摘要:

The single particle flow behavior of food (carrot, parsnip and potato cubes) and Nylon spheres was investigated in simulated holding tubes at different temperatures under pressurized (110C) and nonpressurized (80 and 100C) flow conditions using different carrier fluids (water and 2, 3 and 4% starch suspensions). It was found that the particle to fluid velocity ratio (up/u) was a function of carrier fluid effective viscosity, temperature and flow rate, and particle relative size, density and shape. the maximum value of up/u ranged from 0.4–1.9 which increased almost linearly with temperature showing no specific deviations in the flow behavior of particles as conditions changed from the nonpressurized (>100C) to pressurized (110C) flow. In dimensionless form, the particle to fluid velocity ratio (mean and maximum) as well as particle Reynolds number were found be functions of generalized fluid Reynolds number, particle Archimedes number, particle to tube diameter ratio and particle sphericit

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1995.tb00371.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The residence time and the residence time distributions of cylindrical particles (density 1130 kg/m3and particle concentration 20% v/v) in a U‐bend of 22 cm radius of curvature were studied. All experiments were conducted at room temperature and with an aqueous solution of sodium carboxymethylcellulose (0.5% CMC) as the carrier medium. Two levels of particle size (11 and 20 mm) and three levels of product flow rates (0.66 × 10−3, 0.81 × 10−3, and 0.97 × 10−3m3/s) were used. the results obtained from this study showed that the mean and the standard deviation of the normalized residence time of particles decreased as either particle size or flow rate was increased. the E(θ) and F(θ) curves indicated that flow profile of particles approached the plug flow profile as the particle size or the flow rate was increased. Results obtained from regression analyses revealed that the mean and the standard deviation of the normalized residence time were significantly influenced by particle Froude number and most strongly by particle‐to‐tub

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1995.tb00372.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Headspace gas composition of meat stored in modified atmosphere packaging (MAP) undergoes dynamic changes as a result of packaging film permeability, postmortem metabolic activity, CO2absorption in water and lipid, and bacteria growth and respiration. A combined analytical and experimental method was developed to investigate CO2absorption by packaged fresh meat in a gas‐impermeable environment and during isothermal storage. the ideal gas law was used as a theoretical basis and a gas‐impermeable and constant‐volume chamber was constructed to evaluate the theoretical derivation. Changes in headspace pressure caused by dynamic interactions between beef and MAP atmospheres were monitored to predict concentration changes of CO2within the chamber. the proposed methodology for measuring CO2concentration changes was confirmed by gas analysis and proved valid for prediction of headspace CO2concentration changes in MAP gas‐impermeable systems within the range of initial gas composition 20% to 100% CO2balanced with N2, at temperatures ranging from 3 to 13C, and an initial headspace pressure of

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1995.tb00373.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The model given by Levine has been extended to account for the effects of moisture, salt and fat through appropriate modifications based on theory and computational experience. Appropriate modifications to consistency index and flow behavior index as a function of moisture, salt and fat are given. the thickness of sheeted dough has been modeled as a function of gap, reduction ratio and the flow behavior index which constitutes an important contribution. the model so modified was fitted to experimental data on power consumption in sheeting dough prepared from two flour types, viz., whole wheat flour and resultant atta, respectively, at five combinations of gap and reduction ratios and three levels each of moisture, salt and fat (conforming to actual use ranges) using Nelder‐Mead algorithm for nonlinear optimization. These models provided 12 constants for each flour type which gave fundamental information on the dough properties for each flour type. Three‐dimensional graphics have been used to interpret the model. These models appear to be of much practical

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1995.tb00374.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

This study was conducted to determine water sorption isotherms of cellulose‐based films made from methyl cellulose (MC) and hydroxypropyl cellulose (HPC), and to evaluate the effect of plasticizer concentration and temperature on water vapor permeability coefficient in those films. the equilibrium moisture contents of MC film and HPC film increased slowly with an increase in water activity (aw) up to 0.75, but increased greatly after 0.75 aw. the water vapor permeability coefficient of HPC film increased as the concentration of polyethylene glycol (PEG) increased; however, the water vapor permeability coefficient of MC film which contained 0.22 ml PEG/g cellulose was lower than of films which contained no or higher PEG. an Arrhenius‐type relationship was fitted to examine temperature dependence of water vapor permeability coefficients of cellulose films. the edible films studied exhibited relatively low activation energies (14.56–16.43 kJ/mol) compared with typical food packaging mate

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1995.tb00375.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The design and modeling of a tubular reactor, similar to an extrusion rheometer, which accounts for reacting flow is described. A numerical study (finite differences) of heat transfer to a flowing and reacting biopolymer melt (wheat gluten), similar to extrusion processing, is described and compared to experimental data. the cylindrical wall is nonisothermal in the axial direction, but is adequately characterized by a third‐order polynomial determined experimentally. Convective and viscous dissipation terms are included in the energy equation. the rheological behavior of the melt is described by a power law model,. The consistency coefficient pre‐exponential, m0, is 530,000–2,100,000 Pa‐secnand the power law exponent or flow index, n, is 0.38–0.65 for a 25–30% moisture content range and a 110–209 C temperature range. the flow index decreases with increasing conversion due to polymerization reactions occurring at elevated temperatures. Flow curves, bulk temperatures, and temperature profiles are presented for a variety of cylinder wall temperatures and biopolymer mois

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1995.tb00376.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY