摘要:

For rice kernels uniaxial compressive modulus function, the time‐temperature and time‐moisture content shift factors, the bulk compressive creep modulus, the uniaxial compressive stress relaxation modulus, and the uniaxial compressive failure stress were experimentally determined, while the shear modulus and Poisson's ratio were calculated from the available experimental data.Uniaxial compression tests were carried out at deformation rates of 0.254.0.0508 and 0.0127 cm per min for five temperatures in 11C increments from 25 to 69C for each of the four moisture levels of 12, 17, 22 and 29% (d.b.). Stress relaxation and bulk compression tests were performed at the same four moisture levels and at the temperature of 25C.Master curves for uniaxial compressive modulus and failure strength were developed as functions of reduced time where the temperature and moisture effects were transformed to equivalent time effects by the method of reduced variables. the brown rice kernel was found to have only one time‐temperature and one time‐moisture shift function showing that the material is thermo‐ and hydro‐rheologic

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1994.tb00325.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

In pilot plant flitration tests, using a ceramic microfilter, it was shown that pectinase was effective in increasing flux at an enzyme level as low as 75 ppm and that flux increased with time during filtration. Cellulase was shown to inhibit flux when used alone or in combination with pectinase, even though it contributed to reducing viscosity of the puree.Both cellulase and pectinase were partially held back by the filter; usually more than half the pectinase was retained. This resulted in increased enzyme concentration with time in retentate. Retained enzymes might be used by continuously adding fresh puree with reduced enzyme to retentate after startup.

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1994.tb00326.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Adsorption‐desorption behavior of maize and sorghum between aw= 0.10–0.98 at temperatures of 20, 25 and 40C was studied. the grains exhibited type II sorption isotherm. the sorption data were analyzed using six sorption models and the coefficients of determination were between 0.6965–0.9994. the Caurie model gave the poorest fit and the Henderson model the best. Some models were better for adsorption than for desorption. the GAB and BET monolayer moisture contents were not significantly (p>0.05) different. Monolayer values were temperature‐dependent with activation energy from 1.36–10.08 MJ/mol and the maize monolayer values exhibited the highest sensitivity to temperature. Heat of sorption was obtained by applying Claussius‐Clapeyron equation to the sorption isotherms at the three temperatures. the heat of sorption decreased with an increase in moisture content and an exponential equation was used to describe the relationship. the processing and storage consequences of this information wer

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1994.tb00327.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Transient heat transfer during the forced‐air precooling of cylindrically shaped grapes in a batch of 5 kg was investigated both experimentally and theoretically. Experiments were conducted to measure center temperatures of the cylindrical grapes in air at 4C, and flow velocities of 1, 1.25, 1.5, 1.75, and 2 m/s. From the experimental temperature data, the dimensionless measured heat transfer rates were determined. Considering both convection and radiation, the dimensionless theoretical heat transfer rates were predicted. Good agreement was shown to exist between the predicted and experimental results. Therefore, the simple and accurate method of this study is applicable to the estimation of heat transfer rate

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1994.tb00328.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

A methodology based on central composite experimental design is proposed in order to find the optimal operating conditions of crossflow filtration with a new product/membrane combination. This approach provides an optimal operating zone with good security and fewer pilot plant tests than usual. Interesting results are found when this strategy is applied to the clarification of raw cane sugar by using microfiltration with an inorganic membrane. Maximum fluxes are obtained with the lowest transmembrane pressures and highest crossflow velocities. Analysis of data using forward selection stepwise multiple regression is illustrated with respect to classical response surface method.

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1994.tb00329.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Objective testing of the accuracy of food freezing time prediction formulae requires experimental data to be of high quality. It is shown that there are shortcomings in commonly used experimental methods, particularly relating to minimizing heat transfer in all but the required dimensions in experiments with the slab and infinite cylinder shapes, in maintaining uniformity of surface heat transfer coefficients across a sample, and in measurement of surface heat transfer coefficients. Broad guidelines to ensure that the errors introduced by experimental techniques are negligibly small are proposed. Major published experimental data sets are compared to these guidelines and comments made on their likely accuracy.

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1994.tb00330.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY