Microbicidal effect of hydrostatic pressure on satsuma mandarin juice

Six microbial strains were inoculated into Satsuma mandarin ( Citrus unshiu Marc. ) juices and the effects of hydrostatic pressure on their viability were examined. Five micro-organisms were substantially inactivated under 400 MPa at room temperature for 5 min whereas B. subtilis survived. the effects achieved by treating at 57°C under 100 MPa for 5 min were comparable to those achieved by treating under 400 MPa at room temperature for 5 min. Pectin esterase was not inactivated even after treating at 600 MPa and 57°C for 5 min. Although the high pressure treatment exerted hardly any effect on juice chemical components, the pulp particle size distribution was slightly changed by treating under 600 MPa at room temperature for 30 min. Pressure treatment had little effect on the volatile flavour components.