E numbers are codes for substances that are permitted to be used as food additives for use within the European Union and EFTA. The "E" stands for "Europe". Found on food labels, their safety assessment and approval are the responsibility of the European Food Safety Authority. Having a single unified list for food additives was first agreed upon in 1962 with food colouring. In 1964, the directives for preservatives were added, 1970 for antioxidants and 1974 for the emulsifiers, stabilisers and gelling agents; the numbering scheme follows that of the International Numbering System as determined by the Codex Alimentarius committee, though only a subset of the INS additives are approved for use in the European Union as food additives. Outside the European continent plus Russia, E numbers are encountered on food labelling in other jurisdictions, including the Cooperation Council for the Arab States of the Gulf, South Africa, New Zealand and Israel, they are though still found on North American packaging on imported European products.
In some European countries, "E number" is sometimes used informally as a pejorative term for artificial food additives, products may promote themselves as "free of E numbers". This is incorrect, because many components of natural foods have assigned E numbers, e.g. vitamin C and lycopene, found in carrots. NB: Not all examples of a class fall into the given numeric range. Moreover, many chemicals in the E400–499 range, have a variety of purposes; the list shows all components that had an E-number assigned. Not all additives listed are still allowed in the EU, but are listed as they used to have an E-number. For an overview of allowed additives see information provided by the Food Standards Agency of the UK. Food Chemicals Codex List of food additives List of food additives, Codex Alimentarius Codex Alimentarius, the international foods standards, established by the Food and Agriculture Organization and the World Health Organization in 1963 See their document "Class Names and the International Numbering System for Food Additives" Joint FAO/WHO Expert Committee on Food Additives publications at the World Health Organization Food Additive Index, JECFA, Food and Agriculture Organization E-codes and ingredients search engine with details/suggestions for Muslims Current EU approved additives and their E Numbers Food Additives in the European Union Food Additives, Food Safety, website of the European Union.
Includes Lists of authorised food additives Food additives database The Food Additives and Ingredients Association, FAIA website, UK
Soy sauce is a liquid condiment of Chinese origin, made from a fermented paste of soybeans, roasted grain and Aspergillus oryzae or Aspergillus sojae molds. Soy sauce in its current form was created about 2,200 years ago during the Western Han dynasty of ancient China, spread throughout East and Southeast Asia where it is used in cooking and as a condiment. Soy sauce is considered as old as soy paste—a type of fermented paste obtained from soybeans—which had appeared during the Western Han dynasty and was listed in the bamboo slips found in the archaeological site Mawangdui. There are several precursors of soy sauce. Among them the earliest one is Qingjiang, listed in Simin Yueling. Others are Jiangqing and Chiqing which are recorded in Qimin Yaoshu in AD 540. By the time of the Song dynasty, the term soy sauce had become the accepted name for the liquid condiment, which are documented in two books: Shanjia Qinggong and Pujiang Wushi Zhongkuilu during the Song dynasty. Like many salty condiments, soy sauce was a way to stretch salt an expensive commodity.
During the Zhou dynasty of ancient China, fermented fish with salt was used as a condiment in which soybeans were included during the fermentation process. By the time of the Han dynasty, this had been replaced with the recipe for soy paste and its by-product soy sauce, by using soybeans as the principal ingredient, with fermented fish-based sauces developing separately into fish sauce; the 19th century Sinologist Samuel Wells Williams wrote that in China, the best soy sauce is "made by boiling beans soft, adding an equal quantity of wheat or barley, leaving the mass to ferment. The earliest soy sauce brewing in Korea seems to have begun prior to the era of the Three Kingdoms c. 57 BC. The Records of the Three Kingdoms, a Chinese historical text written and published in the 3rd century, mentions that "Goguryeo people are good at brewing fermented soy beans." In the section named Dongyi, in the Book of Wei. Jangdoks used for soy sauce brewing are found in the mural paintings of Anak Tomb No.3 from the 4th century Goguryeo.
In Samguk Sagi, a historical record of the Three Kingdoms era, it is written that ganjang and doenjang along with meju and jeotgal were prepared for the wedding ceremony of the King Sinmun in February 683. Sikhwaji, a section from Goryeosa, recorded that ganjang and doenjang were included in the relief supplies in 1018, after a Khitan invasion, in 1052, when a famine occurred. Joseon texts such as Guhwangchwaryo and Jeungbo sallim gyeongje contain the detailed procedures on how to brew good quality ganjang and doenjang. Gyuhap chongseo explains how to pick a date for brewing, what to forbear, how to keep and preserve ganjang and doenjang. Chinese Buddhist monks introduced soy sauce into Japan in the 7th century, where it is known as shōyu. Records of the Dutch East India Company list soy sauce as a commodity in 1737, when seventy-five large barrels were shipped from Dejima, Japan, to Batavia on the island of Java. Thirty-five barrels from that shipment were shipped to the Netherlands. In the 18th century and scholar Isaac Titsingh published accounts of brewing soy sauce.
Although earlier descriptions of soy sauce had been disseminated in the West, his was among the earliest to focus on the brewing of the Japanese version. By the mid-19th century, Japanese soy sauce disappeared from the European market, the condiment became synonymous with the Chinese product. Europeans were unable to make soy sauce because they did not understand the function of Aspergillus oryzae, the fungus used in its brewing. Soy sauce made from ingredients such as Portobello mushrooms were disseminated in European cookbooks during the late 18th century. A Swedish recipe for "Soija" was published in the 1770 edition of Cajsa Warg's Hjelpreda i Hushållningen för Unga Fruentimber and was flavored with allspice and mace. Soy sauce is made either by hydrolysis; some commercial sauces have both chemical sauces. Flavor and aroma developments during production are attributed to non-enzymatic Maillard browning. Variation is achieved as the result of different methods and durations of fermentation, different ratios of water and fermented soy, or through the addition of other ingredients.
Traditional soy sauces are made by mixing soybeans and grain with mold cultures such as Aspergillus oryzae and other related microorganisms and yeasts. The mixture was fermented in large urns and under the sun, believed to contribute extra flavors. Today, the mixture is placed in a humidity controlled incubation chamber. Traditional soy sauces take months to make: Soaking and cooking: The soybeans are soaked in water and boiled until cooked. Wheat is roasted, crushed. Koji culturing: An equal amount of boiled soybeans and roasted wheat are mixed to form a grain mixture. A culture of Aspergillus spore is added to the grain mixture and mixed or the mixture is allowed to gather spores from the environment itself; the cultures include: Aspergillus: a genus of fungus, used for f
Wine is an alcoholic drink made from fermented grapes. Yeast consumes the sugar in the grapes and converts it to ethanol, carbon dioxide, heat. Different varieties of grapes and strains of yeasts produce different styles of wine; these variations result from the complex interactions between the biochemical development of the grape, the reactions involved in fermentation, the terroir, the production process. Many countries enact legal appellations intended to define qualities of wine; these restrict the geographical origin and permitted varieties of grapes, as well as other aspects of wine production. Wines not made from grapes include rice wine and fruit wines such as plum, pomegranate and elderberry. Wine has been produced for thousands of years; the earliest known traces of wine are from Georgia and Sicily although there is evidence of a similar alcoholic drink being consumed earlier in China. The earliest known winery is the 6,100-year-old Areni-1 winery in Armenia. Wine reached the Balkans by 4500 BC and was consumed and celebrated in ancient Greece and Rome.
Throughout history, wine has been consumed for its intoxicating effects. Wine has long played an important role in religion. Red wine was associated with blood by the ancient Egyptians and was used by both the Greek cult of Dionysus and the Romans in their Bacchanalia; the earliest archaeological and archaeobotanical evidence for grape wine and viniculture, dating to 6000–5800 BC was found on the territory of modern Georgia. Both archaeological and genetic evidence suggest that the earliest production of wine elsewhere was later having taken place in the Southern Caucasus, or the West Asian region between Eastern Turkey, northern Iran; the earliest evidence of a grape-based fermented drink was found in China, Georgia from 6000 BC, Iran from 5000 BC, Sicily from 4000 BC. The earliest evidence of a wine production facility is the Areni-1 winery in Armenia and is at least 6100 years old. A 2003 report by archaeologists indicates a possibility that grapes were mixed with rice to produce mixed fermented drinks in China in the early years of the seventh millennium BC.
Pottery jars from the Neolithic site of Jiahu, contained traces of tartaric acid and other organic compounds found in wine. However, other fruits indigenous to the region, such as hawthorn, cannot be ruled out. If these drinks, which seem to be the precursors of rice wine, included grapes rather than other fruits, they would have been any of the several dozen indigenous wild species in China, rather than Vitis vinifera, introduced there 6000 years later; the spread of wine culture westwards was most due to the Phoenicians who spread outward from a base of city-states along the Mediterranean coast of what are today Syria, Lebanon and Palestine. The wines of Byblos were exported to Egypt during the Old Kingdom and throughout the Mediterranean. Evidence includes two Phoenician shipwrecks from 750 BC discovered by Robert Ballard, whose cargo of wine was still intact; as the first great traders in wine, the Phoenicians seem to have protected it from oxidation with a layer of olive oil, followed by a seal of pinewood and resin, similar to retsina.
Although the nuragic Sardinians consumed wine before the arrival of the Phoenicians The earliest remains of Apadana Palace in Persepolis dating back to 515 BC include carvings depicting soldiers from Achaemenid Empire subject nations bringing gifts to the Achaemenid king, among them Armenians bringing their famous wine. Literary references to wine are abundant in Homer and others. In ancient Egypt, six of 36 wine amphoras were found in the tomb of King Tutankhamun bearing the name "Kha'y", a royal chief vintner. Five of these amphoras were designated as originating from the king's personal estate, with the sixth from the estate of the royal house of Aten. Traces of wine have been found in central Asian Xinjiang in modern-day China, dating from the second and first millennia BC; the first known mention of grape-based wines in India is from the late 4th-century BC writings of Chanakya, the chief minister of Emperor Chandragupta Maurya. In his writings, Chanakya condemns the use of alcohol while chronicling the emperor and his court's frequent indulgence of a style of wine known as madhu.
The ancient Romans planted vineyards near garrison towns so wine could be produced locally rather than shipped over long distances. Some of these areas are now world-renowned for wine production; the Romans discovered that burning sulfur candles inside empty wine vessels kept them fresh and free from a vinegar smell. In medieval Europe, the Roman Catholic Church supported wine because the clergy required it for the Mass. Monks in France made wine for years. An old English recipe that survived in various forms until the 19th century calls for refining white wine from bastard—bad or tainted bastardo wine; the English word "wine" comes from the Proto-Germanic *winam, an early borrowing from the Latin vinum, "wine" or " vine", itself derived from the Proto-Indo-European stem *win-o-. The earliest attested terms referring to wine are the Mycenaean Greek me-tu-wo ne-wo, meaning "in" or " of the new wine", wo-no-wa-ti-si, meaning "wine garden", written in Linear B inscriptions. Linear B includes, inter alia, an ideogram for wine
Sulfites or sulphites are compounds that contain the sulfite ion, SO2−3. The sulfite ion is the conjugate base of bisulfite. Although its acid is elusive, its salts are used. Sulfites are substances that occur in some foods and the human body, they are used as regulated food additives. The structure of the sulfite anion can be described with three equivalent resonance structures. In each resonance structure, the sulfur atom is double-bonded to one oxygen atom with a formal charge of zero, sulfur is singly bonded to the other two oxygen atoms, which each carry a formal charge of −1, together accounting for the −2 charge on the anion. There is a non-bonded lone pair on the sulfur, so the structure predicted by VSEPR theory is trigonal pyramidal, as in ammonia. In the hybrid resonance structure, the S-O bonds are equivalently of one-third. Evidence from 17O NMR spectroscopic data suggests that protonation of the sulfite ion gives a mixture of isomers: Sulfites are used as a food preservative or enhancer.
They may come in various forms, such as: Sulfur dioxide, not a sulfite, but a related chemical oxide Potassium bisulfite or potassium metabisulfite Sodium bisulfite, sodium metabisulfite or sodium sulfite Sulfites occur in all wines to some extent. Sulfites are introduced to arrest fermentation at a desired time, may be added to wine as preservatives to prevent spoilage and oxidation at several stages of the winemaking. Sulfur dioxide protects wine from not only oxidation, but from bacteria. Without sulfites, grape juice would turn to vinegar. Organic wines are not sulfite-free, but have lower amounts and regulations stipulate lower maximum sulfite contents for these wines. In general, white wines contain more sulfites than red wines and sweeter wines contain more sulfites than drier ones. In the United States, wines bottled after mid-1987 must have a label stating that they contain sulfites if they contain more than 10 parts per million. In the European Union an equivalent regulation came into force in November 2005.
In 2012, a new regulation for organic wines came into force. In the United Kingdom, similar laws apply. Bottles of wine that contain over 10 mg/l sulfites are required to bear "contains sulphites" on the label; this does not differ whether sulfites are occurring or added in the winemaking process. Sulfites are used as preservatives in dried fruits, preserved radish, dried potato products. Most beers no longer contain sulfites. Although shrimp are sometimes treated with sulfites on fishing vessels, the chemical may not appear on the label. In 1986, the Food and Drug Administration in the United States banned the addition of sulfites to all fresh fruit and vegetables that are eaten raw. E numbers for sulfites as food additives are: Allergic reactions to sulfites appear to be rare in the general population, but more common in hyperallergic individuals. Sulfites are counted among the top nine food allergens, but a reaction to sulfite is not a true allergy; some people have positive skin allergy tests to sulfites indicating true allergy.
Chronic skin conditions in the hands and face have been reported in individuals that use cosmetics or medications containing sulfites. Occupational exposure to sulfites has been reported to cause persistent skin symptoms, it may cause breathing difficulty within minutes after eating a food containing it. Asthmatics and people with salicylate sensitivity are at an elevated risk for reaction to sulfites. Anaphylaxis and life-threatening reactions are rare. Other potential symptoms include sneezing, swelling of the throat and migraine. A 2017 study has shown negative impacts of sulfites on bacteria found in the human microbiome. In 1986, the U. S. Food and Drug Administration banned the use of sulfites as preservatives on foods intended to be eaten fresh; this has contributed to its salts as preservatives. U. S. labeling regulations do not require products to indicate the presence of sulfites in foods unless it is added as a preservative. And sulfites used in food processing are required to be listed if they are not incidental additives and if there are more than 10 parts per million in the finished product Products to contain sulfites at less than 10ppm do not require ingredients labels, the presence of sulfites is undisclosed.
In Australia and New Zealand, sulfites must be declared in the statement of ingredients when present in packaged foods in concentrations of 10 mg/kg or more as an ingredient. In the United Kingdom sulfites are included in the list of known allergens and should the concentration of sulfites exceed 10 ppm, bottles of wine should bear the warning'contains sulphites' Sulfites that can be added to foods in Canada are potassium bisulfite, potassium metabisulfite, sodium bisulfite, sodium dithionite, sodium metabisulfite, sodium sulfite, sulfur dioxide and sulfurous acid; these can be declared using the common names sulfites, sulfiting agents. High sulfite content in the blood and urine of babies can be caused by molybdenum cofactor deficiency disease which leads to neurological damage and early death unless
Foodborne illness is any illness resulting from the spoilage of contaminated food, pathogenic bacteria, viruses, or parasites that contaminate food, as well as toxins such as poisonous mushrooms and various species of beans that have not been boiled for at least 10 minutes. Symptoms vary depending on the cause, are described below in this article. A few broad generalizations can be made, e.g.: the incubation period ranges from hours to days, depending on the cause and on how much was consumed. The incubation period tends to cause sufferers to not associate the symptoms with the item consumed, so to cause sufferers to attribute the symptoms to gastroenteritis for example. Symptoms include vomiting and aches, may include diarrhea. Bouts of vomiting can be repeated with an extended delay in between, because if infected food was eliminated from the stomach in the first bout, like bacteria, can pass through the stomach into the intestine and begin to multiply; some types of microbes stay in the intestine, some produce a toxin, absorbed into the bloodstream, some can directly invade deeper body tissues.
Foodborne illness arises from improper handling, preparation, or food storage. Good hygiene practices before and after food preparation can reduce the chances of contracting an illness. There is a consensus in the public health community that regular hand-washing is one of the most effective defenses against the spread of foodborne illness; the action of monitoring food to ensure that it will not cause foodborne illness is known as food safety. Foodborne disease can be caused by a large variety of toxins that affect the environment. Furthermore, foodborne illness can be caused by pesticides or medicines in food and natural toxic substances such as poisonous mushrooms or reef fish. Bacteria are a common cause of foodborne illness. In the United Kingdom during 2000, the individual bacteria involved were the following: Campylobacter jejuni 77.3%, Salmonella 20.9%, Escherichia coli O157:H7 1.4%, all others less than 0.56%. In the past, bacterial infections were thought to be more prevalent because few places had the capability to test for norovirus and no active surveillance was being done for this particular agent.
Toxins from bacterial infections are delayed. As a result, symptoms associated with intoxication are not seen until 12–72 hours or more after eating contaminated food. However, in some cases, such as Staphylococcal food poisoning, the onset of illness can be as soon as 30 minutes after ingesting contaminated food. Most common bacterial foodborne pathogens are: Campylobacter jejuni which can lead to secondary Guillain–Barré syndrome and periodontitis Clostridium perfringens, the "cafeteria germ" Salmonella spp. – its S. typhimurium infection is caused by consumption of eggs or poultry that are not adequately cooked or by other interactive human-animal pathogens Escherichia coli O157:H7 enterohemorrhagic which can cause hemolytic-uremic syndromeOther common bacterial foodborne pathogens are: Bacillus cereus Escherichia coli, other virulence properties, such as enteroinvasive, enterotoxigenic, enteroaggregative Listeria monocytogenes Shigella spp. Staphylococcus aureus Staphylococcal enteritis Streptococcus Vibrio cholerae, including O1 and non-O1 Vibrio parahaemolyticus Vibrio vulnificus Yersinia enterocolitica and Yersinia pseudotuberculosisLess common bacterial agents: Brucella spp.
Corynebacterium ulcerans Coxiella burnetii or Q fever Plesiomonas shigelloides In addition to disease caused by direct bacterial infection, some foodborne illnesses are caused by enterotoxins. Enterotoxins can produce illness when the microbes that produced them have been killed. Symptom appearance varies with the toxin but may be rapid in onset, as in the case of enterotoxins of Staphylococcus aureus in which symptoms appear in one to six hours; this causes intense vomiting including or not including diarrhea, staphylococcal enterotoxins are the most reported enterotoxins although cases of poisoning are underestimated. It occurs in cooked and processed foods due to competition with other biota in raw foods, humans are the main cause of contamination as a substantial percentage of humans are persistent carriers of S. aureus. The CDC has estimated about 240,000 cases per year in the United States. Clostridium botulinum Clostridium perfringens Bacillus cereusThe rare but deadly disease botulism occurs when the anaerobic bacterium Clostridium botulinum grows in improperly canned low-acid foods and produces botulin, a powerful paralytic toxin.
Pseudoalteromonas tetraodonis, certain species of Pseudomonas and Vibrio, some other bacteria, produce the lethal tetrodotoxin, present in the tissues of some living animal species rather than being a product of decomposition. Many foodborne illnesses remain poorly understood. Aeromonas hydrophila, Aeromonas caviae, Aeromonas sobria Prevention is the role of the state, through the definition of strict rules of hygiene and a public services of veterinary surveying of animal products in the food chain, from farming to the transformation industry and delivery; this regulation includes: traceability: in a final product, it must be possible to know the origin of the ingredients and where and when it was processed.
Fruit preserves are preparations of fruits and sugar stored in glass jam jars. Many varieties of fruit preserves are made globally, including sweet fruit preserves, such as those made from strawberry or apricot, savory preserves, such as those made from tomatoes or squash; the ingredients used and how they are prepared determine the type of preserves. In English, the word, in plural form, "preserves" is used to describe all types of jellies; the term preserves is interchangeable with jams. Other names include: chutney, conserve, fruit butter, fruit curd, fruit spread and marmalade; some cookbooks define preserves as cooked and gelled whole fruit, which includes a significant portion of the fruit. In the English speaking world, the two terms are more differentiated and, when this is not the case, the more usual generic term is'jam'; the singular preserve or conserve is used as a collective noun for high fruit content jam for marketing purposes. Additionally, the name of the type of fruit preserves will vary depending on the regional variant of English being used.
A chutney is a relish of Indian origin made of fruit and herbs. Although intended to be eaten soon after production, modern chutneys are made to be sold, so require preservatives – sugar and vinegar – to ensure they have a suitable shelf life. Mango chutney, for example, is mangoes reduced with sugar. While confit, the past participle of the French verb confire, "to preserve", is most applied to preservation of meats, it is used for fruits or vegetables seasoned and cooked with honey or sugar till jam-like. Savory confits, such as ones made with garlic or fennel, may call for a savory oil, such as virgin olive oil, as the preserving agent. Konfyt is a type of jam eaten in Southern Africa, it is made by boiling selected fruit or fruits and sugar, optionally adding a small quantity of ginger to enhance the flavour. The origins of the jam is obscure but it is theorized that it came from the French; the word is based on the French term confiture via the Dutch confijt. A conserve, or whole fruit jam, is a preserve made of fruit stewed in sugar.
Traditional whole fruit preserves are popular in Eastern Europe where they are called varenye, the Baltic region where they're known by a native name in each of the countries, as well as in many regions of Western and Southern Asia, where they are referred to as murabba. The making of conserves can be trickier than making a standard jam; this process can be achieved by spreading the dry sugar over raw fruit in layers, leaving for several hours to steep into the fruit just heating the resulting mixture only to bring to the setting point. As a result of this minimal cooking, some fruits are not suitable for making into conserves, because they require cooking for longer periods to avoid issues such as tough skins. Currants and gooseberries, a number of plums are among these fruits; because of this shorter cooking period, not as much pectin will be released from the fruit, as such, conserves will sometimes be softer set than some jams. An alternative definition holds that conserves are preserves made from a mixture of fruits or vegetables.
Conserves may include dried fruit or nuts. Fruit butter, in this context, refers to a process where the whole fruit is forced through a sieve or blended after the heating process. "Fruit butters are made from larger fruits, such as apples, peaches or grapes. Cook until softened and run through a sieve to give a smooth consistency. After sieving, cook the pulp... add sugar and cook as as possible with constant stirring.… The finished product should mound up when dropped from a spoon, but should not cut like jelly. Neither should there be any free liquid."—Berolzheimer R et al. Fruit curd is a dessert topping and spread made with lemon, orange, or raspberry; the basic ingredients are beaten egg yolks, fruit juice and zest which are cooked together until thick and allowed to cool, forming a soft, intensely flavored spread. Some recipes include egg whites or butter. Although the FDA has Requirements for Specific Standardized Fruit Butters, Jellies and Related Products, there is no specification of the meaning of the term Fruit spread.
Although some assert it refers to a jam or preserve with no added sugar, there are many fruit spreads by leading manufacturers that do contain added sugar. This can be verified by searching the listings under fruit spread on common web sites, such as those of Amazon or Walmart, or to look at the ingredient list and nutritional information on specific fruit spread products. Jam contains both the juice and flesh of a fruit or vegetable, although one cookbook defines it as a cooked and jelled puree; the term "jam" refers to a product made of whole fruit cut into pieces or crushed heated with water and sugar to activate its pectin before being put into containers: "Jams are made from pulp and juice of one fruit, rather than a com
Citric acid is a weak organic acid that has the chemical formula C6H8O7. It occurs in citrus fruits. In biochemistry, it is an intermediate in the citric acid cycle, which occurs in the metabolism of all aerobic organisms. More than a million tons of citric acid are manufactured every year, it is used as an acidifier, as a flavoring and chelating agent. A citrate is a derivative of citric acid. An example of the former, a salt is trisodium citrate; when part of a salt, the formula of the citrate ion is written as C6H5O3−7 or C3H5O3−3. Citric acid exists in greater than trace amounts in a variety of fruits and vegetables, most notably citrus fruits. Lemons and limes have high concentrations of the acid; the concentrations of citric acid in citrus fruits range from 0.005 mol/L for oranges and grapefruits to 0.30 mol/L in lemons and limes. Within species, these values vary depending on the cultivar and the circumstances in which the fruit was grown. Industrial-scale citric acid production first began in 1890 based on the Italian citrus fruit industry, where the juice was treated with hydrated lime to precipitate calcium citrate, isolated and converted back to the acid using diluted sulfuric acid.
In 1893, C. Wehmer discovered. However, microbial production of citric acid did not become industrially important until World War I disrupted Italian citrus exports. In 1917, American food chemist James Currie discovered certain strains of the mold Aspergillus niger could be efficient citric acid producers, the pharmaceutical company Pfizer began industrial-level production using this technique two years followed by Citrique Belge in 1929. In this production technique, still the major industrial route to citric acid used today, cultures of A. niger are fed on a sucrose or glucose-containing medium to produce citric acid. The source of sugar is corn steep liquor, hydrolyzed corn starch or other inexpensive sugary solutions. After the mold is filtered out of the resulting solution, citric acid is isolated by precipitating it with calcium hydroxide to yield calcium citrate salt, from which citric acid is regenerated by treatment with sulfuric acid, as in the direct extraction from citrus fruit juice.
In 1977, a patent was granted to Lever Brothers for the chemical synthesis of citric acid starting either from aconitic or isocitrate/alloisocitrate calcium salts under high pressure conditions. This produced citric acid in near quantitative conversion under what appeared to be a reverse non-enzymatic Krebs cycle reaction. In 2007, worldwide annual production stood at 1,600,000 tons. More than 50% of this volume was produced in China. More than 50% was used as an acidity regulator in beverages, some 20% in other food applications, 20% for detergent applications and 10% for related applications other than food, such as cosmetics, pharmaceutics and in the chemical industry. Citric acid was first isolated in 1784 by the chemist Carl Wilhelm Scheele, who crystallized it from lemon juice, it can exist either as a monohydrate. The anhydrous form crystallizes from hot water, while the monohydrate forms when citric acid is crystallized from cold water; the monohydrate can be converted to the anhydrous form at about 78 °C.
Citric acid dissolves in absolute ethanol at 15 °C. It decomposes with loss of carbon dioxide above about 175 °C. Citric acid is considered to be a tribasic acid, with pKa values, extrapolated to zero ionic strength, of 5.21, 4.28 and 2.92 at 25 °C. The pKa of the hydroxyl group has been found, by means of 13C NMR spectroscopy, to be 14.4. The speciation diagram shows that solutions of citric acid are buffer solutions between about pH 2 and pH 8. In biological systems around pH 7, the two species present are the citrate ion and mono-hydrogen citrate ion; the SSC 20X hybridization buffer is an example in common use. Tables compiled for biochemical studies are available. On the other hand, the pH of a 1 mM solution of citric acid will be about 3.2. The pH of fruit juices from citrus fruits like oranges and lemons depends on the citric acid concentration, being lower for higher acid concentration and conversely. Acid salts of citric acid can be prepared by careful adjustment of the pH before crystallizing the compound.
See, for example, sodium citrate. The citrate ion forms complexes with metallic cations; the stability constants for the formation of these complexes are quite large because of the chelate effect. It forms complexes with alkali metal cations. However, when a chelate complex is formed using all three carboxylate groups, the chelate rings have 7 and 8 members, which are less stable thermodynamically than smaller chelate rings. In consequence, the hydroxyl group can be deprotonated, forming part of a more stable 5-membered ring, as in ammonium ferric citrate, 5Fe2·2H2O. Citric acid can be esterified at one or more of the carboxylic acid functional groups on the molecule, to form any of a variety of mono-, di-, tri-, mixed esters. Citrate is an intermediate in the TCA cycle, a central metabolic pathway for animals and bacteria. Citrate synthase catalyzes the condensation of oxaloacetate with acetyl CoA to form citrate. Citrate acts as the substrate for aconitase and is converted into aconitic acid.
The cycle ends with regeneration of oxaloacetate. This series