Acidulation

Acids carboxylic Acid soaps Acid suppressor Acid treatment Acidulants... 

Protein acidulant Protein additives Protein ammo acids a-l-Proteinase inhibitor Protein-based mimetics Protein Ca [42617-41-4] Protein channels Protein chromatography Protein crystal growth... 

Manufacture of Fatty Acids and Derivatives. Splitting of fats to produce fatty acids and glycerol (a valuable coproduct) has been practiced since before the 1890s. In early processes, concentrated alkaU reacted with fats to produce soaps followed by acidulation to produce the fatty acids. Acid-catalyzed hydrolysis, mostly with sulfuric and sulfonic acids, was also practiced. Pressurized equipment was introduced to accelerate the rate of the process, and finally continuous processes were developed to maximize completeness of the reaction (105). Lipolytic enzymes maybe utilized to spHt... 

Chemistry ndProperties. The chemistry of phosphoric acid manufacture and purification is highly complex, largely because of the presence of impurities in the rock. The main chemical reaction in the acidulation of phosphate rock using sulfuric acid to produce phosphoric acid is... 

In addition to the main acidulation reaction, other reactions also occur. Free calcium carbonate in the rock reacts with the acid to produce additional by-product calcium compounds and CO2 gas which causes foaming. Other mineral impurities, eg, Fe, Al, Mg, U, and organic matter, dissolve, the result being that the wet-process acid is highly impure. 

Israel Mining Industries developed a process in which hydrochloric acid, instead of sulfuric acid, was used as the acidulant (37). The acidulate contained dissolved calcium chloride which then was separated from the phosphoric acid by use of solvent extraction using a recyclable organic solvent. The process was operated commercially for a limited time, but the generation of HCl fumes was destmctive to production equipment. 

Nitric acid acidulation of phosphate rock produces phosphoric acid, together with dissolved calcium nitrate. Separation of the phosphoric acid for use as an intermediate in other fertilizer processes has not been developed commercially. Solvent extraction is less effective in the phosphoric—nitric system than in the phosphoric—hydrochloric system. Instead, the nitric acid acidulate is processed to produce nitrophosphate fertilizers. 

Chemistry and Properties. TSP is essentially impure monocalcium phosphate monohydrate, Ca(H2P0 2 20, made by acidulating phosphate rock with phosphoric acid according to... 

Nitrophosphates are made by acidulating phosphate rock with nitric acid followed by ammoniation, addition of potash as desired, and granulation or prilling of the slurry. The acidulate, prior to ammoniation, contains calcium nitrate and phosphoric acid or monocalcium phosphate according to the foUowiag equations ... 

FlavorFicpunct. A substance used in or with a flavor but not essentially a part of it. These include solvents, antioxidants, enzymes, adjusting agents, emulsifiers, and acidulants. 

Citric Acid. By far the most extensively used food acidulant is citric acid (qv) [77-92-9] C HgO. This acid is favored because of its solubiUty, fresh flavor character, low cost, and low toxicity. It is commercially synthesized by fermentation (qv) of molasses hy Aspergillus niger (6). 

In aqueous solution, malic acid can be mildly corrosive toward aluminum and corrosive to carbon steel. Under normal conditions, it is not corrosive to stainless steels, which usually are the constmetion materials for processes involving malic acid. Malic acid is also virtually noncorrosive to tinplate and other materials used to package acidulated foods and beverages (Table 3) (27). 

Fig. 3. Effective buffer ranges for food acidulants piC values are given in parentheses.

Ca.ndy. Its low melting point and sugar inversion properties make malic acid a desirable acidulant, especially in hard candy products (44,45). Due to their insolubiUty, hard water salts can cause clouding of the finished product. However, because of the higher solubiUty of calcium malate [17482-42-7] relative to alternative acidulants, clarity of the finished product is enhanced. Additionally, in sugar confectionery products where acidulation may exceed 2.0%, malic acid can provide economic benefits. 

Cda.rhona.tedBeverages. Tartaric acid has been used like citric acid as an acidulant in carbonated beverages (qv). However, it has almost been completely replaced in the marketplace by less expensive acidulants like phosphoric, citric, mafic, and fumaric acids. 

Fumaric acid occurs naturally in many plants and is named after Fumaria officinalis, a climbing aimual plant, from which it was first isolated. It is also known as (E)-2-butenedioic acid, aHomaleic acid, boletic acid, Hchenic acid, or /n j -l,2-ethylenedicarboxylic acid. It is used as a food acidulant and as a raw material in the manufacture of unsaturated polyester resins, quick-setting inks, furniture lacquers, paper sizing chemicals, and aspartic acid [56-84-8]. 

Fumaric acid and malic acid [6915-15-7] are produced from maleic anhydride. The primary use for fumaric acid is in the manufacture of paper siting products (see Papermaking additives). Fumaric acid is also used to acidify food as is malic acid. Malic acid is a particularly desirable acidulant in certain beverage selections, specifically those sweetened with the artificial sweetener aspartame [22839-47-0]. 

Many plants outside of North America pfill or granulate a mixture of ammonium nitrate and calcium carbonate. Production of this mixture, often called calcium ammonium nitrate, essentially removes any explosion hazard. In many cases calcium nitrate recovered from acidulation of phosphate rock (see Phosphoric acid and the phosphates) is reacted with ammonia and carbon dioxide to give a calcium carbonate—ammonium nitrate mixture containing 21 to 26% nitrogen (23). 

The anaerobic reaction of sulfur dioxide with aqueous ammonia produces a solution of ammonium sulfite [10192-30-0]. This reaction proceeds efficientiy, even with a gas stream containing as Httie as 1 wt % sulfur dioxide. The sulfur dioxide can be regenerated at a high concentration by acidulation or by stream stripping of the ammonium sulfite solution, or the sulfite can be made to precipitate and the ammonia recovered by addition of lime (243). The process can also be modified to produce ammonium sulfate for use as fertili2er (244) (see Fertilizers). In a variant of this process, the use of electron-beam radiation cataly2es the oxidation of sulfur dioxide in the presence of ammonia to form ammonium sulfate (245). 

The Reich test is used to estimate sulfur dioxide content of a gas by measuring the volume of gas required to decolorize a standard iodine solution (274). Equipment has been developed commercially for continuous monitoring of stack gas by measuring the near-ultraviolet absorption bands of sulfur dioxide (275—277). The deterrnination of sulfur dioxide in food is conducted by distilling the sulfur dioxide from the acidulated sample into a solution of hydrogen peroxide, foUowed by acidimetric titration of the sulfuric acid thus produced (278). Analytical methods for sulfur dioxide have been reviewed (279). 

In kaolin (clay) processing, sulfur dioxide reduces colored impurities, eg, iron compounds. In the bromine industry, sulfur dioxide is used as an antioxidant in spent brine to be reinjected underground. In agriculture, especially in California, sulfur dioxide is used to increase water penetration and the avadabiHty of soil nutrients by virtue of its abiHty to acidulate saline—alkaH soils (327). It is also usefiil for cleaning ferric and manganese oxide deposits from tile drains (328). 

Process Sequence. The process sequence consists of recovery of tall oil soap from the pulping blackhquor, acidulation, ie, conversion of the soap into CTO with sulfuric acid, fractional distillation to separate rosin, and fatty acids and purification of the fatty acid fraction. 

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