Editor's Note:
Before we begin, I want to get this out of the way. Sometimes malolactic fermentation is referred to as MLF, and lactic acid bacteria are referred to as LAB. Well, I hate acronyms. I've always hated acronyms, and I will forever hate acronyms. Damn them all to hell! I find them to be annoying, lazy, witless and a defecation upon the natural beauty of language. After all, say out loud "malo-lactic fermentation" and observe how those phenomes roll velvety off the tongue. Consequently, as God is my witness and over my dead body, you will NEVER catch me using acronyms. So dive right in, enjoy this article, and learn some things about MLF and LAB.
Understanding Malolactic Fermentation (MLF - ha ha, just kidding)
Malolactic fermentation is a secondary fermentation process in which lactic acid bacterial convert malic acid into lactic acid. This process reduces cider's overall acidity and can impart a smoother and more complex flavor profile. Unlike the primary fermentation driven by yeast that we've explicitly added, malolactic fermentation is a bacterial fermentation that occurs naturally under the right conditions. If you are using fresh, preservative free and unpasturized cider, there is a good chance that the malolactic bacteria will be present.
Incidentally, in the context of cider and wine making, the term "malolactic bacteria" is often used interchangeably with "lactic acid bacteria" to specifically refer to those bacteria that carry out malolactic fermentation.
Advantages of Natural Spontaneous Malolactic Fermentation
It's gotta be good for something, or we wouldn't be talking about it, right?
1. Enhanced Flavor Complexity:
- Malolactic fermentation can add depth and complexity to the cider's flavor profile. The conversion of malic acid to lactic acid can create buttery, creamy notes and enhance the overall mouthfeel.
2. Reduced Acidity:
- The process reduces the sharpness of malic acid, which is replaced by lactic acid, resulting in a smoother and more balanced cider. This can be particularly beneficial for apples high in malic acid, which might otherwise produce a very tart cider. Think about biting into a Granny Smith apple and the tremors that ripple through your teeth and across your tongue. That's malic acid.
3. Natural Process:
- Yes, malolactic fermentation is all natural, and if you're using organic cider, then we can say it's organic too. Can't get more earthy-crunchy than that!
- Natural lactic acid bacteria are often present with the apples, and the malolactic fermentation occurs spontaneously and without any annoying intervention from us. For cider makers wanting to produce a beverage with minimal intervention and additives, this is a bonus.
Disadvantages of Natural Spontaneous Malolactic Fermentation
Okay, so this is too good to be true. Something's got to be wrong, right? So let's lay out our "get out of jail free" disclaimers so in the exceedingly rare chance your cider doesn't come out absolutely perfect, we can say, "Ha ha, sucker, you screwed up. You trusted us!"
1. Unpredictability:
- Since spontaneous malolactic fermentation relies on naturally occurring bacteria, the process can be unpredictable. In other words, sometimes it just doesn't happen. Okay, so technically if you're a textbook weenie, you can say there is no guarantee that the desirable strains of lactic acid bacteria will dominate, which can lead to inconsistent results. True, but in practice we've never heard anyone report a problem.
2. Risk of Off-Flavors:
- If undesirable bacteria outcompete the beneficial lactic acid bacteria, they can produce off-flavors and spoil the cider. This risk is higher in less controlled environments. Once again, for completeness, we're repeating textbook stuff. Cider is amazing in its high acidity and low pH. Under proper anerobic conditions, we've never actually heard of "undesirable bacteria" outcompeting our beneficial bacterial friends. On the other hand, we have heard about our asshole friends drinking our fermenting cider before it was ready.
3. Extended Fermentation Time:
- This is a big disadvantage. Spontaneous malolactic fermentation will significantly extend the time until the cider is ready to drink. This conjures up the old phrase "a watched pot never boils." You can stare at your fermenter for one or more months with these tiny annoying bubbles that keep rising magically from nowhere, and you want them to stop so your cider will finally be ready, but the bubbling just keeps going....If you've got the patience, it's worth the wait.
- Recognizing if have a malolactic fermentation is important. Because the lactic acid bacteria tend to work annoyingly slow and over long time periods, it's easy to miss. But if you bottle your cider while malolactic fermentation is still occurring, you run the risk of developing too much carbonation, which in tern increases the chance of exploding bottles.
How to Recognize Natural Spontaneous Malolactic Fermentation
1. Visual Signs:
- Malolactic fermentation typically produces tiny bubbles that seemingly and endlessly rise up the fermenter. This contrasts with the primary yeast fermentation which is quite vigorous, or in textbook speak, bubbles like crazy. Unlike the yeast (alcohol) fermentation, malolactic fermentation may also appear sporadic, meaning it could seem to start and stop. Such exceedingly slow but apparently long-term bubbling behavior is the typical indication that malolactic fermentation is occurring.
2. pH and Acid Testing:
- If you are an enthusiastic hobbyist, then monitoring the cider's pH and acid levels can help identify malolactic fermentation. A decrease in total acidity and an increase in pH are indicators that MLF may be occurring. But let's face it: most of us are (circle one: too lazy, disinterested, ambivalent) to measure pH and acid. We just let it ferment to completion in gnawing anticipation of when we can finally drink the cider!
3. Sensory Evaluation:
- You can taste the cider regularly. If the cider becomes smoother and less tart, with the development of buttery or creamy notes, malolactic fermentation is likely underway. By the way, a buttery flavor indicates the presence of diacetyl, which, in addition to lactic acid and CO2, is another byproduct of malolactic fermentation. However, if malolactic fermentation progresses to completion, which in our case is typical, the buttery diacetyl flavor will disappear, as the lactic acid bacteria will reuptake the diacetyl.
4. Presence of Lees:
- Lactic acid bacteria typically produce fine lees (sediment) at the bottom of the fermentation vessel. This sediment is different from the yeast lees, and once again is a sign of malolactic fermentation.
Encouraging Natural Spontaneous Malolactic Fermentation
While this article focuses on spontaneous malolactic fermentation without adding a malolactic strain, certain conditions can encourage the natural process:
- Temperature Control: Keep the cider in a slightly warmer environment (18-22°C or 64-72°F) to encourage bacterial activity.
- Avoid Sulfites: Sulfites can inhibit and kill lactic acid bacteria, so avoid adding them during or after primary fermentation if you wish to promote spontaneous malolactic fermentation.
What if We Don't Want Malolactic Fermentation?
There are reasons why we might not want malolactic fermentation. For example, we want to drink the cider sooner, or we want a drier, crisper (more acidic) cider. What should we do?
- Use pasteurized cider. The heat will have eliminated all lactic acid bacteria.
- Kill them all. Okay, so I know this sounds cold (and potentially psychotic), but that's what we do. Malolactic bacteria are very sensitive to sulfites, and it doesn't take much to annihilate the entire population. Fifteen parts-per-million (ppm - damn, I've used an acronym!) typically does the trick. For reference, one Campden tablet per gallon achieves 30 parts-per-million with no taste contribution, so that's all you need.
Natural spontaneous malolactic fermentation can enhance your home-made cider's complexity, softening its acidity and balance. However, if you have a malolactic fermentation, you should recognize the signs and decide how you want to proceed. It comes with challenges, with patience being the greatest obstacle. I'm too lazy to add a cultured strain of lactic acid bacteria, but I'm always happy when I develop a spontaneous malolactic fermentation. It softens the cider's natural bracing tartness and produces a beverage I'm happy to age for years to come.