Effect of Sub- and Super-critical Water Treatment on Physicochemical Properties of Porcine Skin

Super- and sub-critical water treatments have been of interest as novel methods for protein hydrolysis. In the present study, we studied the effect of sub-critical water (Sub-H(2)O, 300℃, 80 bar) treatment as well as super-critical water (Super-H(2)O, 400℃, 280 bar) treatment on the physicochemical properties of porcine skin (PS), which has abundant collagen. Porcine skin was subjected to pre-thermal treatment by immersion in water at 70℃, and then treated with sub- or super-critical water. Physicochemical properties of the hydrolysates, such as molecular weight distribution, free amino acid content, amino acid profile, pH, color, and water content were determined. For the molecular weight distribution analysis, 1 kDa hydrolyzed porcine skin (H-PS) was produced by Super-H(2)O or Sub-H(2)O treatment. The free amino acid content was 57.18 mM and 30.13 mM after Sub-H(2)O and Super-H(2)O treatment, respectively. Determination of amino acid profile revealed that the content of Glu (22.5%) and Pro (30%) was higher after Super-H(2)O treatment than after Sub-H(2)O treatment, whereas the content of Gly (28%) and Ala (13.1%) was higher after Sub-H(2)O treatment. Super-H(2)O or Sub-H(2)O treatment affected the pH of PS, which changed from 7.29 (Raw) to 9.22 (after Sub-H(2)O treatment) and 9.49 (after Super-H(2)O treatment). Taken together, these results showed that Sub-H(2)O treatment was slightly more effective for hydrolysis than Super-H(2)O was. However, both Sub-H(2)O and Super-H(2)O treatments were effective processing methods for hydrolysis of PS collagen in a short time and can be regarded as a green chemistry technology.