Brewing and bacteria, how bacteria can both hurt and help a good ale.
From time to time every brewers’ bell gets rung! I got mine coming off late last summer’s hectic tourist season. One of our beers got infected!
Outright, it must be said; there has never been a known case of a pathogenic organism surviving in beer. (That’s why, when travelling through third-world countries, it can be hazardous to drink the water, but ok to drink the beer.) But there are plenty of organisms around that can ruin a good beer! Most of the time our methods work to prevent that from happening. Every once in a while something gets past the net. The two primary reasons our sanitary safeguards fail when they do are both because we are human. The first reason is that our own bodies are vector number-one when it comes to microbial transfer. It’s no coincidence that the most common bacterial infection (in fact the one my beer got) is from the Lactobacilli family of bacteria. These are the bacteria that make cheese, yoghurt, and sauerkraut. They are the organisms of probiotics and they make possible our digestion of food. Our guts are full of them and they are teaming all over our skin. In fact there are more bacteria on the surface of a brewers’ skin than there are cells in his/her body. Of course our hair and clothes are like sponges for everything else we come into contact with as well. Easy transference to whatever we touch.
Aseptic technique is what microbiological lab technicians call the discipline of handling things in a way so as not to touch anything that touches the media. They also work close to a flame or under a laminar flow hood to maintain airflow away from the area where they are working. It’s what we do in the brewery on a larger and somewhat cruder scale. We handle gaskets by their edges and keep hose ends off the floor. We maintain a positive pressure with CO2 inside the tank so that if we need to open a door or valve, what’s inside the tank blows out, not the other way around. The second reason humans are the cause of sanitary safeguard failures is human error. I could spend an hour cleaning & sanitizing hoses, clamps, pumps, and valves for a transfer from one tank to another, then get a phone call in the last five minutes; get distracted, and then grab a dirty hose or fitting and use it, nullifying all my efforts in scrupulous cleaning.
As so often happens in life, events seem to conspire all at once to bring about a full awareness of a situation. Coincidence we call it. On a Monday morning, I read the GABF judges’ notes on our recent entries; one of our beers, the astute judges noted, had potential contamination. By this time we had long sold out of the beer, never heard any customer complaints about it; in fact, it even had fans. I know those judges’ identities only by a number; they know mine by my name! OUCH! Next, I went downstairs to check beer tanks and noticed the perennial pressure leaker on which we had recently changed the pressure relief valve (which we assumed was faulty), was still flat. I went to the top of the tank to check the pressure relief valve, which we’d transplanted from another tank, and discovered the vector. The gasket was flattened to the point it was shearing off inside, and the seal was compromised by dried gunk. Upon closer inspection, the gunk turned out to be congealed and hardened yeast. This had been the tank that held the beer that went south on us. Pressure relief valves don’t often get dirty owing to their close proximity to the sprayball in the top of the tank where the beer rarely reaches anyway. They’re easy to overlook, considering they’re usually squeaky clean when we look at them. But this one had been taken off by yours truly, during a brew of one of our IPA’s, (which incidently turned out fine). I’d removed the pressure relief valve to add an additional 500-g US05 yeast to the IPA wort as we were knocking out, because the gravity was a little higher than expected, and I wanted to augment the culture yeast. But I never went back to clean that gasket after the beer was transferred out of the tank. The spilled, coagulated yeast on the gasket seat made an imperfect seal and so it lost pressure. With no pressure in the tank for a while, it breathed in and out according to temperature and barometric pressure changes. (The reason the gasket was squashed is that we brewers had been continually cranking down on the DIN valve seat in hopes of stopping the leak.) The tank was sucking air in and out past what was becoming B-vitamin rich Vegemite for microbes! That’s how it happened! We kept some bottles of the beer we had sent the GABF judges. We opened one, and sure enough, the beer in question, was by now quite obviously sour!
So Now What? New beer transfer hoses for starters. Butyl rubber is good stuff, but it only stays smooth and uncracked on the inside so long. Giving the tanks a thorough going over and already I’m finding areas of concern, which indicates this wake up call is working. We are now routinely autoclaving door gaskets, valves and carbonating stones. (An autoclave is a pressure cooker; we apply steam at 20psi/240F degrees for 15 minutes to kill bacteria and their spores). We’re installing proper sanitary sampling valves for all tanks so we can adopt a new regime of collecting culture tube and petri dish samples for incubation and analysis of each beer taken at three stages. First is from the heat exchanger before the yeast brink, second is from fermenter before racking, and third is from the brite tank. This will aid in the brewery-forensics. Anything that tests positive will represent one of three stages in the brewing process, which will help us isolate problem areas.
Absolute sterilization is quite literally “over-kill” in a brewery, and in reality very difficult if not impossible to achieve. What then, is considered an appropriate degree of cleanliness & sanitation in a brewery? Typically, it’s a bit more than in a winery, but not as much as in a dairy. That’s because wine is ten times more acidic and much higher in alcohol than beer, therefore more resistant to infection. Milk has no alcohol, has higher pH than beer and therefore is more susceptible to infections than beer or wine. The USDA imposes higher standards on dairys than they do for breweries and wineries because the risks are higher and pathogenic organizms can survive in dairy products. But, the standards are nowhere near as stringent as in an immunological laboratory where the streets are paved with gold and expensive valves and fittings are routinely thrown away when they reach their FDA determined throw-away date. Over time and use, all fittings, valves and hoses will wear, and tiny pits & scratches will develop, providing places where microbes can florish untouched by cleaning and sanitizing chemicals. Certainly, the back end of a restaurant, where most brewpubs make their beer is no place to maintain much environmental control either. Therefore we rely on positive pressure and careful cleaning, sanitizing and handling techniques to keep our beers clean.
It is ironic that some of the worlds most interesting and exalted beers are brewed deliberately with microorganisms that are closely related to the very critters we seek to avoid. Brettanomyces, Lactobacillus, and Pediococcus abound in these beers. But those beers are in a class of their own; the Belgians made an art form out of spoilage and the English accepted low level infections as part of the traditional flavor of Old Stocks, Porters and Stouts. Even the Germans have their ‘critter-beers’ in Berliner Weisse & Gosse. Explorations into brewing authentic versions of these ales calls for old school brewing methods and avant-guard inoculations, usually into barrels, (and hopefully kept confined there). Our own Barrelage Run project that we released last year (Weisse, Sour Ale & Old Stock Ale) does beg the question; did we not invite the devil to our door? Too late now! Stricter Vector Control will be our first line of defense! That means autoclaving parts that make a seal between rubber and stainless steel, as in valves or door gaskets, or carbonating stones, because there could be unseen beerstone buildup inside the pores, which could harbour microbes. The heat penetrates where sanitizers do not. Good cellar hygiene is key! Our second line of defense has to do with the maintenance of healthy, though mostly invisible populations of brewer’s yeast in all our beers (whichever yeast we brewed that beer with). We don’t filter our beer, and we baby the yeast by making gradual Yeast is my ally. I imagine it crowding out other microorganisms. Indeed yeast is approximately five to ten times larger than competing bacteria. I visualize letting a herd of elephants out to pasture with goats. The goats are there, but the elephants really do crimp their style. That’s my somewhat holistic, “probiotic” approach to brewing. Having yeast in the beer doesn’t mean the beer is necessarily cloudy. Even though yeast cells are much larger than bacteria, they’re still invisible. Scale is the key to understanding microbiology. (That’s how there can be more bacteria on the surface of a brewer’s skin than cells in his/her body.) Most of our beers have an unusually long life of their own, staying fresh and mostly finishing out brilliantly. Clarity is rarely a problem. We do fine our beers in the mash tun, kettle, and conditioning tank with gallo (nut) tannins, Irish moss, and Isinglass respectively. In most cases we achieve optical brilliance in our beers and we do it without filtration. Some types of filtration like “crossflow filtration” is gentle, and centrifugation, though loud and expensive, I’m told, gives a good result. But plate and frame-pad, and pressure-leaf DE filters depend on adsorption, and therefore also remove flavor-positive compounds. Robert Parker once described the effect of filtration on wines he tasted from barrel, then later after filtration and bottling. He said; “you can reliably predict the flavor impact on the wine, post filtration, by adding 10-15% water to the wine”. Filtration does seem to strip out flavors, which is another reason I don’t favor it for beers served in a brewpub! Why spend hours filtering flavor and yeast out of the beer, rendering it prey to microbes and accidental oxidation, when you can serve your beer as flavorfully and naturally as possible instead? It’s a no brainer to me! I know there are plenty of brewers out there who disagree with me on this point, but I consider it my credo!
I’ve been reading an excellent primer on setting up a small QC lab called: “The Microbrewery Laboratory Manual: A Practical Guide to Laboratory Techniques and Quality Control Procedures for Small Scale Breweries (3 parts)” written and published in Brewing Techniques magazine in the mid-nineties by Fal Allen (last I heard Allen was brewing at Anderson Valley Brewery). In it, he states: “I now believe there are only two types of breweries; those that have had an infection and those that will.” Check out the article to learn more.
I now believe that setting up a quality assurance lab at our brewery this year is a sign of our maturity. We’ve had a remarkably long run without incident until now, but we will be better brewers with our eyes wide open to the invisible.