Food Science & Technology · Commodity Processing Technologies · also Beverage Technology, Plantation Products Technology, Brewing and Winemaking, Alcoholic and Non-alcoholic Beverages
Every major beverage: water treatment and carbonated soft drinks, tea, coffee and cocoa processing, and the brewing, winemaking and distilling of alcoholic drinks, with their quality control.
In the exams: GATE XE-G Section 2 (alcoholic beverages, vinegar) and Section 3 (tea, coffee, cocoa); ICAR AIEEA-PG Code 18 Unit III (alcoholic and non-alcoholic beverages)
Beverage technology is the science and engineering of drinks: how water is made fit for a product, how a soft drink is formulated, carbonated and filled, how tea, coffee and cocoa are turned from a farm crop into a stable commodity, and how sugars are fermented into beer, wine and spirits. It sits at the meeting point of chemistry (acids, sugars, polyphenols, aroma compounds), microbiology (yeasts, lactic and acetic acid bacteria), and unit operations (filtration, heat exchange, evaporation, distillation, drying). Every beverage is mostly water, so small changes in water quality, dissolved gas or a few milligrams per litre of a compound decide whether the product is right or rejected.
In practice the subject matters because beverages are high-volume, low-margin products sold on consistency. A bottling line filling tens of thousands of containers an hour must hold sugar, acid and carbon dioxide within narrow limits; a tea factory must judge withering and oxidation by leaf condition; a brewery must reproduce the same wort extract and bitterness batch after batch; a winery must manage sulphur dioxide and oxygen so the wine survives the bottle. Many legal standards for beverages, especially for alcohol and for packaged water, are detailed and differ between countries.
In examinations the subject is asked mainly through GATE XE-G and XL-U (alcoholic beverages and vinegar in the microbiology section; tea, coffee and cocoa in food products technology) and ICAR AIEEA-PG Code 18 Unit III (alcoholic and non-alcoholic beverages). Expect definitions (withering, cut test, mashing, malolactic fermentation, proof), process sequences, and short calculations such as alcohol from sugar, volumes of carbon dioxide, Brix after dilution, roasting loss and moisture balances. Fruit juices, squashes, nectars and ready-to-serve drinks are covered in fruit-vegetable-processing; heat treatment theory in thermal-processing-canning; and the microbiology and kinetics of fermentation in fermentation-food-biotechnology. This manual refers to those rather than repeating them.
A soft drink is typically around 85–90% water, a beer more than 90%, and even a cup of tea or coffee is an extraction into water. Water that is safe to drink is not necessarily fit for a beverage. Chlorine and chlorophenols give medicinal off-flavours; iron and manganese give metallic taste, haze and discolouration; alkalinity, mostly bicarbonate, neutralises the acid in a soft drink so that it tastes flat and lets microbes grow at a higher pH; hardness from calcium and magnesium causes scale in heat exchangers and can form deposits with phosphates. Suspended solids and organic matter carry microbes, protect them from disinfectants and provide nuclei for gushing when a carbonated drink is opened. For brewing, water composition is deliberately managed: calcium lowers mash pH and helps enzyme action and yeast flocculation, while carbonate raises pH. Historic brewing centres became known for particular beer styles partly because of their local water, which brewers now reproduce by treatment. The beverage technologist therefore specifies water by taste, microbiological quality, alkalinity, hardness, turbidity and residual disinfectant, not just by potability.
A typical beverage plant treats municipal or well water through a sequence chosen for the raw water. Coagulation with aluminium or iron salts and flocculation gather fine particles into flocs that settle; lime treatment can be used at the same time to precipitate carbonate hardness and lower alkalinity. Sand or multimedia filtration removes the floc. Chlorination, or another oxidant, disinfects and oxidises iron and manganese so they can be filtered out. Activated carbon filtration then removes the residual chlorine and organic taste compounds; it must itself be kept clean, because a carbon bed removes the disinfectant and can grow bacteria. A polishing filter, often a cartridge filter of a few micrometres, protects the product from carbon fines. Ultraviolet treatment is often added as a final barrier against microbes. Where dissolved salts must be reduced, reverse osmosis or ion exchange is used: cation exchange softening replaces calcium and magnesium with sodium, dealkalisation removes bicarbonate, and reverse osmosis removes most dissolved ions together. Ozone is used widely for packaged drinking water because it leaves no lasting residue, but with bromide-containing water it can form bromate, which is regulated.
Hardness and alkalinity are conventionally reported as milligrams per litre of calcium carbonate equivalent so that different ions can be added. To convert, multiply the ion concentration by the ratio of the equivalent weight of calcium carbonate (50.04) to that of the ion: about 2.50 for calcium and about 4.12 for magnesium. Thus 60 mg/L calcium is about 150 mg/L as CaCO3. Carbonate (temporary) hardness is the part balanced by bicarbonate and can be removed by boiling or lime; non-carbonate (permanent) hardness is balanced by sulphate or chloride. Disinfection is often specified as a CT value: residual disinfectant concentration multiplied by contact time, in mg·min/L, which allows plants to trade a higher dose against a shorter time. Limits for packaged drinking water and natural mineral water differ by country: Codex has a standard for natural mineral waters, and in India packaged drinking water and natural mineral water carry mandatory BIS certification under their own Indian Standards. A natural mineral water must not be treated in ways that change its essential composition, which is the main legal distinction from purified packaged water.
A carbonated soft drink is water, sweetener, acidulant, flavour, colour, preservative and carbon dioxide. Sugar is dissolved as a simple syrup, often around 60–65 °Brix, filtered and sometimes treated with carbon; the final syrup is made by adding flavour emulsion or extract, acid, preservative and colour. The final syrup is diluted with treated water at a fixed ratio called the throw, for example one part syrup to five parts water, and the finished beverage is checked by its Brix. Colas use phosphoric acid; fruit-flavoured drinks mostly use citric acid, sometimes malic. Low- and no-sugar drinks replace sucrose with high-intensity sweeteners whose permitted list and limits differ by country. Sodium benzoate and potassium sorbate are the common preservatives; benzoate works as undissociated benzoic acid, so it is effective only at the low pH of acidic drinks (pKa about 4.2). When ascorbic acid and benzoate are present together, traces of benzene can form under heat and light, and formulators now avoid or control that combination. Cloud emulsions for citrus drinks use weighting agents and emulsifiers so the oil phase neither creams nor sinks.
Carbon dioxide gives sparkle, bite (from carbonic acid) and a mild antimicrobial effect. Its content is expressed in volumes: the volume of gas, at 0 °C and one atmosphere, dissolved in one volume of liquid. Because the density of carbon dioxide under those conditions is about 1.98 g/L, one volume is close to 2 g/L. Solubility follows Henry's law: it rises with pressure and falls with temperature, so carbonation is done cold and under pressure. Air must be removed first, by deaerating the water, because dissolved air reduces carbon dioxide uptake and promotes foaming and oxidation. Carbonation levels vary by product; colas and lemon-lime drinks are highly carbonated, fruit drinks less so. Carbonation is measured by reading the equilibrium pressure and temperature in a sealed sample after shaking and converting with a chart. A drink filled warm or shaken during distribution loses gas faster and is more likely to fob or gush, so carbonation, filling temperature and headspace are specified together.
Carbonated drinks are filled by counter-pressure (isobaric) fillers: the container is first pressurised with carbon dioxide to the pressure of the filler bowl, then the liquid flows in by gravity while the gas returns to the bowl. Filling cold reduces foaming and gas loss. Containers are capped or seamed immediately. Problems in filling include fobbing (excess foam), low fill and gushing on opening, which is usually caused by nucleation sites such as particles, rough container walls or air. Because most soft drinks are acidic, carbonated and preserved, they are not given a full heat sterilisation; hygiene of the syrup room and line, and the hurdles of acid, preservative and carbon dioxide, control spoilage by acid-tolerant yeasts and moulds. Juice-containing drinks are more vulnerable and may be pasteurised in the container or flash-pasteurised before filling; the theory is in thermal-processing-canning. Fill level is checked by light or X-ray sensors after the filler, and closure torque or seam dimensions are checked at set intervals, because a weak closure lets carbon dioxide escape and lets spoilage organisms in.
Sports drinks are formulated to replace water, electrolytes and carbohydrate lost during prolonged exercise. Their design rests on two properties: carbohydrate concentration and osmolality. Drinks with roughly 6–8% carbohydrate are emptied from the stomach and absorbed well; much more concentrated drinks slow gastric emptying. A drink is called isotonic when its osmolality is similar to that of body fluids (around 270–330 mOsm/kg is the range commonly quoted), hypotonic when lower and hypertonic when higher. Glucose, sucrose and maltodextrin are used together because glucose and fructose use different intestinal transporters and maltodextrin adds carbohydrate with less osmotic effect than glucose. Sodium is included because it aids water absorption through sodium-glucose co-transport and maintains the drive to drink. Oral rehydration solutions used medically follow WHO formulas with lower glucose and defined sodium; they are medical products, not sports drinks. Hypotonic drinks are absorbed fastest and suit short, intense exercise in the heat; hypertonic drinks deliver more carbohydrate but are emptied from the stomach more slowly.
Energy drinks are carbonated or still drinks containing caffeine, often with taurine, glucuronolactone, B vitamins and sugar or sweeteners. Their caffeine content per serving and the maximum permitted concentration are fixed by national regulation and vary between countries; many authorities require a high-caffeine warning and advise against consumption by children and pregnant women. Functional drinks more broadly include drinks with added vitamins, minerals, fibre, protein, plant extracts or probiotics. The technical problems are stability and taste: vitamin C and some B vitamins degrade with heat, light and oxygen; minerals can precipitate or catalyse oxidation; proteins can coagulate at low pH unless chosen for acid stability; probiotics lose viability in acidic drinks over shelf life. Claims about health effects are tightly regulated, and in most jurisdictions a health claim must be authorised for the specific ingredient and amount. Colour and flavour also suffer: added minerals such as iron can darken polyphenol-rich drinks, and plant extracts often bring bitterness that must be masked.
Most formulation work is mass balance. If a finished drink must contain 11 °Brix sugar and is made from a 65 °Brix syrup, the syrup is 11/65, about 16.9%, of the drink by mass. If 1 kg of a 55 °Brix syrup is mixed with 4.5 kg of water, the result is 55/5.5 = 10 °Brix. Brix strictly measures sucrose by mass; acids and other solids also raise a refractometer reading, so labs correct Brix for acid in high-acid products. The sugar in a serving is volume × density × Brix fraction, so 330 mL of an 11 °Brix drink with density 1.044 g/mL holds about 38 g of sugar. Mineral additions are calculated on the ion, not the salt, so the molar mass ratio of ion to salt must be applied. Every calculation should be checked by an independent route, for example by computing the water added as well as the syrup, because a slip in a batch sheet is repeated in every bottle of that batch.
Tea is made from the young shoots of Camellia sinensis, classically 'two leaves and a bud'. The fresh shoot is about three-quarters water. Its key constituents are the flavan-3-ols (catechins, chiefly epigallocatechin gallate), caffeine, the amino acid theanine, and the enzymes polyphenol oxidase and peroxidase. The style of tea is decided by what is allowed to happen to the catechins. In black tea the leaf is disrupted so that polyphenol oxidase oxidises catechins into theaflavins, which give brightness and briskness and an orange-red colour, and thearubigins, larger brown pigments that give colour and body. In green tea the enzymes are inactivated early, so catechins remain largely unoxidised. Oolong lies between: the leaf is partly oxidised and then heated. Fine plucking gives better quality and coarse plucking more yield; plucking standard is the first quality control in the factory. Leaf quality falls quickly after plucking, so leaf is carried to the factory without bruising, heating or delay; damaged leaf starts uncontrolled oxidation in the field basket.
Black tea passes through withering, rolling or maceration, fermentation (a long-established term for enzymic oxidation, not microbial fermentation), drying and sorting. Withering reduces moisture and makes the leaf flaccid, and chemical changes during it develop aroma precursors; it is done in troughs with air blown through the leaf. Orthodox manufacture rolls the withered leaf to twist and break cells, giving leafy grades. CTC (crush, tear, curl) machines cut the leaf finely between grooved rollers, giving rapid, uniform oxidation and granular teas that brew strong and fast, which suits tea bags. During oxidation the leaf is spread thin at controlled temperature and humidity, often in the low twenties to around 30 °C, and changes from green to coppery. Drying in hot air stops the enzymes and brings the tea to about 3% moisture. Moisture balance is a common calculation: 100 kg of leaf at 77% moisture holds 23 kg dry matter, which as made tea at 3% moisture weighs 23/0.97, about 23.7 kg.
Green tea is made by inactivating enzymes with heat immediately after plucking: by steaming, the classic Japanese method, or by pan-firing, the classic Chinese method, followed by rolling and drying. Oolong is withered, bruised by shaking to start partial oxidation at the leaf edges, then fired. Instant tea is made by extracting black tea with hot water, removing the 'tea cream' that forms when the extract cools (a complex of caffeine with theaflavins and thearubigins), concentrating the extract with aroma recovery, and spray- or freeze-drying. Decreaming may be done by cooling and separating the cream or by treating it with enzymes such as tannase so that it stays soluble; this matters for iced-tea products. Ready-to-drink teas face the same cream and sediment problem and are usually acidified and heat treated. Green tea keeps more catechins and less colour than black tea, and its quality is judged by green colour, freshness and the absence of the brownness that comes from slow enzyme inactivation.
Coffee comes mainly from two species: arabica (Coffea arabica), with finer acidity and aroma, and robusta (Coffea canephora), with more body, more bitterness and roughly twice the caffeine. The fruit, or cherry, contains two seeds covered by silver skin, parchment, a sugary mucilage and a pulp. In the dry or natural method whole cherries are sun-dried and the dried husk is then removed by hulling; it is simple and uses little water but gives heavier, fruitier coffees and more defects if drying is uneven. In the wet or washed method the pulp is removed by a pulper, the mucilage is broken down by a short natural fermentation in tanks (pectinolytic microbes and enzymes liquefy it), the beans are washed, and the parchment coffee is dried, usually to around 11–12% moisture, then hulled. Washed coffees are cleaner and brighter. A semi-washed or pulped-natural route dries the bean with some mucilage left. Wet processing produces large volumes of effluent with high organic load, which must be treated before discharge.
Roasting turns the hard green bean into the brittle, aromatic roasted bean. Beans are heated in drum or fluid-bed roasters with bean temperatures typically rising to around 200–240 °C over several minutes. The bean first dries, then turns yellow and brown as Maillard reactions and Strecker degradation generate colour and hundreds of aroma compounds; sugars caramelise; chlorogenic acids, the main acids of green coffee, partly break down; and carbon dioxide builds up inside the bean. Audible 'first crack' marks rapid gas and steam release; darker roasts go on to 'second crack' with more oil migration and bitterness. Caffeine is relatively stable through roasting. Roasting loss, usually expressed as the fall in mass from green to roasted bean, comes from moisture and organic losses and rises with darkness; if 60 kg of green coffee yields 50.4 kg roasted, the loss is 16%. Freshly roasted coffee releases carbon dioxide for days, which is why it is degassed or packed with one-way valves.
Instant (soluble) coffee is made by extracting ground roasted coffee with hot water under pressure in a battery of columns, so that more solids dissolve than in home brewing; the extract is clarified, concentrated by evaporation or freeze concentration with aroma recovery, and dried by spray-drying or freeze-drying. Freeze-dried coffee keeps more aroma but costs more. The extraction yield is the fraction of roast coffee mass that ends up as soluble solids; from 1000 kg of roast coffee at 45% yield, 450 kg of solids is obtained, which as powder at 3% moisture is about 464 kg. Decaffeination is done on green beans after moistening, by water (with the caffeine removed from the water by carbon), by supercritical carbon dioxide, or by organic solvents such as dichloromethane or ethyl acetate, with residue limits set by regulation. The drying principles of spray and freeze drying are covered in evaporation-dehydration. Decaffeinated coffee keeps only a small residual caffeine content, and the permitted residue of caffeine and of any solvent is set by regulation in each market.
Cocoa beans are the seeds of Theobroma cacao, embedded in a sweet, acidic pulp inside the pod. Unfermented beans are bitter, astringent and lack chocolate flavour; fermentation is essential. Beans with pulp are heaped under leaves or placed in wooden boxes for about five to seven days, depending on variety and method, and turned to aerate them. A microbial succession drives the process. Yeasts first ferment pulp sugars to ethanol, while pectinolytic activity drains the pulp. Lactic acid bacteria follow, then, as air enters with turning, acetic acid bacteria oxidise ethanol to acetic acid in a strongly exothermic reaction that raises the mass to around 45–50 °C. Acetic acid and heat penetrate and kill the seed embryo. Cell walls inside the bean break down, allowing enzymes to act: proteins are cut to peptides and free amino acids, sucrose is inverted to reducing sugars, and polyphenols are partly oxidised. These products are the precursors that will form chocolate flavour during roasting.
After fermentation the beans are dried, usually in the sun or in artificial dryers, from around 55–60% moisture to about 7–8%, a level safe for storage without moulds. Slow drying lets excess acetic acid evaporate; drying too fast traps acid and gives over-acid beans, while smoke from poorly run fire dryers gives smoky taint. Quality is judged by the cut test: a sample of beans is cut lengthwise and the cotyledons are inspected. Well-fermented beans are brown with an open, cracked texture; partly fermented beans are purple or purplish brown; unfermented beans are slaty grey and compact. Mouldy, insect-damaged and germinated beans are counted as defects. International trade grades are based on the proportions of slaty and defective beans. Beans are stored in clean, dry, ventilated warehouses, because dried beans take up moisture from humid air and become mouldy, and they are fumigated or protected against storage insects where necessary.
Dried beans are cleaned and roasted, commonly somewhere around 120–150 °C depending on the product, to develop flavour through Maillard reactions between the amino acids and reducing sugars formed during fermentation, to loosen the shell and to reduce microbial load. Winnowing separates shell from the broken kernels, called nibs. Nibs are ground to cocoa liquor (mass), which is about half fat. Pressing the liquor yields cocoa butter and press cake; the cake is ground to cocoa powder. Alkalisation (Dutching), treating nibs, liquor or cake with an alkali such as potassium carbonate, raises pH, darkens colour, softens flavour and improves dispersibility of the powder in drinks. A mass balance on pressing: 100 kg of nibs at 54% fat contains 46 kg of non-fat solids; a press cake at 12% fat therefore weighs 46/0.88, about 52.3 kg, and about 47.7 kg of butter is expressed. Chocolate making then adds sugar and milk solids, refines particle size, conches for flavour and texture, and tempers the fat to form the stable form V crystals that give gloss and snap.
Beer is made mainly from barley malt. Malting is a controlled germination: barley is steeped in water, with air rests, until it reaches roughly 42–46% moisture; it is then germinated for several days in cool, humid, aerated conditions so that the embryo produces hydrolytic enzymes (α-amylase, β-glucanase, proteases) and the endosperm cell walls and protein matrix are degraded, a change called modification. Gibberellic acid from the embryo signals the aleurone layer to produce these enzymes. Germination is stopped by kilning, drying the green malt with hot air, first gently to protect the enzymes, then at higher temperature to develop colour and flavour. Pale malts are kilned lightly and keep high diastatic power; darker and roasted malts contribute colour and flavour but little enzyme. Malting losses come from respiration and from rootlets removed after kilning. Malt quality is described by its extract, moisture, colour, diastatic power and degree of modification, and these figures are agreed between maltster and brewer for each batch.
In the brewhouse, milled malt is mixed with water (mashing in) and held at temperatures chosen for enzyme action. β-glucanases and proteases act at lower temperatures, around 45–55 °C. Starch must first gelatinise; then β-amylase, most active around 60–65 °C, produces fermentable maltose, and α-amylase, most active around 70–75 °C, cuts starch into dextrins. A low saccharification rest gives a more fermentable wort and drier beer; a higher rest gives more dextrins and body. Unmalted adjuncts such as rice or maize are cooked separately first because their starch gelatinises at higher temperature. The sweet wort is separated from the spent grain by lautering in a lauter tun or mash filter, with sparging to rinse out extract. The wort is boiled for about an hour or more with hops. Boiling sterilises the wort, stops enzymes, coagulates protein (hot break), concentrates the wort, isomerises hop α-acids into the bitter iso-α-acids, and drives off volatile compounds such as dimethyl sulphide formed from its malt precursor S-methylmethionine. The hot wort is clarified in a whirlpool, cooled and aerated for the yeast.
Ales are fermented with top-fermenting Saccharomyces cerevisiae at warmer temperatures, commonly around 15–24 °C; lagers with bottom-fermenting Saccharomyces pastorianus at cooler temperatures, commonly around 8–14 °C, followed by long cold storage (lagering). Yeast converts wort sugars into ethanol and carbon dioxide and forms flavour compounds: esters, higher alcohols (fusel alcohols, from amino acid metabolism), and vicinal diketones such as diacetyl, which gives a buttery off-flavour. Diacetyl is reabsorbed and reduced by yeast during a warm 'diacetyl rest' or maturation. Beer is then chilled, clarified by filtration or centrifugation, stabilised against haze (silica gel to remove haze-forming proteins, polyvinylpolypyrrolidone to remove polyphenols), carbonated and packaged. Strength is often estimated from gravities: one widely used approximation is ABV ≈ (OG − FG) × 131.25 with specific gravities, so OG 1.048 and FG 1.010 give about 5.0% ABV. Extract in wort is expressed in degrees Plato (grams of extract per 100 g wort).
Wine is fermented grape juice. Ripe wine grapes carry roughly 180–250 g/L of sugar, mainly glucose and fructose, and their main acids are tartaric and malic. By the Gay-Lussac equation, C6H12O6 → 2 C2H5OH + 2 CO2, one gram of hexose can give at most 0.511 g of ethanol and 0.489 g of carbon dioxide. A must with 200 g/L sugar could therefore give at most about 102 g/L ethanol, or about 13% by volume (ethanol density 0.789 g/mL); real yields are somewhat lower because yeast uses sugar for growth and by-products such as glycerol, and the practical conversion factor used in wineries varies with conditions. Where law allows, sugar is added to must to raise alcohol (chaptalisation), or acid is adjusted; both are tightly regulated and differ by region. Grape ripeness is followed in the vineyard by Brix (or a similar density scale), titratable acidity and pH, and harvest date is chosen for the balance among them that suits the wine style.
For white wine, grapes are crushed and pressed promptly and only the juice is fermented, usually cool (often around 10–18 °C) to keep fruity aromas; the juice may be settled and treated with sulphur dioxide before inoculation. For red wine, the crushed and destemmed grapes are fermented with their skins, usually warmer (often around 20–30 °C), because colour (anthocyanins) and tannins are extracted from the skins during this maceration; the floating cap of skins is punched down or pumped over, and the wine is pressed off the skins at or after the end of fermentation. Rosé uses a short skin contact. Many reds and some whites then undergo malolactic fermentation, in which lactic acid bacteria (often Oenococcus oeni) convert malic acid to lactic acid and carbon dioxide, lowering acidity, softening the wine and improving microbial stability. Sulphur dioxide is the main antioxidant and antimicrobial; only its molecular form is strongly antimicrobial, and the molecular fraction falls as pH rises, so a wine at higher pH needs more free SO2 for the same protection. Clarification and stabilisation follow: bentonite removes heat-unstable proteins in white wine, gelatin or egg white fining softens tannin, and cold stabilisation precipitates potassium bitartrate before bottling.
Sparkling wines carry carbon dioxide from a second fermentation: in the traditional method this happens in the bottle, followed by riddling and disgorging of the yeast sediment; in the tank (Charmat) method it happens in a pressure tank before filtration and bottling. Fortified wines have spirit added. In port-style wines, grape spirit is added during fermentation, which stops the yeast and leaves natural sugar, giving a sweet, strong wine. In sherry-style wines, the base wine is fermented dry and fortified afterwards; some are aged under a film of flor yeast that protects them from oxidation and gives a distinctive aldehydic character, and blending through a fractional system called the solera keeps a consistent style. Fortification is a blending calculation: to bring 1000 L of wine at 7% to 19% ABV with spirit at 77%, the spirit needed is 1000 × (19 − 7)/(77 − 19), about 207 L, ignoring volume contraction.
Distillation separates ethanol from a fermented wash because ethanol is more volatile than water. The vapour above a dilute ethanol-water mixture is richer in ethanol than the liquid, so repeated vaporisation and condensation concentrates it. Ethanol and water form a minimum-boiling azeotrope at about 95.6% ethanol by mass (about 97% by volume), so ordinary distillation cannot exceed that strength; anhydrous ethanol for fuel needs molecular sieves or another method. Batch pot stills give limited separation per run, so malt whisky and many brandies are distilled twice: a first distillation produces low wines, and the second is divided into heads (foreshots, rich in volatile compounds such as acetaldehyde and ethyl acetate), the heart, which is kept as new spirit, and tails (feints, rich in higher alcohols and less volatile compounds). Continuous column stills, such as the patent or Coffey still, run steadily with many plates and give a lighter spirit at higher strength, used for grain whisky, neutral spirit and many rums.
Spirits contain congeners besides ethanol: higher alcohols (fusel oils), esters, aldehydes, acids and, in some products, methanol. Methanol comes mainly from the hydrolysis of methyl esters in pectin by pectin methylesterase, so fruit spirits and pomace brandies, made from pectin-rich material, carry more methanol than grain spirits; regulations set maximum methanol levels for each category. Methanol cannot be removed reliably by careless cuts, and illicit spirit adulterated with methanol causes blindness and death. Copper in stills reacts with sulphur compounds and improves spirit quality. Fusel oils are formed by yeast from amino acids and concentrate in the tails, from which they can be drawn off in column stills. Cuts between heads, heart and tails are therefore made by temperature, strength and the distiller's judgement of aroma, and the heads, which carry acetaldehyde, ethyl acetate and part of the methanol, are set aside or redistilled. Analysis of methanol and higher alcohols by gas chromatography is the usual check on compliance.
Many spirits are matured in oak casks. During maturation the spirit extracts colour, vanillin, oak lactones and tannins from the wood; slow oxidation forms acetaldehyde, acids and esters; harsh sulphur compounds are reduced, partly by the charred layer of the cask; and some liquid evaporates through the wood. Legal definitions often fix the cask and time: for example, Scotch whisky must be matured in oak casks in Scotland for at least three years, and bourbon must use at least 51% maize and new charred oak containers. Spirits are reduced to bottling strength with demineralised water, allowing for the contraction that occurs when ethanol and water mix; ignoring contraction, 1000 L at 65% diluted to 40% needs about 625 L of water. Alcoholic strength is stated as % by volume at 20 °C in most countries. US proof is twice the percentage by volume, so 40% is 80 proof; the older British proof scale set 100° proof at about 57.15% by volume, so 40% is about 70° proof.
Fruit wines are made from fruits other than grapes, such as apple, plum, jamun, mango, pineapple or berries. Most fruits have less sugar and more or less acid than wine grapes, so the must is usually adjusted by adding sugar to reach the target alcohol, diluting or adding acid to a suitable level, adding nitrogen sources for the yeast, and treating with pectolytic enzymes to increase juice yield and prevent pectin haze. Sulphur dioxide or another preservative is added to suppress wild microbes before inoculation with wine yeast. Cider is fermented apple juice and perry is fermented pear juice; traditional ciders were fermented by the natural flora of the fruit and mill, while commercial ciders use selected yeasts and are often diluted, sweetened and carbonated. Methanol in fruit wines is generally low but higher than in grape white wines when pectinase is used, so it is checked. Juice preparation and its enzymes are covered in fruit-vegetable-processing.
Vinegar is made by a two-stage fermentation: yeasts convert sugar to ethanol, then acetic acid bacteria (Acetobacter and Komagataeibacter, the latter formerly placed in Gluconacetobacter) oxidise ethanol to acetic acid, which requires oxygen. Stoichiometrically, one mole of ethanol (46.07 g) gives one mole of acetic acid (60.05 g), so 1 g of ethanol can give at most 1.30 g of acetic acid. A cider at 6% ABV contains about 47 g/L ethanol, and could therefore give at most about 62 g/L acetic acid, about 6.2% w/v. Three production methods are classical: the slow Orleans or surface method, in which the bacteria grow as a film on the liquid in barrels; the quick generator method, in which the liquid trickles down over wood shavings carrying the bacteria against rising air; and the submerged method, in which air is bubbled through the liquid in a stirred fermenter, which is fastest and now dominant. Vinegar strength is stated as acetic acid in g per 100 mL, and minimum strengths are set by national standards.
Many societies have their own fermented drinks, usually made with mixed natural cultures. Palm wine or toddy is the fermented sap of palms, made by yeasts and bacteria within hours and consumed fresh because it soon turns sour. Sake is a rice wine in which the mould Aspergillus oryzae (koji) saccharifies rice starch while yeast ferments the sugar in the same vessel, a process called multiple parallel fermentation. Many Asian rice beers use starter cakes containing moulds and yeasts. Pulque is fermented agave sap; tequila and mezcal are spirits distilled from cooked agave. Kvass is a low-alcohol drink fermented from rye bread; kombucha is sweetened tea fermented by a symbiotic culture of yeasts and acetic acid bacteria. Traditional products are valued but variable; their safety depends on acidity, hygiene and, for spirits, on methanol control. Scaling such a product up for sale usually means defining a starter culture, controlling temperature and acidity, and applying the same hygiene and labelling rules as for other fermented beverages.
Glass is inert and impermeable to gases but heavy and breakable; its colour matters, because amber glass blocks the short-wavelength light that causes 'lightstruck' or skunky flavour in beer, while green and clear glass protect much less. Lightstruck flavour comes from 3-methyl-2-butene-1-thiol, formed when riboflavin, excited by light, degrades hop iso-α-acids. Aluminium and tinplate cans are light-tight and gas-tight but need an internal lacquer to prevent corrosion and metal pick-up. Polyethylene terephthalate (PET) bottles are light and shatter-resistant but slowly let carbon dioxide out and oxygen in, which limits the shelf life of carbonated drinks in small bottles (with a high surface-to-volume ratio) and of oxygen-sensitive drinks such as beer and juice; barrier layers or oxygen scavengers are used to extend it. Cartons are used for still drinks, often filled aseptically. Whatever the container, the closure is often the weak point: crowns, screw caps, corks and can ends all differ in their gas and light barrier and in how they behave under pressure.
Beer is commonly pasteurised either in the package in a tunnel pasteuriser, or in bulk by flash pasteurisation in a plate heat exchanger before filling, or is sterile-filtered and filled aseptically. Pasteurisation of beer is measured in pasteurisation units (PU): one PU is one minute at 60 °C, and the lethal rate at other temperatures is commonly taken as 1.393^(T − 60), which corresponds to a z value of about 7 °C. Holding beer for 10 minutes at 62 °C therefore gives about 10 × 1.393² ≈ 19 PU. Acid drinks such as juices and juice-containing soft drinks are hot-filled or flash-pasteurised; spoilage risks include acid-tolerant yeasts and moulds and, in juices, heat-resistant spore-formers such as Alicyclobacillus, which cause medicinal (guaiacol) taint. The fundamentals of D, z and lethality are in thermal-processing-canning. Over-pasteurisation must also be avoided, because excess heat gives beer a cooked or bready flavour and speeds oxidation, so plants specify a minimum and a maximum number of PU.
Beverages fail in storage in predictable ways. Beer develops haze from protein-polyphenol complexes (colloidal haze), and stale, cardboard-like flavour from oxidation, partly through trans-2-nonenal; low dissolved and total package oxygen is the main control. Wine browns with oxygen and can throw tartrate crystals or protein haze. Soft drinks lose carbonation through closures and PET, fade in colour under light, and can show flavour emulsion instability (ringing or sediment). Tea drinks form cream and sediment, coffee drinks can separate fat and protein, and cocoa drinks need stabilisers to keep particles suspended. Shelf-life testing combines real-time storage with accelerated tests at higher temperatures, but accelerated results are interpreted carefully, because the reactions that dominate at high temperature may not be the ones that limit shelf life in the market. The way to a stable product is usually removal of the reactants (oxygen, haze precursors, metal ions) at the plant rather than correction after packing.
Beverage quality control checks the same few properties many times a shift. Soluble solids are measured as °Brix by refractometer or density meter. Titratable acidity is determined by titrating a sample with standard sodium hydroxide to a phenolphthalein end point or pH 8.2 and expressing the result as the main acid: for citric acid (anhydrous, equivalent weight 64.04), acidity in g/100 mL = titre (mL) × normality × 64.04 × 100 / (sample mL × 1000). The sugar–acid (Brix–acid) ratio summarises taste balance. Carbonation is measured by the pressure–temperature method; dissolved oxygen by electrochemical or optical sensors; colour of beer in EBC or SRM units; bitterness of beer in bitterness units by solvent extraction and absorbance; alcohol by distillation followed by density measurement, or by calibrated instruments. Sensory panels taste every batch against a standard. Microbiological tests target yeasts, moulds and spoilage bacteria appropriate to each product, often by membrane filtration of large volumes.
Legal standards for beverages differ by country, so the technologist works to the law of the market. Typical regulated items are: definitions and compositional standards (what may be called a fruit drink, a mineral water or a whisky); maximum levels of additives such as preservatives, sweeteners and caffeine; contaminant limits such as methanol in spirits, heavy metals and pesticide residues; and labelling, including alcoholic strength by volume, allergen declarations and warning statements. In India, alcoholic beverages are covered by specific regulations under the Food Safety and Standards Act, packaged drinking water and natural mineral water require BIS certification, and carbonated beverages and fruit beverages have product standards; many other countries follow Codex standards with national variations. Alcohol excise and licensing are usually separate from food law and administered by revenue or excise authorities. Labels must also be truthful about category: a drink may only use a reserved name such as a protected geographical indication if it meets that definition, and fruit content claims must match the formulation.
Beverage plants apply HACCP and prerequisite programmes like any food plant, with particular hazards: chemical carry-over from cleaning-in-place (CIP) systems into product; glass fragments on bottling lines; microbial contamination of water and syrup; foreign bodies in returnable bottles; and, in breweries and distilleries, carbon dioxide accumulation in enclosed spaces, which is a serious worker-safety hazard. Returnable glass bottles are washed in caustic soakers and inspected electronically for residues and damage. Water treatment, syrup preparation and filling are monitored as control points. Traceability from ingredient lots to finished batches allows recall. The general principles of HACCP and food safety management are covered in food-safety-management-systems. Records of water treatment, CIP cycles, pasteurisation units, fill checks and laboratory results form the evidence of control. They are reviewed before each batch is released and are examined at audits. Many beverage plants also hold certification to a GFSI-recognised scheme, which adds requirements for food defence, supplier approval and allergen control. Training of line operators in these checks is part of the same system.
A student should be able to draw the flow chart of each major beverage from raw material to package and explain what each step changes chemically or microbiologically: why tea is withered, why cocoa must ferment, why wort is boiled, why white wine is pressed before fermentation. The same student should handle the standard calculations without hesitation: alcohol and carbon dioxide from sugar, acetic acid from ethanol, Brix after mixing, moisture balances, proof and dilution. These are the skills tested in GATE and ICAR examinations and they are the vocabulary of any beverage plant interview.
A technologist five years into a bottling plant, brewery, tea factory or winery runs the daily checks and solves problems on the line. Typical tasks are setting the throw and checking Brix and carbonation every hour; tracing gushing to particles or poor deaeration; adjusting wither and oxidation times as the leaf changes through the season; finding the cause of a buttery note in a lager or a haze in a white wine; and keeping water treatment, CIP and filler hygiene under control. The decisions are practical: hold or release a batch, adjust a process, or call the supplier.
A senior manager with twenty-five years' experience decides formulations, capacities and compliance across markets. That person approves new products against each country's standards for additives, caffeine, sweeteners and labelling; chooses between glass, can and PET for a market; sets shelf-life targets and the oxygen, light and temperature controls to meet them; designs water and effluent treatment for a new site; and handles recalls, audits and excise rules. Judgement comes from knowing which failures are common, which are rare but serious, and how regulation differs between the countries where the product is sold.
A researcher with long industrial experience works on the open questions: the chemistry of flavour formation and staling in beer and coffee, theaflavin and thearubigin structures in tea, the microbial ecology of cocoa and traditional fermentations, yeast and bacterial strain development, low-alcohol and no-alcohol processes, sugar reduction without loss of mouthfeel, sustainable water and energy use, and rapid analytical methods for authenticity and contaminants such as methanol. Such work supervises students, advises regulators and translates laboratory findings into processes that can run at plant scale.
This manual gives principles and standard textbook values; it does not reproduce any country's full legal standards for beverages, and it gives no numerical caffeine, sweetener or preservative limits, because these differ by country and change. Hop chemistry, yeast genetics, sensory science and distillation column design are treated only at introductory level. Spices, essential oils and oleoresins (also plantation products) are not covered here. Fruit juices, squashes and ready-to-serve drinks are in fruit-vegetable-processing, and the kinetics of fermentation in fermentation-food-biotechnology.
Original practice questions written to the syllabus and pattern of the exams named in each question's examTags. They are not past papers and do not reproduce any board's questions. Every numerical answer was computed by script. Process temperatures, moisture levels and compositions are standard textbook values that vary with raw material, plant and country; legal limits are not quoted because they differ between jurisdictions.
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