Showing posts with label infection. Show all posts
Showing posts with label infection. Show all posts

Understanding Yeast Traps in Beer Brewing

Friday, November 3, 2023
In the context of brewing, the term 'yeast trap' can evoke images of a sophisticated mechanism designed to capture superfluous yeast cells. However, its reality is far less intricate. A yeast trap, colloquially known as a 'yeast raft,' refers to an occurrence during the fermentation process where yeast aggregates float atop the wort, the liquid extracted from the mashing process during the brewing of beer.

yeast traps

The Dynamics of Yeast Behavior

Yeast's role in brewing is pivotal, as it is the agent responsible for fermentation, converting the fermentable sugars in the wort into alcohol and carbon dioxide. While it's common for dead yeast to settle at the bottom, creating a layer known as 'trub,' live yeast can behave differently. Post pitching, or the process of adding yeast to the wort, the yeast cells may clump and rise to the surface.

This clustering is often a benign byproduct of the yeast beginning its fermentative activity.

The Natural Course of Fermentation

Experienced brewers will attest that these floating clusters are generally not a cause for concern. Over time, these clumps diminish as the yeast engages in fermentation. This process can be observed over several days, where the yeast rafts gradually disperse, indicating that the yeast is active and fermentation is proceeding as expected.

beer yeast traps

Differentiating Between Yeast Rafts and Infections

It is essential to distinguish between yeast rafts and potential beer infections. The sensory cues of smell and taste are invaluable here. A healthy fermenting wort may carry a range of odors, some of which are byproducts of yeast metabolism, but none should resemble the odor of rotten eggs—a telltale sign of contamination.

Similarly, the taste profile of an infected batch can be markedly unpleasant, often warranting the disposal of the entire batch.

Visual Signs of Infection

Visually, an infected wort may exhibit a white film or flakes post-Krausen, the foamy head that forms during the early stages of fermentation. These films, known as pellicles, are often the result of bacterial or wild yeast infiltration. While they can appear alarming, not all pellicles indicate spoilage.

Some may be benign, and the beer beneath can be racked—transferred to another container—to separate it from the pellicle before bottling.

Preventative Measures and Sanitation Practices

The occurrence of pellicles can also underscore the imperative of rigorous sanitation practices in brewing. Maintaining cleanliness and proper sanitation of all brewing equipment is crucial in preventing infections. It is a constant reminder that while yeast traps are a natural part of fermentation, vigilance against contamination is a cornerstone of successful brewing.


The appearance of yeast traps in homebrewing is a natural and often innocuous part of the beer fermentation process. While they require monitoring, they typically resolve without intervention. Conversely, potential infections demand a brewer's keen senses and swift action to prevent spoilage. The distinction between these scenarios lies at the heart of brewing—where the interplay of science, art, and a bit of patience can lead to the delightful outcome of a well-crafted beer.

How to tell if your brew is infected by bacteria

Thursday, October 26, 2023

There's a super simple way to determine if your beer brew is contaminated

Ready for hot tip?

You taste it. 

If it tastes like the scummiest thing you've ever put in your mouth, it's infected.

tasting infected beer

If the sensation mirrors that of the foulest thing you've ever tasted, it's tainted. If it induces nausea, it's tainted. A sulfur bomb that smells of rotten eggs aroma? Infected. An explosion reminiscent of a rigorously shaken bottle upon opening? Likely contaminated due to over-carbonation from rogue yeast or bacteria. Don't confuse this with the aftermath of adding excessive sugar during priming, known as a beer bomb.

Remember, if you're questioning whether your beer is contaminated, it probably is.

Before bottling, consider visually inspecting your beer. Keep an eye out for a 'pellicle' or yeast raft at the wort's surface, signaling a congregation of microbes. Though not every infection results in this formation, its presence is a clear sign:

infected beer wort in fermenter drum

Discovering such an infection is undeniably disheartening. You've not only lost time and resources, but your hard-earned efforts have gone down the drain.

Yet, this misadventure is an invaluable lesson in the essence of brewing:


Having learned my lesson, it's been years since I encountered an infected batch. Cleaning may seem laborious, but if you crave a perfect pint, it's non-negotiable.

Root Causes of Infection

The primary culprit? Lack of cleanliness. Any remnants offer bacteria a haven, escalating the risk of infection. Every piece of equipment, from fermenters to mash tuns, requires meticulous cleaning. Hot to boiling water paired with a reliable cleaning agent, like Powdered Brewery Wash, will serve you well.

Then comes sanitization. Sodium percarbonate is a top choice. It's not only effective but also conveniently found in everyday laundry soak.

For bottling or kegging, the same rules apply. Clean, then sanitize. A nifty trick for bottles is to rinse them thoroughly, then cycle them through a dishwasher on its hottest setting. This annihilates any lingering microbes. Store them in a pristine container, and on bottling day, a brief soak in sodium percarbonate ensures they're ready.

If only a few bottles from a batch taste off, the problem likely lies with individual bottles, not the entire batch.
mega pellicle for an infected beer batch
This "mega Pellicle' was from a beer brew that was found to be infected.

Addressing the Rotten Egg Smell Mystery 

The signature rotten egg aroma can be a telltale sign of contamination. Yet, it doesn't always spell disaster. Some yeast strains naturally exude this scent. Bottle-conditioned beers, if opened prematurely, can also exhibit this aroma. Over time, as yeast continues its work, the odor dissipates.

In areas with water high in sulphate, like Burton-on-Trent, England, this scent is inherent – the famed 'Burton Snatch'. But if bacteria are the cause, the aroma, combined with an unpleasant taste, confirms your beer's unfortunate fate.

For wine or cider enthusiasts, fruits' natural yeasts can be disruptive. Many cider makers employ Campden tablets to neutralize wild yeast, substituting with yeast strains better aligned with their desired product.

Why does my beer smell like rotten eggs?

Monday, October 23, 2023

The Mystery of the Rotten Egg-Scented Beer!

Who in their right mind would enjoy the putrid scent of rotten eggs wafting from their freshly poured beer?

A memory surfaces from last year when I embarked on the adventure of bottling my own beer. Freshly sterilized bottles lined my counter, eagerly awaiting their contents. However, as the amber liquid flowed from the fermenter to the bottle, an overpowering stench enveloped the room.

Imagine the revulsion of cracking open a fetid egg and letting its stink engulf you. The smell was akin to a malevolent hydrogen sulfide explosion, its malefic aroma threatening to singe my senses. But why, one might wonder, did my beer exude such a repugnant odor?

The unfortunate revelation: my brew had been tainted.

A myriad of factors could be at play behind this 'rotten eggy' aroma. Primarily, it points towards the presence of hydrogen sulfide gas. This is a telltale sign of contamination in your beer, often the result of unwanted yeast strains or rogue bacteria (a stark reminder of the paramount importance of sanitizing your equipment).

rotten eggs smell in beer explanation.

The Lager's Tricky Aroma

However, the situation might not be as dire as it seems. If the origin of the sulfide is the yeast, salvation is possible. Lager yeast strains, notorious for their tendency to produce sulfide aromas, can be tricky. 

The silver lining? 

Proper conditioning of your bottled beer can make the scent dissipate. It’s essential to let the lager stand for several weeks, allowing the aroma to vanish before indulgence.

For novices in brewing, it's advisable to start with brewing ales. 

This reduces the chances of facing such aromatic dilemmas and can ensure a more pleasant introduction to the brewing world. And if you're particularly apprehensive about unwanted scents, an abundant use of hops can serve as a masking agent. 

Yet, remember, the key lies in proper conditioning.

The Grim Reality of Bacterial Infection

On the flip side, bacterial infections spell doom. My personal experience serves as a testament. Despite the off-putting odor and a taste that hinted at a brewing disaster, my obstinate nature led me to bottle the beer, hoping time would rectify the mishap. But alas, tasting it post-conditioning was akin to a cruel gustatory punishment. The overpowering carbonation that ensued upon opening each bottle further confirmed my suspicions: unwanted bacteria were running amok, fermenting the malt in unintended ways.

The takeaway? 

The cornerstone of brewing is hygiene.

If you encounter a compromised batch pre-bottling, the only recourse is to discard it and commence a thorough cleaning spree.

smelly beer how to prevent

Beware the Skunked Beer

While discussing the pitfalls of brewing, it's imperative to touch upon 'skunked' beer. This phenomenon arises when bottled beer undergoes a chemical transformation due to UV radiation exposure. The result? A smell reminiscent of a skunk's defense mechanism. This reaction is triggered when UV rays break down the so-alpha acids in the beer, leading to the formation of a pungent compound.

The antidote? 

Opt for brown glass bottles that shield the beer from harmful UV rays. Avoid using green bottles or clear glass, and always store your beer in a dark environment.

In the intricate world of brewing, a plethora of factors can influence the final product. From the type of beer being brewed to external factors like light exposure, every element plays a crucial role. Thus, it's vital to be vigilant and meticulous, ensuring that every sip of your beer is a delightful experience.
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