Rheologische Untersuchungen zum Einfluß von Hydrokolloiden auf die Gefrier-Tau-Stabilität von Stärkekleistern

Rheological Examination of the influence of Hydrocolloids on the Freeze-thaw-stability of Starch Gels. On thawing, frozen food containing starch often exhibits synaeresis, which is clearly related to structural changes. In order to determine the extent of synaeresis generated by freeze-thaw-cycles (FTC), rheological measurements were conducted with potato starch, waxy rice starch and 4 different maize starches. The relative growth of the storage modulus due to an FTC was defined as a measure of the freeze-thaw-stability (FTS). A value of less than 1 indicates an adequate FTS. Comparison of different maize and waxy maize starches revealed no correlation between FTS and amylose content. Potato starch, which exhibits very poor FTS, was chosen as a medium to examine the influence of hydrocolloid addition on the freeze-thaw-properties. First no or only little improvement of FTS was detected when examining tara gum, l-carrageenan and locust bean gum. Maximum FTS was achieved with mixtures of 5%-gels containing 10% of hydrocolloids as either l-carrageenan or locust bean gum. On the basis of the viscoelastic data, the mechanism by which hydrocolloids improve the FTS was deduced as a combination of network coupling and exclusion effect.     

Untersuchungen zum Einfluß ausgewählter Strukturparameter von Spanplatten auf die Schallemission bei Biegebelastung

The elastomechanical properties as well as the acoustic emission of laboratory scale particleboards made fromPinus radiata chips were measured. The number of acoustic counts increased in parallel with board density and solid resin content. Between the total number of count at 40% MOR and the MOE a highly significant correlation was found which, however, is partly caused by the wide range of board densities applied in this project.     

Untersuchungen zum Einfluß ausgewählter Strukturparameter auf die Porosität von Spanplatten

Using the mercury-porosimetry, the influence of bulk density, the amount of solid resin, the portion of millings, and the chip thickness on the porosity of particle boards has been analyzed. Increase of bulk density causes a reduction of the portion of pores with diameters >0.2×10³ nm while an addition of millings causes an increase of average pore volume. The increase of the component of solid resin causes an incorporation of binding medium into the pores. This leads to a clear diminuation of the portion of pores with diameters >10×10³ nm. It proved to be impossible to analyze exactly the influence of chip thickness on the structure of pores in chipboards using the measuring method applied.     

Einfluß von Sorte und Standort auf die Viskositätseigenschaften von Kartoffelstärke

Influence of Sort and Locality on Viscosity Properties of Potato Starch. Regarding its rheological properties potato starch holds a special position compared with all other starches, which is mainly due to the phosphoric acid, resp. phosphate groups bound ester-like to the amylopectin. The present work was carried out in order to find out, whether rheological properties of potato starch are also affected by outer influences such as year of cultivation, locality and sort. A marked influence of year of cultivation and locality as well as a less marked influence of the sort on phosphate and ash content of the starches became apparent. Locality exerts the strongest influence on viscosity. An influence of the sort can be stated, but it is mostly obliterated by superimposition.     

Kernresonanzuntersuchungen zum Einfluß der technischen Aufarbeitung auf die Wasserbindungsfähigkeit von Kartoffelstärke

Nuclear Resonance Investigations Regarding the Influence of the Preparation on the Water Binding Capacity of Potato Starch . In a preceding paper we stated that an increased content of more tightly bound water has been observed in a sample of industrial potato starch in comparison with a sample of starch which has been isolated under carefully controlled conditions. Now it can be shown that the conditions of drying and also the size of the starch granules have no influence on the above mentioned difference, in spite of the fact that the portion of more tightly bound water distinctly depends on the granule size. The differences in the behaviour of the bound water can be explained by the ion content of the water used during the isolation of the starch. The mechanism of this effect, however, is not yet clear.