This week in part 4, I cover common beer infections including wild yeast and bacteria as well as some equipment and material concerns related to cleaning and sanitation. In Part 1 I provided an introduction to cleaning and sanitation and explained why it is a two step process. Part 2 covered cleaners for home brewing and Part 3 discussed popular sanitizers.
Bacteria, Wild Yeast and Off Flavors
Having gone into some detail in the first three parts on how to properly clean and sanitize your equipment, brewers occasionally make mistakes, so things can still go wrong. So how can you tell if your beer has been infected? The strongest indication is in the flavor and aroma of your beer. So lets discuss what some of the most common bacteria and wild yeasts are and what off-flavors are associated with each:
- Lactobacillus – A naturally occurring bacteria on malt and around households. Lactobacillus creates the classic “sour beer” flavor you’ve tasted if you ever bought a sour beer. The sour flavor is a direct result of lactic acid that lactobacillus produces. It can be a persistent bug, continuing to act well after fermentation is complete. It is widely used for sour beer production.
- Pediococcus – Another naturally occurring bacteria that produces a sour lactic acid flavor along with a buttery flavor not unlike diacetyl (buttery popcorn). Pediococcus will sometimes manifest itself with a hazy finish or strands in the beer. Pediococcus is also used in sour beer production.
- Acetobacter – A bacteria strain that produces acetic acid instead of lactic acid and manifests itself as a vinegar flavor in the finished beer. Acetobacter is a less common infection in beer as it requires oxygen to reproduce, so if you have a vinegar flavored beer you may have an oxygen issue as well as an infection.
- Wild Yeasts – Like lactobacillus, wild yeast is a very common infection as it is present on most surfaces in your home. Wild yeasts compete against the yeast you pitch to ferment, but typically produce more off flavors than cultured beer strains. More than half of the off flavors listed on the BJCP score sheet are related to yeast and these include: acetylaldehyde (green apple flavor), high fusel alcohols (moonshine flavors), diacetyl (buttery flavor), esters (fruity), phenolic (clove, spice, band-aid), solvents (paint thinner), sour (lactic), sulfur (rotten egg odor) and yeasty. Wild yeasts can also produce lactic acid so they can sour the beer. While it can be difficult to isolate wild yeast from other yeast problems, I usually look for a bit of sourness plus the presence of another off flavor to indicate a potential wild yeast.
Equipment and Material Considerations
In addition to the cleaning and sanitation process, you also need to maintain your equipment to keep it free from problems. Here are some common problems related to cleaning and sanitation that are specific to certain materials or pieces of equipment.
- Sour Beer Equipment: Some brewers and pros maintain separate fermentation vessels and tools for working with sour beers because the bacteria used can be very hard to completely remove, and they don’t want to run the risk of cross contamination with their regular brewing equipment.
- Plastic Equipment – Plastic equipment has a limited lifetime as it is easily scratched and porous. Bacteria and wild yeast can embed itself in the scratches and crevasses, creating an infection issue. Also as plastics age they tend to break down over time, creating additional risk. I recommend replacing your plastic equipment periodically.
- Gaskets and Tubing – Gaskets that seal your stainless equipment or kegs as well as silicone or plastic tubing suffer from the same weaknesses as plastic equipment. They require thorough cleaning, are easily scratched, are porous and will deteriorate over time. At a minimum you should disassemble gaskets and seals on your equipment when cleaning and sanitizing to include pumps, seals on stainless vessels, gaskets on kegs and tubes. Replace these on a regular basis as they age.
- Aluminum Pots/Pans – Aluminum pots and pans should not be cleaned with PBW, Bleach, Oxi-Clean, One-Step or other acidic cleaners as these will oxidize the aluminum. This is the one exception where you should actually use unscented dish soap to clean your aluminum pots. You should not use aluminum for fermentation vessels.
- Teflon – You should not use Saniclean, Starsan or other acidic cleaners with teflon pans.
- Stainless Steel – Bleach can pit stainless steel. In addition, never store dissimilar metals in your stainless steel pot or fermenter or use metal scouring pads. This can break down the chromium oxide layer that protects the metal and can actually cause it to rust. In addition some cheap stainless equipment is shipped with a thin layer of oil on it and not properly passivated (protected). You can read my article on passivating stainless steel equipment for more information on how to treat and restore stainless steel.
This concludes my four part series on cleaning and sanitation. Please subscribe for regular weekly delivery, check out the podcast, and don’t hesitate to retweet, link, like or mention any of my articles on social media.
