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Part 3 - Juicing and Fermenting
Materials of construction
Before we go any further it is worth considering the equipment whichwillbe used for milling, pressing and fermenting. I shan't repeat thedescriptionof the mills and presses themselves which was given in the firstarticle,but it's worth stressing that only certain types of materials should beallowed to come into contact with juice and cider. Most metals shouldbeavoided, with the noteable exception of food-grade stainless steelwhichis excellent but costly. Aluminium is permissible for short periodsonly.Iron and copper should never be in contact with cider or juice becausethey dissolve in the fruit acid to give strange colours and flavours.Leadis particularly dangerous, because it dissolves to give a sweetcompoundwhich is potentially fatal. Indeed in the 18th century the so-called'Devonshirecolic' claimed a number of lives and this was eventually discovered tobe caused by cider which became contaminated when standing in leadpipesovernight in pubs and inns. Similarly the old practice of lining juicetubs or press trays with lead sheeting is highly dangerous.Wood is quite permissible and of course for many years was the onlypracticable material for fermentation and storage vats. It may bedifficultto keep clean and free from bacteria but at least it will not poisonanybody!Wood coated with modern polyurethane varnish (e.g. for press racks) ismuch easier to keep clean than is unsealed wood. For fermentation andstoragetanks, food grade stainless steel, plastics, fibreglass and epoxyresinsare generally preferable to wood, because they contain no pores whereundesirablebacteria and moulds can lurk. Glass is also very satisfactory on asmall-scale.If you particularly want to use wooden barrels, make sure that they arewell scoured, bleached and rinsed or steamed beforehand. They shouldalsobe 'sweetened' with 5% sulphur dioxide solution (see Table) before afinalrinse with clean water. It should go without saying that all equipmentand containers in contact with juice or cider should be well cleaned(andwell rinsed) beforehand. Modern non-foaming sterilising detergents suchas 'VWP' are most effective in this role, and should be usedaccordingto the instructions given on the packet.
Fruit and juice blending
Once the apples have been chosen, washed and milled to a pulp, theymustbe transported to the press in a suitable container - probably theubiqitousplastic bucket! In the present article we shall assume that this isdonealmost immediately without 'cuvage' or 'maceration'. Even so, the juiceand pulp will become quite brown in a matter of minutes and it is herethat the natural colour of the product is determined. The press juicethenneeds to be collected in another container and at this point it isconvenientto measure its sugar level, acidity and pH so that blending may becorrectedwith other batches of juice pressed on the same day. A fair amount ofsugarstill remains in the dry press-cake (or 'pomace') so by adding a litreor two of water to each 5 kg of broken-up pomace before re-pressing, auseful yield of slightly weaker juice may be obtained, which is usuallyadded to the first pressing.Previously we described the composition of the ideal cider fruit interms of materials such as sugar, acid and tannin. Sugar levels are setlargely by the weather - in a good summer we might expect them to be ashigh as 15%, but in a cool wet summer less than 10% might be achieved.The sugar levels can be measured directly on a drop of juice squeezedoutfrom the fruit, using a hand held refractometer. This equipment isexpensive(ca £70), but is often used by grape-growers, who need to measuresugar content daily as harvest approaches. For cider-making, thechangesin sugar levels are not so critical and the fruit will usually havebeenstored for a while to convert all the starch into fermentable sugaranyway.So it is usual to measure the juice 'specific gravity' (S.G.) afterpressing,using a hydrometer, which is much cheaper (ca £5). Roughly speaking, 15% sugar corresponds to an SG of 1.070 anda total potential alcohol of 8.5 %; 10% sugar is SG 1.045 and apotentialalcohol of 6%. If the juice S.G. is less than 1.045 and you have nosweeterjuice for blending, it should be brought up to this level by theadditionof sugar or apple juice concentrate. Otherwise the resultant alcohollevelmay not be sufficient to protect the final cider during storage. Toraisethe S.G. in 5° steps, dissolve 12 - 15 grams of sugar in eachlitreof juice and re-test with the hydrometer until the desired level isreached.
Acidity and pH
The acidity is controlled more by the variety of fruit than theclimate.Acidity has two aspects - total acid and pH - and both are useful toknow.The total acid relates well to our perception of acid flavour, whilethepH relates better to various aspects of fermentation biochemistry.Thesetwo are connected but not in a simple way, although the acidity alwaysgoes up as the pH goes down and vice-versa. In terms of totaltitratableacid (as malic), we should be looking for 0.3 - 0.7% in a cider juice.If the total acid is too low, the pH will be too high and thefermentationwill be susceptible to bacterial infections. If the total acid is toohigh,the pH will be low enough to safeguard against infection but the finalcider will be unacceptably sharp to the palate and may never bepleasantto drink. Acidity can be measured by titration - details will be foundin any good wine-making book or here. Kits for measuring titratable acidity areavailable.Measurement of pH has to be done by a dedicated 'pH meter'. Theseusedto be very expensive, costing several hundred pounds, but modern 'chiptechnology' has now brought them down to the range of £30 or so.However, beware the very cheap pH meters which are sold in gardencentresfor soil testing - these are not accurate enough for cidermakingbecausewe need to measure to at least the nearest 0.1 pH unit or it is notworthmaking the measurement at all! Narrow range 'pH papers' (e.g. pH 2.8 to4.2) are now available cheaply from some home brewing suppliers and area reasonable substitute although not as accurate. A desirable juice pH range forcider-makingis say 3.2 - 3.8. At higher pH the fermentation will be subject tomicrobialinfection and at pH 4.0 or above this can lead to serious flavourproblems.Many traditional bittersweet cider apples tend to be high in pH whichiswhy they need blending with more acid fruit, preferably beforefermentation.That is one reason why bittersharp apples, such as 'Kingston Black',havebeen regarded as near perfection in terms of their composition forsingle-varietycider making.
If you cannot measure the acidity or the pH, taste the juiceinstead.Trying to ignore the sweetness and the tannin, judge whether the juiceis insipid, balanced or sharp. If insipid, and you have no other juicefor blending, malic acid may have to be added in steps of 1 gram perlitre(0.1%) until the balance is improved. If the juice is too acid, and youcannot blend it out, you may have to encourage a malo-lacticfermentationto reduce it (see later), or you can add a little calcium carbonate toneutralise it, in 1 gram per litre steps.
Other juice parameters, such as tannin, are difficult to measure,butonly people using a high proportion of bittersweet fruit are likely tosuffer from excessive tannin and this can usually be detected by tastealthough the juice sugar does tend to mask it. Deficiencies here can becorrected after fermentation, however. The purpose of blending beforefermentationis to give a juice as close in composition to the 'ideal' which wasdescribedin the previous article. Although this may not always be possible, itisalways worth the attempt at least in terms of sugar and acid levels.Blendingafter fermentation is a worthy and useful art but it cannot correct agrossbiochemical imbalance beforehand!
Juice preparation
Apart from the blending corrections described above, you can of coursealways add sugar, glucose syrup, synthetic malic acid and apple juiceconcentrateto any desired extent along with water. On a commercial scale there areconsiderable cost advantages to be be gained by doing so, since sugarandwater are much cheaper than apple juice (and many commercial ciders arenow made from around 35% juice and 65% glucose syrup) but these have tobe weighedupagainst the ultimate quality of the cider you wish to make. Excessivedilutionwill make the cider 'thinner' in its overall complexity of flavour andcannot be recommended for a high quality product.The blended juice should now be strained through a coarse plasticmeshinto a suitable clean vessel for fermentation. Whatever scale you areworking on, you must also have some sort of 'airlock', whch canbe fitted beforefermentation begins or shortly afterwards, toallow carbon dioxide gas to escape but to prevent air getting in. Atthis point anumberof other additions may be made. If it is important that the final cidershould be sparklingly clear, a pectolytic enzyme may be added, whichwillhelp to ensure that all the pectin is broken down. Pectin is a sort ofnatural glue which sticks the apple cells together. Although it iswater-solubleit is precipitated by alcohol, so it tends to lead to persistent hazesby the end of fermentation. Dessert fruit, or long-stored fruit, tendsto suffer more from pectin release than does bittersweet fruit and willoften give a very cloudy cider unless depectinised. Although there arenatural enzymes in both apple and yeast which will break down thepectinduring fermentation, these enzymes are often rather weak and requiresomeassistance. The dosage rates for the commercial enzymes are given bythesuppliers.
The next potential addition is that of vitamins and yeast nutrient. These maybe bought as such or may be added as thiamine and ammonium sulphate (orphosphate) respectively. The dosage rate is up to 0.2 milligrams perlitreof thiamine and up to 300 milligrams per litre of ammonium salt. Thisiswhat was meant by 'amino nitrogen' in Table 1 of the previous article,and it is needed by the yeast to make protein and amino acids for itsowngrowth. (This is not unlike human and animal nutrition - the yeast'scarbohydrateor energy source is of course the apple sugar which is not in shortsupply!)Apple juices are generally very low in yeast nutrients (unlike beerwortsor grape musts) and so your fermentation rate will probably be muchimprovedif you add these. The fermentation is also much less likely to 'stick'orto grind to a halt before completion. The cider can therefore be rackedand bottled sooner, reducing the chances of spoilage in store. On theotherhand, it is undeniable that some of the finest ciders are fermentedveryslowly without the addition of nutrients, but the risks of failure arecorrespondingly greater. You pays your money and you takes your choice!Traditional cider-makers used to hang a leg of mutton or a side of beefin the fermenting vat to boost the nutrient levels. The meat broke downslowly in the acid juice, releasing soluble amino nitrogen which theyeastcould use for growth. The supposed requirement of a few dead rats ineveryvat is a more colourful manifestation of the same idea!
Sulphur Dioxide
The next addition is that of metabisulphite, sulphur dioxide or SO2,whichare all synonyms for the same thing. This topic always inflames greatpassionsamongst the purist cidermaking lobby, who regard it as dancing with thedevil - perhaps it is the connection with brimstone which worries them!However, it has a long and honourable history and the use of burningsulphurcandles as a sterilant in wine-making is supposed to date back as farasHomer. Certainly it was in use for cider-making from Elizabethan times,and the controlled addition of metabisulphite is far more accurate thanthe haphazard application of sulphur candles could ever be.In simple terms what happens is that the sulphur dioxide inhibitsthegrowth of most spoilage yeasts and bacteria, while permitting thedesirablefermenting yeasts (such as Saccharomyces cerevisiae or uvarum)to multiply and to dominate the conversion to alcohol. Only smallamountsof sulphur dioxide are used, and its effectiveness depends on the pH ofthe juice. The Table shows the appropriate levels to use when acultured yeast is being added for the fermentation. Lower levels areneeded if a 'wild' Saccharomyces fermentationis required (see below), or there is a danger that all the wild yeastwill be killed. In the absenceof sulphur dioxide, the fermentation is much less likely to be 'clean'although with care it is possible to do without it. A great deal of theconcern about sulphite derives from its excessive use at bottling notduringfermentation, and from the fact that a very few people arehypersensitiveto it in the free state. However, it must be stressed that no sulphurdioxideremains free by the end of fermentation, since it becomes bound tovariousintermediate chemicals (principally acetaldehyde) which the yeastproduceson its route from sugar to alcohol. I would always advise the beginnerto use sulphur dioxide to minimise the risk of taints and infection.Lateron, the experienced cidermaker can omit it at his discretion and seewhatdifference it makes.
| | | |
|---|---|---|
| Above 3.8 (insipid) | .....Lower pH to 3.8 with addition of malicacid..... | |
| 3.8 - 3.5 | 150 | 3 |
| 3.5 - 3.3 (balanced) | 100 | 2 |
| 3.3 - 3.0 | 50 | 1 |
| Below 3.0 (sharp) | None | None |
Notes:
1. If a pH meter or test strips are not available, use the taste ofthe juice as aguide. If you cannot measure pH but you are using dessert fruit, youcan assume the pH of your juice will probably be in the range 3.0 -3.3, so the best plan is to use just 1 Campden tablet per gallon ofjuice.
2. To make a 5% stock solution of sulphur dioxide, dissolve around10 gramsof sodium or potassium metabisulphite in 100 ml of water. (Themetabisulphite salts contain around 50 - 60% of available SO2 dependingon how they've been stored). Then 1 ml of this perlitreof juice (5 ml per gallon) corresponds to 50 ppm (parts per million) ofSO2.
3. Campden tablets are formulated with metabisulphite and give theequivalentof 50 ppm sulphur dioxide when each is dissolved in 1 (Imperial) gallon of liquid.
The Yeast
This brings us to the final addition, that of yeast. There are so manygood dried wine-making yeasts on the market today that it is well worthconsidering their use. All of them will get a fermentation off to agoodstart within hours, by providing a massive inoculum of healthy yeastcellswhich will multiply quickly and swamp out anything undesirable. Some ofthese are more cold-tolerant than others and are capable of fermentingeven down to 5° C, which can be a great boon to a Britishcidermakerwhose raw material may not be ready until early November. Some yeastsclaimto confer specific flavours e.g 'Burgundy', 'Champagne' but theseclaimsshould be taken with a pinch of salt and in any case are probably notrelevantto cidermaking. Stick to a good general purpose wine yeast - not abrewer'syeast and never a baker's yeast, since these have been selected to haveother properties which we do not require. There is no need to select ayeast with a high alcohol tolerance since the natural sugar of appleswillrarely produce more than 8% alcohol. If you fortify significantly withsugar and you want alcohol levels up to 12%, then you are making applewine - not cider! Large commercial cidermakers do just that (known as'chaptalisation')and then dilute the cider with water for retail sale, but this seriesisnot concerned with that sort of business.Small quantities of branded wine yeasts can be purchased from home winemaking suppliers. On a larger scale,you can buy specific strains of S. cerevisiae, bayanus or uvarumwhichare mostly produced overseasfor the wine and fruit wine industries there. Modern dried yeasts aresometimes 'pitched' direct, but often the yeast is rehydrated and grownon overnight as a 'starter' in sterile juice or sugar solution, andthen pitchedintothe main bulk the next day. Sometimes the yeast only needs hydratingfor 20 minutes or so. Whatever the case, it isimportant to followthe yeast supplier's directions.If sulphur dioxide is used, it isalsoimportantto wait overnight before adding the yeast culture. This is because thesulphur dioxide needs time to act against the wild organisms, and itwillalso inhibit the added yeast too strongly if they are all addedtogether.By standing overnight, the free sulphur dioxide largely disappears onceits work is done, giving the added yeast a chance to get away withoutsignificantinhibition.
Fermentation should commence within 2 or 3 daysif an active yeastcultureis used. As an alternative, it is possible to rely on the few wild Saccharomycesyeastswhich will be present in the juice after sulphiting, and allowthemto multiply to sufficient levels to start the fermentation, but thismaytake up to 2 or 3 weeks. In this case you might prefer to use aroundhalf the addition of sulphite given in the Table. This is equivalent tothe traditional practice of burninga 'sulphur candle' in thebarrel before adding fresh juice. If neither sulphite nor yeast areadded, thejuicewill probably start to ferment within a day, but the wild yeasts whichmultiply under these conditions cannot be guaranteed to producedesirableflavours. In any case, they will begin to die after a few days as thealcohollevel rises, leaving the fermentation at the mercy of any otherdominantorganism which has been able to establish itself. If you are lucky,thismay be a useful Saccharomyces species - if you are unlucky, youhave only yourself to blame!
In summary, therefore, I recommend the beginner to use a pectolyticenzyme, to use sulphur dioxide and to add a cultured wine yeast afterstandingthe sulphited juice overnight. Later on you can try out a 'wild yeast'fermentation. You can perhaps skip the nutrients unless thefermentationbeginsto 'stick' or unless you know that your fruit comes from big old treeswith very low nutrient levels and you are not prepared to wait a fewmonths. The progress of the fermentation should be monitoredevery few dayswitha hydrometer and the fall in S.G. plotted on a graph against time (afallof one degree S.G. per day is pretty reasonable). This makes it mucheasierto see whether sticking is occurring, and the nutrient and vitamin canbe added then if necessary.
Conduct of the fermentation
In the initial stages of fermentation, there can be considerablefrothingandevolution of carbon dioxide as the yeast multiplies and begins to breakdown the sugar into alcohol. There may be as many as 10 million yeastcellsper single ml. of juice at this stage, so it is easy to understand thatthere is a lot of microbiological activity going on! A loose plug andtheoutpouring of gas will probably ensure that nothing undesirable cancreepback into the fermentation vessel. When the initial frothing subsides,however,it will be worth topping up the vessel with more juice or a 10% sugarsolution andfittinga fermentation lock to ensure that the flow of gas remains one-way.From now on, air should always be kept out. Asyou follow the drop in S.G. with time, it will begin to level off andyoushould consider the first racking of the cider from its yeast oncetheS.G. is at 1.005 or below. The final SG for a fully dry cideris actually 0.997. If it stops fermenting at an S.G. much higher thanthis, thenit may be 'stuck', and nutrient addition together with twenty minutesvigorousaeration may help the yeast to grow again (the yeast does need someoxygenfor growth). It may also stop if the temperature falls too low, butthisshould need no attention from the cidermaker. When the weather warms upagain, the fermentation should re-commence. In fact, a coolfermentation(ca 15° C) is generally preferred for cider and there is no needto keep the fermentation especially warm.If the cider is particularly acid at this stage, the first rackingmaybe delayed for a month or so to encourage the 'malo-lacticfermentation'which is described below. In general, however, it is regarded as bad practice toleavea fully fermented cider on its yeast lees for more than a few weeks.
The first racking should be into another clean vessel, trying toleavebehind as much yeast as possible and with the minimum of aeration tothecider. This is generally done with a clean plastic syphon tube fixed toa plastic rod so it rests just above the yeast deposit or, on a largerscale,with a suitable pump. The transferred cider should be run gently intothebottom of the new vessel without splashing. Now that there is much lesscarbon dioxide to protect the cider, it is important to minimise theheadspaceand to prevent air contact as much as possible. This is partly to keepout any undesirable film yeasts or bacteria, and partly to prevent'oxidation'which leads to flat dull flavours and a loss of freshness. This is whysome people add 50 ppm of sulphur dioxide at every racking, although atthe first racking this is probably unnecessary because of the remainingcarbon dioxide. Sulphite added at this stage will almost certainlyinhibitthe malo-lactic fermentation, which may or may not be required (seebelow).
Maturation and Bottling
After the first racking, the air-lock is re-fitted until it is clearthatgas evolution has ceased, when the vessel should be topped up withwateror cider and tightly closed. More yeast will drop out asthecider settles down. The cider may remain in this state for severalweeksor months, before a final racking to a closed container for bulkstorageor directly into bottle. It is generally recommended that it should notsit forlongon a heavy crop of yeast, because in the time the dead yeast may'autolyse' whichtends to give unpleasant flavours. In practice I have rarely found thisto be a problem in my own cidermaking, even when standing on theprimary lees for several months. Also, a small amount of autolysisfrom the second yeast crop may be helpful, because this releasesnutrientswhichstimulate maturation through the so-called 'malo-lactic' fermentation.This phenomenon is due to a specialised group of bacteria (Lactobacillusor Oenococcus species) which convert the malic acid of theappleto lactic acid, giving off more carbon dioxide in the process. Often,thishappens in the spring when the trees are flowering, giving rise to thenotion that somehow the trees and the cider are working in sympathy!Generallythe malo-lactic fermentation is to be welcomed, since it lowers theacidityand gives additional rounder smoother flavours, although in very lowacidciders it can reduce the acidity too far. In bittersweet ciders itproducescharacteristic 'spicy' notes (often detectable in ciders fromNormandy).It may be recognised by the evolution of gas without renewed turbidity(if a yeast re-ferments a sweet cider it becomes cloudy because theyeastcells are so large (typically 10 microns). Malo-lactic fermentations,unlessvery heavy, tend to remain clear because the bacteria are so small(typically0.5 microns).The malo-lactic fermentation is difficult to produce at willalthoughsome strains of lactic bacterial cultures are now available commercially for usein the wine industry and can be used in cider. It may definitely be prevented by the additionaluse of sulphur dioxide at racking. Sometimes it reduces the acidity toofar and sometimes the 'wrong' organisms take hold, producing otherdefectssuch as 'ropiness' (which will be covered in a later article). But iftheoriginal juice pH was no higher than 3.8, the chances are that thisfermentationwill be beneficial if it happens at all. Even if it does not, the ciderwill mature for several months as its flavour balance stabilises andtheharsher notes are smoothed out by slow chemical and biochemicalreactions.
However, ciders do not generally profit by extended ageing and bylatespring or early summer the cider will be ready for bottling anddrinking,or for a second racking into bulk store. The golden rule at this stageis to minimise air contact whenever the cider is handled - it is amatterof preference whether you wish to add sulphur dioxide (ca 50 ppm) tohelpwith this, but in any case you should not exceed a total addition of200ppm SO2to any cider when all additions at fermentation and bottlingaresummed up. A dry cider with no added sugar and sufficient alcoholshouldbe quite stable in clean, closed and well-filled bottles, and shouldstanda minimal risk of any unwanted conversion to vinegar! Glass bottleswith crown or screw caps are preferred since they will not allow anyair in. PET bottles are air permeable and hence not generallyrecommended, although some are soldfor home brew use with anoygenbarrier and these are worth hunting out e.g. Coopers Oxbarbrand.
We have now looked at the steps in producing a still, dry ciderwhichis the easiest sort to make. In the next article we shall look atvariationsof this process to produce other types of cider.
© Andrew Lea 1997. Lightly updated 2015Suppliers of Equipment and SundriesMenu and Home Page
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