The invention belongs to the agricultural
natural product extraction field, in particular relating to a method for extracting unmodified collagen from
freshwater fish scale. The method comprises the following steps that: (1) cleaned scale is added in
distilled water and is stirred intermittently by a motor stirrer for 3 to 5 minutes till the surface of the scale has no attachment of
pigment and fat, etc.; the scale is crushed to 40 to 50 meshes after natural
air drying and low-temperature
drying; (2) the materials of the step (1) are added into 8 to 10 percent of
citric acid and
malic acid solution according to a ratio of between 1 to 10 and 1 to 20 so as to carry out ice-water bath
microwave treatment for 2 minutes and decalcification at a temperature of between 10 and 20 DEG C for 8 to 24 hours; then, the solution is filtered and the filtrate undergoes standing at a temperature lower than 10 DEG C for 5 to 10 hours so as to obtain
calcium citrate precipitate; (3) according to a ratio of between 1 to 5 and 1 to 20, 1 percent
malic acid or
citric acid solution (containing
protease) is added into the de-
calcification scale obtained after the treatment of step (2), and is stirred and extracted 2 to 4 times at a temperature of between 0 and 20 DEG C with each time lasting 12 to 48 hours; then,
centrifugation is carried out, and supernatant is taken out; NaCl is added till final concentration reach 0.7 to 0.90 mol / L, and then
salting out is carried out over night;
centrifugation and deposition are carried out, and the obtained substance is dissolved in 0.50mol / L
acetic acid; then,
salting out and dissolving operations are repeated one more time, and the precipitate undergoes
dialysis so as to obtain the product of the invention through
freeze drying.