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Pressure Cycle (pressure + cycle)
Selected AbstractsHIGH PRESSURE INACTIVATION OF PECTIN METHYL ESTERASE IN ORANGE JUICE USING COMBINATION TREATMENTSJOURNAL OF FOOD BIOCHEMISTRY, Issue 6 2001S. BASAK ABSTRACT The contribution of several high pressure (HP) processing related factors (pressure level, 300-400 MPa; pressure cycle, 1-3, and pressure-hold time, 30,120 min) on the inactivation of pectin methyl esterase (PME) in single strength (pH 3.7 and 11.4 °Brix) and concentrated (pH 3.5 and 42 °Brix) orange juice was evaluated. A response surface methodology was employed to model the combined effects of factors on the enzyme inactivation. The main effects were described by linear or quadratic functions. For both single strength and concentrated orange juices, the effects of all three main factors and some interactions (pressure level, cycle and holding time) were statistically significant (p<0.05). The dual nature of pressure inactivation of PME (with an instantaneous inactivation due to a pressure pulse, instantaneous pressure fall, and first order rate of inactivation during the pressure hold, yielding D and z values) reported in earlier studies was confirmed. Combination models were developed to predict the residual enzyme activity as influenced by the pressure level, number of pressure cycles and pressure hold time. [source] Characterisation of pressure-treated skimmed milk powder dispersions: application of NMR spectroscopyJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 10 2002Colin D Hubbard Abstract Skimmed milk powder (SMP) (bovine) and skimmed milk powder/sucrose dispersions before, during and after high-pressure treatment have been studied by nuclear magnetic resonance (NMR) spectroscopy (principally P-31). The P-31 spectra of samples at 293,K before and after pressure (400,600,MPa) treatment were not significantly different from one another, whether or not sucrose was present. This indicates that physicochemical changes relating to phosphorus-containing components occurring during a pressure cycle are either reversible or result in re-immobilisation, while protein components may be rearranged. The P-31 NMR spectra of these dispersions at 293,K under pressure (100,300,MPa) showed that pressure caused a considerable increase in the free inorganic phosphate concentration and that the increase was proportional to the magnitude of pressure. Decompression to ambient caused an exact reversal of this trend. These findings are discussed in terms of characterisation and properties of pressure-treated SMP dispersions by other methods and techniques. © 2002 Society of Chemical Industry [source] Pressure dependence of the optical properties of wurtzite and rock-salt Zn1,xCoxO thin filmsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2007J. A. Sans Abstract In this paper we investigate the electronic structure of Zn1,xCoxO by means of optical absorption measurements under pressure. Thin films of Zn1,xCoxO with different Co content (from 1 to 30%) were prepared by pulsed laser deposition on mica substrates. Absorption spectra exhibit three main features that are clearly correlated to the Co content in the films: (i) absorption peaks in the infrared associated to crystal-field-split internal transitions in the Co 3d shell, with very small pressure coefficients due to their atomic character; (ii) a broad absorption band below the fundamental edge associated to charge transfer transitions, that exhibit relatively large pressure coefficients, indicating that the Co 3d final states must be strongly hybridized to the conduction band; and (iii) a blue-shifted fundamental absorption edge associated to band to band transitions with a pressure coefficient close to that of pure ZnO. In the up-stroke the transition pressure from wurtzite to rock-salt phase decrease almost linearly as the Co increases, from 9.5 GPa in pure ZnO to about 6.5 GPa for x = 30%. In the down-stroke pressure we observe a similar behavior, yielding a metastable rock-salt phase at room pressure, after a pressure cycle up to 15 GPa. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] HIGH PRESSURE INACTIVATION OF PECTIN METHYL ESTERASE IN ORANGE JUICE USING COMBINATION TREATMENTSJOURNAL OF FOOD BIOCHEMISTRY, Issue 6 2001S. BASAK ABSTRACT The contribution of several high pressure (HP) processing related factors (pressure level, 300-400 MPa; pressure cycle, 1-3, and pressure-hold time, 30,120 min) on the inactivation of pectin methyl esterase (PME) in single strength (pH 3.7 and 11.4 °Brix) and concentrated (pH 3.5 and 42 °Brix) orange juice was evaluated. A response surface methodology was employed to model the combined effects of factors on the enzyme inactivation. The main effects were described by linear or quadratic functions. For both single strength and concentrated orange juices, the effects of all three main factors and some interactions (pressure level, cycle and holding time) were statistically significant (p<0.05). The dual nature of pressure inactivation of PME (with an instantaneous inactivation due to a pressure pulse, instantaneous pressure fall, and first order rate of inactivation during the pressure hold, yielding D and z values) reported in earlier studies was confirmed. Combination models were developed to predict the residual enzyme activity as influenced by the pressure level, number of pressure cycles and pressure hold time. [source] | ||||||||||