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  • 1
    Electronic Resource
    Electronic Resource
    Degradation Kinetics of Chlorophyll in Peas as a Function of pH (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 65 (2000), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of chlorophyll degradation in pea puree were determined in a specially designed reactor with on-line pH control capability. Without pH control, the pH of the pea puree decreased continuously with heating due to acid formation; the pH was maintained within ±0.1 of the desired value with on-line pH control. Chlorophyll (both a and b) degradation followed the first-order reaction model. The temperature dependence of the rate constant was adequately modeled by the Arrhenius equation. The activation energy was independent of pH and was 17.5 kcal/mol and 17 kcal/mol for chlorophyll a and chlorophyll b, respectively. The degradation rate constant decreased log-linearly as the pH was increased. A mathematical model was developed to predict the chlorophyll concentrations as a function of time, temperature and pH.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.2000.tb10600.x
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  • 2
    Electronic Resource
    Electronic Resource
    Methodology to Obtain True Thermal Conductivity of Low Porosity Food Powders (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 65 (2000), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: : A technique was developed to measure, at a porosity close to zero, the true thermal conductivity of food powders. Samples of low porosities were prepared by mechanically compressing the food powder using a hydraulic press at pressures up to 3.035 × 105 kPa (abs) in specially designed stainless steel cylinders with a dummy probe in place. Variation in porosity of the samples was less than 5%. Thermal conductivity was measured as a function of porosity (0.086 to 0.7), moisture content (0 to 37%, dry basis), and temperature (30 to 150 °C) by the thermal conductivity probe method. The thermal conductivity values decreased with an increase in porosity and increased with an increase in moisture content and temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.2000.tb09400.x
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  • 3
    Electronic Resource
    Electronic Resource
    Degradation Kinetics of Green Color and Chlorophylls in Peas by Colorimetry and HPLC (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 61 (1996), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of chlorophyll degradation and visual green color loss in pureed green peas with 80% moisture (w/w) were determined at 70, 80 and 90 C. The –a value from a tristimulus colorimeter was chosen as the physical property and a technique based on fractional conversion was developed in the determination of kinetic parameters of visual green color loss. The degradation of chlorophyll a, chlorophyll b and greenness followed a first order reaction and the temperature dependence of these reactions indicated an Arrhenius relationship. The activation energies were 19.5, 17.1 and 18.2 kcal/mol, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.1996.tb10903.x
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  • 4
    Electronic Resource
    Electronic Resource
    Drying Kinetics and Time-Temperature Distribution of Pregelatinized Bread (2002)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 67 (2002), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: : The experimental method of measuring the effective moisture diffusivity of bread, the representative hygroscopic porous material, was investigated. Drying curves and temperature profiles were obtained from cylindrical bread samples (0.3 and 0.6 porosity, and 0.011 and 0.018 m dia) under convective hot air conditions (50 to 90 °C oven temperatures and 1 to 3 m/s air velocity). The normalized drying curves were linear, suggesting that Fick's diffusion equation was applicable in determining the diffusion coefficient, and the effective moisture diffusivities were in the range of reported values. Experimental determination of the temperature dependent diffusion coefficient requires isothermal conditions to exist in the material, but temperature gradients existed throughout drying of the bread samples. Thus, the linearity of normalized drying curves is not a guarantee that the moisture diffusivity is properly determined. The need to develop an apparatus to achieve isothermal conditions during experimental measurement of the effective moisture diffusivity is shown.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.2002.tb09456.x
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  • 5
    Electronic Resource
    Electronic Resource
    Fractional Conversion for Determining Texture Degradation Kinetics of Vegetables (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 62 (1997), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fractional conversion (f) takes into account the nonzero texture property upon prolonged heating. This was applied as an alternate technique for reanalyzing texture degradation kinetics based on published data which indicated that the softening of vegetables followed a dual mechanism first order kinetic model. The plot of the logarithm of 1-f vs heating time was linear through log cycles indicating the reaction was first order with a single rate constant and the substrate b was better characterized by the equilibrium (or maximum retainable) texture property. A possible explanation was developed for negative activation energies which had been reported for the second mechanism with some vegetables.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.1997.tb04356.x
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  • 6
    Electronic Resource
    Electronic Resource
    Reference Materials for Calibrating Probes Used for Measuring Thermal Conductivity of Frozen Foods (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 58 (1993), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Reference materials which contained either 8% or 10% bentonite pastes and very fine pure copper powder (300 mesh, 30–.55%), provided thermal conductivities ranging from 0.9 to 1.9 W/mK. These materials were used to calibrate probes for measuring thermal conductivity of frozen food materials. Thermal conductivity values measured by the steady-state (parallel plate) method, the unsteady-state heat transfer (heating curve) method, and the probe method agreed within 5%. Although experimental density and heat capacity data of copper-filled bentonite pastes agreed with a mass average value of component properties, measured thermal conductivity values were much lower than the volume fraction average values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.1993.tb03240.x
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  • 7
    Electronic Resource
    Electronic Resource
    Permeability Measurements of Porous Food Materials (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 58 (1993), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Permeability of air through porous pre-gelatinized flour dough was measured as a function of porosity (0.10–0.60), moisture content (15–50%, wet basis), and fat content (0–6%). At free stream velocities 〈2 cm/sec, flow rate and pressure drop followed Darcy's law for flow through porous media. Permeability values ranged from 0.02 darcies at 0.10 porosity to about 23 darcies at 0.60 porosity. Permeability of dough does not follow the Kozeny model for granular materials, possibly due to differences in tortuosity between dough and granular materials. Moisture content 〈50% and fat content to 6% did not directly affect permeability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.1993.tb06176.x
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  • 8
    Electronic Resource
    Electronic Resource
    The Use of Fractional Conversion Technique to Investigate the Effects of Testing Parameters on Texture Degradation Kinetics (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 65 (2000), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: : To study the effects of testing parameters on texture degradation, texture loss of potatoes heated at 80 °C was measured using an Instron universal testing machine as well as a texture analyzer under 2 instrument crosshead speeds, 2 sample sizes, and either compression or shear modes of mechanical deformation. Using the fractional conversion as a texture index, the kinetics of texture degradation of potatoes fitted a single 1st order reaction model, and the rate constant (or D value) was shown to be independent of the test used to determine the texture index. The average D value was 30 ± 1.2 min at 80 °C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.2000.tb09401.x
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  • 9
    Electronic Resource
    Electronic Resource
    Dielectric Properties of a Pregelatinized Bread System at 2450 MHz as a Function of Temperature, Moisture, Salt and Specific Volume (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 62 (1997), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Dielectric properties [dielectric constant (ɛ') and loss factor (ɛ”)] were measured using the transmission line technique. Dielectric constant was independent of salt content while ɛ” increased when salt was added. Dielectric constant increased when temperature increased from 25 to 60°C then became virtually constant from 60 to 95°C for all samples. Loss factor increased linearly from 25 to 95°C for samples containing 1% salt and decreased linearly when no salt was present. Both ɛ’ and ɛ” increased linearly with respect to mass concentration of water (gwater/cm3sample). Ground bread crumb had lower ɛ’ and ɛ” than intact bread when other parameters were kept constant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.1997.tb04387.x
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  • 10
    Electronic Resource
    Electronic Resource
    Microwave Assisted Thawing of Model Frozen Foods Using Feed-back Temperature Control and Surface Cooling (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 62 (1997), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An apparatus was developed that combined microwave energy and cold air with different ambient temperatures to reduce thawing time and avoid run-away heating during microwave assisted thawing. Effects of microwave power level, sample thickness and surface air temperature on thawing time were investigated. The microwave power was cycled on and off using two temperature control schemes to maintain a predetermined temperature gradient based on hot and cold points. Thawing time was reduced by as much as a factor of seven compared to convective thawing at ambient temperature when appropriate conditions were used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.1997.tb04388.x
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