Micellar changes induced by high pressure. Influence in the proteolytic activity and organoleptic properties of milk

We investigated the effects of high-pressure treatments at 400 MPa, applied for 15 min at temperatures of 25 to 60°C, on micelle structure, proteolytic activity, and sensory properties of milk. Pressure treatments at 25°C considerably reduced micelle size, while pressurization at higher temperatures progressively increased micelle dimensions. Pressure-induced denaturation of β-lactoglobulin (β-LG) amounted 76% at 25°C and was almost 100% in milks treated at 40 to 60°C. α-Lactalbumin (α-LA) was resistant to pressure at temperatures up to 40°C, but its denaturation reached 56% at 60°C. Plasmin resisted pressurization at room temperature; however, pressure treatments at higher temperatures increased plasmin inactivation, which reached 86.5% at 60°C. Pressurization at temperatures from 40 to 60°C reduced the proteolytic activity and improved the organoleptical properties of milk, compared with the same treatments at 25°C, which suggested that these combined treatments could be used to produce milk of good sensory properties with an increased shelf life. These results are discussed in the light of the changes found in micellar structure.This work received financial support by the projects 06G/053/ 96 (Comunidad de Madrid) and ALI97-0759 (Comisión Interministerial de Ciencia y Tecnología)