Does copper kill yeast?

[bobsbeer]

I have been reading various articles on the beneficial properties of copper as an anti microbial product. This is gaining popularity especially in the healthcare setting where copper is being used in commonly touched surfaces to kill bacteria and other nasties. There appears to be a good body of evidence to support this. Which brings me on to brewing.

I have seen a number of examples of people using copper pipe in FV's as cooling/heating coils. Will this have a negative impact on the yeast? I suspect it will, although given the high concentration of yeast in an active ferment how much impact is debatable. But in other areas where the antimicrobial properties may have a beneficial impact is in recirc pipes such as HERMS, counterflow chillers etc. Bacteria will not be able to colonise the internal surfaces of coils between brews, even though a very efficient growth medium may be present.

Maybe we need to be selective where we use copper in our systems? Shiney may not always be best.

 

[pittsy]

i would of thought the use of copper for this reason would be a good thing , after all the yeast is pitched after using copper and not while using it .

 

[pittsy]

p.s the old school brewers nearly always used copper boilesr and they made mostly good beer .

 

[bobsbeer]

That was my thinking. Using copper in any pre fermentation applications would appear to be good in terms of ensuring nasties are kept at bay. But brewing is not just about yeast. We use enzymes in the mash for their beneficial properties to extract or breakdown the sugars in the malt. These would also be affected if copper were used in abundance in the mash process. I have seen some very elaborate mash filters made out of copper. I use one myself. Does this have a negative impact on the mash? Again probably yes, but marginal given the contact area. Just something to think about. Old traditional coppers would again have the beneficial properties, but as we boil the wort, this denatures and intentionally kills off any microbial or enzymatic activity.

 

[ayepee]

To quote from George Fix ( Principles of Brewing Science)

"Yeasts also require trace quantities of copper (0.012ppm)"

Also when I started work most of the FVs at the brewery were copper squares and we never had any yeast problems.

 

[bobsbeer]

Yeasts also require trace quantities of copper (0.012ppm)

That is probably true, but an excess of copper can be lethal. One paper I read discussed dry copper contact, which destroyed the cell membrane in S. cerevisiae. Causing death of the cells within minutes. Moist contact did also destroy the cells, however contact time and destruction was longer. It would appear that direct contact with copper is the culprit. So the cells in contact with the metal surface would be killed off. Using Copper Squares the death rate of the cells was probably less than the multiplication experienced by the cells in the central part of the vessel, resulting in no noticeable reduction in yeast activity. Here is one paper discussing the subject HERE Although there are quite a few available, I have yet to come across one specific to brewing. Although in modern practice most commercial brewers will use nearly 100% stainless steel in their plants, so this issue is not so important to them. We on the other hand use copper pipes quite frequently.

 

[mabrungard]

Some copper metal in your brewing system is a good addition. There have been many examples of breweries going 'all stainless' and then having problems with their brewing. The inclusion of minor copper components has been utilized to provide the trace copper content to the brewing water. One important function of trace copper in the brewing water is the reduction of sulfides from the finished beers. If you have sulfury aromas or flavors, including some bare copper metal contact with the wort is helpful in providing that trace copper content. Including a foot or so of copper tubing in the system is wise. If necessary, you can just place a piece of copper pipe in the boil kettle to deliver the trace copper to the wort.

Be aware that yeast will uptake virtually all dissolved copper from wort and will leave the finished beer copper-free. The state of California conducted an extensive analysis of copper in beer and found this result.

 

[bobsbeer]

Interesting. I suppose it's getting the right balance of materials. I work in health care so the upsurge of interest in copper as an antibacterial substance made me think about my use in brewing and the possible benefits and downsides. At least I know my copper counter chiller is safe. I wonder if it needs steralising before use? Not sure I would want to risk it, but it makes you wonder.