Collagen is an extracellular interstitial component, which exists in the body as an insoluble macromolecular structure and is combined with protein polysaccharides, glycoproteins, etc. Therefore, the extraction technology of collagen is complex and has many steps, usually including the selection of tissue materials, pretreatment, Collagen extraction, separation, and purification of different types of collagen, among which the extraction of collagen is the most critical.
Tissue material selection and pretreatment
The tissue material used for collagen extraction must be carefully pretreated, the most important thing is to scrape off non-collagen appendages such as minced meat, fat, etc., and extract the fat with an organic solvent to avoid ending up with fat-containing collagen milk. turbid liquid. After further removal of calcium in bone tissue and proteoglycan in cartilage tissue, the tissue material can be sliced, crushed, or homogenized for collagen extraction.
Extraction of animal-derived collagen
Traditionally, collagen is mainly extracted from the skins and bones of terrestrial animals such as pigs and cattle. It has recently been found that fish skin, bones, and scales are also rich in collagen. Extracting collagen from aquatic animal tissues can not only make full use of aquatic resources and increase the added value of aquatic product processing but also reduce pollution and be more environmentally friendly. At the same time, due to the existence of livestock diseases such as mad cow disease and foot-and-mouth disease, people are more willing to believe that aquatic collagen has higher safety than livestock-derived collagen. Therefore, the extraction of collagen from aquaculture waste, such as fish skins, scales, and bones, is gaining more and more attention.
Common collagen extraction protocols:
The acid extraction method is an extraction method in which the raw materials are pretreated by acid soaking and then purified by a series of operations such as centrifugation. Common acids include hydrochloric acid, oxalic acid, acetic acid, acetic acid, citric acid, and lactic acid. The bound fat undergoes a saponification reaction with an alkaline solution to remove the non-helical terminal peptide and dissolve the collagen fibers. Sodium hydroxide, sodium carbonate, and calcium hydroxide are often used alkali treatment agents. Under alkaline conditions, the peptide bonds of collagen are easily hydrolyzed, and its supercoiled structure will be destroyed. Therefore, there are few studies on the extraction of collagen by the alkaline method. It dissolves in acidic solutions or neutral salt solutions. One of the reasons why enzymatically extracted collagen is widely used in biomedical materials is its low immune performance, and the frequently used enzymes include trypsin, pepsin, papain, and neutral protease.
How to make collagen at home?
Collagen is the most important fibrin in raw hides and is the main component of animal skin.
1. Using cowhide as raw material, through the steps of cowhide pretreatment, quantitatively adding caustic soda, adjusting pH, adding alkaline protease, leaching, collecting filtrate, salting out, centrifuging the precipitation, and freeze-drying, the solid collagen of yak cowhide is finally extracted. For protein products, the optimal preparation conditions of yak skin collagen determined by the orthogonal test are a leaching solid-liquid ratio of 1:35 (g: mL), protease dosage of 1.5% (mass fraction), and leaching time of 12 h, leaching time of The temperature was raised to 36 °C.
2. The extraction process of pigskin collagen is as follows: add 0.1 mol/L NaOH solution according to the ratio of 1:10 (g: mL), soak and degreasing for 6 h, enzymatic hydrolysis for 24 h, add dropwise completely dissolved sodium chloride solution for salting out, followed by dialysis and purification of collagen with acetic acid solution and deionized water, and lyophilized to obtain collagen samples.
3. The operation steps of extracting collagen from fish skin by acid method and enzyme extraction method are shown in the figure:
