Mikromechanische Eigenschaften von Weizenkörnern

The investigation of deformation and breakage behavior of wheat grains by compression test was carried out. The force‐displacement curve was obtained at stressing rate 0.02 mm s^–1. The elliptical wheat grains show quasi‐elastic and elastic‐plastic deformation behavior depending on applied force. The simple transformation procedure was applied to adapt the contact model for spherical particles to elliptic wheat grains. The breakage force, energy, strength and displacement distributions were fitted with normal distribution function.     

Der Einfluss von Beanspruchungsgeschwindigkeit und Partikelgröße auf das Bruchverhalten von Agarperlen

For the selection and design of enzyme and cell immobilizates the mechanical characterization is of particular importance for their usage in bioreactors. Against this background, a texture analyzer was used to perform rigidity tests on agar pearls with varying agar concentrations. The results suggest the independence of the bursting behavior from surrounding media and a significant dependency from loading speed and particle size.     

Einfluß des Verstreckens und Temperns auf das Dehnungs- und Bruchverhalten von Polyäthylenterephthalat

The stress-strain diagrams of undrawn and drawn polyethylene terephthalate were measured at room temperature and above the glass transition temperature. Before the stress-strain measurements the undrawn samples had been crystallized at various temperatures, whereas the drawn samples had been crystallized in the undrawn state, then were drawn at various temperatures and finally were crystallized again. The influence of the temperature of crystallization and the temperature of drawing on the Young's modulus, the tensile strength, and the fracture strain were of special interest. The fracture strain as a function of the crystallization temperature shows a minimum at room temperature. This minimum disappears above the glass transition temperature. Young's modulus and tensile strength generally are found the higher, the higher the degree of orientation in the sample. Crystallization of the undrawn samples therefore does not change these values significantly. But a drawing of the samples leads to a significant increase which is still more pronounced if the sample is crystallized after the drawing. Crystallization before drawing of a sample leads to a decrease of Young's modulus and tensile strength because in this case apparently the formation of a sufficient orientation during the drawing cannot take place. An increase of the drawing temperature above the glass transition temperature also leads to a decrease in the mentioned values.     

Einfluß der Fütterung unterschiedlicher Öle und Fette auf das Fettsäurenmuster des Abdominalfettes von Broilern

Influence of Feeding of Different Oils and Fats on the Fatty Acid Pattern of the Abdominal Fat of Broilers The fatty acid pattern of the abdominal fat of broilers depends to a high degree on the fatty acid pattern of the ratio. It can be absolutely reasonable to change the fat component during the fattening period. But the exchange should have taken place at last till the end of the 3rd life week, because afterwards a sufficient alteration of the fatty acid pattern can not longer be achieved because of the increased embedment. Besides, there are fatty acids which are embedded only to a small amount. Erucic acid and stearic acid, as well as caprylic and capric acid belong to them. These fatty acids are obviously mostly transformed to oleic acid.     

Einfluss der Partikelgröße und Partikelform auf das Fließverhalten von kommerziellen Magermilchpulvern

Because of the numerous application as food ingredient skim milk powder is of prime economically importance among milk powders in Germany. However, the ease of powder handling, which is determined by the flow properties, is often not regarded as a real quality attribute. To better understand the powder handling characteristic of skim milk powders this work deals with flowability measurement of commercial skim milk powders by using shear cell testing technique. Furthermore relationships between particle size, particle shape and flowability data are highlighted.     

Möglichkeiten zur Lösung von Verpackungsproblemen unter besonderer Berücksichtigung des Einflusses der Feuchtigkeit auf die Haltbarkeitsdauer eines Produktes

Possible Solution of Packaging Problems with Special Emphasis on the Influence of Humidity on the Storage Stability of the Product When developing a packaging in the laboratory, it must be known how the product behaves upon mechanical stress and how it changes under climatic conditions. This information then must be related to the stresses occurring during transport, storage and distribution. Test methods for the investigation of the mechanical properties are compiled. Then, the protection of the product from moisture is discussed in detail. The protection from moisture offered by a package is characterised by a half-value period, i. e. the time during which the packed product has absorbed half the amount of water taken up by the product during storage. The half-value period under laboratory conditions is graphically determined. From this half-value period, the half-value period applying to practical storage conditions is calculated and from this the shelflife of the package can be determined. Conversely it is shown, how the permitable water vapour permeability of a packaging can be calculated from a keepability requirement given for a product.     

Einfluß der chemischen Struktur auf das Luftabscheidevermögen und die hydrolytische Stabilität von Estern

Influence of the Chemical Structure in Regard to the Air Release Properties and the Hydrolytic Stability of Esters Esters, based on fatty chemical basis, are of great importance for the lubricant industry as efficient, biodegradable basestocks and additives. The structure possibilities and synthetic variations of ester oils are described. Basic datas are presented inclusive application areas. Parameters like air release properties and hydrolytic stability possess a central function in special applications like hydraulic fluids or compressor lubes. Oil dispersed air bubbles influence the compressibility and can cause disturbances in oil containing systems. Esterhydrolysis by water are followed by precipitation, decompositions and increased corrosivity. The determination of the air release according DIN 51 381 and the hydrolytic stability leanded against ASTM D-2619 are explained. A great number of esters based on primary and polyhydric alcohols in combination with branched and unbranched, saturated and unsaturated mono- and dicarboxylic acids were tested. Structure-effects rules were fixed in dependence of viscosity, iodine value, branching degree and carbon chain length in order to improve the choice of esters for synthetic oils.     

Einfluss des Bindemittels und der Feuchtebeladung auf die Festigkeit von Zeolith 4A‐Granulaten

A comprehensive analysis of the material behavior and the strength of (temporary binder) binderless and binder containing zeolithic molecular sieves in granular form is presented. The material behavior has been studied using single granule uniaxial compression tests until primary fracture. The received force‐displacement curves have been approximated using the Hertz and the Tomas model, respectively. The rate independent micro‐mechanical properties and specific fracture characteristics are presented.     

Über den Einfluß von Sonnenblumen-Krankheiten auf das Samenöl und auf die Veränderungen der freien Fettsäuren

Influence of Sunflower Diseases on the Seed Oil and on Changes in Free Fatty Acids The relationships between the widespread sunflower diseases like peronospora, botrytis disease, etc. on reduction of yield as well as on the deterioration of the quality of oil were investigated. It can be seen from the results obtained that the damage caused by such diseases can be minimized by suitable measures like dressing of the seeds, appropriate nutrition, proper sequence of planting etc. However, the breeding of resistant varieties remains an important task. Promising results were obtained in this respect by the author on the basis of an artificial infection procedure carried out in pathological breeding grounds.     

Einfluss des Wasservolumenstroms auf die Abspülwirkung von Körpernotduschen

Standards for overhead emergency safety showers used for decontamination in laboratories and production sites specify the spray pattern and the water flow rate. Up to now, there has not been a scientific basis for these requirements. The decontamination of water‐soluble contaminants has been investigated using 15 customary shower heads at 20 to 110 L min^–1 water flow rate. A general relationship between water flow rate and decontamination effectiveness could not be established: At a flow rate of 30 L min^–1 the wash‐off time in general did not exceed the time observed at considerably higher flow rates. The shortest decontamination time has been found with a spray pattern that does not fulfill current standards.     

Anwendungen der Magnetresonanz zur Untersuchung von Wasser‐, Temperatur‐ und Porenverteilung bei lebensmittelverfahrenstechnischen Prozessen

Applications of Magnetic Resonance for Investigating Water‐, Temperature‐ and Poredistributions in Food Process Engineering Various methods of nuclear magnetic resonance (NMR) and their application for determinig water‐ and temperature distributions as well as self diffusion coefficients during food processing operations are presented. Starting from the physical basics of the magnetic resonance, various NMR applications are shown, which may contribute to a more comprehensive understanding of the food processes: Presented examples are the determination of water distributions during the rehydration of dried samples, of temperature distributions during a microwave heating process and of self diffusion coefficients during microwave vacuum drying. These observation time dependent self diffusion coefficients may be used to receive further information about the internal tissue structure, like tortuosity and pore radii.