Spoiler Alert: If you haven’t taken Cider Quiz #1, click here to take it before exploring the answers. Question #8 explores malolactic fermentation (MLF). You will find various related articles, including one specifically focused on this questions at the bottom of this page.
Question #8: How do you encourage malolactic fermentation (MLF) in your cider?
Malolactic Fermentation (MLF) isn’t actually a fermentation process. It doesn’t create ethanol like fermentation, but it does release carbon dioxide (CO2). This decarboxylation process, the releasing of CO2, is why it was incorrectly given the “fermentation” moniker. For cider makers, it is one of the most misunderstood and under appreciated processes in your toolkit. How is it misunderstood? Because, so many cider recipes and online forums include advice that could delay or restrict malolactic fermentation from happening. You really should be encouraging the MLF process as it can help reduce acidity (i.e. make your cider taste sweeter) and encourage aging characteristics. How do you encourage MLF?
1. Age the cider on fine lees (sediment) at around 18-21C (66-70F): Correct Answer – Unlike gross lees, fine lees are mostly yeast cells, which are full of nutrients and compounds needed by lactic acid bacteria. When the yeast settles to the bottom of the container, they start dying. This creates the process called autolysis, which is where dead yeast cells rupture and release the many nutrient compounds needed by lactic acid bacteria. You can age on gross lees, which is the sediment from primary fermentation but this often contains a lot of apple solids. This harbors air and enables acetic acid bacteria to form acetic acid. Also, aging at warmer temperatures encourages the autolysis and MLF process. Cold slows all reactions so storing your cider on fine lees at a slightly elevated temperature is the best way to encourage malolactic fermentation.
2. Add sulfites (Campden) after fermentation completes: Incorrect Answer – This is the worse thing you can do to encourage malolactic fermentation. Sulfites are very effective at inhibiting the organisms that perform malolactic fermentation, lactic acid bacteria. There is the incorrect perception that adding sulfites kills or inhibits the “bad” organisms, but what you are really doing is inhibiting lactic acid bacteria. The single most important organism for cider once fermentation completes.
3. Use EC-1118 yeast: Incorrect Answer – Inoculating with yeast, EC-1118 or something else, generally doesn’t impact the malolactic fermentation process. MLF generally occurs after primary fermentation completes, or very near the end of the fermentation process. Yeast tend to naturally inhibit bacteria so active fermentation need to stop or reduce before the lactic acid bacteria can start growing. The one exception is if you inoculated with a yeast like Lalvin 71B, which actively converts malic acid to lactic acid using a malo-ethanol fermentation pathway. In this situation, you no longer have the malic acid to convert for MLF.
4. Pasteurize the juice before fermenting: Incorrect Answer – This action can be even worse than adding sulfites to your juice prior to fermentation. Heat pasteurizing your juice kills all the natural organisms in it. That includes the lactic acid bacteria needed for malolactic fermentation. If you want to encourage malolactic fermentation and you only have access to heat pasteurized juice, consider adding some fresh apple peel to the cider. The skin will contain the natural organisms originally found on the fruit, which includes lactic acid bacteria.
Don’t be afraid of the lactic acid bacteria you find naturally on your apples. It’s an often misunderstood organism that should be embraced by cider makers. Encouraging this process will often lead to sweeter and better tasting ciders. Want to explore more details about MLF and lactic acid bacteria, check out the following articles or search MLF on the site.
Hard Cider Tip #28: Malolactic Fermentation
There is an often referenced but just as often confusing process in hard cider making called malolactic fermentation. You might see it abbreviated by the acronym MLF and sometimes referenced…
Cider Question: How can I encourage Malolactic Fermentation (MLF)?
Malolactic fermentation (MLF) is a process that usually occurs after primary or alcoholic fermentation completes. Fundamentally, it’s the conversion of malic acid to lactic acid. Malic acid is more acidic…
The Overview: Lactic Acid Bacteria
In other articles, I described how the apples and yeast you use are the two most important elements in defining the quality of your hard cider. However, there is another…
Cider Words: Autolysis
Why does the flavor of cider change when it ages? Part of those changes can come from bacteria or yeast. This micro flora can make malolactic fermentation (MLF) occur or…
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