Abstract:

Collagens extracted from the skin of the Chinese longsnout catfish Leiocassis longirostris by alkali, salt, hot
water, acid and pepsin were comparatively evaluated for their chemical and structural properties (amino acid compositions,
thermo-stability, molecular weight distribution and scanning electron microscope) and rheological characteristics. The
results showed that all collagens presented similar UV spectrum with the absorption peak at 230 nm. SDS-PAGE indicated
collagens extracted by acid, pepsin and water belonged to collagen I with well-preserved structure. The denaturation
temperatures of collagens extracted by alkali, water, salt, acid and pepsin were 63.21, 71.70, 49.49, 29.8 and 22 ℃,
respectively. The salt-extractable collagen was polypeptides as analyzed by high-performance liquid chromatography
(HPLC). The water-soluble collagen from the fish skin presented the highest gel stability. Therefore, different extraction
methods could result in differences in the chemical and structural properties of fish skin collagens.

Key words: Leiocassis longirostris, collagen, alkali extraction, salt extraction, hot-water extraction, physicochemical properties