Jaroslav Buchar

Shape and Size Variability of Roasted Arabica Coffee Beans

Quantification and evaluation of selected Arabica (Coffea arabica L.) coffee beans shape and size was performed. Twenty different coffee types originating from 13 different countries were analyzed. The main dimensions for individual coffee types were quantified. Sphericity, as a useful parameter for the calculation of processing and handling operations, was also quantified and ranged from 0.006536 to 0.009452. Calculation of shape variability using elliptic Fourier descriptors showed relevant differences among individual coffee samples. A dominant importance and the relevance of length-to-width ratio were quantitatively confirmed. A simple mathematical formula describing coffee grain contour was used with a satisfying correlation coefficient. Applicability of the approach was shown on the calculation of curvature radius.

Novel Approaches in Mathematical Description of Hen Egg Geometry

Precise quantification of the profile of a hen egg can provide a powerful tool for analysis of egg shape and following solving of various technological problems. The article presents a new approach of the eggshell geometry determination using and analyzing the egg digital image and edge detection techniques. The detected points on the eggshell contour were fitted by the Fourier series. The obtained equations describing an egg profile were used to calculate the egg volume, surface area, and radius of curvature with a much higher degree of precision in comparison with previously published approaches. It was shown that radii of curvature at the critical points of the egg profile are independent on the egg shape index. The article shows and quantifies the limitations of the common and frequent procedures. This author is deceased.

Fluid dynamics of liquid egg products

The rheological behavior of liquid egg products (egg yolk, egg white, and whole liquid egg) was studied using a concentric cylinder viscometer. Eggs of three poultry specimens were used: hen (Isa Brown), Japanese quail (Coturnix japonica), and goose (Anser anser f. domestica). Rheological behavior was pseudoplastic and flow curves fitted by the power law model (Herschel–Bulkley and Ostwald–De Waele). The meaning of rheological parameters on friction factors and velocity profiles during flow of liquid egg products in tube has been shown.

Behaviour of Japanese Quail Eggs Under Mechanical Compression

In this study, the mechanical behaviour of Japanese quail eggs was determined in terms of average rupture force, deformation, and energy absorbed during fracture. Eggs were characterized by some physical and geometrical properties, such as mass, length, width, eggshell thickness, geometric mean diameter, surface area, sphericity, volume, and eggshell radii of curvature. Egg samples were compressed along the axis of their symmetry (X axis) and perpendicularly to this axis (Z axis). Four different compression rates were used: 0.0166, 0.166, 1.666, and 5 mm/s. The highest rupture force, deformation at the egg’s rupture, and energy absorbed up to the fracture were found when Japanese quail eggs were loaded along their X-axis. The rupture force increased with the compression (loading) rate. The rate sensitivity of the eggshell rupture force was close to that observed for the hen’s eggs.

Effect of the loading rate on compressive properties of goose eggs

The resistance of goose (Anser anser f. domestica) eggs to damage was determined by measuring the average rupture force, specific deformation and rupture energy during their compression at different compression speeds (0.0167, 0.167, 0.334, 1.67, 6.68 and 13.36 mm/s). Eggs have been loaded between their poles (along X axis) and in the equator plane (Z axis). The greatest amount of force required to break the eggs was required when eggs were loaded along the X axis and the least compression force was required along the Z axis. This effect of the loading orientation can be described in terms of the eggshell contour curvature. The rate sensitivity of the eggshell rupture force is higher than that observed for the Japanese quail’s eggs.

Effect of storage duration on the rheological properties of goose liquid egg products and eggshell membranes

In practice, goose eggs are increasingly used and, therefore, the rheological properties have to be known for processing. The eggs of geese (Landes Goose, Anser anser f. domestica) were stored for one, 2, 3, 4, 6, and 8 wk at a constant temperature 4°C. First of all, the egg quality parameters were described in terms of egg weight, egg weight loss, egg shape index, yolk height, albumen height, yolk index, albumen index, and Haugh units. In the next step the rheological behavior of liquid egg products (egg yolk, albumen, and whole liquid egg) was studied using a concentric cylinder viscometer. Flow curves of all liquid egg products exhibited non-Newtonian shear thinning behavior. This behavior can be described using the Herschel-Bulkley model and for technical application using the Ostwald-de Waele model. The effect of the storage duration on the rheological behavior is different for the different liquid egg products. With the exception of very low shear rates, the viscosity of the egg yolk as well as of the whole liquid egg decreases with storage time. At lower shear rates there is a tendency toward increased albumen viscosity with storage duration. The storage duration also affects the mechanical properties of the eggshell membrane. This effect has been evaluated in terms of the ultimate tensile strength, fracture strain, and fracture toughness. All these parameters increased with the loading rate, but decreased during the egg storage. These mechanical phenomena should be respected, namely in the design of the egg model for the numerical simulation of the egg behavior under different kinds of the mechanical loading.

Rheological behaviour of egg white and egg yolk from different poultry specimen

The main goal of this study is differences in rheological behaviour of hen (ISA BROWN), goose (Anser anser f. domestica) and Japanese quail (Coturnix japonica) egg white and egg yolk. The rheological behaviour of egg white and egg yolk was studied using a concentric cylinder viscometer. Rheological behaviour was pseudoplastic and flow curves were fitted by the Herschel–Bulkley model and Ostwald–de Waele model with high values of coeficients of determination R2. The meaning of rheological parameters on friction factors during flow of egg white and egg yolk in real tube has been shown. Preliminary information on time–dependent behaviour of tested liquids has been also obtained.