Food Industries Manual 010

7/30/2019 Food Industries Manual 010

1/21

GRAPESWines are traditionally made from the fruit ofVitis vinifera of which there are a multitude ofvarieties growing in many parts of the world.Wine can be made from other species. Americanspecies are used as phylloxera-resistant rootstocks(see below), while in the eastern states of the USAthe indigenous species Vitis labrusca is commonlygrown. The labrusca flavour is different from V .vinifera and though quite acceptable in America itis not preferred and therefore not grown in Eur-opean countries.

Table 7.1 lists some of the best known wine-making grape varieties.Wine grapes are normally different from tablegrapes and the skin colours, ranging from darkred or purple to pink or from deep golden togreenish-white, allow a wide range of differentwines to be made. Most varieties have white juice,so that white wines can be made from red, as wellas white, grapes.

Ripeness is normally achieved about 100 daysafter the flowering of the vine and is judged by thethickness and colour of the skins, but principallyby the accumulation of sugars and diminution ofacids (see Figures 7.1 and 7.2). Some of the finestwines need the grapes to ripen beyond normalmaturity and for the juices to be concentrated.This concentration can be done in a number ofways: leaving the bunches on the vine; letting'noble rot' concentrate the juice; spreadingbunches on straw mats in the sun; leaving buncheson trays under cover in an airy place; letting thegrapes freeze on the vine and pressing the frozengrapes; or freezing the juice after pressing.A preharvest cull can focus the vine's energieson a smaller number of bunches and special quali-ties can be made by selective picking of the ripestgrapes. These demand labour-intensive hand har-vesting. Mechanical harvesting, which may shakethe grapes off the stalks onto a moving band, canreduce costs for ordinary wines, but can alsoallow the makers of fine wines to seize 'windows

7 Alcoholic Beverages

WINE

GrapesPage 236

ProcessingPage 238

AlcoholicfermentationPage 239

SecondaryfermentationsPage 239

MaturationPage 242

BlendingPage 243

WinesPage 242

FillingPage 243

LabellingPage 244

Quality aspectsPage 244


2/21

of opportunity' during changeable weather. Rainduring the harvest can produce dilute wines, eitherby swelling the grapes or by incorporating the rainon the outside of the bunches during crush.Care and vigilance are needed to protect thevines and grapes against pests and diseases. Somewill respond to curative measures, bu t others likemildew and similar cryptogamic diseases demand

preventive spraying. Phylloxera, caused by a rootlouse, requires the fine grape-bearing scions to begrafted onto resistant root-stock varieties. The greymould Botrytis cinerea can ruin the crop when itattacks unripe grapes, yet paradoxically, on fully-ripe grapes it is called the noble rot and helps toproduce the top wines of Sauternes and Tokay, aswell as the German Trocken-beeren-auslesen.

Total acidityM alic acidTartaric acid

Acidity (gl'1)

Days after colour change of the grapes from the initial opaqu e greenFigure 7.1 Acidity of ripeninggrapes. ,Total acidity; , malic acid; D, tartaric acid.

Table 7.1 Some of the most widely grown winemaking grape varietiesVarietyAirenCabernet FrancCabernet SauvignonCarignan (Carinena)ChardonnayChenin BlancGamayGewurtztraminerGrenache (Garnacha)Malvasia (Malvoisie)MerlotMuller-ThurgauMuscatNebbioloPalominoPinot Blanc (Pinot Bianco)Pinot Gris (Pinot Grigio)Pinot NoirRieslingSangioveseSauvignon Blanc (Blanc Fume)SemillonSercialSilvaner (Sylvaner)Syrah (Shiraz)TempranilloTorrontesTraminerTrebbianoUgni BlancVerdelho

White

WhiteWhiteWhiteWhiteWhiteWhiteWhiteWhiteWhiteWhite(White)WhiteWhiteWhiteWhiteWhite

WhiteWhiteWhiteWhite

Wine

Rose

RoseRose

Rose

Rose(Rose)

RedRedRed

RedRedRed(Red)Red

RedRed

RedRedRed

RemarksSpanish origin, large quantities

especially fo r Burgundyespecially fo r Beaujolaismeans 'spicy Traminer'best known for Malmsey MadeiraSwiss origin, large quantitiesseveral sub-varietiesespecially northwest Italyespecially for sherry

especially for Burgundy (and Champagne)especially for Chianti

fo r d ry Madeira

especially in Spainprincipally in Argentinaoriginally from north Italyprincipally in ItalyItalian origin, large quantities


3/21

OTHER RAW MATERIALSBrandies and similar spirits have long been dis-tilled from wines and compulsory distillation hasfo r a number of years been a principal means ofreducing the 'wine lake' in Europe. Such brandiesand rectified grape spirits are used in the makingof fortified wines, and when added to unfermentedgrape juice, making wines such as Pineau desCharentes, vins de liqueur or Mistelas.

There is also significant production of unfer-mented grape juice in Europe and in America,partly for the production of grape juice soft drinksand partly as another means of reducing the 'winelake'. In Europe the juice is usually concentratedto give concentrated grape must.

In the European Union, wines made from con-centrated grape juice or from dried grapes aredenominated 'made wines', while 'fruit wines' arethose made from fruits other than grapes. Fruitflavours, such as peach juice, are added to somesparkling wines. Aromatized and flavoured wines,such as Vermouths, as well as so-called 'tonicwines', make use of a wide range of traditionalherbs and spices, with their essential qualitiesobtained in a variety of ways according to thedesired style of product.

Cane or beet sugars are commonly added to thegrape juice in more northerly vineyards, and alsoin unsatisfactory vintages, to make up for a defi-ciency in grape sugars. The acidity of the grapejuice inverts the sucrose of cane or beet sugarsinto the glucose (dextrose) of grape sugar. InFrance, sucrose is added in dry form (drysugaring), also known as 'chaptalization', whereasin Germany it has been traditional to dissolve thesugar in water. This wet sugaring has the furtheradvantage of reducing the acidity slightly. The

excessive production of grapes in the EuropeanUnion, as noted above, has led also to a campaignto replace chaptalization with the use of rectifiedconcentrated grape must. Many German wines aresweetened after fermentation, using sterile-filteredgrape must (Siissreserve) which may have beenkept back from a previous vintage.

PROCESSING OF GRAPESFor the finest types of wine the bunches may besorted to eliminate faulty or unripe grapes. Nor-mally the next process is to separate the grapesfrom the stalks and crush the berries. This used tobe done by treading with the foot but is noweffected with a crusher-destemmer.

For nearly all white wines it is important toseparate the juice from the skins, pulp and pipswithout delay, especially when white wine is beingmade from red-skinned grapes as may be the casewith champagne. This is done in one of manytypes of wine press. It can be a batch process (forchampagne, fine white wines or sherry) or in acontinuous press for the speedy and economichandling of quantities of lower priced wines.

For red and rose wines the colour, which isunder the skin of the grape, needs to be extractedinto the juice. This skin contact (maceration) maylast fo r only one night or 24 h (for pale rosewines) or continue for three weeks or more, fo rdeep red wines. Colour extraction is related totemperature (see Thermovinification, under TEM-PERATURE CONTROL below) as well as time. Somewines are made by putting whole bunches withoutdestemming or crushing into closed vats, wherethe start of fermentation from the ripest grapescrushed under the weight of the mass bathes the

Days after colour change of the grapes from the initial opaqu e greenFigure 7.2 Maturity of ripening grapes. ,degrees Oechsle; D, maturity index. Maturity index = 10x -iwhere density is measured in degrees Oechsle and acidity is in g I"

1.

total acidity

Maturity index = I Q x density, OechsleTotal acidity, g/1

Degrees OechsleMaturity index

Index


4/21

remainder of the bunches in carbon dioxide gas(carbonic maceration) giving special flavour andcolour extraction.During maceration, bubbles of carbon dioxidegas tend to lift the skins, pips and pulp to thesurface to form a 'cap'. Various techniques areused to keep the skins in contact with the juice,such as punching down the cap, pumping the juiceover the cap, keeping the cap submerged with agrid part of the way down the vat or by havingmechanical paddles inside the vat. When sufficientcolour has been achieved or the fermentation fin-ished, the free-run wine can be drawn off, afterwhich the pulp, pips and skins can be put in awine press and the press wine extracted from thepomace. If desired, pips can be removed from thepomace with a special depipping machine and coldpressed to yield grape seed oil as a by-product.The yield is small (6 to 10% of the seeds) com-pared with 20 to 50% from other oil-producingseeds and nuts.

Vinification

Grape juice may be processed as such (seeChapter 6) but for it to be considered as wine thepresence of alcohol is essential. This may simplybe added to the unfermented grape juice, as inMistelas, Pineau des Charentes or Tokay Essenzia,or added after fermentation in the case of wineslike port and sherry. However, most winemakingrequires the action of fermentation micro-organ-isms on the sugars and other constituents of thegrape juice.

C6H12O6 -> 2C2H6O + 2CO2 + 23.5 calsThis is called the primary fermentation and iscarried out by the enzyme zymase, produced byyeasts, usually Saccharomyces ellipsoideus. A s arule-of-thumb one can reckon that each 18 g sugarper litre of juice has the potential to produce 1 %alcohol; hence a grape must with 216 g I"1 sugar(about 12 Baume) would be needed for a drywine with 12% alcohol by volume (ABV).Yeast cells absorb nutrients (sugars, etc.)through osmosis and dispose of the products(alcohol and carbon dioxide) similarly throughthe cell wall. They are therefore influenced by themedium in which they find themselves. If thesugar concentration in the grape must is too greatthe yeast cells are apt to dehydrate and collapse,and similarly if the concentration of alcohol inthe wine becomes too high. Thus fermentationm ay be difficult to start with very rich grapem usts, while special alcoho l-resistant strains of

yeast may be needed for the vinification of highstrength wines.A second fermentation by adding more sugarand yeast is used to make sparkling wine, wherethe production of carbon dioxide gas is the prin-cipal objective. A different second fermentation,called the 'governo', is used in some Italian wines,adding unfermented grape juice and yeast to thewine to give it extra strength and body. Fino sher-ries have a 'flor' second fermentation by filmyeasts growing on the wine surface which strip thesherry of oxygen creating a reductive state andkeeping the wine fresh and crisp. Proliferation ofyeast cells during fermentation results in 'winelees', mainly dead yeast cells, tartrates and grapefragments, so that young wine requires clarifica-tion or racking, or disgorging in the case of spark-ling wines.Lactobacilli are the ferments in a different sec-ondary fermentation in which the sharp tastingmalic acid of some young wines is converted intothe milder lactic acid.

HO2CCH(OH)CO2H + H2O - HO2CCH(OH)CH3 + CO2Malic acid Lactic acid

This malo-lactic fermentation also produces CO2gas, giving the characteristic 'petillant' style ofcertain wines, like the Vinho Verdes of northernPortugal. Lactobacilli seem to have a symbioticrelationship with the yeasts of the primary fermen-tation, relying on yeast by-products for their acti-vation.Ferm entation stops naturally when all the fer-mentable sugars have been converted to alcohol.It can also end if the alcoholic strength reachesthe limit of tolerance of the strain of yeastinvolved, causing the cells to dehydrate and col-lapse. It can therefore be stopped artificially byadding alcohol (fortification) either to the fer-menting wine (in the case of port) or even tounfermented grape juice, as in Mistelas or Pineaudes Charentes. Fermentation can be stoppedmechanically by sterile filtration or centrifugingwhich remove the yeast from the wine. Tempera-ture control, by cooling to inactivate the yeasts orheating to pasteurize them, is another methodavailable. Sulphur dioxide or sorbic acid preserva-tives may also be used.

AcidsThe predominant acid during the early stages ofdevelopment of the grape is the 'green-apple'malic acid (see Figure 7.1). As the grape changescolour and matures, aided by warmth and


5/21

moisture, the malic acidity diminishes while thetypical grape acid, tartaric, begins to predominate.During the alcoholic fermentation some of the tar-taric acid comes out of solution in the form oftar-trates (known in the past as 'argols' or winestones) which can be a useful by-product, manu-factured, fo r example, into baking powder.

During vinification and maturing, the wine-maker has to guard against or control volatileacidity. This is caused by the action of Aceto-b a c t e r , which convert alcohol into acetic acid, andif uncontrolled can cause spoilage and turn thewine into vinegar. In very small quantities,however, Acetobacter can help to develop esters,giving finesse to the aroma.

A number of wines, such as the Moselles, owetheir crisp and refreshing character to a quite highcontent of malic acid, but for other styles ofwines, expected to be mild and smooth, the wine-maker may wish to encourage the action of lacto-bacilli to convert the malic acid into lactic acid inthe malo-lactic fermentation. The total acidity ofa must or a wine is a useful indication of thematurity of the grapes and the development of thewine.Other acidsCitric acid has been used in the past to complexand control metal contamination in wines. Tracesof succinic, propionic and some other acids mayresult as by-products of fermentation.

Sulphur dioxide

Sulphur dioxide has a distinctive role in wine-making, as a preservative, a sterilizing agent andas an antioxidant. It has a tendency to combinewith sugars which reduce its effectiveness both asan antioxidant and against micro-organisms. Assulphurous acid it can impart a harsh or 'hot' endflavour to a wine. It can also react to producemercaptans or bottle stink in an old wine. Table7.2 shows quantitative relationships amongvarious practical sources of SO2 when added towine.

Carbon dioxideCarbon dioxide or carbonic acid is a by-productof the alcoholic fermentation. From still wines it isallowed to disperse into the atmosphere but forpetillant and sparkling wines it is retained in solu-tion in the bottle. Its solubility is greater at lowertemperatures. It may also be lost from solution byformation of complexes with sugars. The size andfrequency of the bubbles in a sparkling wine arereferred to as the mousse.

Sparkling winesThe classic 'methode champenoise' consisted firstof making a still wine from the champagne grapes,

Table 7.2 Dosage of sulphur dioxide for the treatment of grape musts and winesSO2 content required(mgr1)

51015202530354045505560657075

100125150

SO2 (applied as)Liquid SO2(ghr1)

51015202530354045505560657075

100125150

SO2, solution(rnlhP1)100200300400500600700800900100011001200

130014001500200025003000

5% Potassium metabisulphite(ghr1)102030405060708090100110120

130140150200250300

Sulphur candles(no. of thin sheets)1-1V 22-33-41A4-65-7 !/26-97-1O 1A8-129-131X 210-15


6/21

then adding sugar and a special yeast, bottling thewine in strong bottles and corking it securely,often using crown corks. Here the primary objec-tive is not the conversion of sugar into alcohol bu tthe production of carbon dioxide gas for thesparkle.The subsequent removal of the dead yeast cellsand tartrates resulting from this process requirestheir manipulation on to the corks. Traditionallythis is done with the bottles placed with their necksin racks slanted at about 30-40 to the vertical.Each bottle is first shaken to loosen the sediment,rotated fractionally on its axis and oscillated andgradually titled to become neck downwards. Theseoperations are repeated every few days, over aperiod ranging from a few weeks to severalmonths. The necks of the bottles can then beimmersed in a freezing bath, so that the lees aresecured in a lump of ice attached to the cork. Thusthe bottle can safely be stood upright, and the corkwith its attached ice and sediment removed. Thedryness of the wine may be adjusted to give Brut(very dry), dry, half-dry or sweet styles by theaddition of an appropriate dosage of wine andsugar solution, then the bottle is recorked andwired to prevent the cork from blowing off later.

The 'Charmat' or 'cuve-close' method wasinvented to avoid such labour-intensive processesfor lower priced sparkling wines. In this systemthe second fermentation is carried out in an insu-lated pressure vessel; cooling allows more CO2 tobe dissolved. The sparkling wine is then forced outunder counterpressure of the CO2 gas through afilter to remove the yeast sediment, into the bottlesand corked.An intermediate procedure, known as the'transfer method', is used fo r some mediumquality sparkling wines. The secondary fermenta-tion takes place in bottle and in due course thebottles are uncorked, placed in a star wheel,emptied under CO2 counterpressure which drivesthe wine through a filter to remove the yeast,thence into clean bottles which are recorked.Some of the labour of the traditional methodsmay be reduced, fo r instance if the shaking ofthe sediment onto the cork is assisted bymechanical means, after which the necks can befrozen and disgorging and recorking proceedsnormally.P artial ferm entation is used in m aking a num berof special types of wine. L ow alcohol wines likesome Lambrusco, are sterile-filtered under CO2counterpressure, leaving semi-sparkling wine withresidual sweetness. Port has its fermentationstopped by the addition of brandy, producing arich sweet high strength wine.

TartratesA s the alcohol content of the ferm enting wineincreases, the saturation point of tartrates in solu-tion falls and they may crystallize out into thewine lees or onto the walls of the wine vessels. Afall in temperature will also increase tartrate preci-pitation (Table 7.3).

To avoid deposition of tartrates in the wineafter bottling it is usual, particularly with whitewines, to hold the bulk wine just above its freezingpoint fo r 7-14 days, then centrifuge or filter (orboth) to remove the crystalline deposit. Clarifica-tion may be accelerated by 'seeding' the cold winewith a small quantity of potassium bitartrate.Tartrates can be extracted from wine lees,pomace or the deposits in storage vats, by treatingthem with boiling water and then cooling the

resultant solution. O ne litre of water at 9O 0C candissolve 57 g potassium bitartrate (cream oftartar) bu t when cooled to 1O 0C it will retain only4 g, the rest crystallizing out. The potassium bitar-trate is usually accompanied by a small quantityof calcium tartrate. Precipitation of tartrate froma wine also reduces the acidity of the flavour.Temperature control

Temperature control is important in the art ofwinemaking. Micro-organisms have different meta-bolic rates at higher or lower temperatures andchemical reactions such as oxidation are similarlyinfluenced. In the simplest way, temperature maybe controlled by judging the best size for the winevessels and encouraging air currents (in aboveground wineries), or by storing the wine in under-ground cellars.

Table 7.3 Solubility of potassium hydrogen tartrate (potas-sium bitartrate) in water and alcoholTemperature(0Q

O5101520253035404550

Solubility (g 1 l ) in water containingthe stated percentages of alcohol

0%0.300.320.410.440.490.540.690.840.961.131.25

10%0.170.190.210.240.290.360.400.490.540.730.87

20%0.110.130.160.160.170.210.250.290.380.440.54

30%0.070.070.090.090.110.120.130.190.230.260.30


7/21

Technology adds thermovinification to extractcolour and flavour from the skins, autovinificationto reduce the labour of breaking the 'cap' andpumping-over, while cooling equipment canprovide lo w temperature fermentation.

MATURATIONAlthough some wines are made fo r early drinking,as 'Primeur' wines, most wines benefit fromcareful maturing, during which sharpness an droughness diminish while aromas and flavours candevelop and gain in complexity.

The winemaker's skill is required to judge theoxidoreductive state of the intended wine. Thisprocess m ay best be envisaged through the dif-ferent styles of sherry. After the primary 'tumul-tuoso' fermentation is ended, the various casks aretasted and graded. Some are neutral rayas suitablefo r blending. Others are destined for maturing ina reductive state state as finos, in which a floryeast strips the wine of oxygen. Others again areleft with an airspace in the cask to develop in anoxidative state as olorosos. Combinations of thetwo maturing methods yield other styles an dsubtleties. Once the style has been established inthe nursery cellar ('criadera'), it is maintained bytransferring the young wine little by little, cask bycask and row by row, through the stack of casksmaking up the 'solera' of that particular style andquality. Sherry is also different from most otherwines by being left on the lees so that the yeastresidues remain at the bottom of the casks and areslowly autolysed producing aldehydes.

CH3CH2OH + 1X 2O 2 -> CH3CHO + H2Oalcohol acetaldehyde

Such aldehydes contribute significantly to thetypical aromas and flavours of sherries. Howeverif oxidation is unchecked acetic acid can be pro-duced.CH3CH2OH + O2 -> CH3COOH + H2O

acetic acidThis imparts vinegar tastes and 'volatile acidityaromas'. Other than the sherries, most wines incask need to be clarified by taking them off thelees ('racking' them) into clean casks. Carbondioxide or other inert gas such as nitrogen may beused during racking if the wine needs to be pro-tected from the oxygen in the air so as to be keptin a reductive state. A relatively high acidity helpsto keep a wine in a reductive state, as does thepresence of dissolved carbon dioxide under pres-sure.

Clarification may need to be aided by 'fining'.Traditionally, high quality red wines were finedwith egg white and white wines with gelatin orisinglass. Other products such as bentonite areno w used. Most finings act by flocculation andadsorption and they need to be thoroughly dis-persed throughout the wine. Centrifuging and fil-tering are other ways of clarifying grape must andwine; filter aids such as diatomaeceous or infu-sorial earth may be used.Wine vesselsWinemaking and storage vessels, originally ofstone, pottery or wood, may now be of stainlesssteel, fibreglass or ceramic-lined concrete. Self-emptying vats reduce the labour of handlingpomace from red wine production. Insulated pres-sure vessels are now used for the 'Charmat'system of sparkling wine production.TYPES OF WINEWine is a long term product. Clearing the landan d planting m ay require several years before thefirst wine is marketed and there is a return on theinvestment. Therefore wineries m ay start bybuying in grapes from existing growers an d mar-keting a range of styles: red, white and rose dry(fully fermented) wines. Wineries use noble grapesfo r classic styles needing maturation an d moreordinary varieties fo r making 'quaffing wines' forcash-flow. They m ay produce medium-dry orsweeter table wines, either by starting with moresugar-rich grape juice or by stopping fermentationand leaving residual sugar and they may makesparkling wines by secondary fermentation (andeven sometimes by carbon dioxide gas injection!).Fortified wines were originally developed towithstand longer sea journeys and traditionallycome from warmer vineyard regions; madeiraowes its particular keeping qualities to the 'estufa'technique, whereby the casks of wine are 'baked'in hot cellars, which stabilizes and oxidizes thewine giving the characteristic 'maderized' style.Mediterranean countries such as Greece andCyprus have marketed their surplus grape produc-tion as raisins and by making vacuum-concen-trated grape must. This has been shipped tocountries like the UK to be reconstituted byadding water and fermented with cultured yeast tomake 'British Wine' (in EU parlance - 'madewine'). This should not be confused with 'Englishwine', made from fresh grapes grown in Englishvineyards.


8/21

Ginger wine is made from grape concentrateand ginger, while tonic wines m ay include phos-phates.Vermouths are normally made with base winefrom fresh grapes and their characteristic ingre-dient is wormwood, Artemis ia absinthium; inItalian vermouth it is usually Roman Wormwood.Japanese Sake, although it is sometimes called'rice wine', is in fact brewed, using the symbioticrelationship of a starch digesting mould and asugar conv erting saccharomyces.

BlendingA grower will find that some of his vineyard siteshave better exposure than others, and that thegrapes ripen at different times; it can be the samewith different grape varieties. So a winemaker,using grapes of several varieties from a number ofdifferent sites, m ay have to make a selection frommany vats of that vintage. Furthermore, fromeach vinification of red wine he may have twovats, one of the free-run wine and another of presswine. If the vintage is such that the free-run islacking a bit in body, an admixture of the morerobust press wine m ay well produce a morebalanced wine.A proportion of the crop may be vinified ormatured in new oak in order to complex thearomas and flavours, while some may be in oldercasks where differences in the timber and its por-osity may give greater or lesser oxidative effects.With the element of chance and so m any variablesat play, the winemaker cannot expect every caskor vat to be exactly the same. Although in thepast, top German winemakers may have sold indi-vidual casks separately and put the cask numberon the label, present-day marketing demands adegree of standardization. In order to iron outminor variations, winemakers put wines of similarquality into a vat for equalization before fillingthem into container, cask or bottle.The ultimate in equalization is achieved inSpain with the solera system (see under MATURA-TION above), where wine fo r despatch is drawnfrom every cask in the bottom row of the stack,each containing a blend of all the vintages goingback to the time when the solera was first estab-lished. It is thus the ultimate in non-vintage wine.Producing a non-vintage wine has two mainadvantages. If for example one vintage is lackingin acidity and the next has high acidity, blendingthe two together may well produce a morebalanced wine, superior to either of the ingredi-ents. Moreover, customers will get a more stan-

dard product, irrespective of weather variationsfrom vintage to vintage and will no t have to keepchanging the vintage year shown on their lists.Vintage wine is assumed to be exclusively of thenamed vintage. In the case of vintage port it istraditionally bottled two years after the year whenit was harvested. The exceptions to this aredenominated 'late bottled 19** port' or 'port ofthe 19** vintage' or 'Colheita 19**'. O ld vintageport will normally need to be decanted to avoidgetting sediment in the glass, as will 'crusted port'.

It should be remembered that a vintage winefrom a southern hemisphere vineyard will be 6months older than the same vintage from anorthern hemisphere vineyard.

FILLINGUntil fairly recently most wines were delivered topoint of sale or marketing area in casks. Transportcasks were of thick-staved chestnut wood, whereasthe cellar casks fo r maturing were more usually ofoak. (Tonnage of ships originated in the numberof 'tuns' of Bordeaux wine they could carry: 1tonneau = 4 Hogsheads, each holding about 225 1or 50 Imperial gallons). These transport casks areno w largely replaced by containerization: regularstainless steel wine tanks for road, rail and seatransport; road tankers (bowsers) for 'roll-on-roll-ofF ( R o - R o ) ferry transport; multicompartmentedtanker ships which ply the Mediterranean withvermouths, sherries and other bulk wines.Bottling at source, in the past restricted to thefinest wines, is now an economic possibility evenfor keenly priced wines, thanks to containerizationwhich allows cartons of bottled wines to traveldirect from producer to point of sale without thehandling costs of breaking bulk.

BottlingBottles come in a variety of colours, shapes andsizes, many dubbed with esoteric names. The Eur-opean Union has agreed some standardized typesand sizes; correctness of fill according to the ECQuantities Directive may be indicated with a lowercase letter 'e' on the label.Corks, from the inner bark of the cork oak,Quercus suber , have been standard closures fo rbottles fo r many years since they replaced oil-soaked rags. 'Full-long' corks are used for thefinest wines which may need to remain in bottlefo r m any years.The shortage of top quality cork has led to the


9/21

development of composition stoppers, combiningcompressed granulated cork with layers ofordinary cork. Champagne and sparkling winesneed over-sized corks, which are squeezed anddriven forcibly into the bottle neck, then mush-room out into the typical champagne cork shapeand wired down to resist the CO2 gas pressure.The corks of vintage port were fo r many yearscovered with sealing wax to prevent the entry ofcork weevils. It is now more usual to protect thecork and decorate the bottle with a capsule, ori-ginally of lead but now of aluminium alloy orplastic. Sparkling wines have foil over the corkan d neck, concealing the ullage resulting from thespace needed for the gas; 80 cl bottles fo r spark-ling wine have the normal fill of 75 cl. Plastic stop-pers are used fo r some lower priced sparklingwines an d crown corks are an alternative, also fo rsome semi-sparkling (petillant) wines. Stoppercorks can be used on wines like sherry which donot need to be laid down and are convenient forthe consumer as no corkscrew is required. Closuresfo r inexpensive wines include 'roll-on, pilfer-proof(ROPP) closures which do not require capsules.

Other retailing containersPottery containers like the classic amphora, whichwere the norm in ancient times, are occasionallyused in place of glass bottles.Plastic bottles (polyethylene terephthalate -PET) are mainly fo r airline use to save weight aswine packed in them has limited shelf life. Blownplastic PVC containers had the disadvantage thattraces of solvents and plasticizers used in theirmanufacture could leach into the wine and bedetectable on nose and palate. They have effec-tively been replaced by the now ubiquitous 'bag-in-box'; these cartons with multilayer collapsiblelinings come in various sizes, usually 3 or 5 1, witha variety of taps. Smaller lined cartons (e.g. Tetra-pak) with various pouring devices can also befound and appear to be growing in popularity,particularly in the New World.Cans are sometimes used fo r lower priced winesbut seem to have limited appeal and little or noprice advantage.

STORAGEWine needs to be stored at an even temperature.Wide variations can cause premature ageing. Wineis a liquid which expands with a rise in tempera-ture when it may force its way into an d through

the cork, while a drop in temperature will causecontraction, drawing in air, and causing oxidation.Wine also needs to be protected against light,which can cause unwanted ageing. Both theserequirements were met in the past by storage inunderground cellars and this still has many advan-tages. However, mechanical handling and palleti-zation can make temperature-controlledwarehouses more advantageous, with greater head-room allowing pallet racking.With high rates of excise on alcoholic beverages,Customs and Excise bonded warehouses may beused fo r long term storage, since excise duty andvalue added tax (VAT) only become payable onremoval from bond an d duty free re-export can bearranged if required.

LABELLING AND DISTRIBUTIONLabelling laws lay down the information thatmust be given fo r wines offered fo r sale, togetherwith the size of lettering to be used fo r much ofthe essential information. In recent years, labellinghas become more 'user friendly' , with back labelsproviding data about how and where the wine wasmade, information about relative fullness or sweet-ness and suggestions how and with what foods itm ay best be enjoyed.Wine trade education is now well-organized andwidely available and is beneficial at all levels ofthe distribution chain. It is arguable whether thewine trade is supply-led or demand-led. Vineyardsare planted for an economic lifespan of 20 to 30years. Public likes and dislikes may change severaltimes during that period. The winemaker and themerchant need all their skills to be responsive tochanging tastes.

QUALITY ASPECTSQuality is easier to recognize than to define. Inmany wine growing areas of the world certainwines have been recognized fo r their quality andhave set benchmarks. These wines may be recog-nizably different from one another but thecommon factor of them all is the harmony of thevarious characteristics which make up the whole.In red wines the winemaker is balancing theextraction of colour and flavour components ofthe anthocyanins (oenotannins) lying under thegrape skins, judging their ripeness, deciding howfar they should be oxidized and the possibilities ofcomplexing them with wood tannins (gallotannins)from casks or vats.


10/21

White wines are pressed so as to extract thejuice q uickly, which results in lim ited extraction ofthe grape tannins, which in turn makes the deci-sion whether or not to use oak aging more impor-tant. In white wines the balance between fruitflavours (or soil characteristics) and aciditybecomes important; the fruit flavours and aromaswill differ according to the grape variety and theripeness of the vintage, as will the acidity.Acidities, alcohol and any residual sugars needto be in harmony, to avoid either 'empty', 'flabby'wines, or 'sharp', 'harsh' wines at the otherextreme. The extract content (see later under COM-POSITION) plays a part in the body of a wine whilethe persistence of flavours on the palate createsthe impression of 'length' and 'aftertaste'.A number of the flavour components of a wineare aroma linked. Wine aromas may be dividedinto primary aromas, such as the flower or fruitnotes related to the grape variety, and secondaryaromas, related to esterification and the com-plexing of the primary notes.

Deposits

The behaviour of tannins in red wines is related tothe pH of the wine. When the isoelectric point oftannin is reached, tannins can change their charge,link to other substances (often in colloidal form)in the wine, flocculate and fall out. So tannin pre-cipitation may be related to the malic acid contentand the state of the malo-lactic fermentation, orto the tartaric acid content and the degree of tar-trate precipitation.Tannin precipitation also depends on whethertrace iron associated with the tannins is in thebivalent or the trivalent state. For instance, if ared wine is fined with a colloidal fining under vig-orous agitation, oxygen will be introduced, ironconverted to the ferric state and tannin precipita-tion will be encouraged.Deposits may also relate to the quality of thevintage: in less ripe years, the nitrogenous matterm ay be mainly amino acids and short chain pep-tides and fallout may be powdery; in ripe vintages,longer chain peptides may be formed and granularfallout can occur; in super ripe years, polypeptidechains may be formed with the result that oldbottles of fine port, for instance, may have 'bees-wing' formation on the sides of the bottles.Bottles of white wine m ay have angular crystalsat the bottom or on the cork. They look ratherlike sugar crystals and are sometimes mistaken forfragments of glass bu t they are in fact deposits ofTARTRATES (see above). When they form on a

cork this may have been triggered by some treat-ment such as cork bleaching by the cork mer-chants, or seeded by cork dust coming out of thestomata of the cork.

CompositionTypical laboratory figures for the composition ofgrape juice are given in Table 7.4.Tables 7.5 and 7.6 show relationships betweenseveral measures of specific gravity and sugarcontent. These are most useful when the degree ofmaturity of grapes is to be estimated (see alsoFigures 7.1 and 7.2). Table 7.7 shows relationshipsbetween different measures and expressions ofalcohol content. The classic analysis of winesincludes measuring the dry extract by evaporatinga measured quantity of wine to drive off the liquidcomponents. The extract may also be estimatedfrom the specific gravity (SG). For this one needsto remember that increasing quantities of alcohollower the density or specific gravity of a mixtureof alcohol and water (Table 7.7) whereas sugars,etc. increase the specific gravity (Tables 7.5 and7.6). The rule-of-thumb formula for the calcula-tion of extract is: ^2 = (d + 1) d \ whered2 = SG of the extractd = SG of the wined \ = SG of the alcohol content.R esults of this calculation are shown in Table7.8. With sweet wines one may wish to calculatethe balance of extract or 'extract without sugar'by subtracting the residual sugars in gl"1 fromthe total extract in g I"1.Typical analyses of wines, as quoted in modernbuying specifications, are given in Table 7.9. Table7.10 shows relationships between alcohol content,acidity and extract to be expected in wines with areasonable balance.Table 7.4 Composition of ripe grape juice ( %)Water 70-85E xtract (solids) 15-30Sugars 12-27Pectins 0.1-1P entosans andpentoses 0.1-0.5Acids:malic 0.1-0.5citric tracetartaric 0.2-0.8*Tannins 0.0-0.2Proteins 0.5-1Ash 0.2-0.6* Mainly as potassium bitartrate.


11/21

Table 7.5 Measures of densitySpecific Degrees Degrees Degreesgravity Oechsele Brix Baume

.000 O 0.00 0.00.005 5 1.25 0.71.010 10 2.50 1.43.015 15 3.75 2.12.020 20 5.00 2.75.025 25 6.25 3.43.030 30 7.50 4.14.035 35 8.75 4.86.040 40 10.00 5.71

.042 42 10.50 6.00.045 45 11.00 6.11.049 49 12.20 7.00.053 53 13.00 7.22

.057 57 14.00 7.77.061 61 15.00 8.32.063 63 15.70 9.001.070 70 17.50 10.00This table is an approximation based on French and Germantables, using different instruments.

Table 7.7 Measures of alcohol in m ixtures of alcohol andwater at 150CAlcoholic Alcohol (grams per Alcohol (grams per Specificstrength 10Og of mixture) litre of mixture) gravity(ABV) (% by weight)0 0.000 0.000 1.000001 0.795 7.936 0.998442 1.593 15.873 0.996953 2.394 23.809 0.995924 3.196 31.745 0.994135 4.001 39.682 0.992776 4.807 47.618 0.991457 5.616 55.554 0.990168 6.426 63.491 0.988919 7.238 71.427 0.9877010 8.050 79.364 0.9865211 8.867 87.300 0.9853712 9.685 95.236 0.984241 3 10.503 103.173 0.9831414 11.324 111.109 0.982061 5 12.146 119.045 0.9810016 12.969 126.982 0.9799517 13.794 134.918 0.9789218 14.621 142.854 0.9779019 15.499 150.791 0.9768820 16.279 158.727 0.9758721 1 7 . 1 1 1 166.663 0.9748722 17.944 174.600 0.9738723 18.779 182.736 0.9728624 19.616 190.472 0.9718525 20.455 198.409 0.9708426 21.495 206.345 0.9698127 22.138 214.281 0.9687628 22.984 222.218 0.9676929 23.832 230.154 0.9675930 24.683 238.091 0.96545

Table 7.6 Measures of sugar content*Specific Degrees Sugar content Ad justed sugargravity Oechsele from Brix tables content( g r1) (gr1)1.060 60 155.7 130.31.070 70 181.9 156.71.080 80 208.1 183.11.090 90 234.2 209.51.100 100 260.6 235.91.110 110 286.8 262.3*The presence of non-sugars in grape must means that sugarmeasurements made by specific gravity or refractometer need tobe adjusted.

Table 7.8 Calculation of wine extractSpecific E xtract Specific E xtract Specific E xtractgravity (gl -1) gravity (gl"1) gravity (gl"1)at 150C at 150C at 150C

.0040 9.6 1.0105 25.2 1.0170 41.4.0045 10.8 1.0110 26.4 1.0175 42.9.0050 12.0 .0115 27.6 1.0180 44.3.0055 13.2 .0120 28.8 1.0185 45.8.0060 14.4 .0125 30.0 1.0190 47.2.0065 15.6 .0130 31.2 1.0195 48.7.0070 16.8 .0135 32.4 1.0200 50.11.0075 18.0 .0140 33.6 1.0205 51.61.0080 19.2 .0145 34.8 1.0210 53.01.0085 20.4 .0150 36.0 1.0215 54.41.0090 21.6 .0155 37.2 1.0220 55.91.0095 22.8 .0160 38.5 1.0225 57.31.0100 24.0 .0165 40.0 1.0230 58.8

Table 7.9 Typical range of analysis of table wines, as bottledAlcohol 7-14 % v/v Variable, depending on typeetc.; (normally declared on thelabel, with a tolerance of

0.5%)Acidity, total 4.5-10 g I"1* Variable, depending on type

and qualityvolatile 0.2-0.5 g I"1* Excess is considered a defect;up to 1.0 mg I"1 may betolerated in some wines

pH 3-3.5Iron 5 mgl"""

1Sometimes as high as2OnIgP1

SO2, total 50-250 mg I"1 Legal maxima vary accordingto winefree 20-50 mgr1

Sorbic acid 200 mgl"1 Maximum* Acidity is usually expressed in grams of sulphuric or tartaricacid per litre: sulphuric acid, H2SO4, 1 M = 49 g I"1; tartaricacid, C2H4O2(COOH)2, 1M = 53 gr1.


12/21

Table 7.10 Alcohol, fixed acidity and extract of winesAlcohol Fixed aciditya Balance of extract13

(minimum) (gl"1)(g I"1 as tartaric)(% by volume) Red & white wines R ed wine White wine7 6.6 11.0 9.08 5.7 11.5 9.59 5.0 12.0 10.010 4.5 12.5 10.5

11 4.1 13.0 11.012 3.8 13.5 11.513 3.6 14.0 12.0a Fixed acidity is calculated by subtracting the volatile acidityfrom the total acidity.b Balance of extract represents the weight of glycerine andsimilar substances (glycols), mineral salts, nitrogenous matter,tannins and colouring matters and other substances of sec-ondary importance. The figure for balance of extract isobtained by subtracting any sugar content from the totalextract and then subtracting the fixed acidity.Source: Benvegnin e t a l . (1951).

Sensory profilesQuality is produced by a combination of grapevarieties, site and soil (terroir), weather andhuman effort. It has to be judged through thesenses of the winemaker and eventual consumer.The winemaker m ay rely to a considerableextent on laboratory analyses to assess the devel-opment of wines, but the ultimate assessment bythe consumer is on appearance, aroma andtaste. These can be put together as a sensoryprofile, as in the following example of some of

the elements which can be considered fo r tablewines:Tasting aide-memoire

A ppearanc eColour: purplish, ruby red, brick red, brownish,rose, salmon, pale pink, blush;greeny-white, water-white, pale yellow,golden yellow, deep gold, brownishRichness: depth of colour, fullness of flowBrilliance: limpid, hazy, cloudy, piecyNoseFlowery: spring flowers, summer flowers, potpourriFruity: soft fruits, stone fruits, apples and pearsSpicy: vanilla, cinnamon, peppery, etc.

Herbs: lavender, thyme, rosemary, bay, etc.Soils: flinty, slatey, smoky, earthy, etc.Yeasty: or winey (vinosity) or volatile (acetic)P a la t eTaste buds: sweet, acid, (bitter), (salty)Mouth-feel: rough/smooth, round/sharp,thin/full, warmth/coolness, flow, lengthR e m a r k stoo young, young and fresh, ready to drink; better in '*' years,mature, will keep for /years; over the top, worn out

Wine jargon relies on terms culled from pre-vious experience or adopted from pundits. A s peo-ple's tastes and experiences are so varied, aperson's wine vocabulary needs to be constantlychecked and revised.If wines can be tasted at different stages of theirdevelopment, a timescale image may be built upand used, by analogy, to prognosticate the futureof a wine. With such a gamut of styles and quali-ties available in the world of wine, it is good totaste widely to establish a personal range of pre-ferences and wherever possible to sample the bestin order to have benchmarks of quality.


13/21

INTRODUCTIONBeer is a beverage produced by a fermentation ofa hopped water extract of germinated barley. Thismeans that the four main raw materials to becomebeer are malt, hops, water and yeast.Barley cannot directly be used for the produc-tion of beer but must be malted. The endospermof barley contains a large amount of starch butonly very small amounts of sugars, whereas thebrewing yeast can convert only fermentable sugarsto alcohol and carbon dioxide. The starch has tobe degraded by enzymes to fermentable sugars, ofwhich the most important for the brewing industryare maltose, maltotriose and glucose. The processthat makes barley suitable fo r brewing is calledmalting. During malting, enzymes are produced oractivated.

The malting process involves the collection ofstocks of suitable barley, steeping the grain inwater, germinating the grain and finally dryingand curing it on the kiln. The brewing processinvolves the enzymatic extraction of malt withwater, filtration of the wort, boiling of the wortwith hops, clarification and cooling of the wort.After the brewing process the fermentation ofthe cooled wort starts by adding yeast, followedby the maturation. Finally the beer can be filteredand bottled, canned or kegged. The world produc-tion of beer is estimated at 900 million hectolitresper annum.

MALTINGThe germination of the grain is a prerequisite fo rthe production of malt. The growth of the germor embryo is incidental to the making of malt andleads to depletion of the endosperm materialthrough respiration of the embryo and its growth.The maltster is especially concerned with thedegradation of the endosperm, the mobilization ofthe enzymes of the grains and the yield of the pro-duction. Thus the maltster's requirements deviatefrom those of the farmer whose primary interest isth e growth of the embryo into a mature fruitingplant.

In the past only tw o rowed barley was used fo rthe brewing industry, now two and six rowedbarley are used.

Selection of the barleyThe selection is based on many criteria includingbrewing capacity, rapid and synchronous germina-

BEERSBarley

Page 248Other cereals

GerminationPage 249

MaltPage 249

MillingPage 250

MashingPage 250

FermentationPage 252

ConditioningPage 253

Alcohol reductionPage 253

F i l l i n gPage 254

Transport and storagePage 255

Quality aspectsPage 255


14/21

tion of the grains, uniform enzymatic degradationof the endosperm, an adequate complement ofenzymes remaining after kilning, low levels offibrous materials and total nitrogen, purity ofvariety, suitability fo r mechanical harvesting, largegrain size (measured as thousand corn weight),disease resistance and an acceptable dormancyperiod. It is also very important that the grains dono t start to germinate on the field before theharvest in damp weather conditions. For thefarmer it is necessary that the barley varieties sui-table to the maltster also have desirable agricul-tural properties, especially good yields. Samples ofbarley may be assessed before purchase by submit-ting them to a pilot- or microscale maltingprocess.

Cleaning up the barleyWhen harvested, barley cannot be immediatelyused for malting. The crop is polluted with dust,straw, stones and possibly small fragments of iron.These contaminants are taken out by air cleaning,sieving and magnetic cleaning.A batch of barley will also contain foreigngrains such as wheat, oats or maize, and brokencorns of barley which are a great risk fo r mouldgrowth. These impurities may be removed in amachine where the corns are sorted out by length.Furthermore barley is not homogeneous, so whenit is steeped in water it may not give synchronousgermination. For that reason the grains areselected fo r size using sieves. The small grains aresent fo r cattle food.

Storing the barleyMany maltsters prefer to receive grain as soon aspossible after harvest, then to dry, clean and storeit themselves to assure that its quality is main-tained. The maximum content of water in thebarley should be 16%. Large amounts of barleyare purchased from the same area to avoid largedifferences in germination.It is necessary to store the barley because imme-diately after harvesting the corns are very watersensitive, that is, they are not strong enough togerminate and during steeping the germ may easilydie. Normally, after a period of six weeks 'dor-mancy' the corns can be used for germination.During storing the barley is still alive, usingoxygen and producing heat, water and carbondioxide, so during storage the temperature andmoisture must be strictly controlled.

Steeping the barleyBarley starts to germinate when its water contentis high enough. O n steeping in water, the moisturein the grain will be increased from about 12 to45%. Steeping the barley is also a washing step.The water steeping periods alternate with drysteeping periods. In the dry steep the barley isaerated to activate germination and carbondioxide is removed, e.g. by suction. The steepingprocess takes about tw o days at a temperaturebelow 2O 0C.Germination

The main purpose of germination is the formationor activation of the enzymes that will be needed inthe brewhouse. This must be done without toomuch loss of reserve substances.Germination (usually 5 to 7 days) is stoppedwhen the germ or acrospire, as it is termed by themaltster, has the length of about 80% of the cornitself. The maltster lets the barley germinate undervery strict conditions. The temperature is normallykept between 14 and 180C and the air humidity iskept high. The barley is aerated and briefly turnedover several times.Kilning the maltDuring kilning the moisture from the green malt isbrought down from 45% to less than 5% byblowing hot air through it. This takes about oneday. Kilning produces a dry product that is stableduring storage. It also adds character to the malt,altering its colour and flavour, but it reduces itsenzyme potential because the enzymes are heatsensitive, especially at high humidity. Thereforethe maltster keeps the temperature of the dryingair at 40-450C at the beginning of the kilning.When the moisture content of the malt is below10% the maltster can use drying air from 80-85 0C. For dark malt higher final kilning tempera-tures are used. The enzymatic activity of darkmalt is therefore less than that of pale malt.The two main systems of germination are floormalting, in which the steeped barley is spread outin a bed which is about 15 cm high, and pneu-m atic m alting with a bed height of abo ut 1.2 m .

Cleaning the maltThe rootlets must be removed from freshly kilnedmalt. These rootlets are very hydroscopic and


15/21

taste bitter making them undesirable fo r brewing.The rootlets are taken from the malt in a specialmachine. These rootlets represent a rich source ofprotein and are used as cattle food.

Storing the maltMalt has to be stored for at least four weeksbefore being used in the brewhouse. Malt which isnot stored long enough presents difficulties duringthe brewing process, in filtration, fermentation andclarification. Before it is stored the malt must becold, dry and free from rootlets. It is importantthat during storage the uptake of water is avoided.

Different malt typesThe brewer sets specifications for the types of maltthat are needed; the maltster buys barley and pro-cesses it to malt which will meet these specifica-tions. Maltsters usually blend malts from differentbatches to meet particular specifications. The maintypes of malt are pale malts, caramel malts, darkmalts, roasted malts, amber malts and acid malts.

BREWINGThe use of raw materials of high quality, modernequipment and the right technology is prerequisitefor making good beer. As the market extendsmore and more, the physical and flavour stabilityof the beer is of great importance.The brewer uses malted barley, water and hopsas primary raw materials. In most countriesunmalted cereals such as maize, rice or corn sugarare commonly used as partial substitutes for malt(adjuncts). In some countries sorghum is alsoused.

WaterAbout 92-95% of the weight of beer is water. It isclear that the water quality has to be suitable forhuman consumption. The presence of variousinorganic ions influences the taste and flavour ofthe beer. During the past millennium, variouscentres have become renowned for the quality oftheir beers, the type of beer in each location beingdistinctive. These distinctions can be attributed, atleast in part, to the water composition in eacharea. Note that in the mashing process, enzymeactivity and enzym e stability are influenced by the

inorganic ions in solution and therefore the yieldof extract is also under this influence.Brewing requires considerable volumes of water.At the present time breweries use on averagebetween 6 and 8 times as much water as the beerthat they produce.Milling or preparation of the gristTo allow degradation by the malt enzymes of thefood store of the grain, the grain has to bemechanically broken down and water has to beadded. Malted barley is carefully ground in a millin such a way that the husk of the grain is leftsubstantially intact (to serve as a filter materiallater in the brewing process) while the restbecomes a coarse powder. This powder is particu-larly rich in starch and in the enzymes capable ofdegrading it rapidly when water is added.The object of the milling is also to produce amixture of particle sizes which will secure thehighest yield of extract as quickly and efficientlyas possible. Milling procedures are determined bythe size distribution of the malt grains, theirmoisture content and their 'modification' (thedegree to which enzymes have broken down thepolymers of the endosperm cell walls). They arealso determined by the intended mashing methodand the wort separation method.The size reduction of the malt corns in thebrewing industries is normally achieved by rolleror hammer mills, depending on the techniques tobe used in the brewhouse. Any adjuncts to beused are finely ground or precooked and added atthis stage.

MashingBy thoroughly mixing of the ground material,called 'grist', with water, compounds such assugars, amino acids and minerals are dissolved.The enzymes of the malt, which were formed oractivated during malting, attack starch and itsdegradation products (amylolysis). Breakdown ofnitrogenous material (proteolysis) also occurs. Bythese means a part of the insoluble m aterial of themalt is dissolved. The process is called 'conversion'and the total dissolved material is called the'extract'.Temperature, pH , time and the ratio of malt towater are all significant. The pH of the mash iskept at the optimum level for the desired enzymeactivity. Each malt enzyme has its own optimumtemperature. For this reason the mash may be


16/21

warmed up to different temperatures and keptthere fo r enough time to let the enzymes do theirwork. Relevant temperatures are:(i) 37 and 45 0C - are imp ortant temperatures forthe breakdown of hemicellulose and gums;(ii) 45 and 520C - peptases and peptidases areactive, by which polypeptides, peptides andfree amino acids are brought into solution.The first two of these components are impor-

tant for the head retention and the fullness intaste of the beer. The last is necessary for theyeast growth. Proteins are also important fo rthe stability of the beer;(iii) 63 and 72 0C - are the most important tem-peratures of the brewing process. 630C isoptimum fo r a-amylase activity, 72 0C isoptimum for p-amylase; the two enzymesdegrade starch to soluble sugars and dextrins.

The temperature of the mash must no t exceed78 0C or most of the enzymes will be destroyed.Components of the husks are also detrimental tothe final beer quality so it is important not toallow them to go into solution.There are several methods of mashing to obtaina satisfactory aqueous extract or 'wort' (see Table7.3).

(i) Infusion m ashi ng . This is the simplest. Itinvolves adding hot water to the groundmaterial and pumping the mixture to themash 'tun' or vessel. The mash produced hasa final temperature of 65-720C and has athick porridge-like consistency.(ii) Decoction m ashi ng . Decoction mashing differsfrom infusion mashing in several respects.The endosperm of the malt that is used maybe less completely enzymatically degraded(less 'modified') and requires more extensiveenzymatic action during mashing. To aid this,the m alt is both ground m ore finely than w iththe infusion process and is mixed with waterat a lower temperature (350C). Extensive pro-teolysis and solubilization occur. During theconversion a portion of the mash (often one-third) is boiled in a mash kettle and returnedto the rest of the mash in the mash vessel fo rmixing. The temperature rises to about 5O 0C.Later, another one-third of the mash is with-drawn and boiled. On return to the mainmash, the temperature increases to about65 0C. After a last decoction with one-third ofthe mash, all enzyme activity ceases in theconsolidated mash at about 750C.

(iii) Temperature-profile m ashi ng . The mashingtemperature is raised by stages through theprocess, so as to allow the best combinationsof time and temperature fo r each of thedesired enzymatic changes. In modern brew-eries the whole process may be under com-puter control.Selection of a mashing method involves consid-eration of the grist composition, the equipmentavailable, the amount and the type of adjuncts

used, the brewing liquor available, the type of beerto be brewed and the number brews required eachday.Wort filtrationThe liquor in the mash tun may be left for aperiod to allow maximum solubilization of extrac-table material. The extract or 'sweet wort' hasthen to be separated from the spent grains andany other undissolved matter. It is important fo rthe beer quality to produce bright sweet worts.A ny leftover grains or other unsuspended matterremaining in the later processes will give inferiorflavour and poor flavour stability in the final beer.After infusion mashing, any necessary delaytogether with the final separation take place in themash tun. After decoction or temperature-profilemashing the mash is transferred to a 'lauter' tu n

(a) Water

MaltMasher

WortMash tu n

(b) Water and malt

Mashkettle ConverterWort

Lauter tu n

(c) Water and malt

WortConverter Lauter tu n

Figure 7.3 Mashing procedures, (a) Infusion mashing,(b) decoction mashing, (c) temperature profile mashing.


17/21

(lauter comes from the German word fo r purifica-tion) for the delay period and final separation.Above the perforated bottom of the lauter tun thelayer of husks and spent grains in the mash formsan effective filter to clarify the wort drainingthrough it. (The wort may be recirculated once ortwice at first, to consolidate the layer.) Instead oflauter tuns some breweries use more efficient mashfilters in which the wort is drawn off through per-forated pipes set below the level of the spentgrains in the tank.The spent grains are worthless fo r brewing bu tthey represent a rich source of proteins and aresold as cattle fo od .

Wort boilingAfter filtration the wort is boiled for one hour ormore in a steam-heated copper. The boilingprocess is associated with the addition of hops orho p extracts; sugars or syrups m ay also be added.Many complex reactions take place during wortboiling. As the wort is heated the residual enzymesare inactivated and the wort is sterilized. Variousother reactions occur, e.g. colour production, coa-gulation of proteins and tannins. The wort is con-centrated, volatile materials are evaporated andthe added hop is extracted and isomerized. Boilingmay take place under ambient pressure or athigher pressure and temperature. Normally 10%of the volume is evaporated.

Wort clarifying

Boiled wort is very hazy and has to be clarified.The suspended particles are called 'hot trub' or'hot break'. The hot trub is made up of proteins,protein-tannin material, insoluble salts, some hopresin material and some of the lipid material thatwas present in the sweet wort and the hops. Ifwhole hops were used in the copper the spenthops have to be removed. The hot trub is takenout of the wort by the whirlpool tank or centri-fuges.

Wort coolingIn order to bring the wort to fermentation tem-perature the wort is cooled, to 6-1O 0C for lagerbeer or 18-250C for top fermented beer. Mostbreweries now use plate heat exchangers to coolthe wort. The plate heat exchangers m ay comprisetwo or more stages so that wort may run counter-

current to water in the first section while a secondstage m ay reduce the wort temperature still furtherby using glycol as refrigerant.An important consideration of wort coolers istheir ability to function as heat economizers; theygenerate considerable volumes of hot water whichmay be used fo r mashing or for cleaning equip-ment.

FERMENTATION

Primary fermentationThe most important conversion during the fermen-tation of wort with yeast is that of sugars toalcohol and carbon dioxide. The complete fermen-tation process is very complex.The process starts in aerobic conditions. Afterthe hopped clear wort is cooled it is aerated andyeast is added. The yeast consumes the dissolvedoxygen, sugars, amino acids and other wort com-ponents during its own propagation. In the nextstep, under anaerobic conditions, fermentationstarts. During the fermentation about 70% of theflavour active components of the beer are pro-duced as esters, sulphur compounds, carbonyls,higher alcohols and ketones. The yeast perfor-mance is influenced by the yeast strain, yeast con-dition, the amount of yeast added to the wort,wort composition, the fermenter, the degree ofaeration and the fermentation temperature andpressure. The yeast cannot convert all the extractof the wort. High molecular sugars and proteinswhich are not converted by yeast are importantfor the fullness of the taste and the head reten-tion.The equipment m ay consist of open or enclosedtanks. In order to minimize the risk of microbiolo-gical contamination al l tanks and rooms must bescrupulously clean. When closed tanks are used,the carbon dioxide produced can be recovered andsold as by-product.After the fermentation the yeast is harvested inorder to avoid contamination with products ofautolysis. In the brewing industry two types ofyeast are used, bottom and top yeast.( i) B ot tom y eas t ferments the wort at low tem-perature (6-120C) and sediments to the

bottom of the fermentation vessel towards theend of the fermentation. The yeast concentra-tion at the start of the fermentation is about15-25 x 106 and the multiplication factor isabout 3. The fermentation time is about oneweek.


18/21

(ii) T op y e a s t ferments the wort at higher tem-perature (18-250C) and the yeast rises to thetop of the fermenter towards the end of thefermentation. The yeast concentration at thestart of the fermentation is about 10-12 x106 and the multiplication factor is about 5.The fermentation tim e is about four days.

ConditioningAfter the primary fermentation the beer is 'green',it contains little carbon dioxide and its taste andaroma are inferior to those of mature beer. Theconditioning process, also called 'maturation' or'lagering', is carried out in closed vessels at lowtemperature ( 1 to 50C). A t this lo w temperaturethe clarification of the beer is promoted. Yeast,proteins, tannins and hop resins precipitate.The small amount of yeast remaining after theprimary fermentation ferments the rest of the fer-mentable carbohydrates. The carbon dioxide pro-duced largely dissolves in the beer. Complexbiochemical reactions take place, such as esterifica-tion and certain reductions which modify andimprove the flavour of the beer.

Nowadays, before the cold maturation, thebreweries use a 'diacetyl rest' which is a period ofwarm conditioning (about 70C) to encourage theoxidative decarboxylation of a-acetohydroxyacidsto the vicinal diketones followed by reduction tothe corresponding diols, e.g.CH3C(OH)CO2H COCH3 CH(OH)CH3I - , | - > |

COCH3 COCH3 CH(OH)CH3oc-acetolactic acid diacetyl 2:3 butylene glycol

The concentration of the total vicinal diketonesis used as a marker of the duration of warm con-ditioning (about 70C). When the concentration ofthe vicinal diketones is less than 0.1 ppm the coldmaturation can start.

Reduced-alcohol beersTo meet the increasing consumer demand forbeers of low or negligible alcoholic strength, thereare basically two options: the brewer may arrangethe brewing processes to restrict the production ofalcohol or he may remove alcohol from otherwisenormally produced beer. The difficulty with theformer is the retention of flavours from the wort,e.g. excessive sweetness, which otherwise wouldhave been removed during the alcoholic fermenta-tion. The difficulty with the latter option is to

arrange the removal of alcohol without removingother desirable qualities. Restricted production ofalcohol may be achieved by(i) starting with a low gravity wort containinglittle fermentable sugar. This gives beer of low

alcoholic strength but also little flavour andthe process appears to be little used;(ii) mashing at high temperature (about 8O 0C)restricts the activity of (J-amylase but not thatof a-amylase and gives a wort high in dextrinsand relatively low in fermentable sugars. Coldmashing restricts the activity of all theenzymes;(iii) the yeast Saccharomyces ludwigii may beused, which ferments only glucose, fructoseand sucrose or about 15% of the normallyavailable fermentable sugars, consequently thebeer has a high content of maltose;(iv) checking fermentation or cold fermentation -the initial fermentation may be checked byrapidly reducing the temperature andremoving the yeast, or fermentation may becarried out entirely at low temperature; thebeer m ay have a high maltose content; withcold fermentation an immobilized yeast maybe used, this allows the yeast concentration tobe high but reduces the risk of autolysis ofthe yeast.

Alcohol reduction of a beer may be achievedby:(i) brewing a concentrated wort to give a highstrength beer, then diluting with water to thedesired lower alcoholic strength. With suitableadjustment of the fermentation conditions asdescribed above, the development of fla-vouring substances may be made to predomi-nate over that of alcohol so that reasonablywell-balanced flavour is produced on dilution;(ii) distillation at atmospheric temperature which

can reduce the alcohol content to below 0.5%although a burnt flavour is unavoidable;(iii) vacuum distillation (at 50-6O 0C) which pro-duces less off-flavour and thin film evapora-tion (at 30-4O 0C) which gives virtually none,however in both cases some of the volatile fla-vours are lost. This may be countered byester recovery at the beginning of the processand by adding other flavour substances asdesired;(iv) reverse osmosis or dialysis which give lowalcohol beers with otherwise good flavour butboth processes are expensive. To reduce thealcohol content below 0.5% is said to beeither not possible or prohibitively expensive.


19/21


20/21

completely automated input of kegs, washing,deterging and steam sterilizing. The selection ofdetergents to be used depends on the material ofthe kegs which now adays are normally aluminiumor stainless steel.FillingThe 'bright' (filtered) beer is put into the containerby an appropriate filling machine, which may bequite complex. It is important to avoid oxygencontact with the beer since dissolved oxygen is det-rimental to the flavour and physical stability.Modern bottle filling machines therefore evacuatethe bottles of air; with cans the air is washed outby carbon dioxide; with kegs also, after steam ster-ilizing the residual water and air are removed withcarbon dioxide.All the containers are filled under counterpres-sure with carbon dioxide. Before closing a bottlewith a crown cork or a can with a lid, the head-space air is remov ed m echanically by overfoaming.Most bottled or canned beer is pasteurized afterbottling or canning. With kegs and tankers thebeer is prepasteurized or sterile filtered.Tanked beer is delivered by the tanker directlyto the sales outlet. The beer is pumped through ahose from the tanker into receiving tanks in thecellar of the inn.

QUALITY ASPECTS

Types of beer

L a g e r beersThese are also known as bottom-fermented beers,since the yeast used sinks to the bottom of thetank at the end of fermentation.Different types of lager beer include 'Pilsener',which is characterized by a medium hop flavour,an alcohol content of 3-4% by weight, its bright-ness and pale colour. The brewing water fo r thistype of beer is soft. 'Dortmund' beer has lesshops then pilsener and is made with water whichcontains large quantities of carbonates, sulphatesand chlorides. 'Munich' beer is a dark aromaticbeer with a somewhat sweet flavour. This beerhas a very mild hop flavour and an alcoholcontent of 2.5-5% by weight. The brewing watercontains high amounts of carbonates but smallamounts of other salts. 'Bock' beer is a seasonalbeverage made with caramel malt or heavilyroasted malt.

Top-fermented beersThe most important types of beers brewed withtop fermenting yeast include ale, porter, stout andweiss beers.'Ale' is a British type of beer brewed with waterof high calcium sulphate content. The hop flavouris pronounced and the alcohol content is 2.5-4%by weight. 'Porter' is dark coloured, less hoppedand sweeter than ale. 'Stout' is a very dark with asomewhat burnt flavour and a strong maltyaroma. This beer is heavily hopped and contains4-6.5% alcohol by weight. 'Weiss' beers are lesshopped, unfiltered beers brewed with a percentageof malted wheat.Microbiological controlThere has always been a measure of disagreementamong brewers on the degree of microbiologicalcontrol needed in breweries. Most modern brew-eries however, wish to eliminate all micro-organ-isms from the brewery except fo r pure cultureyeast and thereby help to achieve a consistentlysatisfactory quality of their products.Fortunately for brewers, microbiological controlneeds to be exercised only over a limited range ofbacteria and yeasts. Pathogenic micro-organismsand also many other bacterial strains fail to grow,or even to survive for extended periods, in beer.This is because the micro-organisms are inhibitedto different degrees by the low pH, high concen-tration of alcohol, high content of hop resins andlow concentration of fermentable sugars.The bacteria that may be found in wort or beerare classified in the usual way according to theirshape, flagellation, Gram-staining, other structuralfeatures and biochemical characteristics. The firstgroup of bacteria that can be found in a breweryare the lactic acid bacteria; the group is dividedinto Lactobacil lus (Gram-positive, catalase-negative rod-shaped bacteria) and Pediococcus(Gram-positive, catalase-negative cocci, mainlyfound in pairs and tetrads). Lactic acid bacteriagrow in anaerobic conditions in the presence ofcarbon dioxide. They can ferment a wide range ofsugars to lactic acid and some strains produce aceticacid, ethanol and carbon dioxide. Strains of Pedio-coccus are rarely found in top-fermentation brew-eries but are m ore comm on in bo ttom -ferm entationbreweries. Spoilage caused by lactic acid bacteriagives rise to acidity, turbid ity and off-flavours.A second group of beer spoiling bacteria are theacetic acid bacteria, Gram-negative, rod-shapedbacteria of the Acet om onas and Acetobacterspecies. The latter is usually motile. Most strains


21/21

oxidize glucose and other sugars and some oxidizeethanol to acetic acid. The growth of the aceticacid bacteria is not restricted by low pH or hopresins, but most strains require oxygen, thereforethese bacteria develop best in wort and beer whenthe liquids are exposed to air. Spoilage by themcauses acidity, off-flavours and ropiness.A third group of beer spoiling bacteria are theGram-negative, rod-shaped, strictly anaerobicstrains of Pectinatus and M e g a s p h e r a . They m ayarise from a secondary contamination while thebeer is being bottled.Yeast strains that are not part of the cultureyeast used by the brewery are called 'wild yeast'and can cause spoilage because their metabolicproducts are different from those of the fermenta-tion yeasts. They can cause off-flavours and tur-bidity.Chemical controlAlcoholFor brewery contro l purposes, alcoholic strengthis usually nowadays measured by rapid methods,gas-liquid chromatography (GLC), densitometryor rapid distillation in the laboratory or even on-line. For taxation purposes as required in mostcountries, official reference methods must be used;these usually require distillation under prescribedconditions in prescribed apparatus.In the UK until recently the excise tax on beerswas based no t directly on the alcoholic strengthbut o n the original gravity or O G, the specificgravity of the wort from which the beer wasbrewed. To find the OG, a sample of beer is dis-tilled, the distillate is made up to a standardvolume, likewise the residue in the distillation

flask (the 'extract') and the specific gravities ofboth are measured. The values of the specificgravities are manipulated according to an officialformula and tables, whereby the O G can be calcu-lated (K irk and Sawyer 1991). This use of the O Gfor taxation purposes was presumably because inthe earliest days of the tax more than two centu-ries ago, it was easier to m easure the O G beforefermentation than to measure the alcohol contentafterwards. Nowadays however, when a value ofthe OG calculated as just described from an ana-lysis of the finished beer may be meaningless for alow-alcohol beer or other modern product pro-duced by some large modification of the tradi-tional brewing processes, the use of OG fortaxation purposes has been abandoned. The alco-holic strength of the final product is now, muchmore sensibly, used instead.

Other chemical a n a l y s e sSignificant components which may be measuredusing normal laboratory methods include totalsolids (extract), sugars, acidity, pH, CO2 and SO2.

O r g a n ol ep t i c and physical controlsFlavour (aroma, taste and after-taste), mouthfeeland appearance are the most important qualityfactors in any beer. Systematic, regular controlledtasting tests should be a feature of every breweryoperation. Colour and turbidity or clarity may bemeasured and controlled by standard laboratorymethods. Foam height (the 'head') and foam sta-bility can be measured empirically by pouringfrom the bottle or can into a graduated vesselunder standardized conditions.

Next Page
http://4419fcae25df9d2f9e22cb86cbc748f.pdf/http://4419fcae25df9d2f9e22cb86cbc748f.pdf/

Documents

Food Industries Manual 010