I. Overview:
Using various refined starches, such as corn starch, wheat starch, or tapioca starch, as raw materials, maltodextrin or glucose can be produced by acid hydrolysis or enzymatic hydrolysis.
The acid hydrolysis method is easy to produce some colored substances or non-fermentable sugars, which will have an adverse effect on the future, so it has been stopped in practice. The production process provided by our company is enzymatic hydrolysis production process. Theoretically, a product with a DE value lower than 20%, that is, a reducing sugar ratio lower than 20%, is called maltodextrin. But in daily use, the distinction is not obvious.
2. Process flow
(1) Liquefaction
The glucoamylase used for saccharification belongs to an external enzyme, and hydrolysis proceeds from the non-reducing end of the substrate molecule. In order to increase the opportunity of saccharification enzymes and speed up the saccharification reaction, a-amylase must be used to hydrolyze the macromolecular starch into dextrin and oligosaccharides. However, the crystalline structure of starch granules is highly resistant to enzyme action. For example, the bacterial a-amylase hydrolyzes starch granules and hydrogelatinized starch at a rate of about 1:20,000. For this reason, the amylase cannot directly act on the starch, and the starch milk needs to be heated first to make the starch swell and gelatinize by water absorption, destroying its crystal structure.
1. Gelatinization and aging
If the starch milk is heated to a certain temperature, the starch granules start to swell and the polarized cross disappears. As the temperature continues to rise, the starch granules continue to expand, up to several times to several tens of the original volume. Due to the expansion of the particles, the crystal structure disappears, the volume expands large, and they contact each other to become a paste-like liquid. Although the stirring is stopped, the starch will no longer precipitate. This phenomenon is called "gelatinization". The resulting viscous liquid is called starch paste, and the temperature at which this phenomenon occurs is called the gelatinization temperature.
The aging of starch is actually a process in which the gelatinized starch whose molecular hydrogen bonds have been broken is rearranged to form new hydrogen bonds, which is a recrystallization process.
2. Liquefaction
There are many liquefaction processes, but jet liquefaction is currently the most ideal liquefaction method. Judging from the production conditions of various domestic factories, when the steam pressure is ≥ 0.8Mp, the high-pressure steam injection liquefaction process is used; when the steam pressure is ≤ 0.5Mp, the low-pressure steam injection liquefaction process is used. The injection liquefaction process is divided into one enzyme addition process and two additions. Enzyme process.
If the production of glucose and fructose syrup products, using potato raw materials, of course, one-time enzyme addition process. Use corn wheat starch, if the starch quality is good (low protein content ≤0.3%), considering the simple enzyme addition process, saving steam, light sugar color, you can use a single enzyme addition process. If the quality of starch such as corn and wheat is poor (the protein content is greater than 0.6-1.0%), and such starch is easy to age, it is easy to produce "insoluble starch granules". Therefore, the protein content in the raw materials is high and the raw material particles are large. The liquefaction can be completed only by adding enzyme method.
(2) Saccharification
At the end of liquefaction, quickly adjust the pH of the feed solution to 4.2 to 4.5 with acid, and at the same time quickly reduce the temperature to 60 ℃, then add saccharification enzyme, 60 ℃ to keep the saccharification, the saccharification process should be stirred regularly to prevent uneven saccharification, after saccharification, when When using anhydrous alcohol to check that there is no dextrin, adjust the pH of the feed solution to 4.8-5.0, at the same time, heat the feed solution to 80 ℃, keep it warm for 20 minutes, and then start filtering. The filtrate enters the sugar storage tank and is kept warm at 60 ℃ or more. use.
(3) Filter
Although the DE value can reach more than 98% after starch saccharification, insoluble and soluble impurities, ash, fat, protein, etc. are brought into the starch during hydrolysis, and at the same time, some impurities are added in the hydrolysis process, such as inorganic salts brought by acid addition, Proteins brought in by the enzyme, polysaccharides and oligosaccharides produced by the decomposition process, 5-hydroxymethylfurfural (5-HMF) and colored substances produced by side reactions, all need to be refined and removed to improve the glucose value and the quality of the finished product. So after saccharification, it needs to be filtered.
When using anhydrous alcohol to test for the absence of dextrin, the saccharification is completed, and then the pH 4.2 ~ 4.5 is adjusted to pH 4.8 ~ 5.0, and heated to 80 ℃, maintained for 20 minutes, began to remove residue filtration. Filtration methods include plate filtration, vacuum drum filtration, membrane filtration, centrifuge separation and other methods. My company's process generally uses plate filtration.
(4) Decolorization
The enzymatic saccharification solution is decolorized, generally neutralized, and the pH is adjusted to about 4.8, but the enzyme itself is a protein, and the pH of the sugar solution is close to the isoelectric point of the protein, and there are many suspended substances. Most factories are pre-coated with diatomaceous earth. The drum filter is filtered first, or the used activated carbon is added to filter the protein and fat impurities with a plate and frame filter, and then decolorized.Because of the light color of the enzymatic saccharification solution, it is generally only necessary to decolor the activated carbon twice. It can be exchanged by cation and anion, and some does not need to be decolorized by activated carbon. It can also be directly exchanged by resin after filtration by drum filter.
In the process of our factory, the decolorization filtering is mainly based on plate filtration. In order to facilitate automatic control and improve the operating environment, candle filters are used abroad to consist of multiple filter tubes or rods, such as DDS filter (thickening) filter, which is a A round or square closed container with a microporous filter tube inside. The filter tube can be made of metal or polyethylene. Generally, the sugar liquid is pumped from the lower part of the filter through the pump before filtration, and the filter mud with impurities is left in the filter to clean the filtrate. The filter tube is pressed out from the upper part. When the filtration speed is slowed, the filtration can be stopped, backwashed, and then filtered again.
(5) Ion exchange
Use the exchangeable ions carried by the functional group fixed on the three-dimensional network skeleton to change the environmental conditions such as ion concentration, so that it can reversibly and repeatedly exchange with the surrounding peripheral ions to achieve the separation, replacement, concentration of substances, The removal of impurities and the catalytic purpose of chemical reactions.
Because the skeleton structure of the ion exchange resin is fixed, the reversible exchange only performs ion exchange on the functional group, so it can be used repeatedly for thousands of times for a long time, but the resin also gradually degrades with the use of time. The distinguishing feature of ion exchange resins is that they can be used repeatedly and repeatedly, that is, they have a long service life, which can simplify the production process, shorten production time, improve quality and efficiency, and reduce costs.
After the exchange, the resin that changed from the hydrogen type of the raw material to the sodium type is the resin that has been used and has lost the exchange ability. Then put the resin into a strong acid (regenerant) such as hydrochloric acid with a large concentration (5%). At this time, the concentration of hydrogen ions in the solution is large. Similarly, due to the effect of the difference in concentration, it is easy to remove the sodium ions on the resin After the exchange, the resin can be replaced with hydrogen ions that can be exchanged to restore the exchange capacity and can be reused. This is the regeneration process.
(6) Evaporation and concentration
For the evaporation process, continuous evaporation or intermittent evaporation, one evaporation or multiple evaporations can be selected according to the process and equipment conditions. The typical sugar liquid evaporation process is as follows: In the production of crystalline glucose, most plants use secondary evaporation, first dilute the sugar liquid in a three-effect vacuum evaporator to continuously evaporate to 45-50oBx concentrated sugar liquid, and then pass through the concentrated sugar liquid After being purified again, it is sent to a single-effect vacuum tank and evaporated to the desired concentration of 72-74oBx for crystallization.In this vacuum tank, evaporation can be continuously fed, but the output is carried out in batches.After steaming, the concentrated syrup volume and concentration meet the requirements. Coarse material; another evaporation process is one-time evaporation to the bottom, generally suitable for the evaporation of enzymatic syrup. The initial concentration of enzymatic saccharification liquid is high, mostly around 35 oBx, and the purified saccharification liquid can be directly subjected to multi-effect evaporation once. Steam to the final concentration; there are also continuous inlet and outlet evaporation. After purification, the saccharified liquid continuously enters the evaporation system. The system includes single-effect or multiple-effect, and multiple-effect combined single-effect, and continuously extracts the syrup that evaporates to the final concentration. This type of evaporation must have a corresponding automatic control instrument, otherwise it is difficult to operate.
(7) Crystallization
Crystallization is a method of transforming an object from a liquid phase to a solid phase and separating the solid phase. It is also the most important method for obtaining pure substances. Crystallization is the most critical process in the production of crystalline glucose, and it is also an important process directly related to product quality and yield.
The glucose crystallization process is relatively complicated, mainly related to the quality and yield of products, which are described as follows.
1. A crystallization process
The process is direct crystallization after starch emulsification, saccharification, purification and concentration. The mother liquor is discharged directly without recycling. The process and equipment are simple, the quality of the finished product is good, but the yield is low, generally only about 50%. It is suitable for units where mother liquor has other applications, such as mother liquor is directly used in fermentation workshop for other products.
2. Secondary crystallization process
In this process, after the product mother liquor is decolorized or separated, most of it is returned to the primary crystallization system. The wet sugar obtained by crystallization and separation can generally only be used for secondary crystallization of sugar or industrial sugar, because the mother liquor is reused too much. , The crystal purity is low, and the quality of the crystalline sugar is poor, but from the perspective of the entire system, the final product is secondary crystallization, the quality is better, and most of the mother drug is reused in the pharmaceutical sugar system, and a small part is returned to a product system , The total yield is higher, which is an important process for the production of medicinal sugar
3. Production process of anhydrous glucose
The process is to produce anhydrous glucose by secondary crystallization, the product quality is high, the pharmaceutical mother liquor can be made into glucose monohydrate, part of the pharmaceutical mother liquor can also be returned to the wet sugar dissolving part, the glucose monohydrate mother liquor is partly returned to the glucose monohydrate system Use, part can be discharged into a product system, a product mother liquor can be reused partly, excess discharge.
(8) Separation and drying
1. Separation
The sugar paste after crystallization of glucose includes crystalline particles and uncrystallized liquid (commonly known as mother liquor or green liquor mother liquor or greens). It is necessary to separate the glucose crystalline particles from the mother liquor by centrifugal separation. The separation equipment is a centrifuge, sugar After the paste is added, it rotates randomly, and the mother liquor is thrown out by the action of centrifugal force, and the crystal is left in the basket and discharged.
2. Dry
Glucose drying equipment includes drum dryers, airflow dryers, fluidized bed dryers, etc., and spray dryers are also used to directly dry high-concentration sugar liquids. Drum dryer, generally a rotating drum, with steam jacket heating, there is a copy in the cylinder, the body has a certain slope, glucose is added from one end, and flows slowly in the cylinder, about 5r/min, such as 1000×5000mm The drum dryer has a production capacity of about 10t/d. The airflow dryer is a commonly used glucose drying equipment. It is composed of an air heater, a blower, an airflow tube, and a cyclone separator. After separation, glucose enters the airflow It needs to be crushed before the dryer, which is brought in by the hot air after heating. The inlet temperature of the hot air is generally 70～75℃, the outlet temperature is 30～35℃, the airflow speed is about 20m/s, if the diameter of the airflow pipe is 400mm, the length is 18m, the air volume is 8000m3/ h, the wind pressure is 4900Pa (500mmH2O), the production capacity is about 10t/h; the fluidized bed dryer is another type of airflow drying equipment, and the hot air is sprayed through the small holes in the lower part of the fluidized bed through the fan to make the orifice plate The glucose in the upper part moves into a fluidized state. After absorbing water, the air is recovered by the cyclone and then discharged to achieve the purpose of drying. In order to ensure the quality of the product, there is also a cold air device added after the dryer to reduce the temperature of the glucose after drying.It is best to reach room temperature before packaging to prevent agglomeration, but it should be noted that the cold air must also be dry and will not cause the sugar to regain moisture after drying. . The drying equipment is the main post of "finishing, baking and packaging" for the production of glucose, so the material of the equipment should be stainless steel, and the air should be purified, and no impurities should be introduced.
(IX) Production of Maltodextrin
Maltodextrin can be divided into three categories:
MD100: DE value,% (m/m) ≤10
MD150: DE value,% (m/m) ≤15
MD200: DE value,% (m/m) ≤20
(MD is the abbreviation of maltodextrin).
There are three main requirements for the senses:
Appearance Amorphous powder with white or slightly yellowish shadow, no visible sundries
Smell It has the special smell inherent in maltodextrin, no peculiar smell
Taste Not sweet or slightly sweet, odorless, no odor
In the production of maltodextrin, it is generally spray dried after concentration. based on digestion and absorption of pressure spray drying towers at home and abroad, our company has developed a series of pressure spray dryers with high product yield and low energy consumption. For details, please refer to the section of Pressure Spray Dryers.
Note: Each set of specific process equipment is generally different due to different raw materials, local conditions, local laws and regulations, market and customer requirements, etc., so the specific configuration and process parameters of each set of equipment are generally different. Please provide as much detailed information as possible when we design, so that we can design and manufacture suitable equipment.
