BEVERAGES

Some beverages are consumed for their food value (e.g., milk), yet others are consumed for them thirst-quenching properties, for their stimulating effects, or simply because consumption is pleasurable. This chapter will discuss three major groups: carbonated nonalcoholic beverages or soft drinks of which “soda pop” is characteristic; carbonated nonalcoholic mildly alcoholic beverages such as beer and wine; and nonalcoholic, noncarbonated stimulating beverages such as beer and wine; and nonalcoholic, stimulating beverages such as coffee and tea.

Each of these beverages must be considered foods in the broad sense, since all are made from food ingredients, all are subject to food laws and regulations, and all are consumed in large quantities. The annual per capita consumption of soft drinks in the United States in 1991 was 43 gals according to the U.S. Department of Agriculture, which was the highest of any category of beverage and well above the per capita consumption of milk (Table 19.1). It is likely that soft drinks consumption exceeds even tap water. In other countries and areas, packaged beverages may be safer to consume than the local water supply. Further, beer, wine and carbonated soft drinks (with the exception of dietetic formulations) furnish calories; coffee and tea, although non-caloric, frequently are consumed with cream or sugar and, thus, are vehicles of caloric intake. The technologies of each of these beverages and their ingredients are comprehensive topics in themselves.

CARBONATED AND NONALCOHLIC BEVERAGES

Carbonated nonalcoholic beverages are generally sweetened, flavored, acidified, colored, artificially carbonated, and sometimes chemically preserved. Their origin goes back to Greek and Roman times when naturally occurring mineral waters were prized for “medicinal” and refreshing qualities. But it was not until about 1767, when the British chemist Joseph Priestley found that he could artificially carbonate water, that the carbonated beverages industry got its start. An early method of obtaining the carbon dioxide was by acidification of sodium bicarbonate or sodium carbonate, and from the use of these sodium salts came the name “soda” which remains today, although most carbon dioxide is no longer generated in this fashion. Gradually, fruit juices and extracts were added to carbonated water for improved flavor.

Ingredients and Manufacture

The major ingredients of carbonated soft drink beverages in addition to water and carbon dioxide are sugar, flavorings, colors, and acids. Typical levels of sugar, carbon.

Sugar

The most common sugar used in soft drinks is high-fructose corn syrup or related corn sugars. Initially, sucrose, purchased as a pure colorless syrup from the manufacturer or made into a syrup at the beverage plant from high-purity crystalline sugar, was most commonly used and is still widely used. Increasingly, however, sucrose has been replaced with high-fructose corn sugars which are sweeter and, thus, less costly on an equal-sweetness basis. The corn sugar (or sugar syrup) is supplemented with flavoring, coloring, and acidic ingredients and may be stabilized with a preservative. Finished beverages contain about 8-14% sugar. The sugar not only contributes sweetness and calories to the drink but also adds body and mouthfeel. For this reason, when dietetic beverages are made with a non-nutritive or low-calorie sweetener to replace all or much of the sugar, an agent such as carboxymethyl cellulose or a pectin is sometimes added to give the same mouthfeel as the sugar product.

Reduced calorie and Non-Nutritive Sweeteners

Soft drinks which provide no calories are sweetened with non-nutritive sweeteners such as saccharin. Acesulfame K, or cyclamate, whereas reduced-calorie soft drinks have sweeteners that have calories but also are high-intensity sweeteners.

This means that considerably less sweetener must be used to get the same degree of sweetness, so the drink ends up with fewer calories. For example, the common artificial sweetener aspartame (trademark NutraSweet) is a dipeptide that yields 4 kcal/g –the same as sugar –but is about 150-200 times sweeter than sugar (sucrose) and so can sweeten in very small amounts. Thus, it is a nutritive sweetener but contributes very few calories.

Flavorings

Synthetic flavor compounds, natural flavor extracts, and fruit juice concentrates are used to flavor soft drinks. These flavors must be stable under the acidic conditions of the beverage and on exposure to light for a year or more, since bottle drinks may be held this long or longer. The flavors do not have to be stable to heat much over 38C, since beverages are not commonly heat-sterilized or pasteurized.

An artificial fruit flavor made from synthetic flavor compounds and natural flavor extracts (Table 19.3) may contain over two dozen components contributing several hundred distinct compounds. Cola flavors may be as or more complex, and their compositions are guarded secrets, sometimes formulated to contain ingredients that will add to the difficulty of chemical analysis and duplication by competitors. Cola flavors may contain a source of caffeine, which is a mild stimulant. There also is a growing market for caffeine-free colas. When fruit derivatives that contain flavor oils are used, it is necessary to employ and emulsifying agent to keep the oils from separating out in the beverages. Water-soluble gums at low levels are the principal emulsifiers employed for this purpose.

Colors

Some important coloring agents for soft drinks are the synthetic colors, particularly U.S certified food colors, which have been approved by the Food and Drug Administration. All certified batches of such colors must meet stringent chemical purity standards in their manufacture. Caramel from heated sugar, a no synthetic color is also commonly used in dark beverages such as colas. These coloring materials are much preferred to the natural fruit colors because of their greater coloring power and color stability. Even when natural fruit extracts or juices are used, their colors are generally supplemented with the synthetic colors.

Acid

Carbon dioxide in solution contribute to acidity, but this is supplemented with additional acid in most carbonated drinks. The main reasons for acidification are to enhance beverage flavors and to act as preservatives against microbial growth. The principal acids used are phosphoric, citric, fumaric, tartaric, and malic acids. Citric, tartaric, and malic are important natural acids of fruits and so they are used, along with fumaric acid, mainly in fruit-flavored drinks, with citric being the most widely employed. Phosphoric acid is preferred for use in colas, root beer, and other non-fruit drinks.

In addition to flavor enhancement, acid acts as a preservative in non-heat-treated beverages. However, unless a very high degree of sanitation is employed in soft drink manufacture, the Ph. imparted by the acid, even in combination with acidic fruit juices, is not sufficient to ensure long-term microbial stability. For this reason, an additional preservative may be necessary, the most common is sodium benzoate at a level of about 0.03-0.05% in the final beverage. In the acid drink sodium benzoate is converted to benzoic acid, which is more effective as a preservative.

Water

The major ingredient in carbonated soft drinks –accounting for as much as 92% by volume –is water. It is essential that the water be as nearly chemically pure as is commercially feasible, since traces of impurities react with other constituents of the drink. In this respect, municipal drinking water, although satisfactory from a bacteriological standpoint, generally is not chemically pure enough for use in soft drinks. The standards for beverage water listed in Table 19.4 would not be met by most municipal water supplies.

The alkalinity of beverage water must be low to prevent neutralization of the acid used in the beverage, which would alter flavor and decrease the preservative property of the beverage. Iron and manganese must be low to prevent reaction with coloring agents and flavor components. Residual chlorine must be virtually nonexistent since it adversely affects the flavor of the drink. Turbidity and color must be low for an attractive appearance of the drink. Organic matter as well as inorganic solids must be low since colloidal particles provide nuclei for carbon dioxide accumulation and release from solution, which results in beverages boiling and gushing when containers are filled or opened.

To achieve these high water standards, bottling plants generally condition water with additional treatments such as chemical precipitation of minerals, deionization, edition of activated charcoal to remove odors, flavors, and residual chlorine, final paper filtration to remove traces that may pass the carbon filter, and deaeration to remove oxygen. Although the water supply in a bottling plant can be adequately controlled by these methods, the big problem occurs when the syrups and flavor bases are shipped to various locations to be used in fast-food restaurants and vending machines. In these locations the quality of the water will vary and frequently not meet the tight specifications of the bottling plant. The quality of the drink may suffer and vary from location to location even though the syrup formula is constant.

Carbon Dioxide

The sparkle and zest of carbonated beverages stems from the carbon dioxide gas Carbon dioxide can be obtained from carbonates, limestone, the burning of organic fuels, and industrial fermentation processes. Soft drinks bottlers buy carbon dioxide in high-pressure cylinders from manufacturers who

Produce the gas to comply with food purity regulations. In the cylinders, the gas under pressure exists as a liquid. The amount of CO2 used in beverages depends on their particular flavor and brand. CO2 improves flavor, contributes acidic preservative action, produces tingling mouthfeel, and gives the sparkling effervescent appearance to the beverage.

The amount of carbon dioxide in beverages is measured in volumes of gas per volume of liquid. A volume of gas is the volume occupied by the gas under standard temperature and pressure. Thus, a beverage containing 2 liters of CO2 (at STP) per liter of beverage is carbonated at 2 volumes. Most beverages are carbonated in the range of about 1.5-4 volumes. This is done with a carbonator, of which there are several designs. In all, however, CO2 gas, cooling the liquid since the solubility of CO2 in water is greater the lower the temperature, and applying pressure to force more CO2 into solution. In practice, the entire flavored drinks may be carbonated, or only the water may be carbonated for subsequent mixture with the flavored syrup.

Plant layout

A common installation of a soft drink mixing, carbonating, and bottling operation is outlined in Fig. 19.1. Flavored syrup containing all of the drink ingredients expect the remaining water and CO2 is pumped to a metering device called a synchro meter. Treated and deaerated water also is pumped to the synchro meter. This device then meters the syrup and water in fixed proportion to the carbonator. The carbonated beverage then goes to the bottling or canning line where it is admitted to sanitized containers under a CO2 pressurized atmosphere to prevent loss of CO2 and beverage boiling. The containers are then capped; thy are not subsequently heat-treated. In restaurants and similar establishments, concentrated syrups containing the sweetener and flavors is directly mixed with carbonated water as the drink is being drawn. Syrup from the beverage manufacturer is held in one tank and pressurized carbon dioxide in a second tank.

BEER

Brewing is a general term for the hot water extraction of plant materials. Thus, making coffee or tea is brewing. Brewing is a critical stop in making beer and the entire process is termed brewing, but this does not completely describe the many steps involved.

Figure 19.1

Brewing of beer goes back over 6000 years, and today’s practice are similar to those used in earliest times. What has been gained is an understanding of the principles of biochemistry and microbiology underlying the beer-making process and a high degree of sanitation and efficiency in manufacturing practices.

Raw Materials and Manufacture

The principal raw materials of beer manufacture are water, hope, and melted cereal grains, principally barley. In many cases, rice, corn, or other un-malted grains are also added as sources of additional or “adjunct” carbohydrate for fermentation by Saccharomyces yeast into ethyl alcohol and carbon dioxide. Hops are used to add the characteristic flavor of most beers, and additional carbon dioxide may be added to the amount naturally produced by fermentation.

Malt

the most important ingredient in beer-making from the standpoint of quantity and function is barely malt. Malt is barley grain that has been germinated to the point where roots and stems just begin to appear. The green malt is then gently dried to stop growth yet leave the enzyme activity intact. Germination results in activation of enzymes which convert starches in the malted barley and in other cereal grains into sugars, which can be easily fermented by yeast during the fermentation step. This is necessary because yeast cannot utilize the starch in the cereal grains for conversion to ethanol and CO2.

Hops

Hops are paints, the flowers of which contain resins and essential oils that contribute a characteristic bitter flavor and pleasant aroma to beer. Hops also contain tannins, which add to beer color. Hops are added during brewing and after the enzymes of the malt have converted the starch to the sugar maltose. Hops also have mild preservative properties and add foam-holding capacity to the beer. All of these functions, however, are secondary to the role of hops in flavor and aroma.

Cereal Adjuncts

Corn, rice, and other cereals are used in beer-making to provide supplemental carbohydrates, principally-starch, for conversion to sugar for subsequent fermentation. Without these adjunct cereals, the limiting nutritional factor for yeast in fermentation would be protein. This means that carbohydrate would remain after fermentation and produce a heavier type beer. In some cases, this is desirable, but some breweries prefer lighter-type beers.

Mashing

The first step in beer-making is to combine the malted barley and cereal adjuncts with water and mildly cook the mixture, known as mash, to extract readily soluble materials and to gelatinize the starches, thus making them more susceptible to extraction and enzymatic breakdown into dextrin and maltose. The mild cooking also releases proteins from the grains; these proteins also under go enzymatic breakdown into compounds of lower molecular weight.

These changes are brought about in specially designed vessels, and the overall operation is known as mashing. Mashing may begin at about 38C with the temperature gradually raised to about 77C. this heating is done in steps with rest periods of about 30 min between each temperature increment; this stepwise heating permits specific amylases and proteinases to function before they are heat inactivated. The mash vessel (called a “tune”) is designed so that on completion of mashing, the liquid fraction now high in yeast fermentable sugars, can be separated from the spent grains. The liquid fraction is known as “wort”.

Brewing

The liquid is next pumped to the brew kettle. The hops are added to the wort, and the mixture is brewed by boiling in the kettle for about 2.5h. after brewing the hips residue is allowed to settle and the wort is drawn from the kettle through the bed of hops, which partially filter the wort. The wort is then cooled, the solids allowed to precipitate, and it is ready for fermentation.

The boiling or brewing of the wort with the hops serves several purposes. It concentrates the wort, nearly sterilizes it, inactivates enzymes, precipitates remaining proteins that would otherwise contribute to beer turbidity, caramelizes sugars slightly, and extracts the flavor, preservative, and tannin like substances from the hops.

Fermentation

The cooled wort is inoculated with Saccharomyces yeast and fermentation of the sugar formed from starch during mashing proceeds. Fermentation in tanks, under near-sterile conditions with respect to contaminating microorganisms, is carried out at temperatures from about 3 to 14C, depending on the strain of yeast and the brewery. The fermentation is complete in about 9 days. It produces an alcohol content in the wort of about 4.6% by volume, which would be 9.2 proof. Fermentation also lowers the Ph. of the wort to about 4.0 and produces dissolved carbon dioxide in the wort to the extent of about 0.3% by weight.

Storage

After fermentation is complete, the beer is quickly chilled to 0C, passed through filters to remove most of the yeast and other suspended materials, and pumped into pressure storage tanks. The young or “green” beer is stored in these tanks for several weeks to several months. This storage is known as “Storage”. During this period of storage at 0C there is further settling of finely suspended proteins, yeast cells, and other remaining materials, and development of esters and other flavor compounds, all of which contribute to improved body and a more mellow favor.

Generally, additional carbon dioxide is added to the beer during storage to increase the level developed and absorbed during fermentation and o purge the beer of any oxygen that may be present and would adversely affect storage life. This may be done by periodically pumping the beer through a carbonator or bubbling carbon dioxide into the storage tank.

Chill haze is a condition caused by remaining traces of degraded proteins and tannins that from a colloidal haze when beer is cooled to low temperature. To prevent this from occurring in the finished product, various chill-proofing treatments may be given to the beer during the storage period. These generally include the addition of earths or clays to adsorb the colloidal materials or use of proteolytic enzymes to further solubilize the protein fraction.

Finishing and Packaging

After storage, the beer is given a final “polishing” filtration to remove traces of suspended materials and give the beer a crystal clear appearance. Additional CO2, may be added and the beer packaged. Analysis of beer at this point shows that it is quite complicated (Table 19.5).

Although clear, the beer is not sterile and a few viable yeast cells and low levels of fermentable sugars remain in the product. These yeasts and other microorganisms could continue to grow during storage and produce considerable pressure within the bottles when stored at room temperature. Beer is, therefore, pasteurize at a temperature of 60C for several minutes after packaging. In the case of beer which is packaged in kegs (so-called draft beer), it is held under refrigeration and does not need pasteurization. Because it is not pasteurized, draft beer has a better flavor than pasteurized beer.

Beer may also be microbiologically stabilized by filtration processes which are fine enough to remove residual yeast and bacterial (Fig 19.2). This is called “cold pasteurization” or filtration and achieves microbiological stability without the heat of conventional pasteurization. Similar cold pasteurization processes can be applied to other products such as fruit juices and wines.

Light Beer

Light beer contains about one-third to one-half fewer calories than regular beer and also less alcohol. It is prepared from a mash lower in solids than that used for regular beer. Its alcohol content can be further modified by changing the ratio of fermentable to non-fermented and thus contribute to caloric content. The various operations and quality control activities in the manufacture of beer are given in Fig. 19.3.

WINE

Like beer-making, the fermentation of grapes to make wine goes back to at least 4000 B.C. In 1991, annual worldwide industrial production of wine was 29 million metric tons, of which more than one-third was produced in France and Italy. Annual wine production in the United States is about 2.6 billion liters. The principal U.S. wine-producing regions are California, the Finger Lakes area of New York, and the Pacific Northwest, although wines are now made in many regions of the United States. Wine can be made from many fruits and berries, but the grape is by far the most popular and the most often used raw material.

Wine varieties

The varieties and names given to wines are legion and reflect their region of origin, varieties of grape used in their manufacture, and certain properties such as degree of sweetness, color, alcohol content, and effervescence. In the United States, wines can be grouped into five classes –appetizer wines, red table wines, white table wines, sweet dessert wines, and sparkling wines. Although these terms are somewhat descriptive, greater insight is gained by considering some of the general characteristics of grape wines and how they are brought about.

Color

Grape varieties range in skin color from deep purple through red to pale green. Red wines result when the crushed grape skins, pulp, and seeds of purple or red varieties are allowed to remain with the juice during the fermentation period. The alcohol produced contributes to pigment extraction, and the longer the skins, pulp, and seeds are allowed to stay with the fermenting juice, the deeper the color becomes. Pink or rose wines can be produced by removing the non-juices “pumace” from the liquid or “must” early in the fermentation period. Thus, only a small amount of pigment is extracted. White wines can be made from pigmented grapes by removal of the skins, pulp, and seeds before juice fermentation, by ion exchange and activated charcoal treatments to remove pigment, and by the use of anthocyanase enzymes, which decolor pigments. White wines are also made from white varieties of crushed grapes with removal of non-juice solids prior to fermentation. Pink wines can also be prepared by blending white wines with small amounts of red wines. Final wine color is determined also by pigment stability during storage, which is dependent to a considerable degree on grape variety.

Sweetness and alcohol Content

The sweetness and alcohol content of wines are interrelated because fermentation converts the grape sugars to ethanol. As more alcohol is produced, sweetness decreases; when virtually all of the sugar is fermented, the wine is without sweetness and is said to be “dry.” Dry wines contain all of the alcohol that the specific grape is capable of yielding under the conditions of fermentation. This generally is 12-14% alcohol by volume.

The relationship between disappearance of sweetness and increase in alcohol content cannot be used to characterize wines, however, because both alcohol content and sweetness of finished wines can be further and independently adjusted. Thus, a completely fermented dry wine of 14% alcohol can be made sweet after yeast removal by the addition of some unfermented juice or sugar. Similarly, a sweet wine does not necessarily mean that the alcohol content is low since additional alcohol can be added to a sweet wine in the form of distilled spirits. The wines in the U.S. designated table wines and sparkling wines generally contain 10-14% alcohol by volume, appetizer and sweet dessert wines contain 14-21%. Any of these classes may be red or white and possess varying degrees of sweetness. The terms “natural” and “fortified” also have been used in relation to alcohol content. Depending on the sugar content of the grapes, characteristics of the yeast culture, and fermentation practices employed, natural fermentation generally yields an alcohol concentration of less than 16% by volume even if more sugars are added. This is because this amount of alcohol is toxic to the yeast and it stop fermentation. The wine must often still be pasteurized after bottling to ensure against growth of unwanted microorganisms.

The term light wine also is used to describe a wine having an alcohol content from about 5% to 10% (the term light has nothing to do with color). Fortified wines are those that have received additional distilled spirits to bring their alcohol content up to 17-21% by volume. They are less perishable and may be stable without pasteurization.

Effervescence

Wines are termed still or sparkling depending on the amount of CO2 they contain. The CO2 occurs naturally as a result of fermentation (natural sparkling wines) but also can be added artificially (“carbonated wines”).

During normal vat fermentation, not enough CO2 is retained by the wine to give it effervescence when bottled. Natural sparkling wines are made by adding about 2% sugar and a special alcohol-strain of wine yeast to previously fermented wine. This causes a second fermentation under conditions that prevent CO2 loss. This second fermentation may be in the final bottle or in closed tanks from which the wine is subsequently filtered and bottled.

The preparation of bottle-fermented wines such as champagne involves an interesting technique for removing yeast, tartrates, and other fine particles that settle in the sealed bottle and would otherwise cloud the finished product. After secondary fermentation that may last a month, the tightly stoppered bottles may be further rested for periods up to several years. Removal of sediment then involves placing the bottles neck-down in racks and periodically twirling them so the sediment moves down the neck toward the special stopper. Next the sediment-containing wine near the stopper is frozen by placing the necks of the inverted bottles in a refrigerant. The bottle is now set right side up and the stopper loosened; carbon dioxide pressure below the frozen plug forces the plug forces the plug containing the sediment out of the bottle. A small amount of wine or champagne is added to make up volume and the bottle is reclosed with its permanent cork.

Fermentation and other Operations

As grapes mature, wine yeast Saccharomyces ellipsoids naturally accumulates on the skins. When the crushed grapes or filtered juice is placed at a temperature of about 27C, the juice proceeds to ferment, yielding essentially equal molar quantities of ethyl alcohol and CO2 and traces of flavor compounds.

In commercial operation, special strains of S. ellipsoids are used to supplement the natural inoculum and better control fermentation. Wine yeast is relatively resistant to SO2 and so this agent commonly is added to the grapes or must to help control undesirable microorganisms, particularly bacteria. Sulfur dioxide also is effective in inhibiting browning enzymes of the grape sand providing reducing conditions by reacting with oxygen. The SO2 treated must may next be fermented directly or after pumace removal. Fermentation causes a rise in temperature, and so cooking is required to prevent yeast inactivation. Fermentation under conditions of limited exposure to air way continue until the sugar is entirely consumed, when it stops naturally, or fermentation may be interrupted prior to this point. At around 27C, fermentation may last for some 4-10 days depending on wine type.

After fermentation has been completed naturally or stopped by addition of distilled spirits, the next step is the first “racking,” which involves allowing the wine to stand until most of the yeast cells and fine suspended materials settle out. The wine is then drawn off without disturbing the sediment or “less.” If lees are not quickly removed, yeast will autolyze and contribute off-flavors to the wine. After the first racking, the wine may be further aged in casks or tanks that prevent entrance of air for periods of several months to years, during which last traces of sugar ferment and flavor further develops. During ageing, additional racking may be performed; these are followed by final clarification and stabilization treatments to produce brilliantly clear wines.

In addition to filtration or centrifugation of last traces of colloidal materials that impair clarity, stabilization also requires removal of the slats of tartaric acid. These tartrates, present in grape juice, tend to crystallize in wine casks, and if not completely removed from the wine before bottling, they slowly reappear as glasslike crystals in the final bottles on storage. Stabilization with respect to tartrates may involve chilling to promote crystallization for efficient removal, or removal of these salts by ion exchange treatments.

If a wine is not above 17% alcohol, it may be heat-pasteurized, or cold-pasteurized through microporous membrane filters, just before bottling. Sparkling wines, whether secondary fermentation is carried out in bottles or in bulk, are not heat-pasteurized even though they generally contain no more than 14% alcohol. In this case, depletion of nutrients from the previous double fermentation, a high concentration of carbon dioxide in solution, extreme cleanliness, and sometimes SO2 addition before bottle closure all help to make microbial growth unlikely.

Naming of Wines

Originally, wines were named for the region where the grapes were grown and the wine was produced. Such famous names as sherry originated in Jerez. Spain; port came from Oporto, Portugal; champagne from the district of Champagne near Paris; Chablis and Burgundy from districts to the south of Champagne; sauterne from Bordeaux in western France; Rhine wines from districts along the German Rhine; Marsala from Sicily; Chianti from the Italian district of Tuscany; and so forth. Grape varieties, soil, and climate contributed to the different characteristics of these wines. Today, wines with similar characteristics are produced in many parts of the world, and to maintain identity as to type they frequently retain the original names or derivatives thereof. In many countries, by international agreement and wine laws, when the original name is used, it must be accompanied by the actual place of manufacture, for example, New York State Port, California Champagne, and Australian Sherry. The Bureau of Alcohol, Tobacco, and Firearms (BATF) of the U.S. Treasury Department issues regulations governing such labeling and taxing of wines and other alcoholic beverages in the United States. Regions of the United States can apply to BATF for designation as a viticulture area and, if granted, reserve the right to label wines as being from a specific region of the United States. Labels also must be consistent with certain labeling requirements of the Food. Drug, and Cosmetic Act.

It now is common in much of the world to name wine aster the variety of grape from which the wine was made. Thus chardonnay, zinfandel, and cabernet sauvignon are wines named after the variety of grape from which they were made.

Among the most popular distinct wine types in the United States are appetizer wines (sherry and vermouth, which is aromatically flavored with herbs or spice), red table wines (claret, Burgundy, and Chianti), white table wines (Rhine wine and sauterne), sweet dessert wines (port, white port, muscatel, and Tokay), and sparkling wines (champagne and sparkling Burgundy). The price of wines includes federal taxation based on alcohol content and for sparkling wines whether they are carbonated artificially or by natural fermentation.

COFFEE

Although there are considerable differences in their starting materials, growing, and processing, coffee and tea share several common characteristics. Both contain virtually no food value in themselves and are consumed entirely for their refreshing and stimulating beverage properties. Both contain caffeine, which provides their physiologically stimulating effect. Both are grown in region of tropical or near-tropical climate and are important exports of these regions. Both are processed to develop flavor in the harvested beans or leaves, which then are brewed to obtain the flavored beverages.

In many parts of the world, coffee is one of the most popular beverages. In the United States, annual consumption in 1991 was approximately 28 gals per person per year, whereas annual per capita consumption of tea was 5.5 gallons. Whereas consumption of tea in the United States is much less than that of coffee. In England, China, Japan, the Soviet Union, and certain other countries, the picture is reversed.

Production Practices

Coffee trees are started in nurseries as seedlings that are later transferred to the plantation. After about 5 years, the trees bear fruit that turns red as it ripens and is referred to as cherries. When ripe, the cherries are hand-picked. One coffee tree yields about 2000-4000 cherries per year. Each cherry contains only two coffee beans; some 3000beans yield only about 454 g (1 lb.) of finished ground coffee. According to the U.S Department of Agriculture, the 1991 worldwide production of coffee beans was 6.3 million metric tons.

The structure of the coffee cherry is shown in Fig. 19.4. The two coffee beans are covered by a thin parchment like hull, which is further surrounded by pulp. Both the cherries are first passed through pulping machines that break and separate the pulp from the rest of the bean. Separation of the pulp leaves a mucilaginous coating on the beans, which must be removed. This is done by various methods including microbial fermentation of beans heaped in large piles, use of commercial pectin-digesting enzymes, and various washing treatments. After mucilage removal, the bean still contains an outer hull.

The coffee beans are now partially dried either by being spread out in the sun or by machine driers. The object is to decrease the moisture level from about 53% down to about 12%. Drying must be uniform throughout; when sun drying is used, beans must be turned frequently. Drying by this method may take 5 days but is dependent on the weather. During drying, color and flavor attributes are modified within the beans; over drying or wide fluctuations in temperature give variable coffee bean quality. Machine drying permits good control of temperature and has several other advantages. After the beans are dried to about 12% moisture, hulls are removed by machines that apply friction to the hulls and then remove them in a current of air.

Hulling is followed by sorting of the beans for color and defects. Hand sorting of beans moving along a belt is still practiced to some extent, but modern electronic sorting is less costly and gives better quality control. In this case, the beans are picked up individually by vacuum and sorted by an electric eye (Fig. 19.5).

The sorted beans are graded for size and color, and cup-tested to determine their potential brewing quality. Up to this point, the beans are still green; that is, they have not yet been roasted. For cup testing (Fig. 19.6), small samples are roasted, ground, and brewed. For the most part, though graded coffee beans are shipped as green beans for further processing by coffee manufacturers.

Figure 19.4 and Figure 19.5

Coffee Processing

Blending

Different manufacturers favor various coffee blends and buy their beans from countries producing the required coffee types. The manufacturer then custom-blends products for special market outlets.

Roasting

During roasting, the characteristic flavor of coffee is developed. Both batch- and continuous roasting equipment is available. Newer types of continuous roasters can automatically control temperature and humidity, recirculate roaster gases, and control residence time of beans in the roaster. Some are being fed with green bean blends that are formulated and combined under computerized control.

Figure 19.6

Much research has been done on the roasting step since various blends require different heat treatments to develop optimum flavor. Further, a given blend roasted to various degrees will yield coffees of different color and taste qualities favored by different markets. Current roasting practices employ gas temperatures of about 260C for about 5 min. the bean temperature rises to about 200C during roasting. All of the free moisture is removed from beans during roasting; in addition, beans lose about 5% more of their green bean weight as volatile chemical substances. One of the newer roasting processes employs heated nitrogen under pressure; among the advantages claimed is improved flavor due in part to removal of oxygen.

Grinding

Following roasting, the beans are cooled and ground. This is not as simple a step as might appear. The size to which coffee is ground depends on its intended end use (Table 19.6); home use in a vacuum, drip, or percolator brewer; restaurant use in a larger urn; vending machine use where extremely fast brewing may be required; or use in the manufacture of instant coffee. In each case, average particle size and particle size distribution affect the brewing time, the degree of turbidity in the cup and other properties of the brewed beverage. Since the aroma and flavor properties of ground coffee are highly unstable to oxygen and to loss of volatiles, coffee that is to be stored for long periods generally is packed in hematic cans and jars under vacuum or under inert gas.

Coffee for restaurants, which is consumed more rapidly, may be packed in sealed bags. Storage stability in each case also is affected by grind size. Ground coffee gives of considerable CO2 and so must be allowed to outgas before packaging or the CO2 will accumulate and distend the package.

Brewing

as pointed out earlier, brewing is the hot water extraction of plant materials. Brewing coffee to the correct strength and flavor depends on several variables. These include the ration of coffee to water, particle size of the ground coffee, temperature of the water, mixing action in the brewer, and time. All will affect the amount of coffee soluble that is extracted from the ground bean. There is an optimum degree of extraction for best flavor; extraction beyond this point removes bitter constituents from the bean and ruins the brew.

Optimum extraction can be measured by determining the soluble solids in the brew. This is done by measuring the brew density with a floating hydrometer. Such a hydrometer has been calibrated by the Coffee Brewing Institute and a chart has been developed relating extracted soluble solids to coffee strength (Fig. 19.7). Such measurements are very useful in developing brewing equipment, of which there are scores of designs, and in quality control measurements on brewed coffee.

Decaffeinated Coffee

Coffee is a major source of caffeine and related stimulants in the diet, although it is present in several other beverages and foods, including tea leaves, cacao beans, and kola nuts. Products made from these materials have different levels of caffeine depending on the method of processing, kind of brewing in the case of coffee and tea, and other factors. Brewed coffee generally contains about 75-150 mg caffeine per 150 ml (5-oz) cup; brewed tea about 30-45 mg per 150 ml cup; cola beverages about 30-65 mg per 360 ml (12-oz) can; and milk chocolate about 6 mg per 28 g (1 oz.).

Figure 19.7

Since caffeine, in addition to its stimulating effect, may produce insomnia, nervousness, and other physiological responses in some persons, coffee and tea may be decaffeinated. Decaffeinated coffee contains about 3 mg caffeine per cup. Decaffeination involves steaming of green coffee beans followed by water extraction prior to the usual roasting step. In some cases, organic solvents are used to extract the caffeine from the bean. This leaves the problem of removing the residual solvent and of recovery of the solvent vapors. A recent advanced process utilizes high pressure CO2 and is known as supercritical CO2 extraction. Under the proper conditions of high-pressure and reduced temperature, CO2 (and other gases) has the solvent power of liquid and the penetrating ability of a gas. This means that lower temperatures can be used and there is no worry about leaving behind traces of solvent in the coffee.

Instant Coffee

Instant coffee, or as it is technically known “solubilized” coffee, is made by dehydrating the brewed coffee; manufacture of this product is carried out in plants that incorporate the most advanced extraction, dehydration, and essence-recovery equipment to be found anywhere in the food industry.

Extraction. Extraction of roasted ground beans is accomplished in an extraction battery that may consist of as many as six to eight percolators connected to be operated as a single unit (Fig. 19.8). Percolators are run at different temperatures, and extract is pumped from one to another at various stages of the brewing operation. Conditions are set to obtain maximum extraction without heat damage or over extraction of bitter constituents. Extraction is also designed to filter the brew through the coffee grounds and thereby remove fats and waxes which otherwise would adversely affect subsequent drying and storage stability. Efficient extraction using a temperature profile decreasing from about 150 to 70C removes most of the readily soluble solids and hydrolyzes less soluble coffee bean carbohydrates (Table 19.7) resulting in a total extraction of about 40% of the weight of the roasted and ground bean. Without high-temperature hydrolysis (150C), only about 20% of the bean weight would be extracted, which is about what is obtained in home and restaurant brewing.

Figure 19.8

The extract from the percolators is rapidly cooled and, when possible dehydrated immediately, since coffee aroma and flavor can deteriorate in as little as 6 h even when cooled to 4C.

Dehydration. The principal method of dehydrating the extract is spray drying, and spray driers have been designed especially for coffee. As in spray drying of other products, the size, shape, density, moisture content, solubility, and flavor properties of the dried particles depend on the droplet size sprayed into the drier, the time required for the particle depend on the droplet size sprayed into the drier, the time required for the particle to descend, the temperature exposure, the trajectory of the droplet to prevent sticking to the drier wall, and so on. A flow diagram of a typical instant coffee plant including spray drier is shown in Fig. 19.9. Spray dried particles commonly are agglomerated to appear more like roasted and ground coffee and to improve solubility and minimize foam in the cup. Spray-dried particles also may be heated between rollers to produce fused particles, which are cooled and ground to give a crystalline flake like appearance.

Since the late 1960s, increasing quantities of coffee extract have been dehydrated by freeze-drying to retain maximum flavor and aroma. This has included the use of freeze concentration to produce very high quality concentrated extracts for the freeze drying process. Currently a significant portion of all instant coffee produced in the United States is freeze-dried. Freeze-drying is a milder treatment than spray drying and produces a higher quality instant coffee but at a higher price due to the expense of the process.

Aromatization. Even the best instant coffee from the drier lacks the full flavor and aroma of freshly brewed coffee. An enormous amount of work has been done to develop treatments of various kinds to improve flavor and aroma; these are referred to as aromatization. This generally involves adding back flavor and aroma constituents recovered during processing to the dry state. These flavor and aroma constituents have been trapped and recovered during roasting, grinding, and extraction and have been obtained from oils pressed from the coffee bean. Hundreds of patents have been granted in this area alone. One interesting technique involves extraction of roasted and ground damage flavor and aroma compound in the coffee oil solvent such as liquid carbon dioxide. The cold CO2 does not damage flavor and aroma compounds in the coffee oil and is easily separated from the extracted oil from recompression and reuse. The extracted oil is then sprayed onto the instant coffee. Such an aromatization scheme, currently being used commercially, is shown in Fig. 19.10. After CO2 removal of the oil, the roasted and ground coffee is still highly suitable for extraction of water-soluble solids in the regular extraction battery operation.

TEA

Although coffee is derived from the beans (seeds) of the tree, true teas come from the young leaves of the tea plant which is a bush. The term tea is somewhat incorrectly also used for hot water extracts of other plant materials such as jasmine.

Figure 19.9 and 19.10

These are often known as “herbal teas.” The tea plant is an evergreen and it is ready to yield tea leaves after about 3 years of growth. It then may yield for 25-30 years depending on growing conditions. The leaves are hand-plucked from new shoots and about 6000 leaves are needed to make 1-lb. of manufactured tea. Depending on plant cultivar, climate soil, and cultivation practices, there are about 1500 slightly different kinds of tea leaves; these can be further modified in processing and contribute to differences in the final brew and provide opportunity for custom blending to satisfy regional performances. Tea leaves contain three important kinds of constituents that affect brew caffeine which gives tea its stimulating effect; tannins and related compounds, which contribute color and strength, often associated with the terms body and estrin------ essential oils, which provide flavor and aroma.

Tea Processing

The three classes of teas are knowing as caffeine, Tannins, and oolong. These three types can be made from the same tea leaves, depending on how the leaf is processed. The appearances result largely from enzymatic oxidations of the tannin compounds in the leaf. If the enzymes are allowed to act, they turn the green leaf black in much the same way that a freshly cut apple blackens. If the enzymes in the leaf are inactivated by heat, as in blanching, then the leaf remains green. If a partial oxidation is allowed to occur by delayed heating, then an intermediate tea of the oolong type is obtained. The enzymatic oxidation of tea leaves is referred to as fermentation. Fermentation leaves give black tea; partially fermented leaves give oolong tea. Along with the color differences there also are subtle flavor variations.

Black tea

The processing of tea to the dried leaf stage involves relatively few steps. In the case of black tea these include:

1. Withering the plucked leaves to soften them and partially dry them

2. Passing the withered leaves under rollers to rupture cell walls and release the enzymes and juices

3. Fermentation the roller leaves by exposing them to the air at 27C for 2-5 h (this relatively short time would be insufficient to bring out the desired color and flavor changes were the enzymes and juices not freed from the cells in the rolling step), and

4. Drying the fermented leaves in ovens at 33C, which inactivates the enzymes and decreases leaf moisture to about 4%. This drying step in the case of tea is known as firing.

Green and Oolong Tea

The processing of green tea involves:

1. Steaming the plucked leaves to inactivate enzymes

2. Rolling the leaves to rupture the cell walls, which makes the leaves easier to drying during subsequent brewing

3. Drying or firing the leaves.

Oolong tea reduce steaming and a partial fermentation step before being fired.

These each of the three broad classes of tea, there are several subtypes and styles depending on the country, region, and estate the tea came from, the season when the leaves were plucked, the size and shape of leaves (straight, curled, or twisted), whether the leaves are from the growing tip or lower on the ranch, and other characteristics, all of which affect cup quality. The percentages of the dry weight of leaves extractable as caffeine, tannin, and total soluble solids on brewing some of these teas are indicated in Table 19.8. Regardless of type, the dried tea leaves are packed into chests and exported. The importer cup-tests various lots for body, flavor, color, and clarity of the brew, and then custom-blends for different markets. In the United States, about 50% of the tea imported goes into tea bags, about 10% is sold as loose tea, and the rest is used for the manufacture of instant tea, mixes, and other tea products.

Instant Tea

The manufacture of instant tea is in several ways like that of instant coffee. Instant tea processing begins with extraction of the selected tea leaf blend. Generally, a fermented black tea type is used –one chosen for reddish color, relative freedom from haze, and strong flavor when brewed. About 10 parts of water are combined with 1 part of tea leaves by weight in the extractors, and extraction is carried out at temperatures between about 60 and 100 C for 10 min. the final extract contains about 4% solids, which represents approximately 85% of the soluble solids in the leaves. Departures from these times and temperatures are common with different manufacturers. This rather dilute extract is concentrated for more efficient dehydration; just before concentration, aromatics are distilled from the extract with specially designed flavor-recovery equipment. The DE aromatized extract is then concentrated in low-temperature evaporators to between 25% and 55% solids for subsequent drying.

Instant tea has grown in popularity largely because of tis convenience in making iced tea. However, tea leaves and tea extract contain both caffeine and tannins. These are in solution in hot water, but in cold water some of the caffeine and tannins form a complex that imparts a slight haze or turbidity to the brew known as “cloud” or “cream.” Since iced tea is generally consumed in glasses rather than cups, this turbidity is readily seen and detracts from the desirable quality attribute of clarity. This haze forming property can be removed from the concentrate prior to drying. One method involves cooing the tea concentrate to about 10C encourage caffeine –tannin complex formation. The complex, which gives a fine precipitate, can be removed by filtration or centrifugation.

This is similar in principle to the chill-proofing of beer and the winterizing of oils, although the hazes in each case differ in composition.

The concentrate with haze removed is supplemented with the essence distilled earlier and is ready for dehydration. Some manufacturers also supplement the tea concentrate with dextrin before drying, to provide a 50% tea solids and 50% carbohydrate solids mixture. This tends to protect the delicate tea aroma during drying and yields a dried product with quicker solubility in cold water. Bulk density of the product is controlled so that a teaspoonful gibes about the same level of tea solids as does an instant tea dried without dextrin. A flow sheet of the overall instant tea manufacturing process is presented in Fig. 19.11.

Instant tea is dried primarily in spray driers and low-temperature vacuum belt driers. Tea flavor and aroma is even more sensitive than that of coffee, and so the spray driers are operated under milder heat conditions than those used for coffee, which cuts down on their capacity. Freeze-dried tea appears to offer few advantages.

In recent years, bottled and canned teas and in some parts of the world coffees have become popular. These products are often sweetened with sugars or reduced calorie sweeteners and may have fruit flavor essences added. Their manufacture is similar to other canned and bottled beverages except that they start with a brewed product which may initially be in the form of a concentrate. If their pH is above 4.6, they would require retort processing. Many are aseptically processed and packaged.