Cold Crashing Explained

February 1, 2010

I wrote a blog about how beer makers don’t know how to make cider. In it, I said that they add sugar when they shouldn’t unless they are trying to make wine, rush the cider instead of letting it age,  and they believe they can cold crash cider to stop fermentation to have a naturally sweet cider without chemicals.

Because I knew that UK craft cider makers allow their cider to ferment outdoors, which allows their cider to freeze, yet it will start fermenting again when it thaws, I said that cold crashing cider is impossible, but I didn’t know why. I asked the Cider Workshop, and Jim K responded to me.  He explained that cold crashing doesn’t kill yeast cells, contrary to home beer making beliefs, but just makes them go dormant, just like in cider making. However, the sugars in beer are not completely ferementable as they are in cider, so the yeast has a much harder time recovering from being dormant. He believes that the yeast could become active in beer eventually after a few months, but because beer makers rush things so much, chances are the beer is consumed before the yeast can be active again.

Jim also added that most good brewers use cold crashing as a way to clear the beer, much like how I use pectic enzymes, but that otherwise mash temperatures are used to control sweetness.

However, I have since been schooled by a beer maker, CvilleKevin. It turns out that I did not know the proper technique of cold crashing. He said, “Cold crashing is not the same as cooling. Chilling will make the yeast go dormant. Most types of yeast will drop to the bottom at that point. To cold crash you rack, cool, and rack again. Keep an eye on for a week or two to make sure you got it, or else you can go straight to a keg at that point.”

He continued, “By cold crashing, you are getting the yeast and nutrients to drop out of suspension and racking them out. You can do it with just about any yeast, but some are easier than others. Nottingham is very easy. One of its properties is that it flocculates at low temps and makes a nice compact sediment. Most ale and wheat yeasts are easy to crash. Wild yeast, lager yeast, champagne yeast and some wine yeasts are tougher.”

“I’ve been cold crashing cider for years without problems. I’ve got about 20 liters right now from last season that have been stored at room temp for over a year with no problems.”

When presented back to the Cider Workshop, Andrew Lea of Craft Cider Making further explained that in this context, it is not the cold temperatures that cause it to work, but instead the allowed “repeated rackings, thereby reducing yeast and nutrient to levels at which refermentation is less likely.  So it fits into that hierarchy, and there are no guarantees!”

Since asking these questions, I found Ben Watson had addressed “cold shocking” in his Cider: Hard and Sweet book on page 166. The process is as CvilleKevin described it, adding after racking that “The cider should remain at a cold temperature, and then, before bottling, you’ll need to add potassium sorbate… to guard against refermentation… All this effort strikes me as way too much of a hassle for the amateur cidermaker… A much more practical solution, and one that doesn’t involve preservatives, is to stabilize the cider after bottling by pasteurizing it, bottle and all.”

Therefore, after much research and asking of question, I now believe that “cold crashing” can be done on cider as long as racking is done with the reduced temperatures with the use of potassium metasulfite and potassium sorbate to ensure that the cider would not start fermenting again.

5 Responses to “Cold Crashing Explained”

  1. Chris Says:

    Awesome post! Fully enjoyed it and answered a lot of questions.

  2. jason Says:

    Do you think I can take a cider that is not quite done in primary fermentation, cold crash it, add sodium metabisulfite, and then force carbonate? I mostly would like to keep the natural sweetness of the original juice.

    • You would really have to dose it with SO2, and you would need sorbate to boot. Keeping it cold would help, but it will be really cloudy. I kind of recommend letting it finish, and then dosing it and adding back in juice, and then force carbonating.

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