To follow up on your comments in the September 2014 issue on Food-Grade CO2; what about food-grade oxygen? I get bottled oxygen from my local welding shop, to aerate wort, and have always pondered the quality of it.
There is one very major distinction separating bottled carbon dioxide from bottled gases like oxygen and air, and that is the primary use of the gas. While bottled carbon dioxide has a wide number of industrial-type uses, bottled oxygen and air are sold specifically for use in respiration systems in addition to use in industrial applications. The cleaning requirements, or lack thereof, of these industrial users is far different from those of the buyers of breathing gases. This is why the valves on oxygen and compressed air bottles intended for use in respiration systems are physically different than valves found on cylinders used, for example, in welding. Suffice to say, it is easy to obtain bottles of oxygen and compressed air to use for homebrewing without having to worry about the gas or cylinder.
But this does bring up a good brewing question. What are the practical differences between compressed air and oxygen in the brewery? The one difference that really matters to me is how the source of oxygen affects oxygen solubility. When air is used as the oxygen source in brewer's wort, the solubility of oxygen is about 8 mg/liter or 8 ppm (based on 12 °Plato wort). Changing the oxygen source to pure oxygen increases the oxygen solubility by approximately fourfold. This dramatic difference can negatively affect
Aside from yeast health, wort oxygen influences the production of nearly all yeast-related aroma compounds present in beer. On paper, one can develop a convincing biochemical argument demonstrating that too much oxygen results in beer that is "too clean" and lacking in aroma, especially those associated with esters. And based on practical experience some brewers find that too much oxygen results in fermentations that stall after a very vigorous start that also tend to throw off lots of acetaldehyde and sulfur. The bottom line is that wort oxygen level plays a very key part in beer flavor development, and is one of those factors that varies with yeast strain and wort properties.
Brewers who successfully use pure oxygen control its delivery into the wort stream during cooling using
a variety of methods. The most common method is metering oxygen based on wort flow rate in order to deliver a measured amount to the batch. As long as the oxygen is introduced as very small bubbles, it is safe to assume that nearly all of it is absorbed into the wort. This assumption makes it easy to meter oxygen with a flow meter into a known volume of wort to yield a concentration without verification with an expensive, and arguably unnecessary, oxygen meter.
Pure oxygen can really help out when brewing higher gravity beers because the solubility of oxygen from air diminishes as wort gravity increases (for more information on this topic, read up on Henry's Law and how gas solubility in liquid is influenced by the concentration of other gases). Aside from these types of beers, however, I prefer using compressed air for wort aeration because wort simply cannot be over-oxygenated using this method, making aeration one less detail that can go wrong during the brew day.
At Springfield Brewing Company we use dry, oil-free compressed air from an air compressor to supply our wort aeration panel. This panel has a pressure regulating valve, gas rotameter for flow measurement and control, and a sterile filter. I believe the latter feature is pretty important to the practical brewer because compressed air can contaminate wort. And the suitability of a gas for breathing purposes has nothing to do with this particular concern. Since pure oxygen is toxic to most forms of life, I don't get too concerned about oxygen as a potential source of contaminants. So if you decide to use compressed air, consider an in-line sterile filter.
What effect on the final product does putting all of the wort from my kettle into the carboy as opposed to removing only the clear portion have? After I chill wort I just dump everything in as opposed to pumping or siphoning into the carboy. My final product is usually clear after fermentation and kegging.
Wesley Chapel, Florida
Right or wrong, I long ago viewed the production of beer to include many steps where things are modified, separated and moved to the next step of the operation. The malting process, for example, includes barley cleaning before steeping, and includes the removal of rootlets following malt kilning. Go to a hop farm during harvest and you will see equipment that separates leaves and bines from hop cones prior to kilning. Most brewing water is treated using a variety of techniques along the path to make the water clear, clean and suitable for use in brewing. And even the yeast we use for pitching is often concentrated before use by decanting off the beer resulting from the propagation step. In a nutshell, we seize the opportunity to remove something that is not needed or wanted in the finished beer when the opportunity presents itself.
Now that I have given some background on my way of thinking, it should come as no surprise that I am not a huge fan of the method you describe for no other reason than because trub and hop solids are easy to remove following the boil. But the contrarian will argue that the overall batch yield will improve if this technique is tempered, for example, in the manner you describe. I have no objection on the basis of yield, but I am concerned about the downstream consequences of this method.
My immediate concern is the quality of the yeast crop. If the plan is to crop yeast from this fermentation and pitch it into a subsequent batch you will have to contend with trub and hop solids in the cropped yeast. This concern is more than simply being picky; trub is known to "foul" the surface of the yeast cell wall and the health of cropped yeast is influenced by what settles with it to the bottom of the fermenter.
And my other concern is how the hop solids will affect flavor. One thing that I find pretty useful when contemplating "flavor what-ifs" is to take a sample of the substance in question and taste it. If it does not taste like something that will be beneficial or neutral to beer flavor (filter aids and brewing tools are examples of things that should be flavor-neutral), then it falls on the list of things to remove sooner than later.
Here is an example of how I consider a hop pellet. The aroma is something I want in my beer, unless the hops smell funky (onion/garlic, etc.). So, funky smelling hops may work for early additions because the funky aromas may be removed during the boil. When I taste the hop pellet I get resin, pine, floral, herbal, citrus and bitter flavors that I want in beer. But the longer I ponder the sensation I start to notice astringency on my palate and grassy flavors. And I am thinking these characteristics are of the type I don't want in beer. So I start by selecting hops that smell nice.
I now stand over my whirlpool looking at the mass of green stuff in the center and wonder what would happen if all of this . . . stuff . . . were in the fermentation vessel instead of laying in the center of the whirlpool vessel. Again I wonder how I would harvest my yeast if this mass of hop and protein matter were intermingled with what is normally smooth and creamy yeast awaiting harvest at the bottom of my fermenter, but that's a different question for another day. The trub smells a lot like hoppy wort because it is surrounded by hoppy wort. When the trub is sampled, however, the thing that really hits the palate is astringency. Not real sure I want this in my fermenter; what is the return on my investment? Is it an extra bottle or two of beer per 5-gallon (19-L) batch? That's not a bad proposition, but will the added yield improve, detract or have no influence on the finished beer?
I find this type of thinking to be very useful when thinking about brewing because at the end of the day it's about beer flavor. Even in a commercial brewery, the financial gains can only seriously be considered if process changes geared towards increases in yield have no obvious negative effects on beer flavor.
Although I believe your beer would taste better if you separated your clear wort from hop solids and trub prior to fermentation, you have pinpointed a very real opportunity for improvements in minimizing wort loss. Almost every commercial brewery these days owns whirlpool vessels to facilitate the separation of these solids from wort. A problem that is becoming more and more significant is wort loss associated with high gravity, highly pellet-hopped batches. Whirlpool wort losses are generally higher when wort gravity increases and when hopping rates are increased, and these two factors are becoming increasingly common as the popularity of high-alcohol, highly-hopped beers continues to grow. If this trend holds, brewers will certainly be looking towards technologies to reduce whirlpool losses. Some of the larger lager brewers have been using decanting centrifuges to address this problem, and this technology will most certainly soon spread.
What are the biggest considerations that i should take into account when crafting my own homebrew recipes?
Developing new recipes is really one of my favorite things about brewing and I have some fairly strong opinions about this topic. Before I begin with my answer I think it is important to state that there are a few schools of thought about recipe development and that my method and general belief is certainly not shared by all brewers.
The most important target to nail in my view is the original gravity (OG) and I believe that learning how to perform brewing calculations is a prerequisite to recipe development. When I say nailing gravity, this also includes wort volume. So if the goal is to produce 5 gallons (19 L) of wort at 1.048 (12 °Plato), I want 5 gallons (19 L) +/- ~2.5% at 12 °Plato +/- 0.1 °Plato. My reasoning is that OG largely determines alcohol content and influences body and wort volume affects bitterness since hopping is based on batch size. If you miss your volume target you also miss your bitterness target. So job #1 is knowing how to nail those brewing targets.
When I am formulating a recipe I absolutely must have a very clear idea of the finished beer. Some brewers "add a pinch of this and a pinch of that" like a grazer at a salad bar. This method of recipe development is completely foreign to me. I begin with an idea of the beer and build my recipe and brewing process to support the pint that is in my mind's eye. Since nailing targets is a given in my method of recipe development, the real job #1 is to have a goal in mind.
I think developing the goal is often a major part of the fun and challenge that comes with recipe development. This process includes tasting beer, imagining flavor modifications to the beers being tasted, researching styles, ingredients, recipes published by other brewers and tweaking the flavor of the beer being developed before actually brewing the beer. The thing most consumers don't understand about brewing is that once a recipe is formulated and the wort is made, brewers still have weeks to wait until we know if our creation matches the plan. While there are some oppor-tunities to tweak a batch after brew day, most of the key attributes of the beer have been determined very early in the process. This is why my particular method involves lots of what I call abstraction, where I zone off into my thoughts and transform ingredients and processes into a finished beer.
In order for this process to actually work, you need to have a fair amount of experience that only comes with time. Every time you develop a new recipe you need to somehow fold the process into your mental collection of brewing ideas. Every time you learn something about a beer you taste, this too needs to be added to your mental brewing library.
Once the general goal has been defined and a working recipe is in place I really focus on a few key things before considering the recipe ready to brew. The two biggies to me are balance and drinkability. No matter the style of beer I am contemplating I want a beer that has these two properties. Balance allows all of the ingredients and techniques to be expressed. And if all turned out well the thing I personally prize the most in a beer is drinkability. This is the trait that makes you want another sip and is one of the hallmarks separating the great from the good.