Thursday, August 21, 2014

Microorganisms In Your Beer?

 Bacteria and fungi are two words that make home brewers around the world cringe. However, what would you say if I told you that there are good bacteria and fungi in the brewing world? Most of you would think that I am absolutely insane, but I know there are a few fellow microbiology oriented home brewers out there that have a grin on their face. Now let me tell you why.

As home brewers you know that there are numerous different kinds of yeast out there, but for our purposes we will stick to two broad strains. Saccharomyces cerevisiae is a top fermenting yeast that gives rise to ales and Saccharomyces carlsbergensis is a bottom fermenting yeast that gives rise to lagers and other beers. I could go through all the organization of these two yeasts but lets keep it simple; these are both fungi. In fact all yeast are fungi! You would actually be surprised how many food products out there are made with different kinds of fungi. If anyone is especially interested in this subject I would highly recommend looking up industrial fungal use on a mycology (the study of fungi) site or checking out a book on the subject from your local library.

Now that I have introduced the good guys lets introduce the bad ones. There are four different types of spoilage patterns among beer: ropiness, sarcinae sickness, sourness and turbidity. Ropiness is when you pour your beer and it comes out in an oily stream. This can be caused by a number of organisms but the most common are Acetobacter or Lactobacillus. P. cerevisiae is the cause of sarcinae sickness, which is where a beer forms a honey-like odor that competes with the aroma of the beer. The cause of this is the production of diacetyl which some people describe as a green apple taste. Sourness is generally caused by Acetobacter species when they convert ethanol into acetic acid giving you a sourness or even a taste of vinegar. Turbidity can be caused by two organims; a bacteria by the name of Zymomonas anaerobia and any one of the Saccharomyces species of yeast.Turbidity is a look of the beer where is is more cloudy than expected. This is because massive amounts of the bacteria or yeast can be growing out of control in the beer after it has been bottled. Because the bottled beer is still a good source or nutrients, it gives the microorganisms a perfect location to grow.

It is time for our home brewing public service announcement that you have heard a million times and you will hear a million more before your home brewing days are over. The MOST important part of the brew day is sanitation. You don't know what microorganisms have landed on your equipment and you need to make sure that they do not get in and spoil the batch of beer you have been working so hard to create. For those of you who do not have a science background, looking up sterile technique is a good start to making sure that you do not have any contamination on brew day. Remember, sanitization and sterilization are two different things and both must be done (in the correct order) so that spoilage organisms like the ones listed above do not enter your brew.

We will leave it at this for right now but be on the lookout for Microorganisms In Your Beer? Part 2 coming soon! Until then, cheers!

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