Citric acid, calcium salt

Citric Acid Separation. Citric acid [77-92-9] and other organic acids can be recovered from fermentation broths usiag the UOP Sorbex technology (90—92). The conventional means of recovering citric acid is by a lime and sulfuric acid process ia which the citric acid is first precipitated as a calcium salt and then reacidulated with sulfuric acid. However, this process generates significant by-products and thus can become iaefficient. 

Two types of magnesia, caustic-calcined and periclase (a refractory material), are derived from dolomitic lime. Lime is required in refining food-grade salt, citric acid, propjiene and ethylene oxides, and ethylene glycol, precipitated calcium carbonate, and organic salts, such as calcium stearate, lactate, caseinate. 

Evaporated milk is a Hquid product obtained by the partial removal of water only from milk. It has a minimum milk-fat content of 7.5 mol % and a minimum milk-solids content of 25.0 mol %. Evaporated skimmed milk is a Hquid product obtained by the partial removal of water only from skimmed milk. It has a minimum milk-solids content of 20.0 mol %. Sweetened condensed milk is a product obtained by the partial removal of water only from milk with the addition of sugars. It has a minimum milk-fat content of 8.0 mol % and a minimum milk-solids content of 28.0 mol %. Skimmed sweetened condensed milk is a product obtained by the partial removal of water only from skimmed milk with the addition of sugars. It has a minimum milk-solids content of 24.0 mol %. AH may contain food additives (qv) as stabilizers, in maximum amounts, including sodium, potassium, and calcium salts of hydrochloric acid at 2000 mg/kg singly citric acid, carbonic acid, orthophosphoric acid, and polyphosphoric acid at 3000 mg/kg in combination, expressed as anhydrous substances and in the evaporated milk carrageenin may be added at 150 mg/kg. 

Lime-Sulfuric. Recovery of citric acid by calcium salt precipitation is shown in Figure 3. Although the chemistry is straightforward, the engineering principles, separation techniques, and unit operations employed result in a complex commercial process. The fermentation broth, which has been separated from the insoluble biomass, is treated with a calcium hydroxide (lime) slurry to precipitate calcium citrate. After sufficient reaction time, the calcium citrate slurry is filtered and the filter cake washed free of soluble impurities. The clean calcium citrate cake is reslurried and acidified with sulfuric acid, converting the calcium citrate to soluble citric acid and insoluble calcium sulfate. Both the calcium citrate and calcium sulfate reactions are generally performed in agitated reaction vessels made of 316 stainless steel and filtered on commercially available filtration equipment. 

Medical Uses. Citric acid and citrate salts are used to buffer a wide range of pharmaceuticals at their optimum pH for stabiUty and effectiveness (65—74). Effervescent formulations use citric acid and bicarbonate to provide rapid dissolution of active ingredients and improve palatabiUty. Citrates are used to chelate trace metal ions, preventing degradation of ingredients. Citrates are used to prevent the coagulation of both human and animal blood in plasma and blood fractionation. Calcium and ferric ammonium citrates are used in mineral supplements. 

Citric acid occurs in the free state, as well as in the form of the calcium and potassium salts, associated with malic and ta.r-... 

Citric acid is a weak acid and loses hydrogen ions from its three carboxyl groups (COOH) in solution. The loss of a hydrogen ion from each group in the molecule results in the citrate ion, C3H50(C00)33. A citric acid molecule also forms intermediate ions when one or two hydrogen atoms in the carboxyl groups ionize. The citrate ion combines with metals to form salts, the most common of which is calcium citrate. Citric acid forms esters to produce various citrates, for example trimethyl citrate and triethyl citrate. 

Citric acid and its citrate compounds are widely used in hundreds of applications. Global production of citric acid in 2005 was 1.6 million tons, with China producing approximately 40% of the world supply. In the United States, approximately 65% of citric acid use is in the food and beverage industry. Citric acid is used as an acidulant to impart tartness, to control pH, as a preservative and antioxidant, as a metal chelator, and to stabilize color and taste. Citrate salts can be used as mineral and metal dietary supplement for example, calcium citrate... 

Citric acid was originally produced commercially from lemons, limes or bergamots by pressing the fruit, concentrating the pressed juice and precipitating citric acid as its calcium salt, from which it was subsequently purified. It is now produced by the action of enzymes on glucose and other sugars. 

If used in beverages, tartaric acid must be perfectly pure and guaranteed for food use. One problem that may need to be addressed is that tartaric acid salts, particularly the calcium and magnesium tartrates, have lower solubility than citric acid. Consequently, there is a tendency for unsightly precipitates of insoluble tartrates to form in hard water, and in such conditions it is preferable to use citric acid. 

Melamine resins are used from this group of thermosets for the manufacture of food contact materials. The melamine can be used in mixtures with urea and in some applications with phenol (< 1 %). The polymerization process is catalyzed in the presence of organic acids (e.g. acetic acid, lactic acid, tartaric acid, citric acid), hydrochloric acid, sulfuric acid, phosphoric acid, sodium and potassium hydroxide, ammonia, calcium or magnesium hydroxide as well as salts of these substances (total < 1 %) which cause the elimination of water and lead to a cured resin system. Stearic acid can be used as a lubricant as can zinc, calcium and magnesium salts, esters of montanic acid with ethandiol and 1,3-butandiol, as well as silicone oil (total < 1 %). 

Citric acid is used in soft drinks, candies, wines, desserts, jellies, jams, as an antioxidant in frozen fruits and vegetables, and as an emulsifier in cheese. As the most versatile food acidulant, citric acid accounts for about 70 percent of the total food acidulant market. It provides effervescence by combining the citric acid with a biocarbonate/carbonate source to form carbon dioxide. Citric acid and its salts are also used in blood anticoagulants to chelate calcium, block blood clotting, and buffer the blood. Citric acid is contained in various cosmetic products such as hair shampoos, rinses, lotions, creams, and toothpastes. More recently, citric acid has been used for metal cleaning, substituted for phosphate in detergents, for secondary oil recovery, and as a buffer/absorber in stack gas desulfurization. The use of sodium citrate in heavy-duty liquid laundry detergent formulations has resulted in a rapid increase in the use of citric acid. 

Salts Compounds formed by the union of acids and bases, by the action of alkalies upon metals, or by the direct union of elements. The term is often incorporated in the common name of salts used as pharmaceuticals bitter salts, epsom salt, or Seidlitz salt (magnesium sulfate), preparing salt (sodium stannate), Preston s salts (ammonium chloride), Rochelle salt or Seignette s salt (potassium and ammonium tartrate), salt of Mars (ferrous sulfate), salt of Saturn (lead acetate), salt of tartar (potassium carbonate), salt of tin (stannous chloride), salt of wisdom (mercury bichloride and ammonium chloride), sore-throat salt (fused potassium nitrate), vinegar salts (calcium acetate), and vomiting salt (zinc sulfate). The term is also applied to some acids, such as salt of lemon or sour salt (citric acid), salt of sorrel (oxalic acid), and spirit of salt (muriatic acid). ... 

---