As mentioned in the previous section, a basic cider fermentation where juice is placed in the carboy and fermented quickly with a solid yeast culture may often produce a cider with little fruit aroma and no residual sugars. This is especially true if the standard wine- and mead-maker's practice of adding yeast nutrients at the beginning of the ferment is followed. The best ciders, in my opinion, are made from the slowest fermentations. This philosophy goes against standard winemaking rules where fermentations may last a week or less, albeit with extended maturation times. A long, slow fermentation allows the cider to retain delicate fruit aromas. The way I see it is that if you can smell fruit aroma coming out of the airlock, as happens in a vigorous ferment, those aromas will not be left behind in the finished cider. Following are number of techniques that can be used to improve a cider or give it certain desired (or undesired) characteristics.
Cold Stabilization ....
My cider room is in the northeast corner of my basement and is insulated off from the rest of the room. Even though there is a water heater, clothes dryer, and two furnaces, one of them wood, just a few feet from the wall of the room, I can keep the 'cider cellar' at a steady 42-ish (F) through the winter and a comfortable 60ish in the summer. This cool temperature makes for some nice, slow fermentations as well as great storage conditions throughout the year. My ciders don't tend to go into the bottle until nearly a year after squeezing, sometimes longer when I bulk age them in stainless 'corny' kegs from which I can bottle anytime while freeing up fermenter space.
This was mentioned in the previous section on juice selection. Generally speaking juice from underfertilized trees may have lower natural levels of nutrients which yeasts may use to multiply and therefore reach a level where they can ferment the cider to completion. The sweet cider should have sufficient original starting sweetness (specific gravity 1.055 or higher) for one to rely on just this to leave a cider a bit sweet. Often a cidermaker looking for a little sweetness in their final cider who uses low nutrient juice would need to use other techniques as well.
Racking is simply the siphoning of fermenting juice off from the layer of spent yeast cells at the bottom of the fermenter. Yeast, like most living creatures, use carbohydrates as their energy source and nitrogen-bearing proteins for reproductive processes. When the initial yeast inocula reproduce at the beginning of a ferment, they tend to use up most of the free nitrogen in the solution. Each individual yeast will do its job eating a little sugar and producing a little alcohol and carbon dioxide, then it will naturally die off. The remaining yeast, as they reproduce, 'feed' off of the decaying dead yeasts, thereby recycling the nitrogen in the juice. If the juice is siphoned off of this layer of dead yeast cells several times during fermentation, the nitrogen load can be diminished, thereby keeping the total yeast population low and maintaining a slow ferment. Care must be taken during rackings to ensure that the cider is not oxygenated in the process. Siphons should be slow and splash-free. Sometimes a pressurized tank of carbon dioxide, argon, nitrogen, or a mixture of these inert gases will be used to purge any headspace or even the cider itself of any oxygen.
After the cider has dramatically slowed or stopped fermentation, it can be transferred to a cold (~32-35 deg F) location for a spell. This will often 'shock' the yeast out of suspension, settling them onto the bottom of the fermenter from which they can be siphoned off.
Okay, this one is pretty wild, and not used often. The keeving process comes from traditional British and French cidermaking, and is still used on a commercial scale in the French cider industry today. The process involves allowing the juice to settle prior to fermentation. Without going too deep into the chemistry of the process, pectin and calcium in the juice gel by enzymatic action, capturing many proteins, yeasts, and bacteria. This gel either falls to the bottom or is risen to the top by the bubbles generated by early fermentation (or a nitrogen tank and air stone) and the clear juiced in between siphoned off. The resulting juice will now be very low in nitrogen as well as being 'cleaned' of a lot of other bacteria and yeasts. Such juice is then fermented and often finishes out quite sweet since the nutrient load is sufficiently low to halt yeast reproduction and therefore fermentation to dryness.
This photo shows three ciders undergoing keeving in various states of completion. Click on the picture for more keeving images.
This whole process involves a lot of trial and error, as well as luck. Ciders made from keeved ferments really can be wonderful. In fact, the French cidre doux industry uses a nearly perfected keeving process as a matter of course, and their ciders are often considered some of the best in the world. The process has all but died in the commercial British industry, and is only catching on amongst a handful of cider enthusiasts here in the US. Thanks are due primarily to Gary Awdey of Eden, New York for digging up samples of the enzyme and distributing it to all of us cider weirdos around the globe. Will I continue to keeve my ciders? Probably a few batches a year, but I will also use most of these other tools to develop fruity cider with a bit more likelihood of replicable success.
Finally a source for the keeving enzyme, pectin methyesterase (PME) is available in the US. Go here: http://www.cidersupply.com/
This subject can raise the hackles of some purists as well as newcomers to the hobby. There are two main chemicals used in cidermaking which help to manage fermentation, sulfite and sorbate. Sulfites are good at knocking down populations of yeast and bacteria in the cider. Used at low levels at the start of the ferment, they can clean the juice of unwanted nasties in the cider while allowing sulfite-tolerant yeasts to build up in the juice. At higher levels they can 'strip' the juice of virtually all yeast, allowing you to add the cultured yeast of your choosing. I am a real proponent of sulfiting at the beginning of fermentation. Used only at the beginning of the ferment, there will be little to no remaining added sulfites at bottling time. I also rinse bottles in a sulfite solution to clean them of anything that might be in there before filling. Sulfites are also used later in the process to prevent oxidation and to maintain a preservative effect in the cider. Sometimes this is helpful, other times it may not be necessary, especially if care is taken during racking and basic sanitation is followed. Finally, high levels of sulfite can halt an active ferment while there is still sugar left in the solution. This must be followed by sorbate addition, since the sorbates are used to prevent regrowth of the yeast population. I occasionally use some sorbate when bottling sweeter ciders to prevent fermentation in the bottle. Anyone using these materials, especially sulfite, should really check over Andrew Lea's website for information on their proper use.
Sometimes a filter is used on finished sweet ciders which will remove any remaining yeast cells from the solution. Special care must be used in this case to make sure that no yeast are introduced later on in the bottling process, or at least a protective addition of sorbate is called for to prevent yeast regrowth. I began using a two-pad plate filter from morewinemaking.com for some of my 2006 ciders. The pads have been easily plugged if ciders with a lot of yeast are passed through; ciders should either be rough filtered first or filtered only when brilliantly clear. That said, I've found that one set of pads will do about fifteen gallons.
I use the plate filter inline between two Cornelius kegs. Sweet cider is filled into a clean keg and a second keg carefully sanitized. For the receiving keg I would add 20 ml of 5% sulfite solution to give a 50 ppm shot to the filtered cider to help ward off oxidation and refermentation. The receiving keg is then pressurized with about 5 psi of CO2, the sending keg with 10 psi, and the 'out' lines of the two kegs connected together. You will have to manually off-gas the receiving keg or use one of these fancy things. I still find that it takes 20 minutes to filter five gallons of clear cider with a clean filter, longer as the pads begin to plug. I run the whole system at 10 psi.
As for whether or not the filter strips the cider of flavor, I'm not sure. The few batches that I have done are quite flavorful; I'll work with it more over time and see how things develop.
Another hot topic amongst purists is pasteurization. This process is also confused by new regulations applying to sweet cider which is sold wholesale in the U.S. Many people to whom I talk of cider think that the fermented type cannot be sold unless it is pasteurized. This is untrue, but many ciders, especially the fizzy, 'draft' six-pack type are pasteurized before or even during bottling. Pasteurization is the process of heating the cider for a sufficient time and temperature to kill any microorganisms that may referment or otherwise spoil the cider after packaging. Pasteurization is done on ciders with residual sweetness, and rarely is performed on dry ciders. The heating process, especially when residual sugars are present, can produce a cooked or caramelized flavor in the final product.
Proper pasteurization is difficult to do, especially before bottling. Any process after treatment but before bottling must be performed under sterile conditions, as any microbe introduction will contaminate the treated cider. Some folks are successful with in-bottle pasteurization where filled and sealed bottles are immersed in a heated water bath. Care must be taken to ensure that the cider heats up enough for long enough to properly treat it without 'cooking' it. Another important item to be aware of is the potential for pressurized bottles to break with the heating.
Many ciders, like many wines, have a natural 'sharpness' or acidity that can be unbalanced by the end of fermentation and even maturation. Malo-lactic fermentation is a process where a type of bacteria, rather than yeast, is introduced to the cider either during or after fermentation. These lactobacillus bacteria convert malic acid, the primary acid component in apple juice, to lactic acid, which is significantly less 'sharp' in flavor. MLF occurs at warmer temperatures (50-60 deg F) than are often found in cold cider cellars, ands often barrels of dry cider would 'reawaken' in spring when the room they were in warmed up. There are both natural and commercial/selected MLF strains available for use in wine and cidermaking. Not all ciders will benefit from MLF, but I have made some particularly sharp ciders which, after MLF, took on a very smooth, buttery flavor. Excess sulfite levels will inhibit MLF in wine and cider.
I haven't yet discussed how to make a cider 'bubbly'. There are a number of ways to carbonate your cider, the first being to bottle-condition. This is done by fermenting the finished cider again in the sealed bottle. The carbon dioxide produced is trapped in the container and goes into solution. Care must be taken to use only strong bottles and closures which can take the pressure generated. People have been hurt before by exploding bottles, so know what you're getting into before trying this. Again, Andrew's website can provide tips for doing this. One drawback to bottle conditioning is the yeast haze which will develop in the bottle. The traditional methode champenoise technique is used to remove yeast cakes from such bottled ciders, as well as traditional champagnes. I have used this technique and while it sounds cool, in practice it's a pain in the ass and can be replicated using other methods (see below).
Another system for carbonating ciders involves storing the cider in stainless steel kegs and either allowing the carbonation to develop naturally or adding it with a CO2 tank. Some people feel that the latter produces poor quality bubbles, but I feel that when done right, it can make a really nice product. Most all of my cider served at home is dispensed through a keg system where the cider picks up a small amount of carbonation. Transferring this cider to a bottle would involve a counterpressure-filler which fills the bottle under pressure. Again, good bottles and closures are a must, as is good bottle sanitation and in the case of sweet ciders, a little sulfite/sorbate may be called for. I think a really good system would be a carbonating keg followed by sterile filter and counterpressure bottle filler. The resulting ciders could therefore be bottled with natural carbonation and sweetness without the yeast sediment that often goes along with bottle carbonation. The carbonation can be either artificial (pressure tank) or natural (secondary ferment in keg), thereby satisfying people from both camps.
All material Copyright Terence Bradshaw 2006-2013
terryb at lostmeadowvt dot com