title: High-pressure processing of apple juice: kinetics of pectin methyl esterase inactivation.
abstract: High-pressure (HP) inactivation kinetics of pectin methyl esterase (PME) in apple juice were evaluated. Commercial PME was dispensed in clarified apple juice, sealed in dual peel sterilizable plastic bags, and subjected to different high-pressure processing conditions (200-400 MPa, 0-180 min). Residual enzyme activity was determined by a titration method estimating the rate of free carboxyl group released by the enzyme acting on pectin substrate at pH 7.5 (30 degrees C). The effects of pressure level and pressure holding time on enzyme inactivation were significant (p < 0.05). PME from the microbial source was found to be more resistant (p < 0.05) to pressure inactivation than PME from the orange peel. Almost a full decimal reduction in the activity of commercial PME was achieved by HP treatment at 400 MPa for 25 min. Inactivation kinetics were evaluated on the basis of a dual effect model involving a pressure pulse effect and a first-order rate model, and the pressure sensitivity of rate constants was modeled by using the z-value concept.
authors.affiliation: Department of Food Science and Agricultural Chemistry, Macdonald Campus of McGill University, Ste. Anne de Bellevue, PQ, Canada H9X 3V9.
authors.forename: Esmaeil
authors.initials: E
authors.lastname: Riahi
authors.forename: Hosahalli S
authors.initials: HS
authors.lastname: Ramaswamy
mesh_terms: D000465:Algorithms; D001628:Beverages; D002265:Carboxylic Ester Hydrolases / Q000737:chemistry*; D020650:Combinatorial Chemistry Techniques; D004789:Enzyme Activation; D004791:Enzyme Inhibitors; D005240:Feasibility Studies; D005511:Food Handling / Q000379:methods*; D005638:Fruit / Q000737:chemistry* / Q000201:enzymology; D007700:Kinetics; D027845:Malus / Q000737:chemistry* / Q000201:enzymology; D011312:Pressure
chemical_list: D004791:Enzyme Inhibitors; D002265:Carboxylic Ester Hydrolases; C022323:pectinesterase