Recognizing Citric Acid

Citric acid, also known as citric acid, is widely distributed in nature. Natural citric acid is found in the fruits of plants such as lemons, oranges and pineapples and in the bones, muscles and blood of animals. Synthetic citric acid is made by fermenting sugar, molasses, starch, grapes and other sugary substances. Many kinds of fruits and vegetables, especially citrus fruits, contain high amounts of citric acid, especially lemons and limes - they contain large amounts of citric acid, up to 8% after drying (about 47 g/L in fruit juice). In citrus fruits, the citric acid content ranges between 0.005 mol/L in oranges and grapes and 0.30 mol/L in lemons and limes. This content varies with different cultivars and plant growth.

Citric acid is an edible acid that enhances normal metabolism in the body and is harmless in appropriate doses. The addition of citric acid to certain foods tastes good and promotes appetite, and its use in jams, beverages, canned goods and candies is permitted in China. Based on the citric acid on the metabolism of calcium can have an impact, often consume canned goods, drinks, jams, sour candy people, especially children, pay attention to calcium, drink more milk, fish head, fish bone soup, eat some small shrimp, etc., so as not to lead to insufficient blood calcium and affect the health of gastric ulcers, hyperacidity, caries and diabetes should not be consumed regularly citric acid. Citric acid can not be added to pure milk, otherwise it will cause pure milk coagulation. The dairy industry often makes citric acid into a solution of about 10% and adds it to a low concentration milk solution, which should be stirred quickly.

At room temperature, citric acid is a white crystalline powder, odorless, acidic taste, density 1.542g/cm3, melting point 153-159 ° C, 175 ° C above the decomposition of water and carbon dioxide release. Citric acid is soluble in water, the solubility is 59% at 20 ℃, and the pH of its 2% aqueous solution is 2.1. The crystalline form of citric acid varies depending on the crystallization conditions, slightly weathered in dry air, hygroscopic in humid air, and can be decomposed into a variety of products by heating and can be reacted with acid, alkali, glycerol, etc. When dissolved in ethanol, it will be dissolved with water and carbon dioxide, and can be dissolved in ethanol. Citric acid dissolves in ethanol and reacts with ethanol to produce ethyl citrate. It should be stored in airtight containers and kept in a cool and dry place.

The fermentation mechanism of citric acid has been gradually recognized since 1940 when H.A. Krebs put forward the tricarboxylic cycle theory. It has been proved that in the biochemical process of generating citric acid from sugar raw material, the process of turning sugar into pyruvic acid is the same as that of alcoholic fermentation, i.e., fermentation is carried out through the E-M pathway (hexose diphosphate pathway). Pyruvate is then further oxidized and decarboxylated to produce acetyl coenzyme A, which is condensed with oxaloacetate produced by the carboxylation of pyruvate to become citric acid and enter the tricarboxylic cycle.

Citric acid is the world's largest organic acid produced by biochemical methods, citric acid and its salts are one of the pillars of the fermentation industry, and are mainly used in the food industry, such as acidulants, solubilizers, buffering agents, antioxidants, deodorizers, flavor enhancers, gelling agents, and colorants, etc. In food additives, they are mainly used in carbonation and deodorization agents. In terms of food additives, it is mainly used in carbonated beverages, fruit juice beverages, lactic acid beverages and other refreshing beverages and pickled products, and its demand is subject to seasonal climate changes. Citric acid accounts for about 2/3 of the total consumption of acidulants.Adding citric acid to canned fruits can maintain or improve the flavor of the fruits, increase the acidity of certain fruits with low acidity when canned (lowering the pH value), weaken the heat resistance of microorganisms and inhibit their growth, and prevent bacterial bloating and destruction that often occurs in canned fruits with low acidity. Adding citric acid as a souring agent in candies is easy to harmonize with the fruit flavor. In the gel food such as jam, jelly in the use of citric acid can effectively reduce the negative charge of pectin, so that the pectin intermolecular hydrogen bonding and gel. In the processing of canned vegetables, some vegetables are alkaline reaction, with citric acid as pH adjuster, not only can play a role in flavoring, but also to maintain its quality. Citric acid has the chelating effect and pH adjustment worthwhile characteristics so that it can increase the performance of antioxidants in the processing of frozen food, inhibit enzyme activity, and extend the shelf life of food.

Citric acid is an organic acid produced by microbial fermentation, which is widely used in the production of detergents, and its own specificity and chelating effect play a positive role. Citric acid in the actual use of the process, has a good performance, mainly in terms of safety is more prominent, the preparation of citric acid raw materials are derived from food, which is safe food-grade microorganisms. The use of citric acid will not affect the environment, in microorganisms and heat and other effects of easier degradation, its own chelating ability is also relatively strong, mainly in time citrate on manganese ions and iron ions and other strong chelating ability, the use of the effect is also more prominent. Detergents in the use of citric acid in the performance of corrosion inhibition is also more prominent, pickling as a chemical cleaning in a more important part, and inorganic acids compared to the citric acid acid is relatively weak, so the corrosive properties of the equipment is also relatively small, citric acid cleaning safety and reliability is relatively strong, the waste liquid is also easier to deal with, will not pose a hazard to the human body.

Citric acid and its derivatives with its special physical and chemical properties, in chemical cleaning and many other areas have a very broad range of uses. Citric acid can be used to clean pipes; compound surfactants can be used to clean gas water heaters; water dispensers can also be cleaned;

Citric acid belongs to a kind of fruit acid, the main role is to accelerate the renewal of keratin, commonly used in lotions, creams, shampoos, whitening products, anti-aging products, acne products and so on. Citric acid in chemical technology can be used as a reagent for chemical analysis, used as experimental reagents, chromatographic analysis reagents and biochemical reagents; used as a complexing agent, masking agent; used to prepare buffer solutions. The use of citric acid or citric acid salts as a detergent can improve the performance of washing products, can quickly precipitate metal ions, prevent pollutants from re-adhering to the fabric, to maintain the washing of the necessary alkalinity; so that dirt and ash dispersion and suspension; to improve the performance of the surfactant is an excellent chelating agent; can be used as a test of the building of ceramic tiles of the acid resistance of the reagent. Citric acid-sodium citrate buffer solution is used for flue gas desulfurization. China is rich in coal resources, which constitutes the main part of energy, however, there has been a lack of effective flue gas desulfurization process, resulting in serious atmospheric SO2 pollution. Citric acid-sodium citrate buffer solution is a desulfurization absorbent with great development value due to its low vapor pressure, non-toxicity, stable chemical properties, and high absorption rate of SO2.

In the conventional dyeing and finishing process, finishing is usually carried out after dyeing. Due to the cross-linking treatment in the finishing, it often leads to the problem of color fastness and color difference, which is more obvious especially when reducing livestock catalyst is used. Using one-step method to treat the fabric can not only reduce the cost and shorten the production time, but also avoid the problem of color fastness and color difference. Currently dyeing and finishing synchronization is mainly used for cotton, cotton blended fabrics, silk, wool and viscose fibers. The common characteristic of these fibers is the need to improve their performance through finishing; dyeing and finishing one-step method and two-step method have obtained better finishing results, but one-step method is more energy-saving, simple process, less pollution, so it has a good prospect for development.

Citric acid can be used as formaldehyde-free dyeing finishing agent. Triethanolamine can prevent citric acid in the fabric baking process decomposition, dehydration to generate unsaturated polycarboxylic acid, thus effectively inhibiting the yellowing phenomenon of the fabric. Citrate esters, which have been approved by the U.S. Food and Drug Administration as non-toxic plasticizers for polyvinyl chloride and cellulose plastic films used in food packaging. Acetylated and butyrylated citrates are used as foaming agents for methyl methacrylate polymers, stabilizers for acrylamide, initiators for polyamide adhesives, and plasticizers for polyvinyl chloride. In particular, butyl citrate and acetylated tributyl citrate are recognized worldwide as non-toxic plasticizers. In addition to non-toxicity, they have superior performance in compatibility, extraction resistance and low volatility. Such as acetylated trihexyl citrate, butyrylated tributyl citrate can be used in the production of high hygiene requirements of the composition of blood vessels and catheters. Citric acid and 80 ℃ temperature joint action has a good bacterial spore killing effect, and can effectively kill the bacterial spores contaminated in the hemodialysis machine pipeline. In the formation of plasminogen activator and the subsequent coagulation process, calcium ions must participate. Citrate ion and calcium ion can form a soluble complex that is difficult to dissociate, thus reducing the concentration of calcium ion in the blood and blocking blood coagulation.

Citric acid is carboxylated from acetyl coenzyme A and oxaloacetate in the body's tricarboxylic acid cycle and is involved in sugar, fat and protein metabolism in the body. Citric acid is found naturally in the fruits of plants (e.g. lemon, citrus, pineapple, etc.) and in the bones, muscles, and blood of animals, while it is synthesized artificially through the fermentation of sugar-containing substances such as granulated sugar, molasses, starch, grapes, and so on. Adding citric acid to compound feed can disinfect, prevent mold and mildew, and prevent Salmonella and other infections in animal feed. Animal feeding citric acid can reduce the proliferation of pathogens and inhibit the production of toxic metabolites, improve animal stress. (1) Increase feed intake to promote the digestion and absorption of nutrients; (2) Promote the health of intestinal flora; (3) Enhance the body's stress resistance and immune ability; (4) As an antimold agent and antioxidant.

In the process of citric acid production discharges more types of wastewater, of which the neutralization of wastewater emissions are the largest, resulting in the most serious pollution, so the treatment of neutralization of wastewater is crucial, directly related to the ecological environment. Neutralization wastewater technology process for neutralization → catalytic oxidation → sand filtration → adsorption, wastewater can be used for agricultural irrigation after treatment, which makes full use of industrial wastewater and saves water resources.