Effects of pressure on gelatinization of collagen and properties of extracted gelatins

Ultra-high pressure (UHP) was applied as a pretreatment to extract gelatins with 1% (w/v) hydrochloric acid as the transmission medium at a skin/solution ratio of 1:1.5 (w/v). The effects of various pressures (ranging from 0.1 to 500 MPa) on the gelatinization of collagen and the properties of the extracted gelatins were investigated. The thermostability of the pressurized collagens and the yield, molecular-weight distribution, gel strength and rheological properties of the extracted gelatins were evaluated. UHP pretreatment could decrease the thermostability and enhance the extent of gelatinization of the collagen. The temperature at which the major endothermic peak was observed (Tm) decreased as the pressure level increased from 100 to 400 MPa but increased as the pressure reached 500 MPa, whereas the opposite trend was observed for the gelatins yields. The UHP gelatins contained more subunit components than traditional gelatin, which increased in content with increasing pressure up to 300 MPa; the amount of subunit components remained nearly constant when the pressure was further increased. The gel strength and rheological properties of the UHP gelatins were better than those of traditional gelatin, and they exhibited similar tendencies to those of high-molecular-weight gelatins with increases in the pretreatment pressure.