RHEOLOGICAL CHARACTERIZATION of COFFEE MUCILAGE

Rheological behavior of mucilage obtained from two varieties of coffee grown in Colombia (Caturra and Colombia) was studied as a function of ripe cherry content (RCC) and postharvest time (PHT). A Brookfleld HB DV-III viscometer was used in concentric cylinder geometry over a shear rate range of 4.8 to 120 s⁻¹. the power-law model was used to describe the shear stress versus shear rate data, and the consistency index (K) and flow behavior index (n) were determined. the mucilage is a highly viscous and pseudoplastic (n < 0.3) fluid. the K increased and n decreased as the RCC and PHT increased. the mucilage of the Caturra variety was more viscous and shear thinning than that of the Colombia variety. Microstructural examination of the mucilage revealed that certain weak structures as phloem vessels found in the mucilage may be destroyed upon application of shear stress and may contribute to the pseudoplastic nature of the mucilage. Diffusion of tannin from the pulp to mucilage with delay in postharvest processing may be responsible for increased apparent viscosity with increased PHT.     

Towards a portable and efficient environment for parallel computing

The availability of more and more cost-effective and powerful parallel computers has enhanced the ability of the operations research community to solve more laborious computational problems. In this paper an attempt has been made to implement a parallel simulation runs dispatcher with an objective to study the feasibility of establishing a portable and efficient parallel programming environment. This parallel simulation run dispatcher can be applied to both terminating type and steady-state type simulation models. The algorithm is then transferred and executed on various other shared-memory multiprocessor systems to illustrate its portability. Another contribution of this paper is to verify whether the performance of the portable code and the non-portable code of a same algorithm is significantly different on a specific parallel system using the analysis of covariance model.     

Modelling the cross-sectional variation of E/P ratios: implications for the E/P anomaly

This paper models the cross-sectional variation of earnings-price (E/P) ratios using Finnish data. Although E/P ratios are very commonly used in practical investment decisions, the cross-sectional determinants of E/P ratios have reached only limited attention so far. In this paper it is shown that a substantial part of the cross-sectional variation of Finnish E/P ratios can be devoted to differences in securities systematic risk estimated by instrumental accounting variables, such as accounting betas, financial leverage, operating leverage and growth. After controlling the E/P ratios for the effects of these instrumental risk variables, the E/P anomaly becomes insignificant in the Finnish stock market. This finding suggests that the E/P anomaly generally observed in major financial markets may be largely due to the serious empirical problems in risk estimation.     

EFFECT OF METHOCEL AS A WATER BINDER ON THE LINEAR VISCOELASTIC PROPERTIES OF MOZZARELLA CHEESE DURING EARLY STAGES OF MATURATION

Changes in the dynamic and transient rheological character of highmoisture, skim milk (HMSM) Mozzarella cheese due to the addition of 0.2% Methocel (methyl cellulose) as a water binder at room (25C) and refrigeration (7C) temperatures during early stages of maturation (1, 5, 7, and 14 days after manufacture) were investigated. The HMSM Mozzarella with 0.2% Methocel was softer (lower dynamic storage and loss modulus, and higher creep and recovery compliance) compared to HMSM Mozzarella without Methocel, due to improved water holding capacity. The age-dependent frequency dispersions of dynamic mechanical spectra (storage and loss modulus) were fitted to a power-law model. A six-element Voigt-Kelvin mechanistic model described the age-dependent retardation spectra (compliances, viscosities, and retardation times) obtained from creep experiments. Strong correlation was obtained between the viscoelastic     

Predicting Soluble Solids Extraction from Fruits in a Reversing, Single Screw Counter Current Diffusion Extractor

A single-screw, intermittent-reversing counter current diffusion-extractor (CCDE) was used. Two mathematical models were developed to predict soluble solids concentration profile along the length of the CCDE. Both models predicted an exponential concentration profile and good intra-flight mixing. Experimentally obtained soluble solids concentration profiles in the CCDE using applies and pears validated the model predictions.     

Stress-Strain Curve Analysis of Cheddar Cheese under Uniaxial Compression

Samples were subjected to uniaxial compression at six deformation rates until fracture occurred. Fracture strain, stress and work, deform-ability modulus, and biaxial extensional viscosity were determined. No significant effect of surface lubrication was observed on magnitudes of the selected mechanical properties. Irrespective of deformation rate Cheddar cheese fractured at a strain of 55.5% when aspect ratio was 0.65, and at a strain of 59.7% when aspect ratio was 1.0. The fracture stress ranged from 34 to 107 kPa and fracture work from 22 to 63 kJ/m³. Mean deformability modulus of Cheddar cheese was 240 kPa. Biaxial extensional viscosity was a decreasing function of strain rate.     

RHEOLOGICAL EVALUATION OF MOZZARELLA CHEESE BY UNIAXIAL HORIZONTAL EXTENSION

Rheological properties of low-moisture part-skim Mozarella cheese were evaluated as a function of storage time, test temperature, and deformation rate by uniaxial extension in a horizontal plane. Proteolysis of Mozzarella cheese caused marked decreases in the tensile strength and the deformability modulus, but not in the fracture strain. As the temperature increased from 10 to 40C, the fracture strain increased more than five-fold. The strength and the deformability modulus decreased about 60 and 85%, respectively, as the cheese temperature increased from 10 to 30C. The fracture strain of the cheese did not exhibit a clear trend with the deformation rate in the range of 50–500 mm/min. However, its strength and deformability modulus increased with the increasing deformation rate.     

A novel wound dressing material — fibrin–chitosan–sodium alginate composite sheet

The present study describes preparation and characterization of fibrin–chitosan–sodium alginate composite (F–C–SA) in sheet form. F–C–SA composite was prepared and characterized for its physicochemical properties like water absorption capacity, surface morphology, FTIR spectra and mechanical properties. The optimum quantities of fibrin, chitosan and sodium alginate to get better mechanical properties to composite were determined. FTIR spectrum confirmed the interaction between amino groups of chitosan, fibrin and sodium alginate and SEM studies revealed composite nature of the material.     

Optimal investment and lot-sizing policies for improved productivity and quality

Productivity and quality are an integrated component of the operational strategy of any firm. An increase in productivity implicitly assumes an improvement in quality. The concept of dynamic process quality control and smaller lot-size production have been employed to eliminate defective items, to reduce the cycle time of a product and to improve quality and productivity. We present a mathematical model to establish the relationship between various parameters of productivity and quality. In addition, the proposed model is used to determine the optimal levels of productivity and quality parameters such as batch sizes, and investment in set-up and process control operations. The basic criterion considered for optimizing the level of such parameters is the minimization of total system cost. The proposed model relates productivity and quality to set-up reduction, queueing of batches, batch sizes, and drift rate reduction. We conclude with an example problem to illustrate the behaviour and application of the model.     

Effect of machine failures in a multi-stage multi-facility and multi-product production-inventory system

A mathematical model for a multi-stage, multi-facility and multi-product production-inventory system is presented to study the effect of machine unreliability on the economic production quantity and total system cost. The production system considered here has multiple spindle and batch blocking facilities. A search method has been used for optimizing the batch sizes. The basic criterion considered for optimizing the batch sizes is the minimization of the total system cost. An example is presented to explain the behaviour and application of the model.