I love biology. One of my undergraduate majors was biology and I have a PhD in biology. If you really understand the subject, it gives you a perspective on life different from most people’s. For example, most biology majors end up taking either a parasitology or an epidemiology course for their undergrad degree. And slowly, as the semester progresses, you are transformed from a happy, well-adjusted human into a Howard Hughes-like recluse, afraid that all your food is teeming with worms and every door handle is a germ-smeared death sentence. (Ah, the memories!)
But eventually you get over it, rediscover sushi and get on your life. And if your life includes brewing, you have some absorbed some information that can help you become a better brewer. I believe one of the biggest benefits of having a biology background is a simple thing — understanding how small bacteria are.
Bacteria are small. Most are just a couple microns across. Brewers yeast cells, which are also small enough to be microscopic, are about 10 times larger than all the standard wort-spoiling or beer-spoiling bacteria. With 40X magnification, you can see yeast cells fairly well with a light microscope. (If the cells are not stained, turn the back lighting way down.) With 100X magnification (the next highest power on most light microscopes), most (stained) bacteria look only slightly bigger than a dot.
Now, just for some scale, let’s compare this to a speck of dust. We’ve all been in a room with a ray of sunshine coming in from a window and we’ve all seen specks of dust floating in the air. The size of dust particles depends on what the dust is made of, but if they are big enough to be visible, but small enough to stay aloft in a mostly still room, they are probably between 50 and a 100 microns — i.e. 10 to 20 times larger than bacteria.
There are many ways that bacteria can come in contact with wort or beer. Bacteria can come from unsanitized surfaces. They can also be introduced with the pitching yeast. Most major problems with contaminated beer probably come from these two sources. But one thing you can be sure of, your wort is going to be contaminated with airborne bacteria.
I’m not saying this to be defeatist. Everyone’s beer -- homemade or commercial -- has some degree of airborne contamination.
So what to do about it as a homebrewer? Well, just as you’ll eventually get back to eating sushi after taking a parasitology course, you’ll get over worrying about the fact that your wort is inevitably contaminated and begin to take steps to keep the level manageable. I would suggest a couple things. During your brewday (and especially when wort or beer may be exposed to the air), assume that you are walking around in a mist of bacteria. (You are, even in environments that are very clean by ordinary standards.) Based on this, take these four precautions:
If your wort is exposed to air, you should cover it with a sanitary cover. (For example, if I’m bottling, I’ll cover the top of the bottling bucket with sanitized aluminum foil.) You should minimize the amount of time your wort (or beer) is exposed to the air. (Don’t rush, but don’t let it sit exposed for longer than necessary.) Clean your environment of things that may harbor bacteria or wild yeast (esp. food). And finally, pitch a lot of yeast. A small amount of contamination (of the size that is inevitable from airborne sources) is easily undone by getting a quick start to your fermentation. With a good pitch, the bacteria should be vastly outnumbered and will quickly perish (or go dormant) from the rising alcohol levels and falling pH.
Now, did you know that Taenia solium, a cestode (tapeworm) that parasitizes pigs can get in your brain and eat it? It can. Enjoy your next pork chop.