Extraction of pepsin-soluble collagen (PSC)
The undissolved residue obtained after ASC extraction was used
for further extraction with the gastric proteinase pepsin. The residue
was soaked in 0.5M acetic acid with a solid/solvent ratio of 1:15
(w/v) and pepsin (20 U/g residues) added. The mixture was
continuously stirred at 4°C for 3 days, followed by filtration through
two layers of cheesecloth. The filtrate was subjected to precipitation
and the pellet dialyzed, as previously described for ASC. The
dialysate was freeze-dried and is referred to as pepsin-soluble
collagen (PSC). The yield of PSC was calculated in the samemanner as ASC. Additionally, the accumulated yield of collagenwas calculated from the total yield of ASC and PSC