摘要:

ABSTRACTEnzymatic hydrolysis of lactose in cottage cheese whey ultrafiltrate was investigated. Lactase of A. niger was immobilized on an alumina‐silica catalyst support by the linking agent tolylene‐2, 4‐diisocyanate. The resulting immobilized enzyme preparation had an activity of 3 standard international units of lactase per gram at pH 4 and 37 °C. The optimum pH and temperature for hydrolysis of lactose by immobilized lactase were 3.5 and 50°C, respectively. Immobilization of the enzyme resulted in reductions of 1.1 pH units and 15°C in optimum pH and temperature, respectively.The two constants of the simple Michaelis‐Menten rate expression were obtained from Lineweaver‐Burk plots of the initial reaction rate data obtained at 37°C. Estimated values for Vmaxand the apparent Kmwere 7.8 (μmoles/min‐g) and 0.26 (M), respectively.Inhibition by the product galactose was measured by studying the hydrolysis reaction in a batch reactor. The inhibition constant Kiwas estimated from batch reactor data to be 0.005 and 0.053 (M) at 35 and 50°C, respectively.Activation energies of 8.1 and 6.4 (kcal/gmole) were obtained for the immobilized and soluble enzyme reactions, respectively.The behavior of the batch reactor as measured in terms of a plot of conversion versus time was essentially the same for both conventional and deionized w

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1983.tb00287.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTThe ability to predict thermal diffusivity from heat penetration data containing normally distributed errors in can dimensions, measurements in time, measurements of temperature, thermocouple probe location, and assumptions concerning surface heat transfer coefficients was investigated using a nonlinear least squares solution of Fourier's heat conduction equation. Thermal diffusivity calculated from heat penetration data is largely dependent on errors associated with temperature measurement and to a lesser extent dependent on errors in thermocouple probe location. Errors in can dimensions and time measurement had only a minor influence on the prediction of thermal diffusivity. Best prediction accuracy is obtained under the following conditions: (1) When a large can with a length over diameter ratio close to 0.8 is used; (2) when the difference between the initial and heating medium temperature is greater than 40°C; (3) when the data used for calculation of thermal diffusivity is limited to the temperature ratio range of 0.15 to 0.85; (4) when the Biot Numbers for the surfaces of the can are measured or known to be greater than 200; (5) when an accurate time clock is used, and when the position of the thermocouple probe is accurately known

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1983.tb00288.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTShear rate‐shear stress data on about fifty tomato concentrates were employed to study the applicability of three flow models: Herschel‐Bulkley (H‐B), Mizrahi‐Berk (M‐B), and Vocadlo. The magnitudes of the three parameters of each model were determined by means of nonlinear regression analysis. The H‐B and M‐B models described very well the flow data. The logarithm of the apparent yield stress values predicted by each model and total solids of the concentrates were related by a quadratic equation. The magnitudes of the flow behavior index of each model did not change significantly over the total solids range studied: 6–36%. The consistency index of the Vocadlo and H‐B model, and the concentration of the tomato concentrates were related by a power relationship. Over the temperature range 15–55°C, the flow behavior index of each model did not change significantly. The yield stress decreased with increase in temperature reaching a nearly constant value at 55°C. The consistency index of each model and temperature could be correlated by t

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1983.tb00289.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1983.tb00290.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY