Oxidation Rates, Creating the Haze, and Pressure Fermenting in a Conical
Q
While reading AN article in A recent issue of BYO I was left with a question about how long it takes oxygen to cause oxidation. I know it depends on temperature, but give me some ranges. For example, when packaging bottle-conditioned beer there is some oxygen exposure but the yeast rapidly consume any oxygen they can. Is the beer oxidized before the yeast can act or does the yeast consume the oxygen before the undesired reactions have time to take place? I cold crash my beer (with a CO2 source for suckback) and bottle while still quite cold (40–45 °F/4–7 °C). This would presumably slow any oxidation reactions but it also slows the yeast metabolism. Which one wins the race as the bottled beer warms up or does it affect both equally?
Richard Swent
Palo Alto, California
A
This is a terrific question and is well suited for a terrifically short answer. Beer oxidation can occur shockingly fast, especially if a beer is the sort to easily show off oxidized aromas. And the rate of oxidation doubles when the storage temperature of beer is increased by about 15 °F (8 °C); for example, beer stored at 39 °F (4 °C) that retains 90% of its freshness after 30 days will have a similar level of oxidation in 15 days when stored at 54 °F (12 °C). Yeast can prolong freshness, but the notion that yeast quickly consume oxygen is not true if the yeast is old and tired, especially if the cell density in the package is low.
The best way to appreciate the speed of oxidation is to perform a simple trial. Grab two or three bottles of a subtle beer, such as Budweiser. Open one bottle, gently fan some air into the headspace to help move the carbon dioxide blanket out of the bottle, recap, and give the bottle a few shakes to help dissolve the headspace gas into the beer. If you want to see how yeast may slow oxidation, shoot in a milliliter of slurry (assuming 1 mL of slurry contains one billion cells, this will give you 2.8 million cells/mL, which is a healthy density). Incubate the sample(s) in a warm environment for 24 hours, transfer to the refrigerator where the control beer is stored, and do a side-by-side tasting in 2–3 hours after the beers are both the same temperature. You should be able to easily differentiate the control from the experimental beer without yeast (not sure about the yeasted sample) and detect the tell-tale signs of oxidation in the experimental sample.
The method described above is pretty extreme, but not uncommon. Growlers, unfortunately, are a great example of mistreated beer because the manner in which they are often filled is sufficiently abusive to oxidize beer within hours of filling. I personally dislike growlers for multiple reasons, but the effect they often have on beer freshness is my #1 complaint about them.
The best way to appreciate the speed of oxidation is to perform a simple trial.
Filling bottles with flat beer is a challenge and should be done with special care. Adding a fresh dose of yeast can help if the fermentation may have been stressful or the beer was aged. Commercial bottle filling (or growler filling using a proper filling device) is a different story because bottle fillers are designed to purge air from the bottle, counterpressure-fill beer into the bottle, and then gently release pressure after filling. A properly filled bottle will be quiet after the fill tube is removed and the beer can be fobbed (intentionally foamed) by knocking the bottle with something like a plastic screwdriver handle or by squirting a small volume of water onto the surface of the beer before capping on foam. Commercial bottling lines are indeed equipped with water jetters or bottle knockers before the capper so that beer is capped on foam. Another thing that makes a good bottling operation better is the use of oxygen barrier caps that have special liners to absorb oxygen that is either in the bottle headspace after filling or diffusing into the headspace through the crown seal during storage.
Q
I am about to rack my New England IPA to the secondary. Should I let it sit for a few days before I keg? How do I make sure it’s hazy? I am a newly “returning” brewer and this is my fourth batch since returning after 25 years, and is my tenth batch overall. It’s also my first New England style. I love the hazies out there.
Bob Hamm
Hot Springs Village, Arkansas
A
Welcome back to the world of homebrewing after your quarter-century hiatus! Not sure where you are in the process of brewing your current batch of New England IPA and hope this answer helps clear up a few things in your quest for unclarity. My basic advice is to give your beer a few days in your secondary to allow fermentation to complete and those hops that you probably tossed in towards the last couple days of fermentation to settle, and then transfer to your keg where you can cool, carbonate, and enjoy.
Hazy IPAs have really exploded as a style over the last five years and there are many twists and tricks brewers use to give these brews their cloudy look. The good news is that brewers can produce these brews by following a few relatively simple steps that will result in solid examples of the style. After the basics are mastered, tweaks can be made to fine-tune appearance, aroma, mouthfeel, foam stability and cling, and yield. But since you are still getting your brewing legs back in shape, it may be best by starting with just a small list of key pointers to consider. And for other readers, I am going to assume that you are beginning from scratch with a new brew.
Let’s begin by loosely defining the style before jumping into the weeds about how to brew a solid New England IPA. Not to get caught up in the numbers game on this as the Brewers Association (BA) now has four style categories designated as “Juicy or Hazy [fill in the blank],” but in general terms, most of these beers, excluding doubles and imperials, have original gravities in the 1.048–1.065 (12–16 °Plato) range, have a very pale, blond/straw color, are low in perceived bitterness, have lots of hop aroma (especially citrus, ripe tropical fruit, and stone fruit notes falling under the giant umbrella named “juicy”), often have a creamy/silky palate, expressive aromas from yeast esters, and sufficiently high carbonation to fit with the body and to puff up into a white and wispy foam.
A good, all-around New England IPA can be brewed incorporating the following pointers:
- Low carbonate water with a 2:1 ratio of chloride-to-sulfate is frequently cited as a great water balance. If you are using reverse osmosis (RO) water, aim for about 150 ppm calcium from a combination of calcium chloride and calcium sulfate. Adding 3.1 grams calcium chloride and 1.7 grams of calcium sulfate to 10 liters of RO will give you 150 ppm calcium, 96 ppm sulfate, and 195 ppm chloride. Water is important, but don’t get too hung up on worrying about the chemistry until you need to.
- Keep the grist bill simple. 80% pale malt, 10% flaked oats, and 10% flaked wheat works well. As with water, add complexity or process tweaks if the finished beer needs help in the grist bill department. Depending on your mashing method, rice hulls definitely help with wort collection.
- Don’t add too much hop bitterness to your wort during boiling; a modest addition at the beginning of the boil lays down a bit of bitterness on the blank canvas and helps suppress foaming during the boil. After the boil, knock the wort temperature down to about 176 °F (80 °C) before adding your aroma hops to hot wort. The reduced temperature will help keep isomerization to a minimum and allows for big additions for aroma. And consider adding about a third of your aroma hops to the hot wort and the remaining two thirds as dry hop additions.
- Use a yeast strain that is known for the style. There are a handful out there that work well, such as Wyeast’s London Ale III and SafAle’s S–04 or Imperial’s Juice just to name a few. Choosing something with a proven track record is a great start. One of the keys to this style is hop biotransformation and this is largely a function of yeast strain.
- A good dry-hopping schedule is to add a third of your aroma hops about 24 hours after vigorous fermentation begins, and the last third 48 hours later. A more advanced approach can be taken by timing your additions based on specific gravity, but this requires sampling and is not a requirement for making a good example.
- Only add hops that smell good. If you have hops that seem off in terms of aroma quality or if they have aromas that you don’t like, don’t use them. Hops are an agricultural product and vary by growing location and crop year. The concept of terroir may seem esoteric, but it’s real.
- Allow your beer to settle well before packaging into bottle or keg, and, like most other beer styles, do be concerned about oxidation.
If all goes well, you will end up with a great beer. But what about the haze? I have talked to lots of commercial brewers about this style and the consensus among the group I have polled is that few brewers are adding mono-tasker ingredients whose only purpose is haze. Some brewers are happy enough with a great tasting brew and don’t obsess about the haze. The basic guide earlier in the answer will definitely end up with a cloudy brew.
In the world of commercial brewing, consistency is pretty important, especially for packaging breweries, so haze stability is a thing. And it’s a perplexing conundrum because cloudy beer is inherently unstable. Why? Because haze particles tend to be more dense than beer and gravity never takes a day off. The interesting thing about this topic is that the vast majority of the hazy volume on the market is centrifuged before packaging. In other words, the haze is not from yeast and it is not from “chunky stuff” floating about in the beer. The cloudy appearance of this style is the product of protein and polyphenol (tannin) interactions, and it seems that a significant portion of these haze particles are not very dense and tend to stay bobbing about in their hoppy homes. Although most hazies contain somewhere between 10–30% flaked grain adjuncts that do bring protein to the party, it appears that the main haze ingredient is the big boost of polyphenols that comes with the massive hop additions commonly used in these brews.
Brewing, and more broadly cooking, marries science with art and the vision of the brewer drives the outcome towards this idea. My view on the haze part of this style is that the turbidity of the beer is secondary to all other attributes. The list of tips above touch on water flavor and pH balance, color, mouthfeel, foam, hop bitterness, hop aroma, and yeast expression. New England IPAs were not developed to look cloudy; the emphasis was on beer flavor and the haze thing came along for the ride. This is your fourth brew since your sixth brew 25 years ago and you are best advised to focus on your technique and beer flavor before looks. One step at a time, Bob. Fact of the day: A lousy-tasting beer rarely improves by altering its appearance!
Q
I’ve just bought a 20-L (5.25-gallon) conical bottom, pressure fermenter and I am keen to try it out. I primarily brew all-grain lagers with the odd ale and do so in 10-L (2.6-gallon) batches using carboys. I like variety in my beer and so keep batches small. My questions are: 1) At what fermenting temperature and for how long? Because of our hot climate I will still need to ferment in a cooled environment during our summers. 2) Is the hopping rate the same for pressure fermenting as for atmospheric fermenting? Please consider that I also hot cube (no-chill method) the beer prior to fermenting — Can’t afford to waste water in Australia. 3) What is the best way to dry hop a pressure-fermented brew? 4) How long will I need to lager the beer?
Terry Le Lievre
Warragul, Victoria, Australia
A
Thanks for the question from down under, Terry! Although the fermenter you describe is pressure rated and has a conical bottom, you can use it as you normally do with your carboys. A few advantages of your new fermenter is that it shields your beer from light, does not break like glass, allows for beer transfers using valves situated on the bottom and/or side of the cone without racking, permits trub removal and yeast cropping from the bottom, and it can be pressurized. Yes, pressurized fermentations and the use of spunding valves has recently become the thing, but these techniques, and the ability to practice them, is certainly nothing new. The vast majority of small-scale, commercial brewers around the globe with stainless steel unitank fermenters have always been able to pressure ferment and, depending on the pressure rating of the fermenter, naturally carbonate to some degree. And most of these brewers ferment their brews without any over-pressure and are happy to have closed vessels that make for handy tanks. Without further chatter, let’s jump into your questions.
I am assuming your fermenter is neither insulated nor equipped with cooling jackets. The lack of insulation means that the beer temperature will not be much different during fermentation than what you have with your carboys. The two variables that have the greatest influence on the temperature inside of a fermenter during fermentation are the area contacted by beer, as this defines where heat flows between the environment and your beer, and the material properties of the heat transfer surface. As fermentation volume increases, the ratio of heat transfer surface area and beer volume usually decreases since beer fermenters typically have shapes that proportionally grow with vessel size. Your 20-L (5.25-gallon) stainless fermenter most likely has a bit less surface area per beer volume than your 10-L (2.6-gallon) carboy.
The second vessel variable influencing beer temperature during fermentation is the resistance of the wall to heat flow, which is a function of the material (glass versus stainless), the material thickness, and the cleanliness of the surface. Glass is a pretty good insulating material and its thermal conductivity coefficient (k) is about 1.0 W/Km, whereas the k of Type 304 stainless steel (the most likely material to fabricate your new fermenter) is around 14 W/Km. The other key part of heat transfer rate is material thickness, and carboys often have glass walls that are ~5 mm thick compared to 1.5 mm for small stainless steel. The bottom line is that your new fermenter, when clean and ready for use, moves heat across its surface at about 50 times the rate of your glass carboy. Without knowing more about your current conditions it’s hard to offer specific suggestions, but if you can set your ambient temperature to around 68–72 °F (20–22 °C), you should be in good shape for most ale strains and certain lager strains. Fermentis yeast has some nice sensory and performance data that support the use of their SafLager W-34/70 up to 68 °F (20˚C).
Hopping rate is one of those variables that may or may not change much with pressurized fermentations. “It depends” is a frustrating answer for folks looking for clear information, but this is the answer to your hopping question. If your current brews have a large volume of liquid that flows out of your carboys during fermentation, you are losing hop bitterness with this blow off. And if you ferment 10-L (2.6-gallon) batches in 20-L (5.25-gallon) fermenters, there may be a good amount of hop compounds stuck to the fermenter wall. Pressurized fermentations often foam less, but not always since carbon dioxide does escape from the fermenter after the set pressure has been achieved, and less foaming usually translates to less bitterness losses. This is something you can tweak with small recipe adjustments as required.
Dry hopping can be a challenge with pressurized fermentations. The easiest way to dry hop is to start your fermentation with no pressure, add your dry hops midway through the ferment, and then attach your spunding valve. If you want to ferment under pressure from start to finish, you need to use a method that allows you to add hops without causing rapid foaming that is guaranteed to happen if you simply dump pellet hops into the top of your fermenter. Perhaps the easiest way to dry hop beer in a pressurized fermentation is to transfer 1–2 L (1–2 qts.) of fermenting beer to a clean 4-L (4-qt.) container and slowly add your dry hop addition while allowing the beer to foam and settle during the process. Allow this to sit for about 30 minutes once all of the hops are added to ensure that all of the hop bits are fully hydrated. Now you can gently de-pressurize your fermenter, quickly pour in the hop slurry, close the fermenter back up, re-pressurize the headspace, and allow the beer to finish fermenting. There are certainly other ways to do this and you should consider other options if this is not to your liking. Whatever you do, be careful of dry hop geysers!
And finally lagering duration: This is one of those things that depends on what you want to accomplish. In my opinion, once the goals of lagering, such as diacetyl and acetaldehyde reduction, yeast sedimentation, and carbonation are accomplished, it’s time to move on. No reason to lager just for the sake of counting days on a calendar. You should be able to ferment and age most ales with original gravities less than 1.066 (16 °Plato) in about 14 days, after which time you can rack to bottle or keg. Most lagers in the same gravity range will take 21–28 days before packaging. And if you have beers that require more time because of something specific, then use more time. One of the advantages of pressurized fermentations is that lagering times can often be shortened without significantly altering beer flavor. I hope this information is helpful to brew great beers with your new equipment!
