Although you may be an experienced home brewer regarding beer, hard cider is substantially different. A common source of confusion among cider beginners is fermentation time, with widely varying recommendations for primary and secondary fermentation. Can you ferment cider too long?
It is possible to ferment cider too long, and leaving it in the primary fermenter for more than a year will yield a spoiled product. However, leaving it for weeks or months will do no damage and even result in a superior cider, although this is subject to personal preferences.
There are many ways of making cider, and which you settle on will depend on your taste. There is a lot of variation in how long people keep it in primary and secondary fermentation. While you can ferment cider too long, you can ferment it longer than you think.
How Long Is Too Long In Primary Fermenter?
There are some things we can state definitively about time in primary fermentation: if you have left your cider for more than a year, you have let it ferment too long. You will almost certainly have bitter off-flavors and likely acetic acid fermentation (vinegar spoilage), which means you now have apple cider vinegar on your hands.
Nevertheless, there is a lot of variability in how long brewers leave their cider in primary fermentation. Some advocate that cider should not sit on the lees (dead yeast) for long as this will introduce off flavors, while others say that some of their best cider has resulted from letting it sit on the lees for months.
Many variables account for such conflicting advice. The pH and temperature of your fermenting cider will affect how long you should leave it in the primary fermenter, as will the type of yeast. If you need more experience, find a good recipe and follow it closely.
Some recipes call for as little as three days, although they generally say that up to seven days will still work for that style of cider. Such recipes typically require you to use a Campden tablet to sterilize the raw apple cider of acetobacter that cause vinegar spoilage and inhibits wild yeast strains from growing.
Most cider recipes specify a minimum of two weeks in the primary fermenter, with three to four weeks preferable. Brewers generally agree that the cider can be left to ferment for much longer.
Other brewers prefer to let wild yeasts do the fermenting and typically leave the cider in the primary fermenter for weeks to months, as these yeasts need longer to do their work.
Personal preference also plays a role, as some cider styles are supposed to sit on the lees for longer to develop a fuller mouthfeel, nuttiness, and funky esters. You will have to experiment to see whether such cider appeals to you.
When Should I Move To Secondary Fermenter?
Knowing when to move the cider to the secondary fermenter can be tricky, as the duration of primary fermentation is a matter of personal preference, fermentation conditions, and the specific yeast used.
Gauging the optimal time to move the cider to the secondary fermenter is about striking a balance between letting it ferment enough in the primary fermentation vessel to develop flavor while avoiding yeasty off flavor or undesired malolactic fermentation.
You should transfer the cider to the secondary fermenter when satisfied that it has obtained the full benefit of primary fermentation but has not deteriorated. Although you can leave it too long, do not worry too much about the timing; cider is forgiving, and you may even have a pleasant surprise from leaving it longer than you intended.
How Do You Know When Primary Fermentation Is Done?
Even if you think your cider has had enough time in the primary fermenter, we recommend you use other methods of assessing whether primary fermentation is done. You can do so by monitoring the airlock or measuring with a hydrometer.
As long as the yeast is still working on the sugars in the cider, it will produce ethyl alcohol and carbon dioxide gas. This gas bubbles out through the airlock at around one bubble per second or less. While bubbles are still escaping from the airlock on the primary fermentation vessel, you know that fermentation is still ongoing.
When the bubbles stop, primary fermentation has likely finished. Take note that S-style airlocks are far more accurate than canister ones.
However, to be more confident of this, we recommend you purchase and use a hydrometer. This device measures the density of sugar in a solution. The more sugar dissolved in a liquid, the higher the specific gravity of the solution, and the higher the level in the hydrometer floats.
As fermentation proceeds, the sugar gets used up by the yeast (converted into alcohol and carbon dioxide), and the density of the solution diminishes. As a result, the level in the hydrometer falls, indicating a lower specific gravity.
Test specific gravity with the hydrometer daily, and when you get the same result for three days in a row, primary fermentation is probably done. The reading should be around 1.006 to 1.008 for fully-fermented cider, although if you prefer more carbonation, aim for about 1.018.
When Should Fermenter Start Bubbling?
Bubbles escaping from the airlock are a sign of fermentation. You may wonder when you can expect to see bubbles coming from the fermenter.
If you have a clear fermentation vessel (glass or transparent plastic), you will see the bubbles forming inside, and this can occur at any time from 24 hours after pitching the yeast to as much as 72 hours afterward. Lower temperatures slow the yeast’s fermentation action, as do higher initial sugar concentrations (higher specific gravity).
You may or may not see bubbles escaping from the airlock. Unless the cover of your fermentation vessel seals tightly, carbon dioxide gas can easily escape from under it, and then you will not see any gas bubbles coming out through the airlock.
So if you have an opaque fermentation container, and there aren’t any bubbles coming out of the airlock, even after three days, you do not need to worry. It may be that the gas is escaping elsewhere and that your cider is fermenting nicely.
So do not rely on observing bubbles coming from your fermenter. Purchase a hydrometer and use it to measure the specific gravity of your cider daily. These measurements will give you a much more accurate picture of what is happening to your cider.
While you can ferment cider too long and spoil it, you probably didn’t realize how long you could leave it in the primary fermenter. The general guide for how long to ferment it is three to four weeks. To ensure that it has finished fermenting, we recommend using a hydrometer.
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