot. Met. / liter. (over 7000 ppm SO2) is really hitting the organisms over the head with a sledge hammer. I am not sure what pH that would be and what would be necessary for you to get the 0.8 ppm molecular SO2 that is required to kill. Contact time and temperature are important. Complete kill is much more important to the brewing industry than it is to the wine industry.

I wish that I had an absolute answer for you. If I had to hazard a guess, I would say that 7000 ppm SO2 plus heat plus contact time would do the job especially if the solution is on the acid side.

I would be concerned about the SO2 released into the air.

Dr. Clayton Cone


4) Any comments concerning it's effectiveness compared to other sanitizing solutions used in brewing (Iodophor, Star San, etc.)

 

RESPONSES:

Iodophors are satisfactory. I prefer acid sanitizers. They not only kill but remove any film that might be left from an alkaline cleaner. A little heat helps. They also leave the surface in an acid condition which minimizes later contamination.

Dr. Clayton Cone



We use peracetic acid in the lab and it works very well. It usually comes in a 5% solution and the concentration to be used (after dilution 2-5 ml /L) is 100-250ppm. One advantage of peracetic acid is that no rinsing is required,(which might be a problem with your very high SO2 concentration you are using) just drain the vessel properly. Peracetic acid breaks down into acetic acid and oxygen, which are both not toxic.

Tobias



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