CIDER (CYDER; HARD CIDER) | The Product and its Manufacture

1312 CIDER (CYDER; HARD CIDER)/The Product and its Manufacture

CIDER (CYDER; HARD CIDER) Contents The Product and its Manufacture Chemistry and Microbiology of Cidermaking

The Product and its Manufacture B Jarvis, Ross Biosciences Ltd, Ross-on-Wye, UK Copyright 2003, Elsevier Science Ltd. All Rights Reserved.

A Brief History of Cider 0001

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The fermentation of apple juice to produce an alcoholic beverage is believed to have been practiced for over 2000 years. Cider is recorded as being a common drink at the time of the Roman invasion of England in 55 bc. Celtic mythology revered the ‘sacred apple,’ and in his famous natural history (ad 77), Pliny the Elder refers to a drink made from the juice of the apple. Cider was drunk throughout Europe in the third century ad, and in the fourth century, St. Jerome used the term ‘sicera’ (whence the name cider was possibly derived) to describe drinks made from apples. Reputedly, cider was a more popular drink than beer in the eleventh and twelfth centuries in Europe. Cider is produced throughout the temperate regions of the world where apple trees flourish. Such localities include Austria, Belgium, England, France, Germany, the Northern coastal area of Spain, Switzerland, and, more recently, Argentina, Australia, Finland, New Zealand, South Africa, Sweden, and the USA. There are many references to cider in writings from the Middle Ages. The popularity of cider in fourteenth century England was such that William of Shoreham reflected the Church’s concern for the niceties of sacramental rites by stating that ‘young children were not to be baptised in cider’! William Langdon in Piers Plowman and Shakespeare in A Midsummers Night’s Dream make reference to the consumption of cider; Daniel Defoe observed that Hereford people ‘boast the richest cider in all Britain,’ and Samuel Pepys noted in his Diary that on 1 May 1666 he ‘drank a cup of Syder.’ From the seventeenth century onwards, cider was praised in numerous poems and other literary works as an aid to good cheer and a homely cure for almost every ailment known to man. Prior to the twentieth century, cider was a popular rural drink, cheaper than beer and often more potent (at c. 7% alcohol by volume (abv)). Farm workers

often had part of their wages paid as truck (i.e., in kind), and every farmer would make his own cider for consumption by his workers and his own family and guests – although it is recorded that the best ciders were retained for his personal use. Most farms in the West of England and the West Country had their own cider press, or used the services of a travelling cider press that was hauled by horse from farm to farm. My own cider mill and press (dated 1717) stand outside my window as I write this account! Commercial cider production commenced during the nineteenth century in England (e.g., H Weston & Sons of Much Marcle, 1880; H P Bulmer of Hereford, 1887; Whiteways Cyder of Whimple in Devon, 1894), although a few farms produced cider commercially from as early as 1727 (e.g., Symonds Cider and English Wine Co. Ltd., Stoke Lacey, UK). Cider production in England was estimated as 250  106 l (55  106 gallons) in 1900. By 1920 the level of cider production had decreased significantly; although some 73  106 l (16  106 gallons) were still produced on farms only 23  106 l (5  106 gallons) came from factory producers. By the late 1980s, cider sales had risen to over 273  106 l (60  106 gallons) per year and, in the 12 months to September 1999, almost 500  106 l (109  106 gallons) were sold in the UK by members of the National Association of Cider Makers, a trade association formed originally in 1920; a further 23  106 l (5  106 gallons) of cider were exported from the UK. Since 1999, UK cider sales have remained constant at 500  106 l (109  106 gallons) p.a. The significant increase in the volume of cider produced commercially each year in the UK up to 1999 followed a period when growth had been inhibited by the imposition of Excise Duty in 1976 and results both from the introduction of new cider products, linked to increased marketing activity, and from changes in drinking habits, especially of younger adults. In 2002, it is possible to obtain cider either on draught or prepackaged in glass and PET bottles and in cans. Products range in alcoholic strength from less than 0.5 to 8.5% (abv), and in sweetness from very dry to sweet. In addition, cider products now include ‘white’ ciders, naturally colored ciders, and blends of

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CIDER (CYDER; HARD CIDER)/The Product and its Manufacture

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cider with fruit juice or other ingredients. Some cider, made from apples of a single crop, may be sold as a defined year Vintage Cider, whilst others are made from a single apple cultivar, e.g., Kingston Black. Because of the significant growth in cider sales in recent years, imitation ciders have appeared on the market in several countries. Such products are produced by compounding distilled alcohol with apple juice and artificial flavors. Such products are not cider. In 1998, the European Association of Cider and Fruit Wines Industries of the EU (AICV) defined the acceptable procedures for production of cider and related products. Fortification of cider or apple juice by the addition of distilled alcohol is not an approved process for a product to be sold as cider.

Cider Fruits 0007

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Traditional ciders are made from the juice of cider apples, believed to have been imported into Britain by the Normans, although it is recorded in Gaulmier’s Traite du Sidre (1573) that a Spaniard named Dursus de l’Etre brought apple trees into France in 1486! Traditional cider apples are of four main types: bitter sweet – low in acidity but high in tannin; bitter sharp – high acidity and high tannin; sharp – high acidity but low tannin; and sweet varieties – low acidity and low tannin. Examples of some cider fruit cultivars are listed in Table 1. In some areas, especially Kent, Suffolk, and Norfolk in the UK, cider is made primarily from culinary fruit varieties such as the Bramley, although blends of bittersweet and culinary juices are frequently used to develop particular flavor profiles in commercial cider blends.

Table 1 Characteristics of cider apple varieties Type

Sweet

Bitter sweet

Sharp

Bitter sharp

Typical varieties

Northwood Sweet Alford Sweet Coppin Ashton Brown Jersey Dabinett Michelin Yarlington Mill Brown’s Apple Frederick Reinette Obry Bulmer’s Foxwhelp Brown Snout Chisel Jersey Kingston Black

Typicaljuice composition Acidity (g per 100 ml)

Tannin (g per100 ml)

<0.45

<0.2

<0.45

>0.2

>0.45

<0.2

>0.45

>0.2

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Cider Orchards

The traditional farm orchard of standard trees still exists, and although generally declining in acreage, many hundreds of such orchards provide both an apple crop and grazing for livestock. Modern cider apple orchards are largely intensive bush orchards, where the trees are frequently planted as closely as 2.4 m apart in rows some 5.5 –6 m apart. After planting, staking, and protecting against rabbits, using a wire guard, the grass under the trees is treated with a suitable herbicide to reduce competition for nutrients and water. Some growers cover the herbicide strips with a mulch of straw or other suitable material to ensure maximum retention of moisture. Although it has become standard practice to retain the herbicide strip into the productive years of an orchard, this practice is currently the subject of research to assess whether a grass sward may be better in relation to the quality of harvested fruit. During the growing season, it may be necessary to spray the trees against pests, such as red spider mite, and diseases such as mildew, apple scab, and canker. In years of heavy potential cropping, chemical thinning (e.g., using paclobutrazol, ‘Cultar’) is frequently recommended, to reduce stress on the tree and thereby minimize the risk of biennialism, a condition that occurs significantly in cider fruit orchards.

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Harvesting

In traditional orchards, fruits are generally allowed to fall naturally, or shaken from the trees using long poles (lugs), and then picked up either by hand or by machine. Traditionally, fruit from standard trees would be raked into piles or filled into sacks that were stored under the trees until the fruit was in a suitably ripe condition to be milled and pressed. In intensive bush orchards, it is normal to shake the trees mechanically to cause the fruit to fall. Such shaking does not harm the tree and permits fruits to be harvested mechanically immediately after falling, so reducing the risk of rots that may occur if fruit are left for any length of time on the ground. The collected fruit is normally washed and then transported by road to the cider mill where, after weighing, the fruit is tipped into a fruit canal or on to a concrete pad for holding prior to milling and juicing.

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Processing the Fruit Milling and Pressing

The fruit is generally transferred into the mill using either a water flume, which provides additional washing, on a conveyor belt or using screw conveyors.

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Detritus such as twigs, leaves, and stones is removed mechanically, and the fruit is milled using a grater, slicer, or hammer mill. The apple pulp is then conveyed to a mechanical press where the juice is extracted. Traditionally, the presses consist of a frame containing a slatted board covered by a cloth into which a measured amount of the pulp is transferred. The corners of the cloth are folded over to form an envelope, the frame is removed, and the next slatted board is added together with the frame and another cloth. This procedure is repeated some 10 –20 times to build a ‘cheese,’ which is then pressed hydraulically to remove the juice, under a ram pressure of some 14 MPa (c. 2 MPa on the ‘cheese’). This method removes up to 80% of the juice. Sometimes, the pomace residue (see below) is soaked in a small volume of water and repressed to remove further quantities of fermentable sugar. Such processes are very labor intensive and, except for farmhouse production, have now largely been replaced by automatic presses such as the Bu¨ cherGuyer, a horizontal cylinder press, or the Bellmer continuous belt press. Such presses are more efficient, often permit countercurrent extraction of the pomace with warm water, and have little demand for labor once properly set up. Processes such as electroacoustic dewatering have been claimed to release a higher yield of juice by passing an electric current through the pulp prior to pressing but have not found application in the cider industry. Pomace

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Apple pomace can be used for the extraction of the natural gelling agent, pectin, used in the manufacture of jam, dairy products, and other foodstuffs, and in certain medical applications. Pomace, either before or after depectinization, can be fed to animals either as a wet slurry or after drying; it can also be spread on to agricultural land as an organic mulch or fertilizer. Although it aids the breakdown of clay soils, its acidity often poses problems. Apple Juice

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The extracted juice is rich in malic acid, tannins, and sugar; it will also be contaminated with a variety of microorganisms derived from the fruit itself, from the orchard floor, from the harvesting equipment, and from the environment of the cider mill. Immediately after pressing, juice is treated with sulfite, either as sulfur dioxide (SO2) or in the form of potassium metabisulfite. Sulfite acts both as an antioxidant, to prevent browning of the juice (due to polyphenol oxidase and chemical browning reactions), and as

an antimicrobial that destroys ‘wild’ yeasts and bacteria. The sulfite-treated juice will normally be stored for some 24 h before being pumped into fermentation vessels. The level of sulfite will normally be adjusted to give 10–30 mg of free SO2 per liter at the time of pitching with yeast. Generally, the juice will not be clarified prior to fermentation. However, if the juice is to be concentrated by thermal evaporation, it will be treated with a mixture of enzymes (pectinases and amylases) and then clarified prior to concentration. Failure to destroy pectins and starch results in a thick viscous mass that neither concentrates effectively nor stores adequately.

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Fermentation of Cider Fermentation Vessels

Traditionally, the apple juice would have been fermented in oak vats. Although many such vats are still used, they have been largely replaced in commercial practice by vats of mild steel with a ceramic or resin lining, by lined fiber-glass resin vats and, more recently, by stainless steel vats. A few cider makers use redundant brewing vessels such as tall conicocylindrical vats. However, there is evidence that tall conicocylindrical vats inhibit effective fermentation by creating excessive hydrostatic pressure on the yeast, although squat conicocylindrical vats are excellent. The Unitank-style vessel used frequently for the fermentation of wine is also excellent for cider fermentation. Figure 1 illustrates some of the styles of fermentation vessels used in cider making.

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Fermentation Substrate

Traditional cider making fermented the whole juice, often with much of the apple solids remaining. Such solids included the pips, which contain glycosides, and so the cider would contain small quantities of cyanide derivatives. In many countries, the practice of chaptalization has become increasingly common. Chaptalization supplements the sugar content of the apple juice with a suitable fermentation sugar (e.g., brewers’ dextrose) and permits the production of strong cider with an alcohol content of 11.5–12% abv. By comparison, fresh juice fermentations, depending upon the sugar content, will rarely exceed 5.5–6.5% abv. In France, where the production of traditional cider is constrained by legislation, only the product of fermentation of fresh apple juice or fresh juice reinforced with juice from concentrate, can be called ‘cidre.’ However, it is now permissible in France to produce a cider

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CIDER (CYDER; HARD CIDER)/The Product and its Manufacture

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(A)

(B)

(C)

(D1)

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Figure 1 Schematic design of cider fermentation vessels. (A) Shallow angle conicocylindrical fermenter suitable for cider. (B) Typical steep angle, tall conicocylindrical fermenter as used for brewing beer. (C) Unitank fermentation vessel, with sloping base. (D) Oval cross-section (D1) horizontal fermentation vessel (D2).

from juice and fermentation sugar, which must be described as ‘un boisson alcoolise´ e a` base de pomme’ (sic an alcoholic beverage derived from apples) to differentiate it from traditional cidre. In the preparation of cider, the apple juice may be fresh or reconstituted from apple juice concentrate; in many countries, pear juice (fresh or reconstituted) may be added to a maximum of 25% of the apple juice content. Other than fermentation sugars, the only other primary addition will be a suitable yeast culture. Fermentations originating wholly or largely from concentrate normally need the addition of yeast nutrients, such as ammonium phosphate, sodium pantothenate and/or thiamine. Fermentation Process

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(D2)

Where a natural fermentation of the apple juice is required, the pressed and sulfite-treated juice is transferred to suitable fermentation vessels and allowed to ferment naturally. The process is monitored by measurement of the specific gravity (SG) of the

juice; the fermentation is deemed to have gone to completion when the SG is 1.0000 or less. However, most commercial cider is inoculated with a selected strain, or a mixture of strains, of a wine yeast capable of growth at elevated alcohol levels. The process consists of partially filling the vat with juice at a temperature at or below 18
C, followed by inoculation with the specific starter culture of yeast. The use of a slightly reduced initial temperature is to prevent excessive temperature development during the initial exothermic growth of the yeast prior to onset of fermentation. The starter culture may be grown in the laboratory from a pure culture or added either as a commercial dried yeast preparation or as an aerated slurry of dried yeast – the latter is the most efficient for commercial processing. Once fermentation has started, additional substrate (i.e., apple juice and/or fermentation sugar) is added from time to time until the vat is filled. Although most cider vats are typically of 45  103 – 9  105 l (10  103 – 2  105 gallons) capacity, much larger vats do exist.

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At H P Bulmer’s plant in Hereford, UK, the world’s largest storage container for alcoholic beverages holds some 7.3  106 l (1.6  106 gallons) of product. The fermentation typically continues with or without control of temperature, pH, or other parameters until all fermentable sugar has been metabolized into alcohol. This process can take from 10 days to 12 weeks, depending upon conditions! The modern cider fermentation plant generally has a facility to control the temperature, although ambient temperature fermentation still occurs widely (e.g., in farmhouse cider making). There is no doubt that good control of temperature can give a more rapid and more consistent fermentation. In France, cider is often fermented at temperatures below 15
C. (See Fermented Foods: Origins and Applications.)

If the cider has a high alcohol content, it may be ‘broken back’ to final product strength using water or dilute apple juice. Other permitted ingredients may be added such as sugars, intense sweeteners (e.g., saccharin), color and/or additional preservative (normally limited to sulfite, although in some countries, benzoic or sorbic acids may be used). The finished blend may be treated with filter aids, such as kieselguhr (diatomaceous earth), to give an optically bright product or it may again be microfiltered. The most modern commercial plants use computer-controlled automated blending and microfiltration to convert the strong raw cider into commercial product blends.

Maturation

Although a small market exists for ‘live’ caskconditioned cider, i.e., cider in a wooden or plastic barrel, to which a small quantity of sugar has been added, together with a further yeast inoculum, the majority of commercial cider is carbonated and pasteurized, or sterile filtered, prior to filling into kegs, bottles, or cans. (See Packaging: Packaging of Liquids.)

When fermented to dryness, the cider is frequently left for a few days on the lees to permit the yeasts to autolyze, thereby adding cell constituents such as enzymes, amino and nucleic acids, etc. to the brew. However, if it is left for too long on the lees, there is a serious risk of development of off-flavors in the cider. The cider is separated from the lees (or tank bottoms) and transferred either directly, or after centrifugal clarification or filtration, into storage vats (traditionally made of oak). The actual process of maturation is generally uncontrolled, although, increasingly, modern commercial cider makers seek to control the storage temperature and the secondary malolactic fermentation. The maturation process is only slowly being understood: malolactic fermentation (carried out by various lactic acid bacteria) reduces the acidity by conversion of malic acid to lactic acid. Many other microbial and biochemical conversions also take place including modification of the tannins and esterification, e.g., of lactic acid to form ethyl lactate. Some of the chemical markers of maturation are now being identified, although judgment as to the extent of maturation and the suitability of the cider for use is still an art vested in the cider maker, who will have many years of experience in judging the quality of the product. Final Processing

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When required for use, different batches of cider, generally made from juices of different apple cultivars, will be blended by the cider maker to provide specific flavor attributes. The raw cider may be fined using agents such as bentonite, gelatin, or chitin and filtered to give a bright product with no haze. Modern processing refinements include the use of microfiltration systems to obviate the need for fining and to speed the process.

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Cider Packaging 0031

Keg Cider

The cider is carbonated and pasteurized in line, through a continuous-flow plate heat exchanger. It is filled into stainless steel kegs in a plant that rinses, washes, and sterilizes the kegs prior to filling. The cider is dispensed in on-trade outlets using either carbon dioxide, or carbon dioxide and nitrogen, over-pressure through a cooling system designed to deliver the product into a glass at a temperature of 10 + 0.5
C. This process is similar to that used for dispensing keg beer.

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Bottled Ciders

Cider to be filled into glass bottles may either be carbonated and flash pasteurized, or carbonated and then in-pack-pasteurized after filling. Since it is generally not possible to pasteurize PET bottles, the product will be flash-pasteurized prior to filling. Bottles will be sealed using either crown closures or tamper-evident metal or plastic screw caps. Glass bottles range in size from 25 cl to 1.13 l and PET bottles from 25 cl to 5 l. Carbonation pressures generally range from 2.5 to 3.5 bar, the higher initial pressures being used in PET bottles, which, due to gaseous diffusion, lose carbonation during storage. Glass bottled ciders have a shelf-life in excess of 2 years (provided that they are not opened!), whereas PET bottled ciders generally have a shelf life of 9–12 months, because of loss of carbonation.

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CIDER (CYDER; HARD CIDER)/The Product and its Manufacture Can Cider 0034

The inside of cans for cider is always lacquered to prevent the product from attacking the metal. Cans are either of extruded aluminum or of mild steel, generally with a retained tag. Since sulfur dioxide is very corrosive to metal, especially if minute pinholes occur in the lacquer, cider for canning is generally prepared with little (< 35 mg l1 total) sulfite. Such products must, of necessity, be prepared in much more controlled conditions than general blend ciders, since at these low sulfite levels, microbial contamination can lead to the formation of undesirable flavours. Cider filled into cans is always bedpasteurized, generally at a process level of 30–40 pasteurization units (PUs). Control of dissolved oxygen levels for can ciders is also most important to prevent the development of oxidation off-flavors. Can ciders generally have a shelf-life of 9 months or less. (See Canning: Principles.) Secondary Packaging

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Bottles and cans are increasingly packaged using trays and shrink wraps, although the higher-value products (e.g., vintage and high-strength cider in glass bottles) are frequently packaged in carboard boxes with or without dividers. Labeling of Cider Products

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Throughout Europe, cider packs are required to conform to EU legislation on food labeling. At the present time, ingredient and nutritional labeling of alcoholic products is not required within the EU, although certain ingredients (e.g., intensive sweeteners) must be labeled. All alcoholic products, including cider, must display the alcohol content (as % abv) and the volume. The labeling requirements in other countries are dependent upon the national legislation.

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processing is rarely seen nowadays. A process used sometimes is that of cuve´ e close, in which a secondary yeast fermentation is done within a sealed tank, thereby developing a natural carbonation in the cider prior to bottling. Under EU legislation, it is illegal to refer to sparkling ciders as ‘champagne cider.’ White cider

White cider is prepared by fermenting decolorized apple juice, or the fermented cider is itself decolorized by treatment with activated charcoal or other suitable decolorizing agent (e.g., PVPP) prior to final blending. The term ‘white’ merely indicates that the product has little or no color – it is not ‘white’ in the sense that gin or vodka is ‘water white.’ De-alcoholized and Low-Alcohol Ciders

De-alcoholized ciders are prepared by removing the alcohol from strong cider, by thermal evaporation, reverse osmosis, or other suitable technology to give a product with an alcohol content not in excess of 0.5% abv. De-alcoholized cider lacks body and flavor and is not sold commercially. Low-alcohol cider (< 1.2% abv) is prepared either using a stopped fermentation or by fortification of de-alcoholized cider with apple juice and/or other ingredients to provide a product with a flavor and aroma close to that of normal alcoholic cider.

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Vintage ciders are made only from fresh juice from a named year. Some vintage and other ciders are made from the juice of a single named apple cultivar. Sparkling Ciders

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Sparkling cider is generally carbonated to a level of 3.5–4 bar pressure. Such products are filled into ‘champagne-style’ bottles with wired closures (generally plastic-mushroom stoppers). The product is normally sterile-filtered prior to bottling. Traditionally, sparkling cider received a secondary ‘in-bottle’ yeast fermentation (me´ thode champanoise), but such

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Organic cider

Following consumer interest in organic foods, a number of cider makers now offer cider made only from fruit grown in accordance with EU Regulations governing organic horticultural practices. The fruit is pressed separately from nonorganic fruit, and at present, it can be treated only with gaseous sulfur dioxide. The other ingredients included in the product must also conform with current legislation on organic products.

Special Ciders Vintage and Single Cultivar Ciders

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See also: Alcohol: Properties and Determination; Barrels: Wines, Spirits, and Other Beverages; Canning: Principles; Lactic Acid Bacteria; Preservatives: Classifications and Properties; Tannins and Polyphenols; Yeasts

Further Reading AICV (2000) Code of Practice for the Production of Cider, Perry and Fruit Wine in the EU. Revised 2000. Brussels: AICV. Beech FW (1972) English cidermaking: technology, microbiology and biochemistry. In: Hockenhull DJD (ed.) Progress in Industrial Microbiology, vol. 11, pp. 133– 213. Edinburgh: Churchill Livingstone.

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1318 CIDER (CYDER; HARD CIDER)/Chemistry and Microbiology of Cidermaking Beech FW and Davenport RR (1983) New prospects and problems in the beverage industry. In: Roberts TA and Skinner FA (eds) Food Microbiology: Advances and Prospects (S.A.B. Symposium Series No. 11), pp. 241–256. London: Academic Press. Charley VLS (1949) The Principles and Practice of Cidermaking. London: Leonard Hill. Jarvis B (2001) Cider, perry, fruit wines and other alcoholic beverages. In: Arthey D and Ashurst PR (eds) Fruit Processing, 2nd edn. pp. 111–148. Gaithersburg, MA: Aspen Publishers Inc. Jarvis B, Forster MJ and Kinsella WP (1995) Factors affecting the development of cider flavour. In: Board RG, Jones D and Jarvis B (eds) Microbial Fermentations: Beverages, Foods and Feeds (SAB Symposiuim Series No. 24) Journal of Applied Bacteriology 79 (supplement): 5S–18S. Lea AGH (1995) Cidermaking. In: Lea AGH and Piggott JR (eds) Fermented Beverage Production, pp. 66– 96.London: Blackie Academic & Professional. Williams RR (ed.) (1991) Cider and Juice Apples: Growing and Processing. Bristol: University of Bristol.

Chemistry and Microbiology of Cidermaking B Jarvis, Ross Biosciences Ltd, Ross-on-Wye, UK

Microbiology of Apple Juice and Cider Freshly pressed apple juice will contain a variety of yeasts and bacteria, many of which will be incapable of growth at the acidity of the juice. Examples of organisms often present in juice are shown in Table 1, together with an indication of their susceptibility to sulfur dioxide and ability to grow at the pH of the juice. (See Microbiology: Detection of Foodborne Pathogens and their Toxins.)

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Role of Sulfur Dioxide in Apple Juice

The use of sulfur dioxide as a preservative in cider making is controlled by legislation, in most countries the maximum level permitted in the final product being 200 mg kg1. The addition of sulfur dioxide to apple juice results in the formation of so-called sulfite addition compounds through the binding of sulfite to carbonyl compounds. The extent of sulfite binding is dependent upon the nature and origin of the carbonyl compounds present in the juice (see below). Similarly, if sulfur dioxide is added to an actively fermenting juice, there is a rapid combination with yeast metabolites such as acetaldehyde. Such juices will require a higher quantity of sulfite addition, if wild yeasts and other microorganisms are to be controlled effectively. Consequently, all additions of sulfur dioxide must be completed immediately after pressing the juice,

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Copyright 2003, Elsevier Science Ltd. All Rights Reserved.

Introduction 0001

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The fermentation of apple juice to cider can occur naturally through the metabolic activity of the yeasts and bacteria present on the fruit at harvest, which are then transferred into the apple juice on pressing. Other organisms, arising from the milling and pressing equipment and the general environment, can also contaminate the juice at this stage. Unless such organisms are inhibited, e.g., through the use of sulfur dioxide, the resulting mixed fermentation will yield a product that varies considerably from batch to batch, even if the composition of the apple juice for fermentation is identical. Hence, control of the indigenous and adventitious microorganisms, followed by deliberate inoculation with a selected strain of yeast, is the preferred commercial route for the production of cider. Transfer of the fermented juice into (traditionally oak) maturation vessels will result in a secondary malolactic fermentation by microorganisms that occur naturally in these vats. Such organisms may produce beneficial or detrimental changes in the chemical and organoleptic properties of the final cider.

Table 1 Typical microorganisms of freshly pressed apple juice Type

Typical species

Ability to grow at the acidity of apple juicea

Sensitivity to sulfiteb

Yeast

Saccharomyces cerevisiae S. uvarum Saccharomycodes ludwigii Kloeckera apiculata Candida mycoderma Pichia spp. Torulopsis famata Aereobasidium pullulans Rhodotorula spp. Acetobacter spp. Pseudomonas spp. Escherichia coli Salmonella spp. Micrococcus spp. Staphylococcus spp. Bacillus spp. Clostridium spp.

þþþþ þþþþ þþþþ þþþþ þþþþc þþþþc þþþþ þþþþ þþþþ þþþþc þ /þ  þ þ  (cells)  (cells)

+ or  + or   þþþ þþþþ þþþþ þþ þþþ þþþþ þþ þþþþ þþþþ þþþþ þþþþ þþþþ  (spores)  (spores)

Bacteria

a

þþþþ, capable of good growth; þ, capable of some growth; /þ, straindependent; , no growth. b , insensitive; +, relatively insensitive; þþ, þþþ, þþþþ, increasingly sensitive. c Only in the presence of air (e.g., on the surface of the cider).

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