How To Brew – Fermentation and Conditioning

Overview

The final two steps of the brewing process are fermentation and conditioning. These two steps are essential to developing a delicious beer. We are almost done, so lets finish strong!

Fermentation

Fermentation is perhaps the most important component of brewing a delicious beer. The yeast is what converts all of those sugars that your enzymes worked so hard to produce into alcohol. Besides alcohol production, fermentation also plays a huge role in flavor and character development. As discussed on the ingredients page, there are two main types of brewer’s yeast – lager and ale yeast. Choosing a strain is an exciting part of designing your beer recipe, because two different strains with the same base will give you a completely different beer. After choosing the strain you intend to use, you also need to determine pitching rates, which are discussed in their own section below.

Pitching Rates

Pitching rates can be determined in a number of ways, and it varies based on whether or not you are using a yeast slurry or dry yeast. Dry yeast is more common with homebrewers, as it is cheaper, has a long shelf life, and gives you plenty of viable yeast cells that can be prepared quickly. Dry yeast typically has about 10 billion cells per gram. Both high pitching rates and low pitching rates have a higher risk of developing off flavors, so calculating an accurate pitching rate is necessary. Some yeast strains, like hefeweizen yeast strains, actually perform better when they are under-pitched, so make sure you research your individual yeast strain before pitching the yeast.

Commercial breweries usually use yeast slurries instead of dry yeast. Weight-based pitching and cell counting with a hemocytometer are techniques that brewers use to determine slurry pitch rates. Weight based is typically somewhat inaccurate because the weight does not account for solids in the slurry. Using a hemocytometer to count cells with a methylene blue stain to determine viability is cheap, easy to use, and are great for determining cell concentration, but it is very time consuming.

A general benchmark for pitching rates is 6 million cells per milliliter of wort for an ale, and 12 million cells per milliliter of wort for a lager. For beers that have a higher starting gravity, you may need to pitch additional yeast. For example, according to Wyeast’s pitching rate estimator, if you are brewing an ale with a starting gravity at 1.070, you will need to pitch 12 million cells per milliliter of wort for a successful fermentation.

Rehydrating Dry Yeast & Yeast Starters

Rehydrating dry yeast is a very simple process that will help ensure your yeast is ready for fermentation as soon as you pitch it. All you have to do to rehydrate your yeast is to put 1 cup of pre-boiled water (to kill all microorganisms) at 77 to 86 degrees Fahrenheit into a sanitized jar and sprinkle the yeast on top. Do not stir it, just cover the jar with plastic wrap or aluminum foil and let it sit for 15 minutes. After 15 minutes, very gently stir the yeast to make sure all cells are wet. Stirring too aggressively will introduce oxygen to the yeast and they will begin to use their nutrients. Re-cover and let sit for another 15 minutes. Swirl the jar right before pitching to get all the yeast in suspension.

Yeast starters are a little more difficult than rehydrating dry yeast. Many homebrewers use yeast starters to propagate additional yeast since liquid yeast is so expensive. You will need a large pot, a glass Erlenmeyer flask, an airlock or aluminum foil, and wort. The steps for creating a yeast starter are below.

Yeast Starter Process

• Determine how much wort you need to propagate your yeast. I would recommend using the 1-step-10 fold method. This means to take your final fermentation volume and divide it by 10. For example, if you are brewing a 10 gallon batch, you would need 1 gallon of wort. You can get this wort from a previous batch, or use malt extract.
• Boil the wort or extract for at least 15 minutes and cover when done. If you have some zinc rich yeast nutrient, I would recommend adding some to the starter.
• Cool the wort to about 70 degrees Fahrenheit by placing the covered pot in a sink of cool water. Once cooled, pour the wort into your sanitized Erlenmeyer flask. Pour everything from the pot into the flask, including the sediment at the bottom.
• Cap your flask and shake the wort vigorously to add oxygen before adding your yeast.
• Sanitize the outside of your yeast package and the scissors you intend on cutting it with. Add the yeast to the flask and give it a slight swirl to mix the yeast in. Put your airlock on the flask if you have one, but if you do not, a clean piece of aluminum foil will work. Both will vent the carbon dioxide while simultaneously preventing airborne microorganisms.
• Propagation should take between 24 and 48 hours. You may want to chill the starter overnight to have the yeast settle to the bottom. That way, if you used malt extract or a different wort than what you are pitching the yeast into, you can pour out the excess starter beer that is covering the yeast slurry and pour the fresh slurry into your wort.

Tips on Fermenting

There are a number different fermentation schedules you can follow, but I will describe the ones I use here. I recommend researching the yeast strain you are using before developing your fermentation schedule. There are numerous forums online where homebrewers and professional brewers alike will discuss what works best with what strain. You can also look at our recipes page to see what we recommend.

Ale Yeast

For ale yeasts, I generally pitch the yeast at 64 degrees Fahrenheit, let the temperature free rise up to 67 degrees and ferment there for 5 to 7 days depending on the specific strain and generation. Once the fermentation begins to slow down towards days 5 to 7, I will let the temperature free rise up to 72 degrees for the diacetyl rest. You can also decide when to start the diacetyl rest based on the gravity of the beer, and begin the rest when you are about 5 points away from terminal gravity. Raising the temperature will re-invigorate the yeast, causing them to clean up byproducts they created early in fermentation. Let the beer rest at 72 degrees for 4 to 7 days, and then cold crash down to 33 degrees. Cold crashing helps force the remaining yeast to flocculate together and fall out of solution. This will help clarify your beer. After about 1 to 3 days at 33 degrees, transfer to wherever you do your carbonation process.

Lager Yeast

Lagers are a little more difficult to ferment. I usually pitch the yeast around 48 degrees and let the temperature free rise up to 54 degrees as fermentation begins. Remember that lagers take double the yeast that ales do. Hold the temperature here for about 5 to 6 days, and then allow the beer to rise up to at least 68 degrees. For lagers, the diacetyl rest is extremely important. Diacetyl reduction is much slower at colder temperatures, so you really need to raise that temperature to let the yeast clean up after themselves.

Once it reaches rest temperature, let it rest for at least one week. I usually let mine sit for around 2 weeks. After your rest, you need to slowly step it down to lager temperature. I lower the temperature of my lagers by 4 degrees a day until it reaches a temperature of 33 degrees. Gradually lowering the temperature prevents shocking the yeast and making them fall out too quickly. After 3 to 5 days at this temperature, transfer to either your secondary, keg, or bottles depending on your next step and have the beer lager between 33 and 38 degrees for 3 to 6 months depending on the style and alcohol content. Higher abv beers will need longer to lager to mellow out.

Conditioning

Once your beer is fully fermented, you will want to transfer it to either a secondary vessel such as a brite tank, or to what you plan on serving it out of such as a keg or bottles. You don’t want to let your beer sit on the yeast for too long, no more than 4 weeks, or the yeast begin to experience autolysis, which is when the yeast cells rupture and release unpleasant off flavors into your beer. This is the final step before consumption.

Kegging From the Fermenter

Kegging is more expensive than bottling, but is very nice to do once you have all the required equipment. You will need a keg, a carbon dioxide regulator, and a carbon dioxide tank. You can buy a brand new stainless steel keg, or you can try and find a used soda keg. If you find a used soda keg, you need to disassemble it, remove and replace all gaskets, and thoroughly clean the remaining parts. I would use pbw as an initial wash, and then an acid wash if you have access to some. Before you use the keg, make sure all the gaskets, tubes, and the keg itself are sanitized before transferring.

Process

Make sure the line you are using to transfer the beer is sanitized. Assemble the keg without the lid, and dump remaining sanitizer out, but do not rinse. Connect your carbon dioxide to the gas-in connection on the keg and set at a low pressure to quickly purge the keg. Turn off the carbon dioxide and transfer the beer into the sanitized and purged keg. Once filled, turn the carbon dioxide back on at a low pressure to purge any remaining oxygen, and then seal the lid. Set the pressure to the required level to get your desired volumes of carbon dioxide at your given temperature, and let it sit for 4 to 6 days. Once your beer is carbonated it is ready to serve. Adjust your carbon dioxide regular for serving so that the residual pressure in the keg is about 0 to 5 psi. This means that your serving pressure is usually around 10 to 15 psi. This balances the pressure difference and gives a less foamy pour.

Bottling

Bottling is a great way to start learning about the conditioning and packaging process. It is inexpensive, and easy to learn. There are just a few things to note beforehand. One is to make sure fermentation is fully finished before bottling. Bottling too early can lead to too much fermentation in the bottles and result in an over-carbonated, foamy mess. Not only this, but the pressure can exceed the bottle strength and shatter, which is one heck of a mess to clean up. You can order new bottles from a homebrew shop, or used ones, but regardless, they need a good cleaning before use. Many homebrewers also use the flip top bottles to take out the capping process. Use pbw and a nylon bottle brush to scrub the inside of the bottles. Make sure any residue is completely out. Once the bottles are clean, rinse them and fill them up with sanitizer. While sanitizing the bottles, also sanitize the priming container, bottle caps, a stirring spoon and a siphon.

Process

To carbonate your beer in the bottles, you will need to first make a priming solution. This is done by adding a small amount of sugar to your beer to re-start the yeast. Any kind of sugar can be used, but keep in mind the flavor it may add. Sugars like molasses and honey can cause a slight aftertaste, while white cane sugar does not. You will want to add about 3 gravity points to your beer to get the carbonation level you want. Below is a list of estimated amounts of sugar to add at room temperature for 2.5 volumes of carbon dioxide in a 5 gallon batch. Feel free to scale up.

Amount of Common Sugars to Add to a 5 Gallon Batch

You’ll want to add the sugar into the beer before bottling. It is a pain to put it in each bottle, tends to be inconsistent, and has a higher risk of over-carbonating. To make your priming solution, follow the steps below.

• After deciding what sugar you are going to use, mix it with about 2 cups of water per 5 gallons of wort and boil it. After it boils for about 10 minutes, let it cool to room temperature.
• If you have a separate vessel for bottling, make sure it is sanitized. Once sanitized, pour your priming solution into the bucket. Gently siphon your beer into the bottling bucket, with the end of the siphon below the surface of the priming solution to prevent splashing. This is to ensure you do not add any oxygen to your beer. When siphoning, make sure you are pulling from above the yeast bed at the bottom of the fermenter. If using a racking arm, keep the racking arm above the yeast bed. Once the beer is all transferred, gently stir the beer to mix in all the priming sugar evenly. Again, make sure to stir very gently to not add any oxygen.
• If you do not have a separate bottling vessel, you can pour the sugar into your fermenter. Just gently pour the priming solution into the fermenter and gently stir it all together to prevent the addition of oxygen. Let everything settle before bottling.

How to Bottle

Now that you have your priming solution mixed into your beer, it is time to bottle it. Make sure the bottles and the caps are sanitized. Empty the bottles and place your filling tube or siphon into the bottle so that it fills without splashing to avoid adding any oxygen. Keep the tube below the beer level to keep agitating the beer to a minimum. Fill the bottles until there is about 1 inch of head space to the top of the bottle. If there is foam in that head space, that is even better. The foam will help prevent oxygen from remaining in the bottle. Cap the bottles as soon as you take the filling tube out, and place the filling tube immediately into the next bottle to keep it clean.

Once the bottles are filled and capped, keep them at room temperature for around 2 weeks to ensure the yeast ferments the priming sugar to carbonate your beer. Once the bottles are carbonated, store them as cool as you can. Cool storage will slow the oxidation process. Also keep them out of direct sunlight to prevent spoilage. Once your beers are carbonated and cooled, they are ready to be enjoyed! But be warned, pour easy as to keep the last bit of yeast that is settled on the bottom of the bottle from going into your glass. The yeast will not taste great, and is a powerful probiotic.

Closing

And that’s it! I know it seems like a lot, but working through it a few times will help it all make sense. Reading it is one thing, but there is no better way to learn how to brew than to do it. You will make mistakes, but you will learn invaluable lessons from those mistakes. Start small and scale up, learn every part of your brewing system, and if something does go wrong, try to pin-point the part of your system that has the issue.

For example, if you have a low starting gravity, utilize a brix reading of your pre-boil gravity to see if it is the mill, the mash, or the boil that is giving you issues. And whatever you do, have fun. There is no better time to start than today. If you have any questions or comments, please feel free to leave a comment or send us a message. Cheers!