A quick reference guide for the Homebrewer
By: Jonathan Plise
Alpha Acid: Hops have Resin in them that contributes to the bitterness of beer. The higher the alpha acid% in the hop the more potential bitterness can be extracted from it. Usually alpha acids range from 2-16% AA depending on the hop varietal. Each year hops produce different amounts of AA% even if its the same hop plant year after year. This is why it is important for homebrewers to calculate out their IBU's each time so you can adjust your quantity of hops before brewing.
Attenuation: Is the amount of sugar absorbed by your yeast during fermentation. Yeast eat sugar and make alcohol. This is how your original gravity drops. A highly attenuated beer will be thinner in body and a beer with lower attenuation wil be maltier in body. Each yeast strain has a threshold of total attenuation. If you are an all grain brewer your mash temperature will effect the possible attenuation your yeast can provide for you. For example: a mash temp at 146F will produce smaller chains of sugar which is easier for your yeast to consume. A mash temp at 155F will produce larger chains of sugar and will make it harder for your yeast to break them down.
Bottle Condition: A secondary fermentation that takes place in a bottle or keg. Usually a homebrewer will bottle their beer after 7-10 days of primary fermentation and transfer to their bottling bucket. Some yeast will stay in suspension after primary fermentation is complete and will perform a secondary ferment in your 12 or 22oz bottle. In the bottling bucket you usually add 2-4oz of corn sugar depending on your final gravity. TIP: A final gravity of 1.015 or higher only add 2oz of corn sugar preboiled with 2 cups of water. The reason being is you still have a lot of residual sugar left. Your yeast will absorb the corn sugar since its a simple sugar and will make it easier for their budding sister yeast to break down the remaining sugars left over from primary fermentation.
Cold Break: The coagulation of proteins during the cooling process of your wort. The quicker you cool your wort the better off you are. With malts that have high DMS precursors like German Pilsner it is crucial to chill as quickly as possible so they are not bound and trapped in solution. Also, when you add your whirlfloc the last 5-10 minutes of the boil it breaks down and sticks to the proteins in suspension causing them to be heavier than your wort thus they settle to the bottom. TIP: If you can take your spoon and make a whirlpool right at flame out (fire off). This will help all your cold break settle in the middle of your kettle and will make a clearer transfer of wort to your fermenter.
Diacetyl: A fermentation by-product that tastes and smells like butter or butterscotch. All yeast produce diacetyl and different amounts of diacetyl depending on the strain. The trick is pitching enough healthy yeast so it reabsorbs its natural waste. Most homebrewers rush fermentation because they don't see any activity or bubbles in their airlock. Patience makes great beer. If you can let your beer go an extra 5-7 days after you think it has completed fermentation the better off you are and your beer will taste cleaner. Temperature control is a key factor too in controlling diacetyl flavors. If you stress your yeast with inconsistent temperatures they will get tired and either die or go to sleep on you and will not beable to reabsorb their waste. If you're fermenting lagers a 'diacetyl rest' is important but not required to eliminate the butter flavor. Diacetyl can also be caused by contamination which becomes more noticeably as beer ages. Usually a haze that never goes away is a sign of contamination.
Diacetyl Rest: Raising your fermentation temperature 4-8 degrees above your set temperature to help your last surviving yeast to reabsorb its diacetyl production. A 4-7 day diacetyl rest is usally enough time to rid of all buttery flavors. INSIDE TIP: A yeast like our Whitelabs 833 at 48-50F has no diacetyl flavors after 6 weeks in the primary fermenter and does not need diacetyl rest. But our Czech Budejovice yeast still has a lot of diacetyl after 6 weeks in the primary fermenter and it needs a 7-14 day rest at 55-58F to eliminate any buttery flavors or aromas. Know your yeast and you will be rewarded.
DMS (Dimethyl Sulfide): An off-flavor and aroma that resembles canned corn or cooked vegetables. TIP: A trick to rid of DMS in your beer is to do a longer boil. We recommend for all light ales and lagers to do a 90 minute boil. The first 30 minutes you boil with no hops and the last 60 minutes is when you start your hop schedule. Always boil with your kettle lid off so any DME precursors can evaporate out of solution. You can smell a corn aroma during the first 20-30 minutes of your boil. We encourage you to chill your beer as quickly as possible so DMS flavors won't be bound and trapped in solution.
Dry-Hopping: The process of adding hops directly to your fermenter or bright tank(keg). Dry hopping imparts aromas and flavors and does not add any bitterness. Most commonly used are hops that have a lot of aroma compounds like amarillo, centennial, or cascade. A typical dry hopping schedule is 10-14 days in the secondary fermenter or bright tank. You don't want to add your dry hops during primary fermentation because active fermentation will vent off all aroma's as CO2 is being produced. There are no rules on which hops to use so experiment a little.
Esters: All yeast produce esters which are the "fruity" aromas and flavors you get in beer. The trick to manipulating how much esters you want in your beer starts with temperature control, how much yeast you pitch, and the temperature you pitch at. The hotter you ferment an ale or lager strain the more esters you produce. Try experimenting with one yeast strain at different temperatures and find what works the best for you. If you under pitch yeast you can get more ester production because the yeast strain has more room to grow and replicate. If you over pitch yeast you can get minimal ester production and off flavors like "graham cracker" or "bread". If you pitch warmer than your desired fermentation temperature your yeast will replicate quicker and make more esters. If you pitch colder and let your yeast naturally rise to your desired fermentation temp you have more control over the ester production in the early stages of fermentation. Both of these practices are desired depending on the yeast strain and what you're trying to do as brewer.
Final Gravity: The amount of residual sugar left over after fermentation completes. Sugar was consumed by your yeast and turned it into alcohol. Now you have Beer!
Fining(s): A clarifying additive added to clear your wort during the end of the boil or after fermentation is complete and beer is stored cold for conditioning. There are a lot clarifiers that exist. The most common one used today in the brewery is Whirlfloc (Irish Moss). The addition of whirlfloc the last 1-5 minutes in the boil sticks to proteins and other solids that are suspended causing them to fall to the bottom during the 'whirlpool' process in the boil kettle. The majority of clarification happens in the bright tanks (kegs kept cold). When beer is stored at 35-40F solids and yeast drop out and naturally clarify in time. To speed up the process, some brewers add Gelatin to their fermenter after fermentation is complete. Gelatin sticks to yeast causing them to drop out within a week. The beer is then transfered to another bright tank (keg) where the carbonating and aging process begins.
Flocculation: Yeast cells "drop out" of solution. Higher flocculation contributes to a clearer beer. A healthy fermentation and healthy yeast have a huge impact on the clarity of the beer. Yeast clean up their environment after they have converted sugar to alcohol. Once their job is done and they have completed the fermentation process they flocculate out to the bottom and settle. Proteins also drop out which affects the clarity of the beer. This is why it is important to have a healthy boil and use a clarifier like whirlfloc. A rolling boil helps proteins separate and evaporates off a lot of undesirable aromas and flavors. See Finings for definition of whirlfloc.
Fusel Alcohol: An alcoholic harshness or "hotness" in the beer. Fusel alcohols are a bi-product of fermentation and are a result of too hot of a fermentation temperature. Yeast love warm temperatures but they produce undesirable flavors if we let them go rampant. This is why it is important for brewers to use a consistent temperature for all ales and lagers. A temperature change of more than 2 degrees can affect your beer dramatically. If your beer finished fermenting in 2-4 days it is most likely you will have fusel alcohols from too quick of a ferment. Your yeast end up consuming all their nutrients too quickly and they release fusel alcohols.
Hot Break: The coagulation (sticking) of proteins during wort boiling. As heat is applied to boil kettle a separation occurs within your wort. The sugars start the carmelization process and proteins begin to separate and rise to the surface. This happens usually within the first 10 minutes of boiling. Always stay by your boil when you are about to reach 212F (Boiling temperature at Sea Level). Boil overs are messy and a pain to clean up at the end of brew day, plus you lose beer wort!
Infusion Mash: Is the process of adding hot water to grain at a certain temperature to convert the starches to sugars. To successfully convert starch to sugar the brewer shoots for a mash temperature range from 145-156F. At certain temperatures specific enzymes play different roles in breaking down barley. A quick tip to remember: if you mash at a low temperature ranging from 145-152F you will convert smaller chains of sugars. This makes it easier for your yeast to consume these sugars thus making a dryer beer. If you mash from 153-158F you will make larger chains of sugars and have a fuller more maltier beer. For a great reference book and a more in depth explanation check out John Palmer's, How to Brew. Read chapter 14.
Single Infusion Mash: This process is the most popular and most efficient with todays available barley. Simply heat your mashtun water to 162-166F. Mix the hot water with your milled grain. Your goal is to make your mash look like porridge. Most brewers use 1.2 - 1.4 quarts of water per pound of grain. After you dough in check your mash temperature. You should be anywhere from 148-154F. Remember the temperature of your grain, kettle, and outside temperature will affect the amount of heat that is loss during the doughing in process.
IBU: International Bitterness Unit. A measure of the bitterness in beer.