Kinetic study of high pressure microbial and enzyme inactivation and selection of pasteurisation conditions for Valencia Orange Juice

Abstract

Keeping quality of fresh orange juice is highly dependent on pectinolytic enzyme activity and the growth of spoilage microorganisms. The inactivation kinetics of indigenous pectin methylesterase (PME) and of the two more pressure resistant species of spoilage lactic acid bacteria (LAB) Lactobacillus plantarum and L. brevis in freshly squeezed Valencia orange juice under high hydrostatic pressure (100-500 MPa) combined with moderate temperature (20-40°C) was investigated. PME inactivation followed first order kinetics with a residual PME activity (15%) at all pressure-temperature combinations used. The values of activation energy and activation volume were estimated at each pressure and at each temperature, respectively. Values of 90 kJ ⁄ mol and )30 mL ⁄ mol at reference pressure of 300 MPa and reference temperature of 35°C were estimated respectively. The corresponding z T and z P values of LAB inactivation were also estimated at all conditions tested. Values of 19.5°C and 95 MPa at reference pressure of 300 MPa and reference temperature of 30°C were estimated respectively for L. plantarum, while the corresponding values for L. brevis were 40°C and 82 MPa, respectively, at the same reference conditions. Pressure and temperature were found to act synergistically both for PME and LAB inactivation. The PME and LAB inactivation rate constants were expressed as functions of the temperature and pressure process conditions. These functions allow the determination of the pressure ⁄ temperature conditions that achieve the target enzyme and microbial inactivation at a selected processing time. The process conditions of 350 MPa at 35°C for 2 min are proposed as effective for Valencia orange juice cold pasteurisation.

High-Pressure Cold Pasteurization of Gilthead Seabream Fillets: Selection of Process Conditions and Validation of Shelf Life Extension

“…was expressed by the z T value. These values ranged from 23.5 to 33.7°C for the tested range of processing pressures (R 2 from 0.92 to 0.96), with no definite trend when the applied pressure is increased, which is in agreement with previous studies for a wide range of tested microorganisms, growth media or processing conditions (Reyns et al 2000;Mallidis et al 2003;Katsaros et al 2010). In all the obtained curves, a tailing was observed with further processing significantly increasing the inactivation of microorganisms.…”

Combined osmodehydration and high pressure processing on the enzyme stability and antioxidant capacity of a grapefruit jam

“…Processing conditions of 600-700 MPa for 1-3 min combined with mild temperatures (50-60°C) have proven to be effective in inactivating native orange PME (Nienaber and Shellhammer, 2001;Polydera et al, 2004;Sampedro et al, 2008). The percentage of pressure-stable fraction estimated in this study (27-40%) is much higher than that obtained by several authors in different plant-based systems; 7-15% in orange juice; 3, 10 and 20% in purified form from carrot, strawberry and white grapefruit, respectively (Goodner et al, 1998;Ly-Nguyen et al, 2002a,b;Guiavarc'h et al, 2005;Katsaros et al, 2010). It has been stated that the amount of PME stable fraction is variable and depends to a large extent on the fruit, and within the same fruit, the variety used and the time of harvest (Snir et al, 1996).…”

Effect of High Pressure Processing on the Microbial Inactivation in Fruit Preparations and Other Vegetable Based Beverages

“…With regard to inactivation effectiveness, many factors can influence the spoilage reduction of various microorganisms, as commented before. Mild conditions (i.e., 100 MPa, <5 min at room temperature can reach only one log reduction or less in L. monocytogenes, total aerobic bacteria, L. plantarum, L. brevis, E. coli, L. innocua, S. cerevisiae, faecal coliforms, and yeast and molds [51,56,65,70,[77][78][79]. Increasing the pressurization conditions (>350 MPa, 5 min and >20 • C), inactivation > 7 log reduction can be achieved for certain microorganisms [40,41,53,54,61,76].…”