Abstract
| - The rennet coagulation properties of highly pressurized milk have beeninvestigated. The initialrate and extent of the enzymatic phase of coagulation, determined onthe basis of the release ofcaseinomacropeptides (CMP) soluble in 4% trichloroacetic acid, wereinhibited by pressures over200 MPa. However, the coagulation time decreased as pressureincreased up to 200 MPa and thenincreased again, until at 400 MPa, it reached values comparable withthose of the raw milk.Therefore, the coagulation time of the pressurized milk was notdirectly related to the degree ofκ-casein hydrolysis, indicating that pressure probably favored theaggregation phase. Addition ofCaCl2 enhanced casein aggregation of native or pressurizedmilk, reducing coagulation time andcurd-firming time, but did not offset the rate-increasing (up to 200MPa) or rate-lowering (at 300and 400 MPa) effects of milk pressurization on subsequent caseincoagulation by rennet. The SDS−PAGE studies of pressure-treated and untreated milk or solutionscontaining κ-casein, β-lactoglobulin, or both in the presence or absence of denaturing agents showedevidence for the formation ofaggregates linked by intermolecular disulfide bonds. Keywords: High pressure; rennet coagulation; proteinaggregation
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