摘要:

ABSTRACTA line heat source thermal conductivity probe was used to measure the thermal conductivity of 28 dairy products and margarines at 0, 20, and 40†C. Water and fat contents and mass density of each sample were also measured and correlated to thermal conductivity.There was a strong positive correlation between thermal conductivity and water content, and an inverse correlation between thermal conductivity and fat content. Temperature did not appear to be a significant factor over the limited temperature range studied. Although there was some correlation between mass density and non‐fat solids fraction, no correlation was observed between mass density and thermal conductiv

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1978.tb00206.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

ABSTRACTA dynamic programming algorithm for determining the optimum operational parameters and size of a multi‐stage concurrent flow dryer with intermediate tempering stages was developed. The objective function was based on energy and capital costs. The operational parameters were constrained by the desired final moisture content and the maximum allowable value of important grain quality factors.The two‐ and three‐stage concurrent flow dryers have a higher investment cost than the single stage unit, but were less expensive to operate due to the decreased grainflow rate in the single‐stage unit. On the basis of operating cost, the multi‐stage concurrent flow dryer was preferable to a comparable crossflow dryer for dr

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1978.tb00207.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

ABSTRACTThe kinetics of ascorbic acid loss in grapefruit juice was determined for thermal and concentration processes. The results indicate an apparent first order anaerobic reaction which is dependent on temperature and degree of product concentration but not on initial ascorbic acid content. The effect of temperature on rate of reaction follows the Arrhenius equation with energy of activation ranging from 5 to 11.3 Kcal/mole for solids content of 11 to 62†Bx, respectively. Using a polynomial curve fitting technique, an empirical kinetic equation correlating rate of reaction with temperature and degree of concentration was established. Based on this empirical equation, a prediction mathematical model was formulated and proved useful in analyzing the extent of ascorbic acid retention in grapefruit juice during commercial thermal and concentration processe

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1978.tb00208.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

ABSTRACTHeat transfer and lethality in foods heated by force‐convection in agitated, reel‐type retorts (Steritort) were investigated. Equations describing the temperature profile at any position in the food were developed and experimentally verified for fluids and fluids with particles. For both types of food, the temperature profiles are a function of the heat transfer coefficient (h) at the inside surface of the container (the fluid container interface). For foods with particulate pieces, the temperature profiles, in both the fluid and the particle, are also a function of the heat transfer coefficient (hp) at the fluid particle interface. Empirical models are presented correlating both heat transfer coefficients (h or hp) with system parameters.Equations describing the temperature profile at the coldest point in the food (i.e. the point receiving least lethal treatment) were used in a modified form of the lethality‐Fourier number equation (Lenz and Lund 1977a) to calculate lethality. This method of calculating lethality agreed with lethalities calculated by the Improved General Method.Confidence intervals for lethality for forced‐convection heated products were determined using the Monte Carlo procedure described in Lenz and Lund (1977b). The 95% confidence intervals for the lethality ranged from 20–60% of the median value of the lethality depending on process conditions. The fluid/particle interface heat transfer coefficient (hp) had a significant effect on the lethality dist

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1978.tb00209.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1978.tb00210.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1978.tb00211.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1978.tb00205.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY