Sugar and Sweeteners
SUGAR AND SWEETENERS
SUGAR AND SWEETENERS. There are many sugars and sweeteners. Sucrose—the sugar obtained chiefly from sugar cane and sugar beets (see "Sugar Crops and Natural Sweeteners")—is the most important sweetener and the substance usually meant when people speak of sugar. In 2000, world consumption of cane and beet sugar marketed by industrial-scale processors reached almost 120 million metric tons (132 million short tons), in white quality terms, equivalent to roughly 20 kilograms (about 44 pounds) per inhabitant. In addition, upwards of 10 million metric tons of indigenous types of cane and palm sugar of different qualities—the product of small rural enterprises—were consumed, mainly in Asia and Latin America. Globally, sugar supplies around 9 percent of the total human dietary energy intake, as all but a small amount produced ends up in food and drink. At the country level, average annual per capita sugar consumption ranges from less than 5 kilograms to more than 60 kilograms, depending on economic factors—price, income, and availability—as well as national customs, habits, and tastes.
Ordinary refined, or white, sugar is at least 99.7 percent sucrose and is one of the purest products in common use. Like other carbohydrates, it is a stored form of energy, providing nearly 4 kilocalories (slightly more than 16 kilojoules) per gram. In the eyes of some Western food writers, this makes sugar merely "empty calories." If that were all there is to it, sugar would not play the dietary role it does. Without its sweetness and other functions, the fact that sugar generally tends to be one of the cheapest sources of dietary energy might not, by itself, enable it to compete against starchy foods—even if these did not, in addition to energy, provide other nutrients. What basically makes sugar a staple food is that it enhances the beverages and other foods in which it is ingested. Sugar cannot be consumed by itself in significant volume. Potatoes or rice can be eaten by the plateful with barely anything else; it is difficult to ingest a teaspoonful of granulated sugar without at least dissolving it in water. Even as a source of energy, sugar rides piggyback on whatever else we eat and drink. It can be consumed in large quantities because, while satisfying the innate human disposition for sweetness, it is sweet in a not very intense way, far less so than numerous other substances.
Nowadays, global sugar consumption grows roughly in line with the increase in world population. In high-income industrial countries, per capita usage tends to stagnate and even decline. In poorer and less developed countries, on the other hand, sugar remains, as a study at the beginning of the 1960s found, one of the first foods to respond to a rise in personal incomes, its chief appeal lying not in its function as a source of energy—often still expensive, compared with locally grown cereals and root crops—but in its ability to make a frequently drab and monotonous diet more appetizing.
Functional properties. Sugar provides not only energy and sweetness. It caramelizes on heating to form complex coloring and flavoring substances, and part of it is inverted (converted by acid hydrolysis or enzyme into a mixture of glucose and fructose) during food preparation, the resultant monosaccharides reacting with other recipe components to lend aroma and browning to the final article. This increases the color, luster, and flavor of bread crust, for example. Well-known, too, is sugar's antimicrobial effect—as in fruit preserves, marmalades, jellies, and jams—where the high concentration of sugar in solution inhibits the growth of spoilage microorganisms by raising the osmotic pressure.
In developed countries, the sugar used at home and in communal catering establishments represents only a minor portion of total consumption. German statistics for 1999/2000, for instance, show 71.7 percent of total domestic sugar sales going directly to industry (principally food manufacturers), 22.9 percent to wholesale and retail traders, 0.2 percent straight to end users, and 5.2 percent to unknown recipients. Even in the United States, where sucrose has been widely replaced by high fructose syrup in food processing (especially in soft drinks, previously the largest single outlet), direct industrial receipts accounted for 58.5 percent of total sugar deliveries for human consumption in 2000. Producers of baked goods and cereals are now in first place among industrial sugar users, followed by makers of sweets and manufacturers of ice cream and dairy products. In addition to its nutritional value, sweetness, and other sensory functions (taste and aroma, texture and appearance), and preservative action, sugar fulfills the specific requirements of different food industries for a binder, bulking agent, fermentation substrate, or stabilizer. This does not exhaust the list of its functional properties, and the fact that sugar always acts in more than one way explains its wide use in food and beverages.
The many types and grades of sugar available in the marketplace reflect the multiple uses to which it is put in households and in industry. More than a dozen different kinds could be encountered in 2002 in a single British supermarket, for example: white beet or refined cane sugar—granulated, caster, icing, and cubes; unrefined cane sugar—golden granulated and caster, Demerara granulated and cubes, light and dark brown soft, light and dark muscovado, and molasses sugar; specialty items—amber sugar crystals, preserving sugar (large crystals), jam sugar (with pectin and citric acid), and a reduced-calorie mixture of sugar and the high-intensity synthetic sweeteners aspartame and acesulfame-K. Several kinds were available also in "organic" versions. One important distinction is the size of crystal. Finer sugar tends to dissolve more rapidly than coarser sugar. Also, the smaller the crystal, the greater the total surface area of crystals per unit of mass or volume. In raw and recoated white or refined sugars, each crystal is surrounded by a film of molasses or syrup containing nonsucrose substances that, while nutritionally insignificant, have technical and sensory effects such as taste. Therefore, the smaller the crystal, the greater the proportion of syrup or molasses in the product, a desirable characteristic in making things like dark fruitcake and gingerbread.
Still other types of sugar reflect national or regional processing technologies, customs, and tastes. So-called amorphous sugar features prominently in Brazil, as does white soft sugar in Japan. The loaves of the sugar bakers, which in their blue wrappers graced the shelves of nineteenth-century grocers' shops before cubing processes were invented, live on in Germany, where they are required on festive occasions for the preparation of mulled wine. Loaf sugar also remains popular in North Africa and the Near East, a legacy attributed to the fact that the loaves were easy to transport hung from the backs of camels. More importantly, altogether millions of tons of sugar, the product of boiling cane juice or the sap of palms in open pans, are still consumed, notably in the countries of the Indian subcontinent and Southeast Asia, China, and Colombia.
Granulated sugar going to processing industries is shipped in bulk or bagged in sacks, for the greater part directly from the factory or refinery, and often tailored to customers' specifications, especially concerning grain size. Many applications, however, require an aqueous solution. Dissolving batches of granulated sugar stands in the way of continuous manufacturing operations. Hence, beginning in the United States in the 1920s, large sugar users have increasingly obtained bulk delivery in liquid form. What is known generically as liquid sugar comes in many guises, in accordance with industry demands: colorless and colored; uninverted sucrose or partially or totally inverted (converted into glucose and fructose); unblended or mixed with glucose syrups and other components. Depending on type, liquid sugar contains 67 to 77 percent dry substance.
Nutritional, health, and safety aspects. Whether robbing wild bees of their honey, as did our ancestors, or extracting sucrose from sugar cane or sugar beets, humans take easily assimilable energy from the environment because we are heterotrophs or feeders on others and cannot fix carbon dioxide from the air. Instead, we have to obtain our carbon in a more elaborate form. Nutritionally, we utilize sugar, like other carbohydrates, as a fuel to obtain the energy to function. Under normal physiological conditions, sucrose must be enzymatically hydrolyzed in the small intestine before it can be absorbed across the intestinal wall. Glucose is the body's preferred fuel and the only one that powers the brain.
As a food, sugar is now subject to international and national standards and public health regulations, on top of the quality assurances and specifications of producers and industrial users. Compliance is underpinned by a large body of sensitive analytical methods.
The Codex Alimentarius, drawn up by a joint commission of the Food and Agriculture Organization and the World Health Organization of the United Nations, recommends international standards for white, powdered, and soft sugars, among other products. The basic white sugar standard lays down the minimum content of sucrose and the maximum contents of invert sugar, conductivity ash, sulfur dioxide (a processing aid), and the contaminants arsenic, copper, and lead. Binding regulations impose similar specifications across the European Union. The U.S. Food Chemical Codex is an example of controls at the national level. Since sucrose is used in pharmaceutical preparations as a binder, bulking agent, and taste corrective, it is also included in international and national lists of drugs and medicinal preparations.
Virtually a pure carbohydrate—even raw sugar supplies practically no minerals or vitamins, no fiber, and no protein—sugar is widely attacked on nutritional and health grounds. The safety aspects of sugar and its impact on human health have been extensively examined by scientists and reviewed by expert committees such as the U.S. Food and Drug Administration (FDA) Sugars Task Force and the British Nutrition Foundation's Task Force on Sugars and Syrups. On the evidence, the consumption of sugar and other fermentable carbohydrates contributes significantly to the incidence of dental caries, which have multiple causes, however. Other than that, no conclusive proof has been found that dietary sugars pose a health hazard to the general public. They are not related to diabetes, except as a nonspecific energy source, nor to behavioral changes. They do not have a unique role as a cause of obesity or constitute an independent risk factor in cardiovascular disease, gallstones, cancer, or hypertension.
History. The word "sugar," like its cognates in many languages, comes ultimately from Sanskrit. Crystalline sugar has been made in northern India since the fifth century b.c.e., if not earlier. Sugar in solid form, possibly imported from Indochina, was also known in China by the third century c.e. To the west, however, the comparatively short move of the industry from India into Persia did not take place until c.600 c.e. From there, it rapidly diffused westward across the Middle East in the train of Arab expansion.
For the better part of 900 years between 700 and 1600, sugar production outside of Asia flourished on the islands and around the shores of the Mediterranean, with Venice initially the foremost center of refining and trading. The second half of the period saw the first exports to central and northern Europe, triggering what Sidney Mintz has called "the conquest of honey by sucrose," albeit that sugar was still a rare and expensive luxury, its use confined to kings and nobles. The Mediterranean industry began to decline from about 1450 onwards, in parallel with the appearance of more efficient producers in the new Portuguese and Spanish colonies in the eastern Atlantic and the Americas, although that was not the sole reason. For a while, Madeira, the Canaries, and São Tomé figured prominently in the burgeoning international sugar trade, forerunners of the West Indian "sugar colonies" and "sugar islands" that Adam Smith spoke of in his Wealth of Nations. But, like the Mediterranean industry, they, too, could not match the natural conditions and space for growing sugar cane that lay waiting in the Western Hemisphere.
When Christopher Columbus carried sugar cane to the Americas on his second voyage in 1493, shortly followed by other Spanish and Portuguese explorers with their cargoes, the seed was sown for a vast expansion of the industry. Within a few decades, supplies doubled and doubled again, prices fell, and consumption extended to the middle classes. Still, about a century and a half after sugar from Brazil and Hispaniola became the first example of profitable agricultural exports from the Western Hemisphere, average per capita sugar consumption in Britain in the first decade of the 1700s is estimated to have amounted to just four pounds a year, less than two kilograms, or about a teaspoonful a day. On the other side of the Atlantic, the growth of the sugar industry had lasting political, economic, social, and cultural consequences: based on plantation agriculture and slavery on a scale many times greater than previously seen in the Old World, it was instrumental in the formation of new nations.
Until the early 1800s, cane sugar had the field to itself, leaving aside sweeteners of no more than regional significance. Honey was a competitor only so long as sugar was still a costly rarity. Even then, the two products complemented as much as competed with each other. All that changed with the arrival of beet sugar early in the nineteenth century, a historically significant event aptly described by Timoshenko and Swerling as "the earliest example of the market for an important tropical product being seriously eroded by the application of modern scientific methods in relatively advanced countries." Extraordinarily, the challenge came not from a substitute but from what was, for all practical purposes, the identical substance, obtained from an entirely different plant. High-grade refined sugar from beet or cane is indistinguishable except by analytical methods that find the difference in the carbon isotope ratio (13C/12C).
Beet sugar added another dimension to the world sugar economy. It allowed temperate zone countries to produce their own sucrose and greatly increased global availabilities, so that sugar could become a staple item of consumption for all classes of society. By 1880, Austria-Hungary, France, Germany, and Russia were turning out beet sugar on a scale comparable to the largest cane sugar producers. Europe's beet sugar industries contributed enormously to its economic development in the second half of the nineteenth century. The Germany of the 1890s, for instance, had around 400 beet sugar factories, producing roughly one-and-a-half million metric tons of beet sugar a year, and sugar briefly headed the list of German merchandise exports. In his work Der moderne Kapitalismus, the German economist Werner Sombart wrote: "The sugar and distilling industries were the industrial sectors through which Germany developed into a great capitalist power, rather as the cotton and iron industries laid the basis for England's greatness."
Nowadays, most countries cover their requirements at least partially with homegrown sugar, and some that do not, such as New Zealand, possess a refinery to process raw sugar imports. The bulk of the world's sugar is today consumed in the countries where it is produced. Not surprisingly, in view of its sundry roles, sugar has become deeply embedded in politics over the centuries, and how much is produced and where is heavily influenced by tariffs, taxation, and subsidies.
Several industry-specific factors have favored the growth of sugar production and consumption throughout history. Sugar's multiple functions, from its first uses as a medicine and condiment, have clearly been an advantage in boosting consumption. So was its long-time association in Europe with wealth and standing—demonstrated, for instance, by its conspicuous display in molded table decorations. In modern parlance, sugar enjoyed "snob appeal." Economists would say that it had a high positive-income elasticity of demand and confirmed Say's law that supply creates its own demand. Even as sugar becomes an inferior good in highly developed countries, consumption is sustained by increased demand for things like ice cream, sweets, and soft drinks, so long, of course, as these continue to be made with sugar and not other sweeteners.
On the production side, the by-products of sugar processing have always played a significant role in the viability of the industry. Sugar mills in many parts of tropical America survived deforestation and the scarcity of firewood because sugar cane brought its own fuel in the form of bagasse, the fibrous processing residue. Indeed, a modern raw cane sugar factory normally produces more bagasse or steam than it needs. The corresponding residue in the beet sugar industry—pulp—provides valuable fodder. Molasses, a by-product in both industries, is likewise utilized directly or in mixed feeds, or as a raw material for fermentation products. Students of U.S. history will be familiar with John Adams's statement in 1775: "I know not why we should blush to confess that molasses was an essential ingredient in American independence. Many great events have proceeded from much smaller causes."
The very nature of the industry facilitated its diffusion to and growth in new territories. A state-of-the-art sugar factory, operating at top technical efficiency, is an extremely sophisticated business—science-inspired, instrument-controlled, and automated. In essence, however, the methods of sugar processing are simple and robust. Although economies of scale have led to ever larger plants, sugar can be made in a wide range of plant sizes. The processes involved are easily scaled up, and factories can be enlarged and updated piecemeal by retrofitting new equipment. Right down to the present, the world cane sugar industry exhibits a technological diversity ranging from back-yard producers of a few tons of sugar, similar to that made centuries ago, to huge installations, pouring out hundreds of thousands of tons a year of high-grade product.
Technology. Sugar processing is basically a series of solid-liquid separations. The core processing stages are: (1) extraction of the juice, with bagasse or pulp the residue; (2) purification of the juice, removing nonsucrose substances; (3) concentration of the purified juice to syrup by evaporating water; (4) crystallization of the sucrose in the syrup by further evaporation; (5) separation of the crystals from the syrup. The methods employed after juice extraction determine the end product. One way leads to raw sugar, which is refined—on site or in a separate plant—by washing and redissolving the crystals and further clarifying and decolorizing the resulting solution. The clear syrup is then again boiled until crystals form, or made into liquid sugar. Much of the world's cane sugar is produced in this way. The alternative is to make white sugar directly after complex purification of the juice, the procedure followed in some cane-sugar factories and throughout the beet-sugar industry.
For two thousand years, machinery, apparatus, and processes underwent a slow and gradual evolution, highlighted by the crucial seventeenth-century innovations of the three-roller mill and the battery of cauldrons, which, once fitted with a single furnace and continuous internal flue, became known as the Jamaica train and survives to this day among small-scale producers of open-pan sugars (not made in closed vessels under vacuum). Development accelerated with the introduction of steam and the rise of industrial chemistry in the nineteenth century. By about 1880 the basic tool kit of the sugar industry was virtually complete, and that date marks the beginning of the modern era in sugar production.
High fructose syrups (HFS) and other caloric sweeteners. Sucrose substitutes fall into two categories: nutritive or caloric substances, which, like sucrose, provide energy and bulk, and high-intensity sweeteners, used principally for their sweetening power, although that is not their only property. The discovery of how to convert starch into sugar (saccharification) in 1811 was the first step toward the development of serious commercial competitors to cane and beet sugar of the first kind. Still, the glucose syrups produced over the next 150 years were less sweet than invert sugar syrup, which restricted their range of industrial applications. That limitation was lifted by the invention of isomerization processes leading to high-fructose syrup, known as high-fructose corn syrup in North America and isoglucose in Europe. While glucose syrups continued to be made, world HFS production rose in less than forty years from zero to an estimated 13.1 million tons, dry weight, in 2001/2002. The United States accounted for 73 percent of global output; another 18 percent was shared by Japan, the European Union, Turkey, South Korea, Canada, and Argentina, and the remainder by more than a dozen other countries.
Location and volume of HFS production are conditioned by several factors:
- Price: World sugar price booms in 1963, 1974, and 1980 greatly stimulated development. In the United States and Japan, two large sugar importers, HFS progressed under the umbrella of protective sugar regimes that kept sugar prices at an artificial level and ensured that, however much HFS manufacturers undercut the price of sucrose, displacement of the latter reduced sugar imports and did not impair domestic sugar production;
- Starch supply: Ample supplies of starch at a competitive cost, net of by-product proceeds;
- Consumer demand: Sufficient sweetener consumption in the form of processed foods and beverages, and the existence of bulk-handling facilities for liquid products;
- Money: Financial resources for investment in research and development as well as in capital-intensive plants and equipment;
- Political climate: Supportive, or at least permissive, government policies; in the European Union, however, isoglucose manufacture—and, more recently, also that of insulin syrup—has been restrained, first by a levy, then by production quotas.
Besides syrups, starch saccharification leads to dextrose or crystallized glucose. Sold in anhydrous (at least 98 percent solids) or monohydrate (at least 90 percent solids) form, dextrose is used in food and other industries.
Also employed industrially as bulking, humectant (moisturizing), and texturizing agents and in diabetic foods are various sugar alcohols or polyols. These have lower calorific values than sucrose and, with the exception of xylitol, only about half the sweetening power. The main one, sorbitol, occurs naturally in many plants—as does its isomer, mannitol—and is used, among other things, to synthesize ascorbic acid (vitamin C). It is commercially obtained by the hydrogenation of glucose or of invert sugar, the latter yielding equimolar amounts of sorbitol and mannitol from the fructose and sorbitol only from the glucose. Other members of this class are maltitol, produced by hydrogenation from high-maltose syrup; isomalt, for which sucrose is the feedstock; xylitol, made from xylose-containing materials, such as corncobs and birchwood sawdust; and erythritol, found in lichens and made from glucose by fermentation.
High-intensity sweeteners. Artificial or natural substances with many times the sweetening power of sucrose, but no or negligible calorific value as used, are known as high-intensity sweeteners. Saccharin, the oldest of the kind, is about 300 times as sweet as sucrose. A derivative of the tar product toluene, it first achieved some market significance during the sugar shortages caused by World War I, when it began to be used as a substitute by people besides those who were unable to tolerate sugar. Newer sweeteners have, to a considerable extent, displaced saccharin, but it continues in demand, particularly in Asia, because it costs a small fraction of the price of sugar in terms of sweetness equivalence. Another older artificial sweetener, cyclamate, roughly thirty times as sweet as sugar, was discovered in 1937 and became popular after World War II, usually in combination with saccharin. Together, each masks the unsatisfactory taste of the other, producing an overall taste profile thought to approximate that of sugar.
Such blending of different sweeteners, nutritive as well as high-intensity, is a striking feature of sweetener usage in processed foods and beverages. One advantage lies in the resultant synergism—the sweetness effect of the mixture is greater than the sum of the sweetening powers of the individual components, enabling manufacturers to save costs and label certain products "reduced calorie." Blends may also produce other taste synergies and enhance the stability of the product.
The scope for blending was greatly increased in recent decades with the introduction of aspartame and acesulfame–K. Aspartame, a methylated amino acid dipeptide, actually has the same calorific value as sugar, but is about 180 times sweeter. Its taste profile closely resembles that of sucrose and, unlike saccharin, it has no bitter aftertaste. Widely used as a tabletop sweetener, aspartame is not suitable for all processed products because it can lose sweetness, depending on temperature, moisture, and degree of acidity. In contrast, acesulfame-K, the potassium salt of methyl oxathiazinone dioxide roughly 200 times as sweet as sugar, while more expensive, is very stable, blends well with other sweeteners, and is highly synergistic.
The latest artificial sweetener to acquire significant market presence is sucralose, which is 600 times sweeter than sugar. Technically trichloro-galactosaccharose, sucralose is actually made from sugar. It has the advantages of a good taste profile and of being acid and temperature stable. Several other substances, some with many thousand times the sweetness intensity of sugar, are waiting in the wings. High-intensity sweeteners are classified as food additives and require approval by national food safety authorities. Gaining approval tends to be a lengthy procedure and, once given, can be withdrawn. In the United States, for instance, cyclamate was banned in 1970, but it is allowed in many other countries.
Sucrose remains the benchmark against which the quality and price of substitutes are judged, but it has lost its former virtual monopoly as the sweetener and conditioner of food and drink. Not all the growth of nonsucrose sweeteners has been at the expense of sugar. Some of it reflects the development of new products, such as diet soft drinks. In certain applications, sugar and other sweeteners have to be blended in order to achieve the desired texture and consistency. Moreover, nonsucrose sweeteners compete not only against sugar, but also among themselves: aspartame against saccharin, and diet soft drinks sweetened with high-intensity sweeteners against regular soft drinks sweetened with HFS. Only in the United States was sucrose no longer the dominant sweetener at the beginning of the twenty-first century. Globally, sucrose still accounted for 70 percent or more of world sweetener consumption.
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