Cold Crashing Explained

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.

Bottling

In my last post, I said that when the must clears, there is another layer of lees, and the airlock stops bubbling, that it is time to bottle. However, before bottling a batch, test it first with the hydrometer to make sure all the sugar is gone. If there is some present and the yeast continue to work on it in a bottle, the pressure from the released CO2 could cause the bottle to explode. I also rack one more time minutes before bottling so that I don’t have to worry about sucking up lees when bottling. Using a hydrometer, a batch is ready to be bottled if it is 1.005 or less. If it is ready, it needs to be chemically treated to ensure it stops fermenting so that it does not release any more CO2 and create a “bottle bomb.”

Bottling works just the same as racking, only instead of having a second jug, there are bottles to fill up. When I bottle, I put the sterilized bottles on a chair with a large towel that I don’t care if it gets stained or not. The sterilized bottles are lined up to make it easier to process. I rack by either putting a clamp on the siphon tubing so that I can stop the flow and move my tubing to the next bottle, or I use a bottling wand. I got mine from my local supply store, and it is a tube with a ball in the bottom that has a little rod sticking out. Gravity and the force of the flow will push the ball down, blocking the flow, but when it is placed in the bottom of a bottle, the rod pushes the ball up, allowing liquid though.

When bottling, keep the hose or wand at the bottom to prevent splashing and too much contact with air. Fill the bottle as full as possible and then remove the hose or wand. The level will drop since the hose or wand was taking up space. Ideally, the bottle should only have half an inch to one inch of space between the top of the fluid to the cap or cork to minimize the amount of air in the bottle, or headspace.

I find bottling easier to do with two people. One person bottles while the other person takes away the full bottles and replaces them with new bottles. The second person may even have enough time to cork or cap the bottles, depending on the equipment. If there is only one person available for bottling, I highly recommend sterilizing a plate so that the tubing that goes in the bottle can be set down without contamination or the need to sterilize it again.

I should note that this is the method used for making a dry still drink, like wine. I’ll talk about how to make the drink sweet or carbonated in a later blog.

Racking

When I was talking about air being the enemy of cider, I mentioned that when there is no more sugar in the batch, the yeast die and fall to the bottom in process called flocculation and create lees. The lees will be a pile of sediment in the bottom of the jug, which will be easy to see if the jug is clear. If there is no more air passing though the airlock, then it is time to move to the next step of the wine and cider making process of racking.

Racking is siphoning the liquid, now called must, off of the lees. If it is not done, the must will take on an unpleasant flavor from the lees. I once heard a cider maker say something about he had never lost a batch of cider racking to early, but he had lost a batch from racking too late. I use that piece of advice in my winemaking.

It is easiest to take the jug and place it on the counter and leave it for a few minutes so that any disturbed lees can sink to the bottom again. A second container that has been sterilized will be placed at a lower elevation from the first container, such as on a chair or on the floor. I prefer a chair because I don’t have to bend down as much, it is easier to see, and it doesn’t require the hose to be as long or as much worry about it coming out. From here, there are two methods. The cheaper method is to take a sterilized hose and put it in the first container above the lees. After swishing your mouth with vodka to “sterilize” you mouth, drop down and begin sucking on the other end of the tube gently to start the siphoning process, and then place the other end in the second container. The better way to siphon is to purchase a siphon device from the supply store, sterilize it, and follow the directions provided.

Try to avoid splashing when racking to avoid contact with air to help prevent oxidization, which dulls the flavor. Pull the tub or siphon out of the first jug slightly before it would suck up any lees. Place an airlock on the second container and set it aside. After the first racking, the must may still be a little hazy and it may continue to push CO2 though the airlock, which is okay. After a few weeks or even months, if pectic enzyme was added, the must will clear, the airlock will stop bubbling, and there will be another layer of lees present. Then it is time for bottling.