Citric acid production: preparation, process and product

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

Citric acid was discovered several hundred years ago, but the history of its full-fledged production at industrial facilities can only be spoken of since 1919. From that moment on, technologists began to apply microbiological processes, the development of which has not stopped to this day. At the same time, the modern production of citric acid is heterogeneous and involves different ways of manufacturing the final product. The choice of one or another method is determined not only by the characteristics of the raw materials of a particular enterprise, but also by the requirements of the target consumer market.

Introduction to Citric Acid

As an acidity regulator, this product is actively used in the food industry. But citric acid is used not only to correct taste. Depending on the manufacturing technology, it can increase the shelf life of the target product. From this point of view, the production of lemonacids in Russia can be put on a par with the technologies for the manufacture of ascorbic, acetic and lactic acids, as well as with their derivatives.

According to experts, due to its qualities as an antioxidant and synergist of antioxidants, citric acid is now used in almost half of all manufactured food products. The popularity of this acidifier is also facilitated by its gastronomic properties. This acid has a pleasant and mild taste - at least when compared with alternative products of this type. Especially these qualities are manifested in drinks and confectionery. There is also a wide group of s alts that are obtained under the conditions of microbiological production of citric acid - in particular, sodium citrate can then be used as a melting s alt. The advantages of sodium citrate include the possibility of obtaining it in solid form, as well as the exclusion of an irritating effect when exposed to the mucous membranes of the digestive and respiratory systems.

Product industrial production

The name citric acid draws attention to citrus fruits, however, this acid is present in varying degrees in all fruits, cotton and needles. Nevertheless, the first production facilities were organized precisely on the basis of the processing of lemon juice. In the 1920s, approximately 25% of all production was obtained in this way. At the same time, the manufacturing technology itself was irrational, since about 25 kg of a pure product was obtained from 1 ton of lemons. Today, the production of food citric acid is being organizedon more technological and resource-intensive methods, involving the use of fundamentally new additives like molasses and mold fungi. By the way, this also determines the logistical decisions on the location of sodium citrate production near the sugar factories.

At the same time, it cannot be said that such production justifies itself by definition in conditions of high demand. The fact is that as the manufacturability of the production process increases, so does the equipment, which means an increase in the cost of technical equipment and maintenance of capacities. Therefore, one cannot do without a well-thought-out business plan for the production of citric acid, which would indicate all aspects of the organizational and economic activities of the enterprise. Along with the design solution for equipping production equipment and developing logistic models with economic justification, it will also be necessary to determine the optimal formulation of the final product so that it can compete in a certain niche in the market. To this should be added an amendment to strict sanitary and hygienic standards that regulate almost all the technological nuances of obtaining this acid.

Physico-chemical presentation of technology

Modern processes for the production of citric acid are mainly based on the hydrolysis of starch suspension, which includes up to 30% of the mass of dry elements with amylolytic ability. Starch of mineral s alts with sulfates of copper, zinc and iron can be added to them. This base subsequently undergoes fermentation in a nutrient medium by a mold fungus.

As a result of fermentation and isolation of fungal biomass, a culture solution is formed, which initially contains up to 85% citric acid. A characteristic feature of acid-resistant enzymes obtained at this stage is increased amylolytic activity. First of all, this concerns glucoamylase and amylase.

The technical result of the production of citric acid after passing through auxiliary operations is evaluated in the laboratory by a wide range of quality indicators, including the amylolytic activity of the culture solution.

Technologies for making "lemon"

The production process is carried out in several technological stages on different equipment. Although there are different configurations for arranging factory facilities - including monoblock and prefabricated modular ones. Among the main processes on which the modern technology of citric acid production is based, the following can be distinguished:

1. Optimized processes for the technological preparation of raw materials to ensure the necessary conditions for an acidic fermentation environment.
2. Reproduction of spores in specially organized conditions.
3. Fermentation process according to the characteristics of specific raw materials.
4. If necessary, adapt all or individual raw materials for fermentation processes.
5. Separation of acid from fermentation solutions. By the way, separation methods are largelydegrees determine the final quality of the product.
6. Purification and crystallization of the resulting acid. At this stage, opportunities open up for product modification and the production of other versions of the acid in different configurations. For example, as part of the general production of citric acid, syrups, monohydrate, dehydrated formulations, and sodium citrate dihydrate can be produced. Chemicals may also be regulated.

Process Equipment

The optimized format of the technical arrangement of modern plants for the production of citric acid involves the use of biotechnological installations. On average, the capacity of such a solution for calculating the volume of output is 200-250 tons / year, while leaving ample opportunities for obtaining modified products based on different sources of raw materials. The basic composition of this equipment for the production of citric acid includes the following reactor and capacitance devices:

1. Fermenters.
2. Evaporators.
3. Filters.
4. Dryers.
5. Crystallizers.
6. Infrastructure to support logistics operations.

Implementation of the biotechnological installation project allows for a full production cycle, locally supplying regional consumers in full with minimal involvement of heat and power resources.

Hardware-technological solution of this type is characterized by the use of producer strains, which leads to an initially low cost of the product. This technology for the production of citric acid is also characterized by an acceptable level of environmental cleanliness for the environment and toxic safety for workers.

As for the quality of the product, it meets the international standards of the food industry. Another thing is that it is also possible to release a technical product intended, in particular, for detergents.

Preparation of raw materials for the production of citric acid

The raw materials enter the production process after special processing. Its method and parameters are determined not only by the properties of the raw materials, but also by the requirements for the product. The possibility of manufacturing derivative products from sodium citrate is also taken into account.

One way or another, the main raw material for the production of citric acid is molasses, which contains the optimal ratio of iron. As for its processing, the main step in this process is pre-fermentation, which is necessary for the precipitation of the composition by means of yellow blood s alt. Without further processing, this s alt in acid can act as an inhibitor of isocitrate dehydrogenases.

Another component that can be used as a raw material base is the fungus Aspergillus Niger. The question arises - why, in the conditions of modern technologies, a mold fungus is used to produce citric acid? Most often, its use is required to ensure the function of the producer. Its chemical formula is optimal forcarrying out several processes at once, which are impossible or technologically unjustified when using synthetic substitutes. In particular, we are talking about dissolution, solicification and subsequent separation and purification procedures.

Special preparation of raw materials is also required in the production of modified citric acid derivatives. In this case, additional inclusions can also be used, including ethyl alcohol, technical and ethanol-containing intermediates with waste from distilleries. In turn, the production of citric acid from molasses will be complemented by hexacyanoferrate clarification, sterilization and boiling processes.

When using starch hydrolysates with a moderate impurity content, raw material preparation will need to include a decationization procedure and a continuous sterilization operation.

Organization of the spore breeding process

Efficient microbiological processes require well-prepared seed. In acid synthesis, this material in the form of spores is introduced into the fermentation tank at the very beginning of the production process. In an optimized form, the technology for the production of molasses-based citric acid separately provides for the preparation of spores for breeding, within which testing is also performed. If long-term production is planned, then the spores are dried. This is necessary both for long-term preservation of their functional qualities and for successful dosing.

At the next step, substrates are prepared, including sucrose, glucose orstarch. Materials containing starch are first saccharified to be converted into glucose, which is used as a production strain.

Since the level of impurities at all stages of processing of raw materials and substrates can be excessively high, many manufacturers are developing special methods for the primary purification of these materials. For example, the further processing of starch hydrolyzate for citric acid in food production may include des alting steps. The same procedures of sterilization and boiling with mechanical filtration can be attributed to the universal and most accessible methods of purification from impurities.

Fermentation process and acid production

In modern technologies for ensuring the fermentation process, special bubbling fermenters are used, which are selected according to prepared strains of the mold fungus discussed above. The selection is carried out together with testing according to certain parameters, which allows organizing fermentation according to individual configurations, taking into account the characteristics of the raw materials used. The most technologically advanced processes for the production of citric acid also involve tools for regulating the metabolic activity of bubbling microorganisms.

At the stage of acid isolation, the task is to obtain a solution from the fermentation medium with an initial level of purification. In order to increase the degree of purification, the generating mixture must be suitably prepared. In particular, it undergoes the following processespretreatment:

1. Separation and settling procedure.
2. Mycelium separation operation.
3. Separation of calcium sulfate and decomposition of the fermentation mass.

For the separation of dry residues in modern industries, belt filters with automatic control are used. Also, for the organization of sediment filtration processes, special centrifuges and separators with electronic control systems are used, which increases the accuracy of material processing.

Purification of the resulting citric acid

The final stage of production, which includes the complex processing of the already received product. This process uses activated carbon with anion and cation exchange resins. The technology of such purification is implemented in fixed-bed reactors in several stages:

1. The process of evaporation at a certain temperature.
2. Crystallization in vacuum.
3. Crystal screening in the centrifuge.
4. Drying with fluid bed.
5. Sifting procedure.

Evaporation is carried out in a multi-stage evaporator unit with a falling liquid film. As a result of this process, the required evaporation coefficient is achieved without reducing the consumer properties of citric acid. The consumption of energy resources at this stage can be significantly reduced due to the provision of thermal compression on vapor.

As for crystallization, this citric acid production process is carried out with forced circulation. In someIn the technical configurations of food industry plants, vacuum crystallizers are designed on the same structural basis together with devices for the production of modified and derivatives of sodium citrate. For example, similar equipment is used in the production of dehydrated products and citric acid monohydrate.

Not the last value at the purification stage is the operation of recycling the fermentation solution, in which the separation of uterine enzymes from the crystalline suspension. Technically, this procedure is carried out by a continuous centrifuge, which makes it possible to finely control the characteristics of the final product.

The final drying and sieving processes require delicate handling of the resulting and purified product. At this stage, the requirements for the form of release of citric acid will play a role - for example, fractionation is performed according to the design particle size.

Domestic citric acid market

The main participants in this segment in the Russian food industry market include manufacturers from China, which control almost half of all output. But a significant share is also accounted for by Russian factories for the production of citric acid, a special place among which is occupied by the Citrobel enterprise located in Belgorod. Actually, this is almost the only domestic plant with world-class capacities. Commercial organizations in the food sector are actively cooperating with factories in theabroad. In this direction, Ukrainian and Belarusian sugar factories stand out, located in Smila and Skidel, respectively.

According to experts, Russian citric acid meets the regulatory requirements of GOST and packaging design standards. This is one of the advantages that allows domestic citric acid plants in Russia to successfully compete with Chinese enterprises. So, in comparison with Citrobel, which provides supplies of consistently high quality citric acid, manufacturers from the Celestial Empire do not always guarantee that products meet strict standards, which is also reflected in prices. The difference is determined by the level of the manufacturer and distribution network. At the same time, even in deliveries from large companies, the characteristics of citric acid in one batch are heterogeneous and may vary. This is also confirmed in consumer reviews, where complaints about the solubility and moisture content of the product are noted.

Conclusion

Today, the volume of production of world manufacturers of citric acid is about 800,000 tons / year. Such a high return of this sector is due to the fact that a number of industries are interested in the use of acidifiers, including traditional segments of the food industry, and the chemical and pharmaceutical sphere. Moreover, derivatives of such acids today find application even in the defense and electronic industries, not to mention agriculture and other industries where the technical function of citric acid is in demand.enzymes. In this regard, the practice of using sodium citrate as a substitute for active processing aids and synthetic detergents can be noted.

If we talk about the production of citric acid in Russia, then at the government level in recent years steps have been taken to protect the domestic market in order to stimulate enterprises operating in this area. But since the Belgorod plant remains the only major supplier of citric acid, there is sometimes a shortage of the product. As a way out, experts suggested changing the customs rules, under which priority for the import of foreign acidifiers was given to European companies that guarantee the proper quality of the product. Citric acid from major biochemical producers in Japan, Switzerland and Germany is superior in quality to domestic products, but the prices are too high, so the Citrobel plant remains competitive without compromising consumer needs.