摘要:

ABSTRACTHeat transfer characteristics of a scraped‐surface heat exchanger (Contherm Model 6 × 2) were evaluated at ultra high temperatures using water and soybean water extracts as model systems. The resistance equation was used to calculate internal (scraped‐side) heat transfer coefficients (hi) from the overall heat transfer coefficient, the wall coefficient and the external (steam‐side) coefficient (calculated from the Nusselt Theory using an iteration procedure). The Penetration Theory of Harriot (1958) predicted hivalues quite well at low axial mass flow rates, where laminar flow conditions prevail. However, turbulent axial flow resulted in experimental higreater than predicted by the theory. A correction factor based on Prandtl number suggested by Trommelen et al. (1971) did not improve the prediction. The Wilson Plots method was useful for explicitly accounting for axial and rotational velocity effects, both of which significantly affected heat transfer, especially at high values of either va

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1982.tb00257.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTFresh produce packaged in polymeric films represents a dynamic respiration‐permeation model. Control of equilibrium concentrations of respiratory gases is an important variable in extending the shelf life if critical vectors of quality deterioration and transport properties of packaging materials are known.Fresh peaches were stored at 5 × 1° C under various modified atmospheres for a period of up to thirty days. Samples were removed at ten day intervals for chemical and physical analyses of vulnerable quality factors. Parameters evaluated include soluble solids, titratable acidity, and texture and profile parameters such as hardness, elasticity, and cohesiveness.An internal atmosphere of 10 to 15% O2and 15 to 25% CO2inside the package provided better retention of quality attributes such as hardness and cohesiveness than any other treatments. Springiness did not provide any significant index of quality. Soluble solids decreased over time as did the amount of acid present in the fruit. Anaerobic fermentation did not occur under any storage conditions.Subsequent to establishing the optimal gaseous concentrations, respiration rates were determined as a function of time and gas composition. Permeability of polymeric films were determined using ASTM method. Analytical equations were employed to optimize packaging parameters or to estimate transient and equilibrium gas concentrations in polymeric packages. Equations were set up to estimate transient and steady state time values for oxygen and carbon dioxide concentrations inside a package. This approach is applicable in extending the storage quality of other fresh prod

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1982.tb00258.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTSoy dough (defatted soy flakes), at 120° C and 30% moisture, was extruded through a series of dies of differing length (L) and radius (R). Rlots of pressure (P) were linear with the length to radius ratios (L/R) of the dies at constant output rate (Q) and R. The intercepts of the P versus (L/R) plots on the P = O axis give the end corrections (e) for capillary flow at each output rate. For soy dough, these end corrections were surprisingly large at low output rates and generally decreased rapidly with increasing output rate. This is contrary to the normal behavior of viscoelastic fluids, such as thermoplastics, where the end correction increases with increasing output rate. Both the end correction, which is a measure of the elastic properties of the soy dough, and the viscosity of the soy dough depended on the output rate as expected and also on the retention time of the material in the system

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1982.tb00259.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

A Guide to Packuging Machinery. By Stanley Sacharow.

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1982.tb00260.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1982.tb00261.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1982.tb00256.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY