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 degrees C, on micelle structure, pr oteolytic activity, and sensory properties of milk. Pressure treatments at 25 degrees C considerably reduced micelle size, while pressurization at hig her temperatures progressively increased micelle dimensions. Pressure-induc ed denaturation of P-lactoglobulin (beta-LG) amounted 76% at 25 degrees C a nd was almost 100% in milks treated at 40 to 60 degrees C. a-lactalbumin (c r-LA) was resistant to pressure at temperatures up to 40 degrees C, but its denaturation reached 56% at 60 degrees C. Plasmin resisted pressurization at room temperature; however, pressure treatments at higher temperatures in creased plasmin inactivation, which reached 86.5% at 60 degrees C. Pressuri zation at temperatures from 40 to 60 degrees C reduced the proteolytic acti vity and improved the organoleptical properties of milk, compared with the same treatments at 25 degrees C, which suggested that these combined treatm ents could be used to produce milk of good sensory properties with an incre ased shelf life. These results are discussed in the Light of the changes fo und in micellar structure.