BeerDorks.com: Reviews, Commentary and Opinions on Midwest Craft Beer and Microbreweries

 
June 9, 2007

Home Brewin’:

Lagged Fermentations Are More Than A Delay

Follow Jug’s simple yeast-pitching techniques to prevent your next batch of home brew from becoming a playground for bacterial beasties.
by Jug Dunningan

Jug Dunningan is just here for the beer.
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You?ve done it all right. You selected the best ingredients, carefully weighed each grain and adjunct, timed your mash and temperatures with scientific accuracy. Your sanitation process is redundant and thorough. You know your recipe and nail the starting gravity (SG) target. You are a homebrew god, life is good. Your wort is aerated and the temperature is just right. You pitch the yeast you know so well, snap the lid on your fermentor and close another chapter in your brewing legacy.

Two weeks later you check your fermentor. The fermentation lock is laying lifeless, as you knew it would be. Time to bottle. You take your hydrometer reading, fill your bottles and cap them. You finish your work and take your traditional sip from the hydrometer flask.

Sourness stabs at your tongue. Your mind reels as an acidic train wreck smashes your pallet and your pride in one deft blow. Its ruined?noooo! The only thing left to do is destroy the evidence. You know a home brewer is only as good as his last batch, and right now that ranks you almost as high as Groundskeeper Willie on American Idol. You dump the carefully filled bottles as quickly as you can, catching one last glimpse of your pride swirling down the drain in a lactobacillic soup.

Yes, tragic. But when good sanitation is used, a complete meltdown is not very common. If you brew enough, though, sooner or later you will create the dreaded bacterial soup. I can only recall two instances out of the hundreds I have brewed that have turned out this way.

Now before you jump to conclusions, I need to let you know this article is not another sermon about cleanliness and sanitation. From this point on we will assume your sanitation is perfect and will focus our attention on the dreaded ?slow fermentation.?

We need to understand that every batch of beer we have ever brewed or tasted has had some bacterial infection. This is not necessarily a bad thing, in fact it is what gives a brewery a ?House Flavor.? Some breweries pride themselves on their house flavor and others do their best to eliminate it, but the simple truth is there are billions of wort-loving microorganisms surrounding us no matter where we brew, and some will find their way into our beloved recipes no matter how well we sanitize. We carry them in to our homes on the very grains we produce our beer from. We buy them with our hard-earned cash every time we purchase our favorite yeast cultures. The simple act of pitching yeast releases future infections into the air. The yeast struggles to live and mutates to do so.

The most common of these infections come from wild yeast and from lactobacilli. The degree to which they will affect our homebrew is dependant on may factors, but as a rule, high gravity and lightly hopped worts will be the most affected.

How It Works
Think of pitching your yeast as a race. We already know that there are some degree of infections in our wort before we even pitch the yeast. Lactobacilli will immediately begin to consume the precious sugars in our wort and change them to lactic acid. After pitching our yeast the lactobacilli are greatly outnumbered and hopefully will be overpowered by the millions of cultured yeast cells we added. The lactobacilli will continue to munch on our sugars and reproduce until the pH level drops below about 4.5 or the alcohol content rises enough to kill them.

When you are pitching yeast, you are usually introducing dormant yeast cells into a nutrient-rich environment they will thrive in. The first stage the yeast will go through is called respiration. During respiration the yeast will collect the oxygen that is dissolved in your wort and reproduce until they number about 50 million cells per milliliter. During this process no alcohol is produced and the lactobacilli have free reign, therefore the faster we can get through the respiration phase, the more control we have on how much bacterial infections will affect our brew.

What We Can Do About It
? Obviously using high quality and new yeast are some of the easiest things we can do. Most brewers prefer liquid yeast and I am especially fond of ?smack packet? yeast. That is yeast that is packaged within another packet containing yeast nutrients. I have no evidence to support this but it really seems a properly prepared smack packet reduces the lag before fermentation begins.

? Make sure to aerate your wort. Boiling wort removes much of the dissolved oxygen. We know yeast will spend the first hours after pitching searching for oxygen before they begin the fermentation stage. Simply stir the wort briskly with a sterilized metal spoon until a lather forms. You do not need to worry about oxidation until after fermentation.

? Make a yeast starter. This is especially useful for worts with a SG of 1.070 or higher. Most yeast manufacturers package the yeast for target SGs of 1.060. Most reputable yeast manufacturers have directions for making a starter on their website.

? Temperature. Make sure your yeast is room temperature before you pitch. However, do not ever try to hasten the process. Yeast will go into shock if it changes temperature too quickly. Most manufacturers recommend letting it warm up for about 2 hours. In my experience 6-8 hours seems to get a faster start. Once fermentation starts I prefer to drop the wort temperature to 65° (for ales). Bacteria prefers 75° and above temps.

Most fermentations should begin within 5-12 hours. The quicker the better, and any wort that has not started fermenting within 24 hours should be repitched. The affects of over-pitching are debatable by home brewers, with low esters being among the biggest worries, however I guarantee it will be less noticeable than a lagged fermentation. As a home brewer you should also note times and temperatures during the pitching process. Some brews ferment faster than others and of course yeast strains vary greatly, but this will give you a guide on how your brew is acting and what you should expect of it.



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