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  • 2005-2009  (2)
  • 2000-2004  (2)
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  • 1
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 68 (2003), S. 0 
    ISSN: 1750-3841
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: This work deals with the hypothesis that kinetic parameters for nonisothermal processes can be reliably obtained using a 1-step method. Parameters were estimated for 3 typical processes: (1) no residence time distribution (RTD), (2) first-order reaction with RTD, and (3) nth-order reaction with RTD. When nonisothermal processes were approximated isothermally, k and δE were underestimated 80% to 3 orders of magnitude, and 30% to 1 order of magnitude, respectively. Reaction order was overestimated by up to 0.81. Therefore, accounting for thermal history and RTD is critical to obtain accurate estimates of kinetic parameters. The 1-step method was also used to solve for equivalent isothermal temperatures and times for an arbitrary nonisothermal process.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 70 (2005), S. 0 
    ISSN: 1750-3841
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: : This investigation was done to determine an energetically feasible method to reduce bean oligosaccharides (stachyose and raffinose) for large-scale bean flour production. Michigan black, red, and navy beans (all Phaseolus vulgaris) were treated by α-galactosidase, germination, or hydration to determine treatment effects on stachyose and raffinose levels. Oligosaccharides were extracted with 70% (w/w) ethanol, and α-galactosidase was added to catalyze hydrolysis of the oligosaccharides. Enzyme treatment was for 1 h at ambient temperature (23°C). For germination, whole beans were incubated in a germinating chamber (100% humidity, 26.7°C) for 48 h. In hydration, whole beans were soaked in excess water at ambient temperature (23°C) for 5 h. Enzyme treatment resulted in 51%± 3.0%, 30%± 1.9%, and 46%± 1.9% reduction in total raffinose and stachyose for black beans, red beans, and navy beans, respectively. Germination treatment resulted in 61%± 12%, 61%± 1.9%, and 70%± 2.8% reduction in total raffinose and stachyose for black beans, red beans, and navy beans, respectively. Hydrated black beans showed a loss of 33%± 9.6%, whereas hydrated red and navy beans showed no reduction of oligosaccharides. Although germination showed the greatest reduction in bean oligosaccharides, this method may not be as cost-effective commercially as the enzyme treatment because of the time required for germination.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 68 (2003), S. 0 
    ISSN: 1750-3841
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: : A model was proposed to predict separate thermal and mechanical effects of extrusion cooking on thiamin retention. Thermal effects were determined by heating small samples of wheat flour mixed with 0.30% (wt/ wt) thiamin hydrochloride isothermally at 140 °C, 151 °C, and 161 °C for different times. The calculated activation energy and rate constants at each temperature were 67.28 kJ/g mol and 0.00869/min, 0.0145/min, and 0.0224/min, respectively. The “extruder constant” was estimated as 27.7/rev, based on a matching-viscosity method. Wheat flour with 0.30% (wt/wt) thiamin was extruded at different screw speeds. Mechanical effects caused 89.7% to 94.4% of total thiamin loss. This research provides a generalized method to “fingerprint” the extrusion process.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Oxford, UK and Malden, USA : Blackwell Science Inc
    Journal of texture studies 36 (2005), S. 0 
    ISSN: 1745-4603
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: New value-added dry bean products, such as sugar-coated beans, require a shorter cooking time (15–30 min) and lower temperature (under 100C) than typical canned beans. Michigan bean classes navy, great white northern, small white, small red, dark red kidney, light red kidney, vine cranberry, bush cranberry, pinto and black beans were cooked at constant water temperatures of 90, 95 and 99C for 5–120 min. Isothermal rate constants for texture were estimated at each temperature for each bean class based on a modified first-order model and an n th -order model. Heat transfer coefficients were estimated using aluminum beans and lumped capacity analysis. Isothermal parameters (rate constant and activation energy) and a nonisothermal parameter (activation energy) were used to predict texture from dynamic-temperature experiments. The first-order model (isothermal) was accurate up to 30 min, but was not appropriate for time greater than 30 min. The n th -order was considered superior to the modified first-order model, because only three rather than four parameters needed to be estimated for similar accuracy. The nonisothermal method can save experimental time compared with the isothermal method, because additional experiments at different constant temperatures are unnecessary. A nomograph of equivalent heating time versus constant heating temperature was shown as a useful tool for process design.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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