MASS TRANSFER AND DIFFUSION COEFFICIENT DETERMINATION IN THE WET AND DRY SALTING OF MEAT

ABSTRACT

Dehydrated salted meat is widely used in Brazil as a very important source of animal protein. The main objective of this kind of processing is water removal. initially by osmotic pressure changes and then by drying, resulting in a product with intermediate moisture levels.

In this work, mass transfer and salt diffusion in pieces of meat submitted to wet and dry salting were studied. Slabs of beef m. trapezius with an infinite plate geometry were salted in a NaCl saturated solution or in a dry salt bed, at two temperatures (10 and 20°C) and different time exposures (120 min and 96 hours). Equilibration studies were extended up to six days.

It was observed that water loss increased with salt uptake, for increasing periods of times. At 20°C the moisture loss was higher than it was at 10°C in both salting processes. On the other hand, the kinetics of salt uptake and moisture loss were of greater importance in the process of dry salting than in that of wet salting.

The salt diffusion coefficient for wet salting was 0.26 × 10^?10m²/s at20°C and 0.25 × 10^?10 m²/s at 10°C and for the dry salting the values were 19.37 × 10^?10 m²/s at 20°C and 17.21 × 10^?10 m²/s at 10°C.     

New Sintered Li2O–Al2O3–SiO2 Ultra‐Low Expansion Glass‐Ceramic

We developed a new Li₂O–Al₂O₃–SiO₂ (LAS) ultra‐low expansion glass‐ceramic by nonisothermal sintering with concurrent crystallization. The optimum sintering conditions were 30°C/min with a maximum temperature of 1000°C. The best sintered material reached 98% of the theoretical density of the parent glass and has an extremely low linear thermal expansion coefficient (0.02 × 10^?6/°C) in the temperature range of 40°C–500°C, which is even lower than that of the commercial glass‐ceramic Ceran^® that is produced by the traditional ceramization method. The sintered glass‐ceramic presents a four‐point bending strength of 92 ± 15 MPa, which is similar to that of Ceran^® (98 ± 6 MPa), in spite of the 2% porosity. It is white opaque and does not have significant infrared transmission. The maximum use temperature is 600°C. It could thus be used on modern inductively heated cooktops.     

Voltage relaxation measurements of the electron and hole mobilities in yttria-doped zirconia

The voltage relaxation of galvanic cells with zirconia electrolytes polarized between an inert silver electrode and either a Pt/air or a Fe/FeO electrode has been analysed to obtain the mobilities of both electronic minority charge carriers. At 900°C the mobility of the electrons is 2.4 × 10^?2 cm²/Vs, that of the holes is 2 orders of magnitude lower, 1.6 × 10^?4 cm²/Vs. The activation enthalpy is 0.55 eV for the electrons and 1.4 eV for the holes. From conductivity data, the concentrations of electrons and holes at 900°C and 1 atm oxygen partial pressure are calculated to be 3 × 10¹⁰ and 6 × 10¹⁷ cm^?3 respectively. With the use of platinum inert electrodes the formation of intermetallic Pt—Zr compounds appears at an oxygen partial pressure of 2.3 × 10^?22 atm at 900°C. From this the Gibbs formation energy of yttria-doped zirconia is calculated to be ?9.1 eV at 900°C.     

Ageing Effect on Ethyl Cellulose Films

The effect of physical ageing on the electrical properties, such as thermally stimulated discharge currents (TSDC) and conduction currents, of ethyl cellulose (EC) has been analysed. The TSDC thermograms of EC samples, poled with 100kVcm^-1 at different poling temperatures (i.e. 50, 70 and 90°C) consist of two peaks located at 70±5°C and 110±5°C, respectively. The conductivity measurements were made over a time period of 10¹–10³min in the temperature range 30–125°C with a poling field of 100kVcm^-1. It has been observed that physical ageing considerably affects the magnitude of the thermally stimulated depolarization and conduction currents of EC films. This ageing effect, which has been attributed to continuous vitrification of a polymer, is considered to enhance the life-time of a polymer electret. © of SCI.     

Short-term low as well as high temperature operation of an MSF plant using Belgard EVN as a scale control additive

During a 40-day low temperature trial, conducted in 1979 using 2.0 ppm of Belgard EVN, the GOR ranged between 10.9 and 9.9 as against the design value of 8.0, while the heater fouling factor (FF) rose gradually from 0.02 × 10^-3 to 0.07 × 10^-3 m² .°C/W. A polyphosphate trial, carried out in 1978 on the same MSF plant, showed the rate of fouling of heater tubes to be four times that during the Belgard EVN trial. During the polyphosphate operation, the heater FF had in the same period climbed from 0.18 × 10^-3 to 0.70 × 10^-3 m² °C/W.In 1980, the top brine temperature of the unit was progressively increased from 87.8 to 104.4°C, whilst increasing the Belgard EVN dosage from 2.5 to 6.0 ppm. The GOR increased from 8 to 9 up to a top brine temperature of 98.9°C and then declined to about 7.7. The heater FF increased gradually from 0.10 × 10^-3 to 0.19 × 10^-3 m² .°C/W.     

Vapor pressure and heat of solution of sulfur dioxide in 1-methyl-2-pyrrolidone and its aqueous solution

A new method was developed to measure the vapor pressure of sulfur dioxide above various liquid absorbents. It was applied to pure 1-methyl-2-pyrrolidone and its aqueous solution at 50°C to 91°C for SO₂ loadings of 3.73 × 10 ⁴ kg/kg to 2.16 × 10 ⁻² kg/kg. A chemical model was developed. The heat of solution was calculated from the dependence of the vapor pressure on temperature and was 3.98 × 10⁷ J/kmol (exothermic) for pure 1-methyl-2-pyrrolidone. The vapor pressures disagreed with the only previously published set of results but were confirmed by independent measurements with a gas chromatograph.     

Preparation and characterization of TiO2 thin films by PECVD on Si substrate

Titanium oxide thin films were prepared on p-Si(l00) substrate by plasma enhanced chemical vapor deposition using high purity titanium isopropoxide and oxygen. The deposition rate was little affected by oxygen flow rate, but significantly affected by RF power, substrate temperature, carrier gas flow rate, and chamber pressure. Morphology of the film became coarser with increasing deposition time and chamber pressure, and the film showed less uniformity at high deposition rates. It was also found that the overall deposition process is controlled by heterogeneous surface reaction below 200°C., but controlled by mass transfer of reactants at higher temperatures. TiO₂ films deposited at temperatures lower than 400°C was amorphous, but showed the anatase crystalline structure upon 400°C deposition. The dielectric constant was about 47 for the films post-treated by rapid-thermal annealing (RTA) at 800°C. The leakage current was about 2×10⁻⁵ A/cm² for the films deposited at 400°C and RTA-treated at 600°C. However, it was decreased to less than 3×10⁻⁷ A/cm² for the film RTA-treated at 800°C.     

Influence of Crystallization on the Conversion of Sm3+→Sm2+ in SrO–Bi2O3–K2O–B2O3 Glass‐Ceramics

Sm³⁺‐doped glass 13SrO–2Bi₂O₃–5K₂O–80B₂O₃ was fabricated by the conventional melt‐quenching technique. The glass‐ceramics were obtained by heating the as‐prepared glasses in air atmosphere at selected temperatures 550°C, 600°C, 615°C, and 650°C, respectively. The luminescence spectra of both Sm³⁺ and Sm²⁺ were detected in the ceramic heated at 650°C where crystalline phase is formed. The as‐prepared glass and the ceramics heated at 550°C, 600°C, and 615°C show only the emission due to Sm³⁺. In the sample heated at 650°C in air atmosphere, however, part of Sm³⁺ ions was converted to Sm²⁺, giving rise to sharp emission lines which are characteristic of Sm²⁺ in crystalline state. It is suggested that Sm²⁺ ions are located at Sr²⁺ site in the ceramic while Sm³⁺ ions are located at Bi³⁺ sites. The Sm²⁺‐doped glass‐ceramic has a high optical stability because the fluorescence intensity decreases by only about 8% of its initial value upon excitation at 488 nm Ar⁺ laser.     

Mechanism of persulfate decomposition in aqueous solution at 50°C in the presence of vinyl acetate and nitrogen

The rate of the thermal decomposition of potassium persulfate has been studied in an unbuffered aqueous solution at 50°C in nitrogen atmosphere in the presence of vinyl acetate (VA) monomer (M). It has been found that the initial rate of persulfate decomposition may be written as in the concentration range of persulfate (1.85 × 10^?2–1.85 × 10^?3 m/dm³) and VA (0.054–0.27 m/dm³). The pH of the aqueous solution of persulfate was found to decrease continuously at 50°C, but there was no measurable change of pH of the aqueous solution containing persulfate and VA at 50°C in the presence of nitrogen at the early stages of the reaction. VA, methyl acetate, and ethyl acetate have been found to undergo very slow hydrolysis in aqueous solution at 50°C. The partition coefficient (β) of the monomer between the polymer phase and the aqueous phase was found to be 21 ± 2 in the presence and absence of electrolytes (K₂SO₄, 10^?4–10^?3 m/dm³) by the bromometric estimation of the monomer present in the aqueous phase containing known amounts of monomer [1.80–2.20%, w/v] and freshly prepared polymer (0.3–0.5 g/100 mL). Above 10^?2 (m/dm³) persulfate, the polymer obtained was found to be insoluble in common solvents, viz., acetone, benzene, etc. Highly purified sodium dodecyl sulfate (0.5–5.0 × 10^?3 m/dm³) had no measurable effect on the rate of persulfate decomposition.     

Effect of γ-radiation on the thermal conductivity of polypropylene

The effect of ⁶⁰Co γ-radiation on the thermal conductivity of polypropylene (PP) has been studied over the temperature range 0–160°C. for radiation doses of 600 and 1800 Mrad. The conductivity of unirradiated specimens rises from 4.5 × 10^?4 cgs units (cal./cm.-sec.-°C.) at 0°C. to 4.8 × 10^?4cgs units at 80°C. and subsequently decreases with temperature to a value of about 3.1 × 10^?4cgs units at 160°C. Upon irradiation to 600 Mrad the thermal conductivity is lowered over the 0–150°C. temperature range. Above 90°C. the conductivity decreases with temperature and becomes relatively constant at 3.4 × 10^?4 cgs units from 120 to 160°C. Differential scanning calorimeter (DCS) measurements from 30 to 200°C. show that irradiation to 600 Mrad lowers the energy associated with crystalline melting and shifts the endotherm melting peak from about 160 to 105°C. Irradiation to 1800 Mrad results in additional lowering of the thermal conductivity over the 50–160°C. range, a further decrease in area of the endothermic peak and a shift of its maximum peak position to about 75°C. The effects of radiation on the thermal conductivity of polypropylene are compared and correlated with the observed effects of radiation on the dynamic mechanical behavior.     

Kinetics of the reaction between steam and the basal plane of graphite

The gold decoration/transmission electron microscopy technique has been used to measure the rate of removal of carbon atoms from the basal plane of gra processes have been determined: removal of edge atoms surrounding the monolayer etch pits, and abstraction of carbon atoms within the basal plane which for edge carbon removal ranges from 0.02 at 600°C to 26 atom/atom active site/s at 900°C. The activation energy of 52 kcal/mole is close to the val of the saturated basal atoms (with 3 sp² bonds) may be expressed in terms of the probabilities of successful collisions of O atoms which are fo for both CO₂ and CH₂O reactions, are of the order of 10^?10 in the above temperature range. Comparison of the two reaction oxygen and water is the species responsible for basal atom abstraction.The gasification of graphite by steam is immensely anisotropic. At 23 torr H₂O the turnover frequency in the prismatic or edge directions, {10$\text{1}$0} and {11$\text{2}$0} faces, is higher than that on the basal {0001} plane by a factor of 4 × 10¹⁰ at 900°C and 4 × 10¹² at 700°C.     

Dielectric and ultrasonic absorption in some linear polyamides

The dielectric behavior of some linear polyamides has been studied over a frequency range from 10² to 10⁵ Hz between 20°C and 90°C. Also the change in attenuation of longitudinal ultrasonic waves has been measured as a function of frequency and temperature. Analysis of the results shows α- and β- relaxations. The movement of amide protons involved in intermolecular hydrogen bonds is also noticed.     

N2-sorptionsmessungen zur bestimmung der spezifischen oberfläche und der porenverteilung von erhitztem normalbeton

The specific surface and pore size distribution of normal concrete is influenced by temperature effects. Therefore, the specific surface area of concrete specimens has been computed from nitrogen adsorption isotherms after a preceding temperature treatment in a thermal balance. It was found that the specific surface area increases from 2,0 m²/g at 100°C to 4,5 m²/g at 400°C. The mean pore radius decreases from 53 Å to 38 Å. A temperature treatment at 665°C is connected with a further decomposition of concrete and yields a decrease of the specific surface area to 2,4 m²/g and the pore size distribution shifts to larger radii ($\text{r}\text{= 51}\text{A}\text{?}$). Due to sintering processes, at temperatures of 1000°C the porosity of the material is decisively altered and a specific surface area of 1,1 m²/g has been calculated.     

Insights into High‐Temperature Uniaxial Compression Deformation Behavior of Ti3AlC2

We report on strain‐rate‐dependent compression deformation behavior of Ti₃AlC₂ at 1000°C–1200°C. At 1000°C and high strain rate (10^?2 or 10^?3 s^?1), Ti₃AlC₂ deforms in a nonplastic manner. Upon increasing temperature and reducing strain rate, Ti₃AlC₂ exhibits a limited plasticity. For instance, the true plastic strain at 1200°C and 10^?4 s^?1 is only 3%, beyond which strain softening following a short hardening regime occurs. The softening results from the formation of localized microvoids and microcracks. Decreasing the strain rate further to 10^?5 s^?1 at 1200°C, strain hardening instead of softening is identified. Under such conditions, the plastic strain remarkably increases, reaching a value as high as 27%. Postdeformation microstructural analyses of the dislocation configurations explicitly evidence the dislocation reactions, formation of hexagonal dislocation networks and dislocation entanglements. These account for the strain hardening. The extraordinary plasticity at 1200°C and 10^?5 s^?1 benefits from the initiation of nonbasal slip systems. Finally, a complete high‐temperature deformation scenario for nanolaminated Ti₃AlC₂ is elaborated.     

Sorption of benzene by poly(ethylene oxide)

The activity of benzene in poly(ethylene oxide), PEO, has been determined over the concentration range 0.3 to ～35 wt% benzene using the piezoelectric sorption method. The temperature range was 64° to 97°C and the molecular weights of polymer samples were 1.0 × 10⁵, 6.0 × 10⁵, and 5.0 × 10₆ g/g mol. The Flory-Huggins interaction parameters, χ, determined in this work agree within experimental error with χ values determined by gas chromatography and by vapour pressure measurement. The values of χ extrapolated to zero solvent concentration, χ^∞, have a minimum and negative value in the vicinity of 85°C for the sample of molecular weight 1.0 × 10⁵, 84°C for the sample of molecular weight 6.0 × 10⁵, and 77°C for the sample of molecular weight 5.0 × 10⁶. In the vicinity of 65°C, χ^∞ is negative for each molecular weight of polymer and increases to positive values with an increase in temperature. For all samples studied, the χ^∞ parameters reach constant values (0.22 to 0.30) at temperatures higher than 90°C.     

Simple dilatometer for polymer density and thermal expansivity measurements

A dilatometer is described to study the temperature dependence of density (ρ) of solid and semiliquid polymers and the following linear relations have been established. Atactic poly(vinylisobutyl ether) (25–90°C): ρ = 0.9166 ? 7.15 × 10^?4 × T. Isotactic poly(vinylisobutyl ether) (25–70°C): ρ = 0.9184 ? 7.13 × 10^?4 × T. Poly(n-butyl methacrylate) (90–150°C): ρ = 1.0622 ? 8.41 × 10^?4 × T. Poly(dimethyl siloxane) (30–51°C, using Lipkins pycnometer): ρ = 0.9846 ? 8.81 × 10^?4 × T; where ρ is in g.cm^?3, temperature T is in Celsius, and the linearity correlation coefficient r is better than 0.9998. Their volume–temperature plots are also linear. As the plots of polyn-butyl methacrylate curved slightly near its glass transition (20°C), the quadratic equation ρ = 1.0402 ? 4.79 × 10^?4 × T ? 1.46 × 10^?6 × T² (standard deviation = 1.57 × 10^?3) has been suggested for the entire range of 30–150°C scrutinized in this study. The data have been utilized to derive thermal expansivity and some equation-of-state parameters of the polymers at the reference temperature (ca. 20°C).     

A preliminary account of char structures produced from Liddell vitrinite pyrolysed at various heating rates

Liddell-seam vitrinite particles were heated to 1000 °C in nitrogen at uniform rates ranging from 10^?1 °C s^?1 to 10⁴ °C s^?1. Little melting or swelling was observed when the particles were heated at 10^?1 °C s^?1 even though the vitrinite is from a coking coal of high-volatile bituminous rank. Particle size (100 μm) and loose packing were probably major influences on the plasticity. Vitrinite particles heated at rates faster than 10^?1 °C s^?1 showed an increase in plasticity with heating rate but the effects related to plasticity and volatile evolution appeared to be approaching a limit. Simple cenospheres (primary vesicles) were formed and preserved at a heating rate of 1 °C s^?1. At a heating rate of 10 °C s^?1 secondary vesicles were produced and preserved in the walls of the primary vesicles. At faster heating rates only secondary and tertiary vesicles were preserved. At a heating rate of 10⁴ °C s^?1 the vesicles preserved were very small.     

The Processes Running during the Induction Period of Inhibiting Oxidation of Polyethylene

Abstract

Oxygen absorption in the induction period of polyethylene oxidation inhibited by a strong amine antioxidant N-phenyl-N-cyclohexyl-p-phenylenediamine (PCHA) in the temperature range of from 200°C to 230°C is investigated.

It is found that the rate of O₂ absorption during the induction period in the presence of antioxidant varies in the range of from 2 × 10^?6 to 2 × 10^?5 mol/kg (210°C).

It is also stated that the main method of antioxidant consumption during the induction period consists of its direct oxidizing by molecular oxygen. The rapid oxidation of the polymer is shown to begin after the current antioxidant concentration reduction to the critical value.

Kinetic parameters of the oxidation reaction in a wide range of initial antioxidant concentration are determined.     

Physical–chemical properties and conductivity of Na<Subscript>2</Subscript>O–SnO<Subscript>2</Subscript>–SiO<Subscript>2</Subscript> glass systems

The effect of tin(IV) oxide on the conductivity and chemical stability of sodium–silicate glass has been studied for five different glass compositions. Dilatometry and DSC were used to investigate the thermal behavior of the glass. The research into transport characteristics of the glass has shown that its conductivity is in the range of 2 × 10^–8–5 × 10^–7 S/cm at 25°C and 10^–3 S/cm at 300°C.     

Electrical conductivity of polymers containing carbon black

Changes in volume resistivity with temperature of carbon-black-filled polymers and a random copolymer of styrene and butyl methacrylate were measured. For polystyrene containing 20 wt % carbon black, of surface area 24 m²/g, the resistivity changes abruptly from 10¹³ to 10⁶ ohm-cm above 150°C. Poly(butyl methacrylate) did not show well-defined changes in resistivity on heating. The random copolymer containing 16.7 or 28.6 wt % carbon black, of surface area 24 m²/g, showed a resistivity exceeding 10¹³ ohm-cm, that decreased to about 10⁷ ohm-cm on heating above 120°C. This Copolymer containing 16.7 wt % carbon black, of surface area 625 m²/g, shows a resistivity of about 108 ohm-cm that decreases sharply to 10³ ohm-cm by 150°C. Decreases in resistivity on increasing the temperature in the quiescent state are correlated with the observation of a yield stress at low shear rates in rheological studies. It is suggested that carbon black agglomerates at elevated temperature and forms an independent conductive network that prevents flow.