摘要:

ABSTRACTPreliminary tests were done on the performance of an existing pulper finisher design with two unadjustable blades. Quality parameters such as consistency index and yield were determined at screen sizes of 0.5, 1.0, 1.5 mm and speeds: 100, 300, 500 and 700 rpm. Design modifications were made on the pulper finisher by addition of another blade and slide tapering of blades to allow smooth flow of material on one direction. Quality parameters such as consistency index, pulp/serum ratio, particle size distribution, total solids and total yield were evaluated.A maximum quality index in terms of total solids, pulp/serum, consistency, particle size distribution was achieved at screen size 1.0 mm and a speed of 700 rpm. Maximum yield of tomato juice however, was obtained with screen size of 1.5 mm and a speed of 700 rpm. Results of the comparative tests done on existing and modified pulper finisher showed that quality and quantity of tomato juice and puree from the modified unit is better and higher. A 3% increase in yield was observed from the modified unit.

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1992.tb00154.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTUnderstanding of the ohmic heating of liquid‐particle mixtures requires preliminary study and model development within a static heater. A mathematical (3D finite element) model was developed for prediction of temperatures of mixtures of liquids and multiple particles within a static heater. Experiments were conducted using cubic potato particles within sodium phosphate solutions, for various particle sizes, orientations, concentrations, and liquid conductivities. the mathematical model was found to yield satisfactory prediction of experimental trends. Critical parameters affecting the relative heating rates of particles and liquid were the conductivities of the two phases, and the volume fraction of each phase. Ohmic heating appears most promising with high‐solids concentration mixtu

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1992.tb00155.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTDesign of safe thermal processes in a continuous flow ohmic heater requires mathematical model development, since temperature monitoring of particles in continuous flow is not presently possible. A mathematical model previously developed and verified for a static heater was modified to predict temperatures of fluids and particles within a continuous heater with high particle concentration suspensions. Results for constant voltage simulations indicate that the presence of large populations of low electrical conductivity particles results in slow heating of the entire mixture rather than a single phase alone. In all these cases, particles tend to heat faster than the liquid. However, if isolated low‐conductivity particles enter the system, the danger of underprocessing exists; hence particle conductivity is a critical control point. Simulations also indicate the role played by residence time distribution and liquid‐particle heat transfer coefficients in the above ca

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1992.tb00156.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTA model for predicting the temperature profiles of simple‐shaped foodstuffs at the end of freezing was developed. It was shown that with appropriate selection of effective thermal diffusivity and initial temperature data, the standard solution of the unidimensional unsteady state heat conduction equation can be used in predicting the average and surface temperatures of infinite slabs at the end of freezing operation. For the calculation of average and surface temperatures in infinite cylinders and spheres, unsteady state solutions were corrected by an empirical factor that was derived from temperature profiles predicted by an accurate finite difference scheme. the temperature profiles calculated from the proposed model were compared with the predicted results obtained from a numerical model. Mean absolute errors between the predictions of the proposed model and the numerical model were 0.54C and 0.46C for average and surface temperatures, respectivel

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1992.tb00157.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTTwo mathematical descriptions based on (1) a modified and additive Arrhenius equation and (2) a modified Arrhenius temperature characteristic equation were developed to describe the combined effects of time, temperature and initial gas composition of modified atmosphere storage on the population growth rate coefficients of Listeria monocytogenes and Pseudomonas fluorescens. Statistical analysis revealed that there was no significant interaction of temperature with [O2]/(1 + [CO2]) ratio, such that a combined temperature and gas composition ratio term was not needed in an additive Arrhenius description. the Arrhenius temperature characteristic term (μ) was found to be related to the [O2]/(1 + [CO2]). Growth rate coefficients of bacterial populations could be estimated by substituting a term functionally relating to [O2]/(1 + [CO2]) ratio for the μ coefficient in the Arrhenius expression. the mathematical descriptions were shown applicable for determining bacterial population growth rate coefficients in modified atmosphere storage for oxygen concentration from 0 to 20.99% and carbon dioxide concentration from 0.03 to 80

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1992.tb00158.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY