摘要:

ABSTRACTDiscrepancies between Ball's equation and his tabulated values associated with his original formula method for thermal process calculations had initially led to arguments for the validity of the equation and finally to revised sets of tables. Here, the validity of Ball's tables (within the accuracy of graphical integration) is established. A typographical error associated with Ball's published equation was identified and the correct form is presented.

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1991.tb00072.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACTThe process time calculation accuracy of five formula methods were evaluated in relation to predictions from a computer model based on finite difference numerical solution to three‐dimensional heat conduction equations with finite surface convection as applicable to processing of packaged foods in thin profile forms. Heat penetration data were obtained from the computer model for a range of package sizes, food properties and processing conditions. the centerpoint time‐temperature data were used to calculate process times required for a target lethality of 5.0 min using the General method approach (employing numerical integration). the study indicated that process time prediction errors for the different methods calculated as percent deviations from those computed using the General method were relatively small (below 4% on average) within the range of experimental conditi

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1991.tb00073.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACTEffect of moisture content, screw rpm and β‐amylase dose on the rate of maltose production in a Baker‐Perkins twin screw food extruder has been studied. Fifteen experiments were conducted using a fixed screw configuration at a fixed mass flow rate of 15 kg/h, under isothermal conditions (t=57°C) and a pH of 5.5. Each of the three variables was found to have a significant effect (P<. 05) on maltose production. Using response surface regression analysis on the experimental data, a quadratic objective function was derived. the function was optimized, subjecting it to three explicit boundary conditions, using the adaptive complex method. the optimization process yielded a maximum maltose production of 34% at 54% moisture content, 30 rpm screw speed and 157 units of enzyme/g of starch. the extent of saccharification was abou

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1991.tb00074.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACTA study was conducted to investigate the osmotic behavior of potato tissue in equilibrium with an osmotic medium consisting of various solutions ranging from 5% to 60% sucrose at 40°C. At equilibrium, the total volume changes of the potato tissue with respect to the initial volume were constant for a wide range of sucrose concentration of osmotic solutions (10% to 40%). In order to explain this behavior, the analysis was transposed from the global description of the entire structure to the analysis of the behavior of the cells. It was found that the cells of the potato tissue were plasmolyzed in osmotic media from 10% to 40% sucrose, that is, the protoplast of the plant cell separates from the cell wall due to the efflux of water from the cell. the extracellular volume, which comprises the cell wall and the intercellular space, increased whereas the cellular volume, which is equivalent to the protoplast, decreased to maintain a constant total volume. When the tissue was in equilibrium with highly concentrated sucrose solution (40% to 60%), a loss of the integrity of the cells seemed to happen.Using a typical composition of the potato tissue and the expressions relating the equilibrium water content of each phase to the chemical potential of water, the calculated volume changes were predicted in good agreement with the experimental volume changes of the lumped cellular volume of the tissue. Thus, from the thermodynamic approach, one can predict quantitatively the repartition of water in the tissue

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1991.tb00075.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACTA two‐dimensional spouted bed with draft plates for grain drying was tested using soybean, wheat and corn. Drying rate and material temperature were measured as functions of the dryer geometry and operating parameters. the hypothesis of intermittent drying, consisting of a heating period in draft channel and a tempering period in the downcomer was verified. the drying rate was found to be related to the measured rate of solids circulation. For mathematical description of the drying process in the configuration investigated, the Page's equation for thin layer drying of grains was used. the two parameters in this model were correlated versus the bed geometry and the operating parameters of the spouted be

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1991.tb00076.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY