2.6. Determination of Degree of Hydrolysis of PSC and Collagen Peptide via O-Phthalaldehyde (OPA) Method

A method as described by Church et al. [11] was used to determine the degree of hydrolysis of PSC and collagen peptide via a spectrophotometer. Briefly, a 20 μL sample of PSC or collagen peptide solution was mixed with OPA reagent (1 mL) and reacted at room temperature for 2 min for the absorbance measurement at 340 nm. The serine standard curve was also prepared and used as a basis for conversion into degree of hydrolysis using a formula as described by Church et al. [11].