In this paper, two research examples are presented for the development of new foods and improvement of food production process by high pressure. First example; Alaska pollack Surimi was pressurized and the properties of gels formed were compared with those of heat-induced gels. The pressure-induced gels showed unique features, having large shear stress, cohesiveness and strength of ashi, small compression stress, and finer textured than the heat-induced gels. Utilizing these characteristics of pressure-induced gels, the development of new foods is expected. Second example; five kinds of pickels were pressurized and their properties were compared with those of heat-treated pickles. Pickles as keepable vegetables after pressurization had the same properties as the original pickles. However, pickles as cooked vegetables were changed in properties even at 200MPa. Shoyu-moromizuke, Shibazuke and Hakusai-asazuke pressurized at 500MPa were stored at 37°C for 10 days without any deterioration nor spoilage. Hinona-sakurazuke and Yuzu-daikonzuke after the pressurization were a little spoiled after the storage. On other hand, the non-treated pickles were all spoiled after the storage even for 5 days. From these results, it is expected that high pressure can be used for improvement of production process of pickles.
Recently, a large number of high pressure equipments have been utilized in industry for high-pressure food processing, forming and sintering of powdered materials and many other purposes. In this paper, recent progress in industrial high pressure technology is reviewed. Among various high pressure equipments, cold isostatic pressing (CIP) is being utilized most in high-pressure food processing. The method and constitution of CIP are described together with its recent progress and applicability to food processing.
“High Pressure Crystallization” is a newly developed crystallization process where pressure instead of cooling temperature is controlled as the motive force to crystallize or to melt. This process has already been applied in industry to separate an isomer from its mixture. Through experiments using this process to apply various organic mixtures, it was found that there are many phenomena different from the concept of the liquid-solid transition under atmospheric pressure, such as eutectic concentration shifts, a change from a solid solution system to a eutectic one, a change in the nucleation pressure caused by the history of the liquid, and others. Most of these phenomena might be caused by a change of the liquid structures under pressure. Some of them are discussed in this article.
For the purpose of disclosing the mechanism of conductivity for halide ions, the limiting molar conductivities of Br- and I- ions in heavy and light water have been determined at 25°C as a function of pressure up to 196.1MPa (2000kgf cm-2). The residual friction coefficients (Δζobs) of the halide ions were compared with the dielectric friction coefficients (ΔζHO) obtained from the Hubbard-Onsager dielectric friction theory. The continuum theory showed a serious limitation: (1) Contrary to the theoretical prediction, Δζobs was negative at each pressure in both D2O and H2O, and was smaller in D2O than in H2O. These discrepancies between the theory and the experiment became larger with an increase in ion size. (2) With increasing pressure, Δζobs (Cl-) and Δζobs (Br-) decreased, while Δζobs (I-) showed a reverse tendency. These results were discussed in terms of the passing through cavities mechanism and the specific interaction between halide ions and water molecules.
The densities and the viscosities of aqueous solutions of 1.000mol/kg tetraalkylammonium bromides (Me4NBr, Et4NBr, n-Pr4NBr, and n-Bu4NBr) were measured at 5.0, 10.0, 15.0. 25.0, 40.0, and 50.0°C and at pressures up to 375MPa. The viscosity minimum, observed for pure water with increasing pressure at the temperatures lower than 35°C, became shallow or disappeared in some cases as the temperature was raised or alkylammonium bromide was added. This solute-addition effect became large in order of the size of alkyl group, that is, Me, Et, n-Pr, and n-Bu. The activation energies of viscous flow estimated from the temperature dependence of the viscosity for R4NBr solutions have a minimum at about 250MPa as in the case of pure water.
The densities and the viscosities of the binary mixtures of water with 2, 2, 2-trifluoroethanol, 2, 2, 3, 3-tetrafluoropropanol, and 2, 2, 3, 3, 3-pentafluoropropanol have been measured using a vibratingtube densitometer and a falling-body viscometer, respectively. The measurements were performed at temperatures ranging from 298 to 323K and at pressures up to 80MPa with the estimated uncertainties of ±0.1% for density and ±2% for viscosity. The excess molar volumes, partial molar volumes, isothermal compressibilities of fluoroalcohol/water systems were determined based on the Tait equation smoothed against the composition with the simple polynomial equation. The temperature, pressure and composition dependences of these properties and those of the viscosities were investigated in comparison with the hydrocarbon-alcohol/water systems previously reported. Furthermore, the comparison between the present results and the spectroscopic data have been also undertaken.
The pressure effect on thermal inactivation, urea inactivation, guanidine hydrochloride (Gu·HCl) inactivation of Taka-amylase A (TAA) and also its pressure inactivation have been studied by measuring the rate of hydrolysis of p-nitrophenyl-α-maltoside (pNαM) catalyzed by TAA in the temperature range of 25-75°C and at the pressures up to 7kbar. The apparent rate of hydrolysis decreased with time above a certain temperature, pressure, and concentration of denaturants of urea and Gu·HCl. The decrease is due to the decrease in TAA activity. The enthalpy change of the thermal inactivation was 580-280kJ·mol-1, which corresponds to the denaturation process of N2 domain of TAA studied by thermal analysis. The volume change of this process was 120-79cm3·mol-1, while TAA was inactivated in the pressure range of 4-7kbar at 25-45°C and the corresponding volume change was -14--20cm3·mol-1. The pressure slightly depressed the urea inactivation and the volume change was 0-7cm3·mol-1. On the other hand, the pressure accelerated the Gu·HCl inactivation at lower concentration of Gu·HCl (1.0M) and the volume change was -10--20cm3·mol-1. At 2M Gu·HCl the volume change of inactivation was nearly zero.
Phospholipid bilayers and surfactant micelles have been used as a model for biological membranes. The temperature-pressure phase diagram of dipalmitoylphosphatidylcholine (DPPC) bilayer liposomes has been constructed. Four states, i.e., liquid crystal (Lα), gel I (Pβ'), gel II (Lβ') and interdigitated (LβI) phases, were observed in the pressure range up to 200MPa. The present study proposes a novel method for the estimation of the partition coefficient of drugs between the aqueous and the lipid phases. Two kinds of partition coefficients of an inhalation anesthetic were estimated from the depression of the main- and pre-transition temperature of DPPC liposome. The Lα phase/water and Pβ' phase/water partition coefficients of halothane were 3390 and 820, respectively. The effect of pressure on the partition coefficient was determined, and then the transfer volume of halothane was estimated. The critical temperature-pressure lines for the micellar dissolution, which represent the pressure dependence of Krafft temperature, were determined for a homologous series of cationic surfactants. The depression of Krafft temperature by solubilization can be used for the estimation of the partition coefficient of solubilizate between the aqueous phase and the micellar phase.
Simultaneous optimization of both material and structural design can be performed by using the characteristics that material design is possible for fiber reinforced composite materials. In the present paper, optimization of thin-walled composite cylindrical beam was carried out under combined loading of bending and axial torque. Several analytical models were proposed by taking account of the manufacturing processes of thin-walled cylindrical composite pipes. Among them, a non-uniform FW (filament winding) model is associated with a newly introduced manufacturing method of composite pipe. A numerical optimization method was used for the search of optimum design solution. As a result, it was confirmed that the optimization by using the non-uniform FW model was realistically useful for thin-walled cylindrical composite pipes.
A material design guideline for the flexural behavior of carbon/aramid hybrid unidirectional FRP laminates (C/A hybrid FRP) was studied from the viewpoint of laminate constitution and time-temperature dependence. As the results, it was found that the flexural behavior under static, impact and cyclic loads changed remarkably with laminate constitution, time or temperature and that the flexural fracture patterns were classified clearly into two modes according to laminate constitution and time-temperature dependence. One is the compressive fracture of the most out CFRP layer in the compression side, and the other is the tensile fracture of the surface AFRP layer in the tension side. Furthermore, the temperature dependent flexural behavior of C/A hybrid FRP predicted by the laminated beam theory using the mechanical properties of CFRP and AFRP agreed approximately with the experimental results mentioned above. Therefore, this proposed deformation and failure criteria are applicable to the material design of C/A hybrid FRP.
ILSSs of 7 kinds of CFRPs whose matrices were thermostable resins including newly developed ones were measured by a short beam method of three point bending in the temperature range between room temperature and 250°C, and the relation with resin properties was examined. By observing the side surface of the specimen whose ILSS had been tested, failure mode at high temperatures was also examined. There were two types of temperature dependent curves of ILSS. ILSS decreased linearly with increasing temperature in one type. In the other type, the degree of ILSS decrease became larger with increasing temperature, and the ILSS-temperature relation did not follow a linear line but bent curve. Such curves were considered to depend on thermal property of the matrix resins. The ratio of the ILSS value at high temperatures to that at room temperature, ILSS retention, was highest for PMR-15 matrix CFRP at 200°C and 250°C. The apparent elastic degree retention of matrix resin estimated from the slope of load-deflection curves on ILSS test corresponded with ILSS retention, and a linear correlation between Tg of the matrix resin and ILSS retention was recognized. It was also confirmed that the failure mode of the specimens measured at 200°C and 250°C was shear failure.
Epoxy acrylate resin has the advantages of toughness and corrosion resistance as a matrix resin of composites. Also it has been recognized as a compatible resin system for the matrix of CF/GF hybrid composites. In this study, some epoxy acrylates were synthesized from bis-phenolic epoxy oligomers and methyl methacrylic acid and were modified with diisocianates to study the effect of chemical composition of resin systems on composite properties. With increasing epoxy oligomer's n value, interlaminar strength increased in CFRP and CF/GF hybrid laminates. In addition, some peculiar chemical reaction seemed to occur at the interface of carbon fiber with isocianate modificated resin systems, which indicates a possibility of creating a new high strength CF-composite from unsaturated resin systems.
Surface modification treatment, which makes various reinforcing fibers compatible with resin matrix, is a very important process contributing to the final properties of products made of fiber reinforced plastic (FRP) and other composites. There are many kinds of surface modification methods available for reinforcing fibers. As one of the dry methods, there is a new surface modification method named photo-oxygenation treatment, in which the surface of reinforcing fiber is modified by ultra-violet irradiation in a flow of an oxygen gas containing ozone at atmospheric pressure. So, the surface of high performance polyethylene fiber (EF), which is promising as one of the advanced composite materials (ACM), was treated by photo-oxygenation and the modified degree was studied in comparison with corona treatment as a general surface treatment. The influence of modified EF on mechanical properties of EFRP made with epoxy resin was also examined. The results are as follows: (1) Photo-oxygenation treatment is useful for surface modification of EF, because the improvements on wetting properties to water and on flexural properties are equal or better than those of corona treatment. (2) Carbonyl group is introduced into the surface by photo-oxygenation treatment, and thereby the wetting properties to water are improved. (3) Flexural properties of EFRP composed of modified EF are better than those of EFRP made of non-treated EF.
Delamination fatigue crack propagation behavior was investigated for four kinds of CF/epoxy laminates (Toray T300/#3601, T800/#3601, T300/#3631, and T800/#3631). Tests were carried out under mode I opening loading by using double cantilever beam specimens. The effect of reinforcing fiber on the delamination fatigue crack growth behavior was very small. The fatigue crack growth behavior was mainly controlled by matrix resin. The analysis of the equivalent stress intensity range proposed by the present authors indicated that the contribution of maximum load was large in delamination fatigue crack propagation of the laminates tested here. The degree of the contribution of maximum load was higher for more brittle resin. The improvement of the interlaminar fracture toughness was not fully transferred to the improvement of threshold value of the fatigue crack growth. The mechanism of delamination fatigue crack propagation agreed well with the fractographic observation.
Various impact characteristics as well as fracture energy can be estimated by using an instrumented impact testing technique. The impact characteristics, such as a load versus deflection curve and maximum load, are used only for comparison among materials, but are seldom used for strength assessment in structural design. The analytical procedure which correlates the simple test data with structural strength under complex boundary conditions has not been established. In the present paper, a numerical method for dynamic strength analysis has been proposed and applied to estimate the multiaxial impact strength of aramid/glass hybrid composite plates. Dynamic fracture simulation based on the maximum stress criterion was carried out by using a finite element method and the numerical results were compared with the experimental data obtained by an instrumented drop-weight impact testing machine. Seven kinds of hybrid laminates were used for the tests, including roving-cloth reinforced composites, glass mat reinforced composite and mat/roving-cloth reinforced composites. The progressive fracture process under impact loading was well simulated and the numerical results showed close agreement with the experimental data which exhibit brittle fracture. The fracture controlling process of mat/roving-cloth reinforced laminates was also discussed quantitatively based on the present analysis.