From Field to Glass

Beer can be produced from a variety of grains, but the barley kernel contains all of the indigenous enzymes required to fully convert the starch reserves into fermentable sugars, and so it is the dominant grain in beer making. It’s almost as if barley’s very existence was designed for producing beer!

NOTE:   this is a general overview of the beer making process.  A deep dive through each step in one article would result in an obscene amount of reading.

Barley (Hordeum Vulgare) is a grass, and a relative of rye and wheat. It can grow in a wide range of conditions but prefers cooler, drier climates. The two main types of barley used for brewing are known as two-row and six-row, referring to the rows of kernels on the head. The two-row variety yields fewer, but plumper, kernels and tends to be lower in proteins than the six-row variety. Specific barley cultivars are grown and harvested for malting. Barley destined for animal feed are designed with a higher protein content, whereas with barley destined for the malthouse, lower protein is desired. Some protein is essential in beer as it helps with foam stability, provides nitrogen for the yeast during fermentation, and contributes positively to mouthfeel. Too much protein however, can not only affect mashing, but cause undesirable haze in the finished product. 

Malting

Once the barley has been harvested, it is sent to the malthouse. The grains are steeped in water until moisture content is between 40-48% of its original weight. The water is then drained away and the barley is left to begin germinating. This germination process prepares the kernel to start a new plant. Rootlets emerge, the embryo develops, and the acrospire, which is the beginning of the stalk of the new plant, starts to grow between the husk and the endosperm, which is the kernel’s energy bank. The endosperm holds a reserve of starches locked in by proteins, and as part of the germination process, enzymes begin to break apart these proteins, releasing the starches. If left unchecked, the kernel would use up these starch reserves for energy and attempt to grow a new full plant. So before the kernels can fully germinate, the rootlets which have sprouted are knocked off and the barley is moved to the kiln. 

The kilning process dries out the malt and adds colour and flavour, but crucially, it halts the germination process. Not only do we not want a new plant, we don’t want all of those starches to be used up or we’d get no beer. That would be devastating. Time spent in the kiln and the temperature determine whether we get a highly fermentable pale base malt, a virtually unfermentable black malt, or everything in between. Every beer and beer style has a unique grain bill or recipe which will typically call for enough base malt to provide enzymes and fermentability, and any variety of additional malts for flavour and/or colour. 

Milling

The malt is then crushed in a mill, taking care to achieve the proper balance between cracking open the endosperm enough to make the starches available, and leaving the husk as intact as possible. We need the husk to be intact for two reasons, first, it makes a good filter bed for the wort to drain through, and secondly, the husk contains a bunch of polyphenols, also called tannins, which can lend a harsh astringency to the finished product.  

Mashing

The crushed grain is put into a mash tun, which is a temperature controlled vessel, along with hot water (strike water), to mash (steep). In a homebrew setting, a cooler with a false bottom or screen and a drain works well. The mashing process hydrolyzes the starch molecules and activates various enzymes which begin breaking down the complex starches into shorter chain sugars. There are a number of enzymes at play here, and they are all activated and denatured at different temperatures. The main enzymes we are concerned with here are Alpha-Amylase and Beta-Amylase. Alpha-Amylase activates at 72-75°C and denatures at 79°C. Beta-Amylase activates at 60-65°C and denatures at 72°C.

Several different mashing regimes exist. Infusion mashing, which involves holding a specified temperature for the duration of the mash has become standard. Decoction Mashing involves pulling a quantity of the liquid out of the mash tun, heating it, and reintroducing it to the tun. This process raises the temperature in steps allowing for the activation and deactivation of certain enzymes. Decoction mashing was more essential at a time when malts weren’t as modified. It is still used in some traditional German and Czech beers. Turbid mashing is an old Belgian technique whereby liquid is pulled from the mash tun at various stages and heated to denature and halt enzymatic activity. This liquid is not reintroduced to the mash-tun until mashout. The result is a hazy dextrin rich wort. Turbid mashing is used for Lambic style beers and in situations where inoculation by wild organisms is encouraged. 

Vorlauf, Lautering, and Sparging

Once all, or at least most of the starches have been converted, it’s time for mash-out, which means raising the temperature, usually with hotter water, to denature all enzymes, and lock in the fermentability of the liquid, which is called wort. Now we need to get this sweetwort into the kettle. Step one, vorlauf, involves recirculating the liquid back through the grain bed. This clears the wort somewhat of particulate and allows the grain bed to settle. The liquid in the tun is then drained off into the boil kettle (lautering) and hot water is then sprinkled over the settled grain bed (sparging), essentially washing any residual sugars into the kettle. This process continues until the pre-boil target gravity or volume is reached. 

The Boil

The boil achieves several things: it sterilizes the wort, concentrates the fermentables evaporation, volatizes off certain undesirable flavour compounds, and isomerizes the alpha acids from the hops. The boil is vigorous and usually lasts 60-90 minutes depending on the brewers preference and the beer style.  

Sterilization is pretty straight forward since 60 minutes at 100°C is going to kill most pathogens.  It’s worth noting that high temperature pasteurization takes place at 72°C, for around 15 seconds. 

Present in malt, and especially paler base malts, is the compound S- Methyl Methionine (SMM).  At around 80°C, SMM breaks down into Dimethyl Sulphide (DMS). The aroma of DMS is often described as cooked corn, or cabbage. Although acceptable and present at very low levels, this is not something very much. The good news is that DMS is quite volatile and through vigorous boiling, it is mostly driven off. 

Hops are introduced into the boil kettle at various stages with various outcomes. The hops added at the start of the boil are called bittering hops. The main bittering compounds in hops are known as alpha-acids, they are adhumulone, humulone, and cohumulone. Pre-humulone and post-humulone are also present, but in such low quantities that they are of little concern here. None of these alpha-acids in their original form are very soluble in water and so they need to be isomerized into trans-iso-hulumlone, cis-iso-humulone, trans-iso-cohumulone,  cis-iso-cohumulone, trans-iso-adhulumlone, cis-iso-adhumulone. Isomerization is the rearranging of molecules within a specific compound, while the original individual molecules remain the same. Think about it like people getting up and switching seats at the dinner table. The people remain the same, the seating arrangement changes. Maybe this provides for better conversation, or worse, I don’t know. Isomerization makes these alpha-acids much more water soluble and reactive with oxygen, allowing them to impart the bitterness into the wort. 

Hop additions made later on in the boil, specifically towards the end, are considered the flavour and aroma additions, since limited time in that heat will restrict any isomerization of the alpha acids. Also, the essential oils responsible for hop flavour and aroma are fairly volatile and would be mostly boiled off if added earlier on. Flavour and aroma hops are added prior to, and at knockout (when the boil kettle is removed from the heat), in the whirlpool which we shall get to next, and in the fermenter, which is called dry hopping. 

The Whirlpool

Now that the boil is done, whirlpooling is a common but non-essential step. A whirlpool is how it sounds. In a commercial setting, there is an inlet in the side of the kettle, or separate whirlpool vessel. Wort is pumped out and then back in through this inlet at a high rate creating the whirlpool effect.  What this does is create a sort of a centrifuge, and separates out the residual hop and grain particulate into a pile. It is a way of pre-clarifying the beer. In a spartan home brew setting, swirling the wort around with a spoon may achieve a less effective version of the commercial whirlpool.

Chilling

As quickly as possible, that hot wort needs to cool down. First, a gradual cooling would open the door for infection, second, that pesky SMM we spoke of earlier is still lurking around and ready to transform into more DMS. We want to get from the boiling zone where DMS is volatilized off, to under 80°C where it isn’t being produced, and then down to yeast pitching temperature. 

There are several types of chillers. Home brewers often use an immersion chiller, which is a long coil of copper tubing through which cold water flows. Counterflow chillers, which either consist of a large number of stacked plates, or a loop or coil of tubes inside tubes allow the hot wort to flow in one direction while cold water, or glycol, flows the other direction. This allows the wort to cool rapidly to the target temperature, generally ~20°C for ale and ~12°C for lager. There are other methods of chilling such as coolships which are large open vessels, but these are used in the production of beers where wild organisms are welcome and essential. The cooled wort now flows into the fermenter.

Aeration and Pitching

Before pitching the yeast into the cooled wort it is essential to ensure there is enough dissolved oxygen. The yeast require oxygen at the beginning stages of fermentation for reproduction and to produce sterols which are essential to cell membranes. Once the desired oxygen level is achieved, the yeast is pitched into the fermenter, which is then sealed off with an airlock which allows gases to flow out, but not in. Most yeast these days are healthy enough to pitch straight from the package, and are available in both dried and liquid form. In the past the dried yeast needed to be hydrated prior to pitching, but nowadays most yeast providers indicate that hydration is unnecessary. In situations where yeast cell count is low, or in high gravity brewing, it may be necessary to make a yeast starter. 

Now the fermentation process begins. 

Dry hopping takes place at this stage as well but it should be noted that the vigorous fermentation activity can carry off some of the hop aromas in the escaping CO₂. More hops can be added after fermentation activity settles down. 

There are a variety of different fermenters. Stainless steel cylindroconical are the most common in a professional setting, but horizontal tanks and flat bottom fermenters also exist. Plastic buckets or glass carboys are often used in homebrewing, although a host of stainless options are now available. Open fermenters can be used in situations where wild yeasts and bacteria are desired. 

Clarifying

Clarifying the beer can be achieved by fining, filtration, or allowing the beer to “drop bright”.  

Fining is a process whereby proteins, polyphenols and a other compounds are attracted to an additive substance that promotes clumping and the subsequent dropping out of solution. Irish Moss ( carrageenan) is a seaweed based fining that is added to the boil. All other finings are added at the end of fermentation. Isinglass, which is the swimming bladder of various fish, consists mostly of collagen, and is commonly used in cask beers. Gelatin, Polyvinylpolypyrrolidone, and silica are other commonly used finings. This process promotes a clearer beer and reduces the chances of chill haze.

Filtration is as it sounds, and various types of filters can be used, usually sheet or plate filters. In some settings a filtration medium is employed. Common media are diatomaceous earth, a sedimentary rock consisting mostly of silica, and perlite, a volcanic glass.  

Dropping bright is a process where the beer allows gravity to pull suspended yeast to the bottom of a vessel. Care must be taken not to rouse the settled particulate when transferring the beer. 

Maturing

By now the wort has transformed into ethanol and carbon dioxide, but it is not yet finished. This is called “green beer”. Various byproducts, acetaldehyde, and diacetyl, to name a couple, need to be reabsorbed by the yeast which takes some time. While ales can be ready more quickly, lagers require a longer cool rest to fully mature. 

Packaging 

The finished beer can be now packaged into bottles, cans, kegs or casks. But of course what would it be without carbonation! Carbon dioxide is one of the two major outputs of fermentation and so beer can bottle conditioned, or cask conditioned. Bottle conditioning involves adding fresh yeast to the beer before packaging, assuming there are enough fermentables remaining in the beer, or adding a priming sugar, usually dextrose in the homebrew environment, assuming there is healthy and viable yeast still in suspension. In the cask situation, the beer is introduced to the cask before it is fully finished fermenting, the result being a gentle carbonation from the conditioning.

Forced carbonation is when CO₂ is forced into the beer until the desired volume is reached. This is how kegging works, and how most commercial beer is carbonated.

The final step of course, is to pour the beer into a glass and enjoy!