Rami Jumah

Rheological properties of plain yogurt during coagulation process: impact of fat content and preheat treatment of milk.

A study of the effect of fat content and preheat treatment of milk has shown their respective effects on the rheological behavior of curd during the coagulation process of plain yogurt. Increase in fat content leads to an increase in viscosity. The highest viscosity was manifested by milk heated at 137°C while the lowest value was exhibited by milk heated at 65°C. The process viscosity curves for three different stages are described by mathematical relationships. Finally, a two-parameter power law model was used to describe the flow behavior of the yogurt during coagulation.

Exploitation of solar energy collected by solar stills for desalination by membrane distillation

The aim of this work was to evaluate the technical feasibility of producing potable water from simulated seawater by integrating a membrane distillation module with a solar still. The relatively hot brine in the solar still was used as a feed to the membrane module. The synergistic action of the solar still and the membrane module in the production of potable water was quantified. For this purpose, two types of experiment were conducted, indoor experiments and outdoor experiments. The sensitivity of the permeate flux to the brine temperature, flow rate, salt concentration and solar irradiation were all investigated. Overall, the flux of water from the solar still was no more than 20% of the total flux. The brine temperature significantly affected the flux of both the solar still and the membrane module, while the effect of salt concentration was marginal. The effect of these process parameters was more noticeable in the membrane module than in the solar still.

The Use of Experimental Factorial Design for Analysing the Effect of Spray Dryer Operating Variables on the Production of Tomato Powder

A two-level factorial experimental design technique was used to investigate the influence of the operating parameters on the production of tomato powder from tomato paste during the spray drying operation. This technique was applied to quantify the influence of feed total solids, feed flow rate, inlet air temperature and air flow rate on the process variables, namely, product total solids, particle size, bulk density and solubility. A factorial model was constructed and used to study all interactions among the considered parameters. The results showed that, at a 95% confidence interval, the effect of air flow rate was relatively insignificant, while the effects of feed total solids, feed flow rate and inlet air temperature were at the same significance level. Most interactions between the studied parameters were insignificant.

ANALYSIS OF HEAT AND MASS TRANSFER DURING COMBINED MICROWAVE CONVECTIVE SPOUTED-BED DRYING

Heat and mass transfer phenomena during the combined microwave-convective batch spouted bed drying are analyzed. Wheat was chosen as a test material. The governing equations, including consideration of internal heat generation and thermodiffusion are formulated and solved using the numerical method of lines. The model allowed variable material transport and dielectric properties. The parameters investigated include electric field strength, electromagnetic field frequency, inlet air temperature, and superficial air velocity. Representative drying and temperature curves as well as moisture and temperature profiles are presented and discussed.

A Comparative Study of Rheological Characteristics of Tomato Paste and Tomato Powder Solutions

Abstract The flow curves and time-dependent flow properties of tomato paste and tomato reconstituted solution (TRCS) were assessed in this study at different concentrations and temperatures. The tomato-reconstituted solution was prepared by dissolving the powders (produced by the spray drying technique) in certain amount of water to provide the concentration required. Bingham model was found to be the most appropriate to fit the flow curves of tomato paste. The yield stress, τ B , significantly increased with concentration and decreased with temperature in both the forward- (increasing shear rate) and backward-measurements (decreasing shear rate). The Bingham viscosity, η B , was found to increase with concentration and decrease with temperature. As for the TRCS, the flow curves were also best fitted by the Bingham model with shear stress values significantly less than that of tomato paste at the same concentration and shear rate. Tomato paste solutions showed a time-dependent rheological behavior while the TRCS showed a time-independent behavior. Tomato paste exhibited a thixotropic behavior at low shear rates and converted to an anti-thixotropic behavior at high shear rates.

MANUFACTURING PARAMETERS AND QUALITY CHARACTERISTICS OF SPRAY DRIED JAMEED

ABSTRACT Spray drying of jameed - a dried fermented dairy product, is investigated. The study covers the effects of the operating variables upon the physical and chemical characteristics of the dried product. The investigated variables were: feed total solids, feed flow rate, inlet air temperature, air flow rate and atomizer pressure. The product characteristics measured were: total solids, bulk density, average particle size, wettability, dipersibility, color, ash content, salt content, fat content and pH. Best overall results were obtained for a feed total solids of 17%, feed flow rate of 36.5 ml/min, inlet air temperature of 100 /C, air flow rate of 632 cm3/s, and atomizer pressure of 1.5 bar.

Constant and Intermittent Drying Characteristics of Olive Cake

The drying kinetics of olive cake, the solid by-product of the olive oil extraction process, has been experimentally investigated in a small-scale tray dryer using both constant and intermittent (on/off) heating schemes. The parameters investigated include inlet air temperature and intermittency of heat input. The drying kinetics was interpreted through two mathematical models, the Page equation and the Lewis equation. The Page equation was most appropriate in describing the drying behavior of olive cake. A diffusion model was used to describe the moisture transfer and the effective diffusion coefficient at each temperature was determined. The dependence of the effective diffusion coefficient on drying temperature can be adequately explained based on an Arrhenius-type relation. The effective diffusion coefficient varied between 7.6 × 10−8 and 2.5 × 10−7 m2/min with an activation energy of 38.55 kJ/mol. Comparison of time evolution of material moisture content due to intermittent and constant drying is also made.

Flow characteristics in a rectangular spout-fluid bed

Abstract Hydrodynamic studies are reported on six different materials, spouted and spout-fluidised with air in a column of square cross-section, using nozzles of five different sizes. Correlations for minimum spout-fluidised flow rate in cylindrical columns were investigated for this geometry. New correlations for predicting the minimum spouting velocity and the minimum spout-fluidising velocity are developed. The velocity profile in the bed agreed well with the observations of Lim and Grace [1], and Mamuro and Hattori [2].

Modeling Intermittent Drying Using an Adaptive Neuro-Fuzzy Inference System

ABSTRACT Artificial intelligence systems such as artificial neural networks (ANN) and fuzzy inference systems (FIS) are widely accepted as a technology offering an alternative way to tackle complex and ill-defined problems. The advantages of a combination of ANN and FIS are obvious. This article presents the application of a hybrid neuro-fuzzy system called adaptive-network-based fuzzy inference system (ANFIS) to time dependent drying processes and is illustrated by an application to model intermittent drying of grains in a spouted bed. An introduction to the ANFIS modeling approach is also presented. The model showed good performance in terms of various statistical indices.

On the effect of inert gases in breaking the formic acid-water azeotrope by gas-gap membrane distillation

Abstract The effect of inert gases, such as helium, air, and sulfur hexafluoride, in breaking the formic acid–water azeotrope by gas-gap membrane distillation process is theoretically investigated under the process relevant operating conditions. A Stefan–Maxwell-based mathematical model that includes all necessary vapor–liquid equilibrium, heat, and mass relations is used for this purpose. According to the model predictions, heavy inert gases such as sulfur hexafluoride help more in breaking the azeotrope than lighter ones such as air and helium. This phenomenal behavior is discussed along with the effect of other associated process parameters.