Citric acid was discovered several hundred years ago, but we can only talk about the history of its full-fledged production at industrial facilities since 1919. From this moment, technologists began to use microbiological processes, the development of which does not stop to this day. At the same time, the modern production of citric acid is heterogeneous and involves different methods of manufacturing the final product. The choice of a particular method is determined not only by the characteristics of the raw materials of a particular enterprise, but also by the requirements of the target consumption market.
Citric Acid Overview
As a regulator of acidity, 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 citric acid in Russia can be put on a par with the manufacturing techniques of ascorbic, acetic and lactic acids, as well as with their derivatives.
According to experts, due to its antioxidant and antioxidant synergist qualities, citric acid is used today in almost half of all food industry products. The popularity of this acidifier is also facilitated by its gastronomic properties. This acid has a pleasant and mild taste - in any case, when compared with alternative products of this type. Especially these qualities are manifested in drinks and confectionery. There is also a wide group of salts, which are obtained under the conditions of microbiological production of citric acid - in particular, sodium citrate can then be used as a salt-melter. 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.
Industrial product manufacturing
The name citric acid draws attention to citrus fruits, however, this acid is present to varying degrees in all fruits, cotton and needles. Nevertheless, the first production was organized precisely on the basis of the processing of lemon juice. In the 1920s, approximately 25% of all production was thus obtained. At the same time, the manufacturing technology itself was irrational, since about 25 kg of pure product was obtained from 1 ton of lemons. Today, the production of food citric acid is organized on more technologically advanced and resource-intensive methods, involving the use of fundamentally new additives like molasses and molds. This, by the way, also determines logistics decisions on the location of the production of sodium citrate next to sugar factories.
At the same time, it cannot be said that this kind of production justifies itself, by definition, in conditions of high demand. The fact is that as the manufacturability of the production process increases, equipment becomes more complex, which means an increase in the cost of technical equipment and maintenance of capacities. Therefore, 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, can not do. Along with the design solution for equipping production equipment and developing logistics models with an economic justification, it will also be necessary to determine the optimal formulation of the final product so that it can compete in a specific niche in the market. To this it is worth adding an amendment to strict sanitary and hygienic standards that regulate almost all the technological nuances of obtaining this acid.
Physico-chemical representation 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. To them can be added starch of mineral salts with sulfates of copper, zinc and iron. This base subsequently undergoes fermentation in the medium with mold fungus.
As a result of fermentation and isolation of fungal biomass, a culture solution is formed, which initially contains up to 85% of citric acid. A characteristic feature of acid-resistant enzymes obtained at this stage is an increased amylolytic activity. First of all, this applies to glucoamylase and amylase.
The technical result of the production of citric acid after undergoing auxiliary operations is evaluated in laboratory conditions with a wide range of quality indicators, among which amylolytic activity of the culture solution.
Manufacturing Technologies "Lemons"
The production process is carried out in several technological stages on different equipment. Although there are different configurations of arrangement of factory facilities - including monoblock and modular modular ones. Among the main processes on which the modern technology of citric acid production is based, the following can be distinguished:
- Optimized processes for the technological preparation of raw materials to provide the necessary conditions for an acidic fermentation medium.
- Reproduction of spores in specially organized conditions.
- The fermentation process in accordance with the characteristics of specific raw materials.
- If necessary, the adaptation of all or individual raw materials for fermentation processes.
- Separation of acid from fermentation solutions. By the way, separation methods largely determine the final quality of the product.
- Purification and crystallization of the resulting acid. At this stage, opportunities arise for modifying the product and producing other versions of the acid in different configurations. For example, syrups, monohydrate, dehydrated formulations, and sodium citrate dihydrate may be produced as part of total citric acid production. The chemical content can also be adjusted.
Equipment for the production process
An optimized format for the technical arrangement of modern plants producing citric acid involves the use of biotechnological plants. On average, the capacity of such a solution for calculating the output volume is 200-250 tons / year, while leaving ample opportunities for obtaining modified products based on different sources of raw materials. The basic structure of this equipment for the production of citric acid includes the following reactor and tank devices:
- Fermenters.
- Evaporating apparatus.
- Filters
- Dryers
- Crystallizers.
- Infrastructure for logistics operations.
The implementation of the biotechnological installation project allows us to provide a complete production cycle, locally supplying regional consumers in full with minimal involvement of heat and energy resources.
A hardware and technological solution of this type is characterized by the use of producer strains, which leads to the initially low cost of the product. This citric acid production technology 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 produce a technical product intended, in particular, for detergents.
Preparation of raw materials for the production of citric acid
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 derivatives of sodium citrate is also taken into account.
One way or another, the main raw material for the production of citric acid is molasses, containing the optimal ratio of iron. As for its processing, the main step in this process is the pre-fermentation necessary to precipitate the composition by means of yellow blood salt. Without further processing, this salt in acid may act as an inhibitor of isocitrate dehydrogenases.
Another component that can be used as a raw material base is Aspergillius niger. The question arises - why, in the conditions of modern technology, mold fungus is used to produce citric acid? Most often, its use is required to ensure producer function. Its chemical formula is optimally suited for carrying out several processes at once, which are impossible or technologically unjustified when using synthetic substitutes. In particular, we are talking about dissolution, saltification and subsequent separation and purification procedures.
Special preparation of raw materials is also required in the production processes of modified derivatives of citric acid. 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 clarification with hexacyanoferrate, sterilization and boiling.
When using starch hydralizates with a moderate content of impurities, the preparation of raw materials will have to include a decationization procedure and a sterilization operation in a continuous mode.
Organization of the process of reproduction of spores
For the effective conduct of microbiological processes, high-quality seed is required. In the synthesis of acid, 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 citric acid based on molasses separately provides for the stages of preparing spores for breeding, in which testing is also performed. If long-term production is planned, then the spores are dried up. This is necessary for the long-term preservation of their functional qualities, and for successful dosing.
In the next step, substrates are prepared, including sucrose, glucose, or starch. Materials with starch content first undergo a saccharification procedure for subsequent conversion to glucose, which is used as a production strain.
Since the level of impurities at all stages of the processing of raw materials and substrates can be excessively high, many manufacturers are developing special methods for the primary cleaning of these materials. For example, the deep processing of starch hydrolyzate for citric acid in food production may include desalination operations. The universal and most affordable methods for cleaning impurities include the same sterilization and boiling procedures with mechanical filtration.
Fermentation and acid release
In modern technologies for ensuring the fermentation process, special bubbling fermenters are used, which are selected according to the prepared strains of the mold considered above. Selection is carried out along with testing for certain parameters, which allows you to organize 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 the regulation of the metabolic activity of bubbling microorganisms.
At the stage of acid separation, the task is to obtain a solution from a fermentation medium with an initial level of purification. In order to increase the degree of purification, the generating mixture should be properly prepared. In particular, it undergoes the following pretreatment processes:
- Separation and precipitation procedure.
- The operation of the separation of the mycelium.
- Separation of calcium sulfate and decomposition of the fermentation mass.
For the separation of solids in modern factories, belt filters with automatic control are used. Special centrifuges and separators with electronic control systems are also used to organize sludge filtration processes, which increases the accuracy of material processing.
Purification of the resulting citric acid
The final stage of production, which includes integrated processing of the product already obtained. In this process, activated carbon with anionic and cation exchange resins is used. The technology of such cleaning is implemented in fixed-bed reactors in several stages:
- The process of evaporation at a certain temperature.
- Crystallization in a vacuum.
- Screening crystals in a centrifuge installation.
- Fluidized bed drying.
- Screening procedure.
Evaporation is carried out in an evaporating multistage unit with a falling liquid film. As a result of this process, the required coefficient of evaporation 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 steam.
As for crystallization, this citric acid production process is carried out with forced circulation. In some technical configurations of food processing plants, vacuum crystallizers are designed on the same structural basis together with apparatuses for producing modified and derivatives of sodium citrate. For example, similar equipment is used to produce dehydrated products and citric acid monohydrate.
Not the last value at the stage of purification is the operation of recirculation of the fermentation solution, in which the uterine enzymes are separated from the crystal-containing suspension. Technically, this procedure is implemented by a centrifuge with continuous operation, which makes it possible to finely control the characteristics of the final product.
The final processes of drying and sieving require delicacy in the handling of the obtained and purified product. At this stage, the requirements for the form of citric acid release will also play a role - for example, fractionation is carried out in accordance with the design particle size.
Domestic citric acid market
The main participants of this segment in the Russian food industry market include manufacturers from China, who control almost half of all output. But a significant share falls on Russian plants for the production of citric acid, a special place among which is the company "Citrobel", located in Belgorod. Actually, this is almost the only domestic plant with global facilities. Actively cooperate commercial organizations of the food sector with factories of neighboring countries. In this direction, Ukrainian and Belarusian sugar factories located in Smela and Skidel stand out 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 successfully competing domestic factories for the production of citric acid in Russia with Chinese enterprises. So, in comparison with the "Citrobel", which ensures the supply of citric acid of consistently high quality, manufacturers from the Middle Kingdom do not always guarantee compliance of products with strict standards, which is reflected in prices. The difference is determined by the level of the manufacturer and the distribution network. Moreover, even in deliveries from large companies, the characteristics of citric acid in one batch are heterogeneous and can vary. This is also confirmed in consumer reviews, where claims to the solubility and moisture of the product are noted.
Conclusion
To date, the production volume of world manufacturers of citric acid is about 800,000 tons / year. Such a high return on this sector is due to the fact that a number of industries are interested in the use of acidifiers, among which are both the traditional segments of the food industry and the pharmaceutical industry. , , , . .
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 field. But since the Belgorod plant remains the only major supplier of citric acid, at times there is a shortage of product. As a way out, experts proposed a change in customs regulations, within which priority was given to European companies to import foreign acidifiers, guaranteeing the proper quality of the product. Citric acid from major biochemistry producers from Japan, Switzerland and Germany is superior in quality to domestic products, but its prices are too high, so the Citrobel plant remains competitive without compromising consumer needs.