Tetragonal to monoclinic transformation and microstructural evolution in ZrO2–9.7 mol% MgO during cyclic heating and cooling

The tetragonal (t) to monoclinic (m) transformation behaviour and its relationship to microstructural evolution were investigated by means of dilatometry and transmission electron microscopy for ZrO2–9.7 mol% MgO during cyclic heating and cooling between room temperature and 1490 K. In the as-sintered specimens, fine oblate ellipsoidal t-phase precipitates, 20–50 nm in diameter and 100–200 nm long, were distributed in the cubic (c)-phase matrix. They were below a critical size for transformation and exhibited no transformation in the first three cycles. In the fourth and further cycles, transformation occurred in two distinct stages. A low-temperature stage appeared at 850–1000 K on heating and at 400–700 K on cooling, while a high-temperature stage appeared at 1350–1400 K on heating and at 1000–1200 K on cooling. With the increasing number of cycles, at first the size of low-temperature stages increased and then decreased above ten cycles accompanying the development of the high-temperature stage. During cyclic heating and cooling, coarsening of ellipsoidal precipitates and decomposition of c- and t-phases occurred. As a result of the decomposition, MgO particles and a new m-phase containing a very low concentration of MgO were produced. The coarsened ellipsoidal t-phase precipitates were responsible for the low-temperature stage. The new m- or t-phase containing very low MgO produced by the decomposition was responsible for the high-temperature stage.     

Fractionation of water insoluble solids and extraction of pectins from residues of juice-extracted satsuma mandarin fruit by wet grinding

The waste biomass residue from satsuma mandarin juice production was extracted by wet-fine grinding and separated by centrifugation into insoluble and soluble fractions. The insoluble material was wet-screened into four fractions and analysed for crude fibre and total hydrolysable sugars. Crude fibre was almost exclusively in fractions containing particles over 50 μm, comprising about 65% of the insoluble material; this could provide a raw material high in crude fibre. The remaining insoluble fraction was almost devoid of crude fibre.
The soluble extract contained up to 63% of the total pectic substances with very similar methoxyl contents and degree of esterification, but double the viscometric molecular weight of a standard citrus pectin. The method provides an alternative to that of hot acid extraction.     

Entrance effect correction on the flow of moisturized soy protein isolate melt in an extrusion viscometer

A newly developed capillary viscometer, having an airtight sample cell and capillary system, was utilized to determine the flow properties of moisturized [70% dry basis (d.b.)] soy protein isolate (SPI) melt at 140°C. Pressure drop measurement with an orifice die was done to clarify the large end effect. An end effect correction method was performed by subtracting the orifice die data from the capillary tube data, and reasonable results were obtained. The flow properties of the SPI melt were thus elucidated and could be classified as those of a power law fluid with flow behaviour index of 0.35. It was concluded that SPI with 70% d.b. moisture is an extremely high pseudoplastic fluid at 140°C.     

Hydration of heat-treated soy protein isolate and its effect on the molten flow properties at an elevated temperature

The relationship between the flow properties of soy protein isolate (SPI) at 140°C, measured using an extrusion viscometer, and changes in the hydration state were investigated. The state of the water in SPI was analysed by measurement of the freezable water content using differential scanning calorimetry (DSC) and by spin-spin relaxation rate (R₂) measurements using pulsed nuclear magnetic resonance (NMR). The dependence of the flow properties on the state of water was indicated by the correspondence between the water content at which the flow characteristics of molten SPI changed, and the critical water content indicated by DSC measurement of the minimum freezable water content, and by the inflection point in NMR measurement of the spin-spin relaxation rate (R₂).     

Microparticulation by Jet Mill Grinding of Protein Powders and Effects on Hydrophobicity

A method was studied for microparticulation of protein for use as fat substitutes by superfine grinding. A jet mill produced particles <3 μm from egg white, casein and soybean hull. Microparticulation by grinding of egg white was easier than with casein or soybean hull. Hydrophobicity of casein increased by grinding to super fine particles but little or no effect was observed on soybean hull and egg white.     

Mechanism of inactivation of heat-tolerant spores of Bacillus stearothermophilus IFO 12550 by Rapid Decompression

The effect of three rapid decompression methods to clear the mechanism of inactivation of heat tolerant spores of Bacillus stearothermophilus IFO 12550 was investigated. Pressurization of the spores at 200 MPa and 75°C for 60 min caused a kill of 10⁴ CFU/mL by the link-motion system but the nonrotational rod valve and E.G. seal methods gave a kill of about 10³ CFU/mL. Sterilization was due to the physical breakdown of spore coat, and was induced by its physical permeability of water at high pressure and temperature. Rapid decompression by the link-motion system at 200 MPa decreased the D-value of the spores from 3000 min (100°C, one atmosphere) to 6 min, 11 min, and 17 min at 95, 85, and 75°C, respectively.     

Denaturation of Bovine Serum Albumin (BSA) and Ovalbumin by High Pressure, Heat and Chemicals

Both native and denatured protein samples were examined by determining fluorescence and specific rotation, and by polyacrylamide gel electrophoresis (PAGE) and differential scanning calorimetry (DSC). Denaturation of ovalbumin by pressure was much less than by heat or by the chemical denaturants. Ovalbumin was denatured under high pressure, as confirmed by the decrease in its a-helical content to 72% and DSC endothermic enthalpy to 61%, but it showed no change in the PAGE pattern. With bovine serum albumin decrease in fluorescence was observed after denaturation by chemicals, but it did not change under high pressure.     

Effect of moisture content on flow behaviour of molten soy-protein isolate under an elevated temperature

The flow behaviour of molten soy-protein isolate (SPI) with moisture content ranging from 17 to 41% was measured with a capillary rheometer under an elevated temperature of 140°C. The flow-starting temperature of SPI under 90 MPa pressure was inversely proportional to the moisture content. The relationship between flow rate and pressure drop for a molten SPI with 17-35% moisture was non-linear on a log-log scale, while it was linear for a molten SPI with 41% moisture. Based on these results, the shear characteristic of a molten SPI with 41% moisture can be classified as a power-law fluid with a flow behaviour index of 0.3. However, a molten SPI with 17-35% moisture may be classified as an unknown type of non-Bingham plastic.     

Oscillatory Compared with Continuous High Pressure Sterilization on Bacillus stearothermophilus Spores

TO ESTABLISH a sterilization method with minimal heating, the effect of high pressure on bacteriostasis was studied using thermoduric spores of Bacillus stearothermophilus. After exposure to 800 MPa for 60 min at 60°C, the spore count decreased from 10⁶ to 10²/mL. However, exposure to the same pressure at room temperature did not cause significant change in spore numbers. The synergistic effect of high pressurization on the bacteriostatic action of sucrose fatty acid ester at low concentration (< 10 ppm) was pronounced with sucrose palmitic acid ester but not with sucrose stearic acid ester. Oscillatory pressurization was more effective for spore sterilization. Six cycles oscillation of 5-min pressurization with 400 MPa at 70°C decreased the spore count from 10⁶ to 10²/mL, and with 600 MPa, complete sterilization was achieved.     

Hydrostatic pressures in wet grinding of soybean with a double-disk attrition mill

Soybean was finely ground with a modified double-disk attrition mill by a wet-grinding process. The hydrostatic pressure in the gap between the rotating and stationary disks of the mill decreased with radial distance between the central inlet and the peripheral exit in the disks. Observed values were in good agreement with theoretical values derived from Bernoulli's equation. The maximum hydrostatic pressure was found at the feed entrance zone of the gap under any given operational conditions. The effects of rotational speed, gap width and soybean feed concentration on the hydrostatic pressure were measured. This implied that increase in hydrostatic pressure from height of feed head and/or increased speed will increase output.