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Homebrew Notebook Page: Summary Homebrew Note
Status: Ready to Use!
Source(s): American Homebrewers Association Article
Contents
Why This is Important and/or Interesting
After dehydration, dry yeast cells are dormant which helps their shelf life but it isn’t so great for fermentation. Rehydration helps revitalize those yeast cells. Think of the rehydration process as your yeast’s morning coffee.
Why not rehydrate the yeast directly in the wort instead of going through this process of rehydrating with water? The primary reason is because the dehydrated state of the yeast cells allow the wort’s sugar and other nutrients to pass through the cell walls, killing some yeast, and reducing cell counts by up to 25-30%. By rehydrating in water, the cells and their walls are in better condition.
Is this absolutely necessary? The short answer is that unless you want to buy several packets of dry yeast, rehydrating is going to be important for reaching your target pitching rate because you’re going to have to assume that 1/4 to 1/3 of each yeast packet will die during wort rehydration. (Don’t know your target yeast pitching rate? Stop here and go calculate the number of yeast cells you need.) Can you get around water rehydration by buying 2-4 yeast packets? Probably, but why spend the extra $4-12? This simple process takes about 30 minutes and you can do other things while that time is passing.
Now it’s time to get your Items Needed and start the process.
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Items Needed
- Dry Yeast
- Water
- 16 oz or larger glass jar with lid (mason jar is ideal)
- Measuring cup (not needed if using mason jar with volume markings) (my measuring cup)
- Thermometer (preferably instant read type)
- Sanitizer (preferably in spray bottle) (my go to: Star San)
- Optional: Rehydration Nutrient (e.g. Go-Ferm)
Process Gallery
Have a quick look at the gallery photos by clicking on the first image and reading the captions as you click your way through the images. Then read the Process section below for context.
Process: Rehydrating Dry Yeast
IMPORTANT: Everything in this process should be sanitized every timebefore it touches the water/yeast mixture.
Yeast health can be impacted by dramatic changes in temperature. With that in mind, start by letting the dry yeast warm to room temperature if it has been stored the refrigerator.
Once the yeast is at room temperature, sanitize your glass jar. This is most easily done with a spray bottle of sanitizer. If you have a spray bottle of sanitizer, just spray the jar’s inside, lip, and underside of its lid. If not, you’ll need to create a bucket of sanitizer to dip your jar, lid, and other equipment in. Once sanitized, close your jar to keep it that way.
ALTERNATIVE: If you don’t have a mason jar, you can use a medium or large-sized measuring cup as your rehydration jar. Simply sanitize it as described above and cover it with plastic wrap instead of a lid.
Turn on your faucet until it is running warm water. Turn on your thermometer and hold its probe under the water stream. Monitor the water stream temperature while you adjust the temperature of the water until it is running steadily in the range of 95-105 degrees F. Once the stream is steady in that range, set aside your thermometer and open the jar.
IMPORTANT: The temperature range is narrow for a reason. If you pitch dry yeast in too cold of water, large populations of the yeast will die. If you pitch dry yeast in too hot of water, all of the yeast will die. Using this method, it’s pretty easy to hit the 95-105 range. Just do it. If you pour your water and realize the temp is a bit too high, cover the jar and let it cool via ambient temps until it reaches the range. If the water is too cool, nuke it in the microwave for 5-10 seconds at a time until it’s in range. Just make sure you’re sanitizing that thermometer probe each time you check.
Pour 10 ounces of water directly from the tap into your jar per packet of dried yeast (1 packet of dry yeast = 10 oz water, 2 packets = 20 oz, etc.) and then cover the jar.
Sanitize your yeast packet and scissors. Re-open your jar.
Cut open yeast and sprinkle the dry yeast on top of water, spreading it to avoid clumps as much as possible and cover your jar.
OPTIONAL: Add rehydration nutrient to the liquid per its instructions for appropriate amounts and re-cover.
Set a timer for 15 minutes and wait. At end of 15 minutes, swirl (don’t shake) the covered jar until the yeast is fully blended and a cream is formed. Set another timer for 5 minutes. At this point, a slight foam has likely formed on top of the liquid. If it hasn’t, no worries.
Sanitize your thermometer and check the temperature of the rehydrated yeast. If the yeast solution temp is within 15 F of your wort’s temperature (remember: yeast are damaged by significant temperature changes), pitch the rehydrated yeast into the fermentation vessel as soon as possible. If not, cover the jar and run the bottom half of the jar under cold water to lower the solution’s temp. If the rehydrated yeast is well-above your pitching temp (e.g. the yeast is for a lager), you could partially fill a pot with cold water and place the covered jar in the water bath to displace the heat and get it within the 15 degree F range.
You’ve successfully rehydrated dry yeast! Now save and/or print the summarized Homebrew Notebook Page for use in the future.
Now that you’ve read this Homebrew Note, let me know if you have a question, recommended improvement, or other thoughts in the comments below. As I mention in About Homebrew Notes, these are living documents and your feedback is appreciated!