15B-21 |
Inhibition of proteolytic enzymes used in Cheddar cheese making by high pressure |
A. S. MALONE1, C. Wick, P. D. Courtney, and T. H. Shellhammer. (1) Department of Food Science and Technology, Ohio State University, Parker Hall, 2015 Fyffe Road, Columbus, OH 43210 High-pressure processing is a novel manufacturing technology capable of activating and/or inactivating many food enzymes. Application of high pressure to Cheddar cheese for short periods of time early in the ripening process has the potential to shorten ripening time. Applying higher pressures later during ripening may allow cheese manufacturers to arrest ripening at a desired level. The objective of this study was to determine the effects of high-pressure treatments on the activities of lactococcal peptidases and chymosin. A commercial recombinant chymosin preparation was pressure-treated without dilution. Lactococcus lactis MG1363 cells were grown to late exponential phase, washed once in phosphate-buffered saline, resuspended in PBS and pressure-treated. Following pressure-treatment, cell concentration and disruption, the peptidase activites of L. lactis cell lysates were determined at 30°C. Samples were pressure treated up to 800 MPa for five minutes at 25°C using a Flow Pressure Systems QFP-6 Cold Isostatic Press. Activity of proteolytic enzymes was assayed using chromogenic substrates under standard assay conditions. Hydrolysis products were monitored spectrophotometrically. Pressure treatment reduced chymosin activity 50% compared with non-pressure treated controls. Lactococcal peptidase activities (PepN and PepC) were insensitive to pressure treatment up to 200 MPa, beyond which pressure caused significant reduction in activity. Maximal reduction of 99.4% was achieved at 800 MPa. Reduction in proteolytic enzyme activity via high-pressure treatment may allow processors to control the extent of cheese ripening.
Session 15B, Dairy Foods: Chemistry, microbiology and sensory analysis of various cheeses
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