Modelle für Struktur und Eigenschaften der Stärke

Models for the Structure and Properties of Starch. Regularly-shaped model substances may be helpful to get insight in starch properties. Suitable compounds are prepared by phosphorolytic synthesis with free maltooligomers as primers and maltooligomers coupled to a support leading to linear and different types of branched products carrying amylose chains of uniform length. In the first part of this paper, the influence of chain length, chain length distribution and density of branching on solubility, retrogradation and gel formation is discussed more generally. Interest is focused on conclusions which may be derived for the special role of the natural starch components. The second part reports on studies with pure maltooligomers which extend results from the synthetic models into the short-chain region. X-ray powder patterns of samples precipitated from aqueous solution gave the B-type in the range DP 20 to 13, and the A-type in the range DP 12 to 10. A limit for retrogradation and crystallization is obviously DP 8 to 9. With the pure compounds the C-type is not observed. Results indicate that the x-ray type of different starches may be related to the length of the outer branches of amylopectin emerging from the cluster regions. – In the presence of amylose I₃^- ions are slowly formed from an iodide-free iodine solution. Corresponding studies with the series of maltooligomers show a close correlation between the extent of I₃ formation and the tendency for helix formation as anticipated. Remarkably, maltotriose was found being equally active as α-cyclodextrin indicating that both substances are quite similar in their conformation in aqueous solution.     

Neue Erkenntnisse über den Abbau der Stärke mit Hypochlorit 6. Enzymatischer Abbau von oxydierter Stärke

New Knowledge on Degradation of Starch by Hypochlorite. Part 6. Enzymatic Degradation of Oxidized Starch . For the detection of structural changes in hypochlorite-oxidized potato starch starches of variously high degrees of oxidation were enzymatically degraded by amyloglucosidase and a mixture of α- and β-amylase. As a function of the number of functional groups, and, therefore, of the degree of oxidation an increased number of non-degradable glucose units (GU's) was traced in the starch molecule. According to the results, not only the GU with a functional group but also the two neighbouring GU's were not affected by enzymatic degradation.     

Stärke als Chemierohstoff — Möglichkeiten und Grenzen

Starch as Raw Material for the Chemical Industry – Chances and Limits. As further, renewable raw material sources for the chemical industry are being opened up, starch may assume an important role. As a natural polymer capable of undergoing conversion and modification it could be adapted in a very flexible way to the requirements imposed on a product that is to be used as a raw material for biotechnical or chemical processes. There are different ways of including starch products in the production and/or processing of synthetic polymers which are explained here by reference to polyolefins, polyurethane foams and various condensation resins. By selective, preferably enzymatic conversion of the starch and by subsequent hydrogenation of the resulting mixtures of mono- di- or oligosaccharides it is possible to obtain a wide range of polyols. Anhydro compounds formed, for example from sorbitol, yield bicyclic polyols with the functionality 2 for which manifold outlets are certain to be found not only in polymer chemistry. The possible uses of starch as a chemical raw material which are described here, as well as other conceivable uses could be a serious contribution to a solution of raw material and energy problems.     

Hydrothermische Behandlung von Stärke in Gegenwart von α-Amylase. Teil 3. Veränderung der rheologischen Eigenschaften von Weizenstärke durch hydrothermisch-enzymatische Behandlung

Hydrothermal Treatment of Starch in Presence of α-Amylase. Part 3: Changes of Rheological Properties of Wheat Starch by Hydrothermal Enzymatic Treatment . In order to change functional properties of wheat starch the feasibility for a hydrothermal enzymatic modification under conditions of excess water (annealing) has been tested. The granular structure of the starch should remain unchanged at the same time. Since wheat starch may be changed negligiblely at usual conditions of annealing (T=50°C) as a consequence of its rather low swelling temperature a bacterial α-amylase has been used for partial degradation of these portions of starch granules which gelatinize irreversiblely at higher levels of annealing temperatures. The resulting spectrum of saccharides consisting mainly of maltose (approx. 50%) allows the protection of the wheat starch matrix even at higher annealing temperatures (54°C). However, the gelatinization and gelation behaviour is changed in a characteristic way, in particular by a serious increase of the hot paste consistency at 95°C. In the following, the obtained consistency collapses significantly and arrives by cooling a level below the corresponding figures of the native starch. With respect to yield of annealed starch the reaction time at elevated temperature is of main importance. In order to demonstrate the protecting activity of the produced saccharides in particular with higher concentrations of maltose samples have been annealed in maltose sirups of varied concentration (6, 12, 25%m/m). Up to concentrations of 12%m/m and reaction temperatures of 50°C the Brabender consistency curves could be raised by 300 to 500BU. The application of 54°C limited the effect of modification. Using a 25%m/m maltose syrup allowed, of course, successfully the annealing at 54°C. As expected, yield losses remained low (< 10%). In applying a temperature-time-regime by steps together with a treatment by α-Amylase or alternatively 25%m/m maltose syrup the expected shifting of consistency curves could be observed as well, however, to a limited amount. Finally, pronounced differences could be found for the yield of modified starches.     

Möglichkeiten einer Standardisierung von Viskositätsmessungen zur vergleichenden Beurteilung der rheologischen Eigenschaften und des rheologischen Verhaltens der Stärke

Possible Standardization of Viscosity Measuring Procedures for a Comparative Valuation of the Rheological Properties and Behaviour of Starches . As generally known, in both starch research and starch industries numerous different apparatus for viscosity measurement are used which produce rheological data by the scale and measuring systems of the instruments applied. However, the test-data obtained can not be compared on principle because of those different scale and measuring systems fixed to each instrument. Furthermore, no suitable procedure as standardized method is availably up to now. The standardization of suitable methods on the other side presupposes that the apparatus for viscosity measurement themselves produce reproducible results when uniform working directions are used. For that reason the viscosities of various potato, maize, rice and wheat starches were determined under different test conditions by utilizing the Brabender viscograph, Rotovisco instrument and Hoeppler falling-ball viscosimeter in order to establish optimum conditions for the reproducibility of results obtained. Thereby those three apparatus for viscosity measurement were selected in particular under technological aspects of application. As result of the comprehensive investigations it seems to be quite possible to criticize and review comparatively the rheological properties and the rheological behaviour of starches with regard to their importance in the special field of technical application, if the existance of suitable and also standardized methods guarantees a sufficient reproducibility of the test-data.     

Bestrahlung von Stärke. Untersuchung der niedermolekularen Spaltprodukte

Irradiation of Starch. Study of the low molecular degradation products. Potato starch was irradiated with 10 MeV electrons. (dose: 5 Mrad). After extraction and separation by twodimensional thin-layer chromatography 16 substances had been obtained. By colour reaction they could be classified into monosaccharides, deoxycompounds, sugar anhydrides, furan- and probably also pyrone compounds. The gaschromatographic separation of the trimethylsilylethers of the substances obtained after reduction of the extract with potassiumboronhydride gave approximately 25 compounds; masspectra were taken of the main peaks. The position of the carbonyl groups in the individual compound was obtained by reducing the extract with sodiumborondeuterid and by observation of the mass-shift of the single fragmentations in the mass spectra. Their evaluation revealed the presence of aldoses, deoxysugars, deoxycarbonylsugars and cyclic compounds, probably dihydropyrones and dihydrofuranes.     

Einfluß der Stärke auf die Textureigenschaften von Kartoffelknollen

Interaction of Starch and Textural Properties of Potato Tubers. By a two years glas-green-house test the influence of starch content on texture of raw and boiled potatoes was studied. Results show that only at certain conditions the starch content can affect a tendency of influencing the texture. Physical properties of starch play as well an important role referring to the texture of tubers. With reference to the influence of starch on texture of potato tubers other factors seem to play a role which still must be investigated.     

Einfluß der Extrusionsparameter auf funktionelle Eigenschaften von Weizenstärke

The Influence of Extrusion Parameters on the Functional Properties of Wheat Starch. The functional properties of native starch can be altered by regulating the technical parameters in the extrusion cooking process. The influence of specific variables on the resultant starch properties can be differentiated by means of system analysis. To make this clear, a model has been put forward which divides individual factors into those which influence the process and those which are influenced by the process, as well as examining their interrelationships. As a result of the experiments, it was possible to use regression analysis to examine the relationships between the various system analysis components. Thus it is possible either to predict the properties of the resultant starch knowing the extrusion and system parameters, or to suggest suitable extrusion conditions in order to obtain a particular starch product.     

Untersuchungen über die Retroaradation der Stärke in konzentrierten Weizenstärkegelen. Einfluß von Stärkeabbauprodukten auf die Retrogradation der Stärke

Investigations on the Retrogradation in Concentrated Wheat Starch Gels. Part 2. Effect of Starch Degradation Products on the Starch Retrogradation . In the present work the influence of added starch degradation products on the rigidity and retrogradation of 50% wheat starch gels was investigated. The gels prepared with the addition of maltodextrin were extracted with 40% ethanol, the extracts were analysed for glucose oligomers. The effect of the added starch degradation products was dependent on the degree of degradation. Weakly degraded, acid modified starches take part in the retrogradation process as do white and yellow dextrins as well as maltodextrins with dextrose equivalents (DE) <30. Maltodextrins and glucose sirups with a DE ≧ 30 act as plasticizers: in concentrations of 5-30% (based on starch d. s.) they reduce gel strength without affecting the retrogradation velocity. The plasticizing effects are particularly evident with maltose and maltotriose as well as maltotetraose and pentaose. Even so the extractibility of oligomers with a degree of polymerisation (DP) ≥ 6 was reduced, the hexamer and octamer might still have a plasticizer effect. With glucose, concentrations ≥ 26% were needed to observe plasticizing. The relation of these findings to bread staling is discussed.