Optimization of pretreatment process
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| Preparation of Raw Materials for Cowhide |
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| Cowhide Cleaning |
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| Processing of Crushed Skin |
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| Acid Immersion Treatment|
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| Enzymatic Hydrolysis Reaction |
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| Centrifugal Separation of Impurities |
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| Concentrated Solution |
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| Drying Treatment |
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| Finished Collagen Powder |
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Collagen extraction technology
Enzymatic Extraction
1.Selection and preparation of enzymes:
Choosing the appropriate enzyme is the key to extracting collagen. Commonly used enzymes include pepsin, papain, trypsin, etc. Among them, pepsin has a higher specificity for collagen and a better extraction effect.
Prepare an enzyme solution of appropriate concentration based on the weight of the cowhide and the content of collagen. The general usage concentration of pepsin is 0.1%-0.5%, and that of papain is 0.5%-1.0%.
2. Enzymatic hydrolysis conditions:
Mix the soaked cowhide blocks with the enzyme solution and put them into the enzymatic hydrolysis tank for enzymatic hydrolysis reaction. The enzymatic hydrolysis temperature is generally controlled at 30-35℃, the pH value is 1.5-2.5 (pepsin) or 6.0-7.0 (papain), and the stirring speed is 50-100r/min.
The enzymatic hydrolysis time is usually 40 to 60 minutes, and the specific time needs to be adjusted according to the type of enzyme and the characteristics of the cowhide. During the enzymatic hydrolysis process, regular sampling and testing should be carried out to ensure that collagen is fully released and does not undergo excessive degradation.
3. Solid-liquid separation:
After enzymatic hydrolysis is completed, the enzymatic hydrolysis solution is passed through a filter press or centrifuge for solid-liquid separation to obtain the extract containing collagen and solid residue. Filter presses are suitable for large-scale production, while centrifuges are suitable for small-scale operations in laboratories.
The separated solid residue can be further processed, such as being used to extract other bioactive substances or as raw materials for organic fertilizers.
Comparison of Acid-Base Methods
• Acid method: Use 0.5mol/L acetic acid as the medium, extract at 32℃ for 6 hours. The molecular weight of the product is relatively low, but it may destroy the triple helix structure.
• Alkaline method: After 48 hours of treatment with sodium hydroxide (pH 11), the fiber yield can reach 50%, but the secondary structure of collagen is severely damaged. It is suitable for low-value-added products.
Purification
Centrifugal separation:
The extract is placed in a high-speed refrigerated centrifuge for centrifugal separation. The rotational speed is generally 8000-10000r/min, and the centrifugation time is 15-20 minutes. After centrifugation, take the supernatant to remove impurities in the precipitate and the incompletely enzymatically hydrolyzed cowhide fragments.
Ultrafiltration and nanofiltration:
The supernatant after centrifugation was filtered using an ultrafiltration membrane (with a pore size of 10-50 kda) to remove macromolecular impurities and some unenzymatically hydrolyzed proteins. The ultrafiltration process should be carried out at a relatively low pressure to avoid damaging the collagen.
Nanofiltration membranes (with pore diameters ranging from 1 to 10 kda) can be used to further concentrate and purify collagen solutions, remove small molecule impurities and moisture, and enhance the concentration and purity of collagen.
Ion Exchange and Adsorption:
Based on the isoelectric point of collagen (pI is approximately 7.5-8.0), select an appropriate ion exchange resin for further purification. Under acidic conditions, collagen carries a positive charge and can be adsorbed on anion exchange resins. Under alkaline conditions, collagen carries a negative charge and can be adsorbed on cation exchange resins.
The adsorbed collagen can be eluted by gradient elution or pH adjustment to obtain a high-purity collagen solution. Ion exchange method can effectively remove impurities such as impurity proteins and polysaccharides, and improve the purity of collagen.
Drying and crushing
1.Vacuum freeze-drying
The refined collagen solution is placed in a vacuum freeze dryer for freeze-drying. First, the solution is pre-frozen at -40℃ to -50℃, and then sublimation drying is carried out under vacuum conditions (with a pressure of approximately 10^-2Pa), with the temperature controlled at -20℃ to -30℃.
Vacuum freeze-drying can effectively protect the active structure of collagen, prevent damage from high temperatures, and the obtained products have good solubility and biological activity.
2. Spray drying
For large-scale production, spray drying is an efficient option. The collagen solution is atomized into tiny droplets through the nozzle of the spray dryer and rapidly dried in the hot air flow to obtain collagen powder.
The inlet air temperature for spray drying is generally 150-180℃, and the outlet air temperature is 80-100℃. It is necessary to control the drying speed and temperature to prevent thermal denaturation of collagen.
3. Crushing and screening
The dried collagen blocks or flakes are crushed through a multi-stage temperature-controlled crushing production line to obtain collagen powder with uniform particle size. During the crushing process, the temperature should be controlled to prevent the denaturation of collagen due to heat generated by friction.
The crushed collagen powder is screened through a screening device to ensure that the particle size of the product meets the requirements (generally 150 mesh -200 mesh). The fine powder after screening can be directly packaged, and the coarse powder can be returned to the crusher for re-crushing.
Conclusion
As a natural biomaterial with a wide range of applications, the production process of bovine skin extracted collagen powder has been optimised continuously, and the quality of the product and the range of applications have been expanding.From raw material pre-treatment to finished product packaging, each link has an important impact on the quality and performance of the final product.With the development of green extraction technology, the application of intelligent equipment and the depth of interdisciplinary research, the cowhide extract collagen powder industry will usher in greater development opportunities.