Citric acid is the most widely distributed organic acid in fruits and vegetables, and it is also the most widely used acid in food. Citric acid is an important organic acid, and citric acid, colorless crystals, often contain a molecular crystal water, odorless, strong acidity, soluble in water. Its calcium salt is more easily dissolved in cold water than hot water, which is often used to identify and isolate citric acid. When the crystal is controlled, the suitable temperature can be obtained with anhydrous citric acid. Citric acid, citric acid, citric acid, citric acid, citric acid, citric acid. At the same time, citric acid has many uses, such as antioxidant synergist, bleach synergist, jam coagulant, fruit color agent and flavoring agent and fish, goats’milk deodorant etc.. In nature, the citric acid is widely found in lemons, oranges, oranges and other fruits. Industrial production mainly uses the synthesis method and the fermentation method, but the industrial use of citric acid by Aspergillus niger fermentation process. Two, characteristics and characteristics of 1 soluble citric acid soluble in water, ethanol, soluble in ethyl ether. The solubility of anhydrous citric acid in water is very large, 100 degrees Celsius is 84%. The solubility of 25 DEG C to 58.9% ethanol in politics. In addition, the citric acid and its derivatives of propylene glycol solution is also soluble in oil. Due to its good solubility in water and fat, citric acid is easy to be distributed in all kinds of foods. 2 pure and mild acidity, in all organic acids are the most delicious, and can be mixed with a variety of spices to produce a refreshing sour taste, the story is used in many foods. At the same time, due to the weak acid of citric acid, in a certain range of pH can inhibit the proliferation of bacteria, play a role in anti-corrosion. 3 chelating ability strong citric acid because it contains three carboxyl so can form three forms of salt, but in addition to alkali metal salt, most of the other salts are insoluble or difficult to dissolve in water. It also has a peculiar nature, which is more readily soluble in cold water than in hot water. 4 with alkali or salt buffer with two sodium hydrogen phosphate with different mixing ratio, can be 2 ~ 8 series buffer. 5 toxic small in the human body citric acid is an important intermediate in the cycle of three carboxylic acids, the toxicity of small. Three, application of 1 citric acid as sour agent widely used in a variety of beverages, fruit juice, canned food, candy, jam, jelly, the sour taste fresh and delicious, sweet and fruity. Citric acid itself is one of the natural ingredients of fruit juice drinks, not only gives fruit flavor, but also has the solubilization buffer, anti-oxidation effect, can make the drinks in the sugar, essence and pigment composition blending coordination, forming proper taste and flavor. 2 citric acid sucrose conversion agent in sucrose solution adding citric acid can be transformed into sugar, to improve sucrose saturation and increase viscosity, osmotic pressure, so as to effectively prevent the sucrose sugar product return sand, and improve product preservation and improve its quality. 3 citric acid as a fruit and vegetable raw material to the fruit and vegetable raw materials in 1% ~ 2% of salt and 0.1% of citric acid mixed solution, can inhibit the fruit and vegetable raw material enzyme browning caused by discoloration.
4 citric acid as the pH value of the adjustment agent citric acid in cans, jam, jelly and other products in the use of the pH value can be reduced, inhibit the reproduction of spoilage microorganisms. When the pH value is less than 5.5, most of the spoilage bacteria can be suppressed. At the same time, the pH value of the citric acid can also be used to improve the quality and flavor of the food. Such as when the grapes or other wine mature over and the acidity is insufficient, can be adjusted by citric acid, to prevent the wine taste thin, as well as antioxidant and protective role of pigment to protect fruit freshness and prevent discoloration. 5 citric acid as an antioxidant synergistic agent such as adding a concentration of 0.1% of the raw material in the cut and peel of fruits and vegetables can prevent the oxidation of raw materials. Citric acid is usually used as a synergistic agent in order to control the activity of the phenolic enzyme and prevent the enzymatic browning. Such as a molecular crystal water citric acid can be used as edible oil antioxidant. Such as adding citric acid can improve the taste of ice cream, increase the stability of the emulsion to prevent oxidation. In the jam and jelly can also enhance the flavor, and has antioxidant effect. Such as all kinds of meat and vegetables in the pickling, join or coated with citric acid can improve the flavor, except fishy smell, antioxidant. 6 citric acid as a loose agent in the pasta products with sodium bicarbonate as a loose agent, the product is often a large alkalinity, taste difference. If the use of citric acid and baking soda at the same time, can make the small soda molecules produced in the reaction process of carbon dioxide is absorbed, does not cause the accumulation of sodium carbonate, so as to reduce the alkalinity of pasta, improve the flavor. 7 citric acid buffer of vegetables and fruits in the process due to variety, origin, harvest time and storage time of different acid will make them different to industrial inconvenience, according to the need to control the acidity of the solution, to ensure product quality, but also can inhibit the growth of bacteria and reduce the sterilization time and reducing sterilization temperature. 8 citric acid and fatty acid mono and diglycerides used as emulsifier of the emulsifier in the margarine, ice cream production in favor of fat emulsion breaking, condensation, and improve the quality of the product, the product is fine. Reference dosage: 10g/kg, cold drink 10g/kg. 9 citric acid as perfume and deodorant citric acid can be added to soft drinks, cold drinks, baked food, confectionery and chewing gum. Citric acid can be used as a spice stabilizer added to many food packaging materials to the fresh-keeping deodorization effect, such as adding 1% citric acid made of polyethylene film for the packaging of fish and pickled products, three days can significantly reduce the odor. In addition, citric acid as seafood, aquatic products and goats’milk etc.In addition, citric acid as seafood, aquatic products and other products, in addition to goats’milk flavor, deodorizing agent has been widely used, such as kelp drink commonly used 10% citric acid and 0.2% hydrochloric acid for deodorization, sardines before processing soaked in pH5.5 citric acid in 30 minutes can remove the fishy smell. 10 citric acid on the VC content of all the sweet orange juice samples in the storage process, the vitamin C content in the decline, but the characteristics of their decline is different. In contrast, citric acid has a certain effect on the decrease of vitamin C. The total number of colonies of samples containing citric acid decreased faster than that of the control samples, and increased with the increase of citric acid concentration. 11 citric acid in the early weaning piglets diets in the application of a to reduce the daily pH value, so that the stomach pH value decreased, improve the enzyme activity. Citric acid can cause diet and gastrointestinal pH value decreased to a certain extent, low pH value can make the inactive plasminogen pepsin activity to become pepsin, provide a suitable environment for the digestion and absorption of nutrients in piglets. Hou Yongqing et al. (1996) reported that the contents of citric acid and trypsin and amylase activity were significantly increased in the diets of weaned piglets. Citric acid by reducing the pH value of the gastrointestinal tract, to improve the suitable living environment of harmful microorganisms or the direct inhibition of bacteria, kill harmful microorganisms, while promoting the fermentation of lactic acid bacteria. B) directly involved in the metabolism, improve the digestibility of nutrients, citric acid is a necessary process of sugar, protein and fat metabolism in the tricarboxylic acid cycle intermediate product of three, by the piglets in vivo after absorption of synthesis of ATP electron transfer system and isocitrate dehydrogenase activity has a positive effect, plays an important role in ATP formation and biomass accumulation, promote piglets The new supersedes the old. use of energy and amino acids, enhance the rate of. C) citric acid regulating the rate of gastric emptying of chyme into the small intestine after acid by chemical stimulation on the wall of the small intestine, the abnormal secretion of gastrin, which reflex inhibition of gastric motility, gastric emptying rate and slow food movement speed in the intestine, prolong the residence time of food in the stomach, so that food and saliva and gastric juice the digestive fluid is fully mixed, is conducive to digestion and absorption of nutrients in food.
D) citric acid to promote the absorption of citric acid citric acid in reducing the pH value of the contents of the gastrointestinal tract at the same time, but also with the formation of a number of mineral elements easily absorbed by the use of the complex. E) citric acid as a protective agent of the feed of citric acid is a synergistic agent of feed antioxidants, the role of the feed metal ions are blocked, so that it can not play the role of catalytic oxidation reaction. 12 canned foods, soy products and spices, citric acid, as well as the role of chelating metal ions, the protection of ascorbic acid, so that the metal ions are not damaged. The addition of citric acid to vegetable oil has a similar effect. Citric acid can be used for the hydrolysis of soy beans, sunflower protein protein, produce a unique flavor. It can also be used for seasoning sauce (soy sauce, etc.). 13 other citric acid in the pharmaceutical, chemical and other industries also have a certain role. Ferric ammonium citrate can be used as a blood agent; sodium citrate can be used as a blood transfusion agent; citric acid can produce food packaging film and pollution-free detergent, such as citric acid esters of two main varieties of three citric acid butyl ester (TBC), acetyl citric acid butyl ester three (ATBC) has been approved by the FDA as safe and nontoxic. Plasticizer, China is recommended for use in packaging materials. Three butyl citrate (TBC) is widely concerned because it has the characteristics of good compatibility, high efficiency, non toxicity, non volatile, strong weather resistance and so on. It has become the first choice to replace the green environmental protection product of two phthalate esters. Citric acid ester plasticizer has good comprehensive properties, good cold tolerance, use still have flexibility, good in cold area and light, water, heat resistance, good thermal stability and sealing when discoloration, safe and durable, anti fungal, biodegradable, and polypropylene (PP), PVC, vinyl chloride vinyl chloride is two (PVDC), vinyl chloride vinyl acetate copolymer and various fiber resin has good compatibility. Citric acid as a food grade PVC film main plasticizer plasticized PVC films with good permeability, effectively maintain oxygen red meat and myosin insurance, sealing performance is good, has overcome the PVC film packaging of meat, because oil is difficult to seal the disadvantages, especially suitable for the packaging of meat with high fat food; film surface gloss, transparent packaging, food at a glance; good permeability, high carbon dioxide permeability, can reduce the dehydration of fresh vegetables, vegetables and prolong the preservation period. Citric acid ester plasticizer in food grade PVDC film and the role of the main plasticizer and heat stabilizer.