Showing posts with label hydrogen sulfide. Show all posts
Showing posts with label hydrogen sulfide. Show all posts

Identifying 'Off Flavors' and Aromas in Your Homebrew

Saturday, October 28, 2023
Brewing is an intricate dance of science, art, and patience. It's not just about boiling grains, adding hops, and bottling. Sometimes, even when you think you've done everything right, you end up with a beer that tastes like cabbage, butter, or has the unmistakable stench of rotten eggs. Is it bad luck? Or is there a science behind these unwanted flavors?

The complex chemical reactions that occur during brewing are natural. At times, the aroma of hops might overshadow these reactions. It's essential to understand when these aromas and flavors are a genuine concern. 

Remember, as many seasoned brewers would attest: time to properly condition is a brewer's best ally.

off flavours in home brew beer

Decoding Common Off Flavors in Beer

Taste of Green or Rotten Apples: This could indicate the presence of acetaldehyde, which forms early in the fermentation process. Yeast eventually converts this to alcohol. By allowing extended primary fermentation and conditioning for a minimum of three weeks, you can reduce the acetaldehyde content. Ensuring you pitch an adequate amount of yeast can also help in its efficient conversion.

Cheesy Beer: This unwanted taste is likely due to isolaveric acid, a result of oxidized alpha acids in hops. Using fresh hops and proper storage can address this. Also, when using fruits in brewing, ensure they are clean to prevent unwanted bacteria.

The Skunked Beer Mystery: Also known as 'lightstruck' beer, this is caused by UV radiation affecting the iso-alpha acids from hops. Brown glass bottles can help prevent this, but the best solution is to store beer away from direct sunlight and UV lights.

The Wet Cardboard Taste: This stale taste is a sign of over oxygenation. Oxygen is beneficial before primary fermentation but detrimental during and post fermentation. To avoid this, ensure your fermenter is sealed well and the airlock is filled.

The Paint Thinner Aroma: This is attributed to fusel alcohols, often produced when fermentation occurs at high temperatures or when the beer has prolonged contact with trub. Using the right amount of yeast and fermenting at recommended temperatures can help prevent this. I've had this happen once and I can assure you there is not recovering if this has happened to your brew!

Grassy Notes: These could arise from using old malt or grains exposed to moisture. Fresh ingredients and proper storage are crucial. Overhopping or extended dry hopping can also contribute to this flavor.

Cider-like Flavors: Using excessive corn or cane sugar can impart a cider taste to your beer. Consider reducing sugar or using alternatives like honey or malt extract.

Fruity Aromas: Isoamyl acetate, a common ester, can give beer a fruity smell. Proper fermentation temperature and using the right amount of yeast can control its production.

Other Noteworthy Flavors:
  • Tartness: Often due to polyphenols from over-milled and over-steeped grains.
  • Butterscotch: Diacetyl can produce this flavor, influenced by temperature and oxygenation after yeast pitching.
  • Metallic Notes: Usually from non-stainless metal kettles or poor water quality.

While we've touched on many off flavors, there are still more out there. Brewing is a continuous learning process. By adhering to tried-and-tested brewing practices, ensuring cleanliness, using fresh ingredients, and maintaining proper temperatures, you're well on your way to crafting delightful brews. Remember, every mistake is a lesson, and every brew brings you one step closer to perfection. Cheers!

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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