Molekulare Struktur und physikalischchemische Eigenschaften von löslichen Stärken und Dextrinen

Molecular Structure and Physico-chemical Properties of Soluble Starches and Dextrins. Physico-chemically modificated starches, so called soluble starches show about ten times increases of reductivity and decrease of molecular weight as compared with native starch. Roasted starch without chemicals undergoes the most significant changes. Smaller and smaller changes are present successively in lintnerizated starches with hydrochloric, nitric and phosphoric acids. Soluble starches slightly α-amylase hydrolyzed in dependence on the reaction time change into high-molecular or medium-molecular dextrins with increasing during reaction degree of reductivity from 0,4 to 4 DE and decreasing molecular weight from 40000 to 6000. During α-amylase hydrolysis of soluble starches to dextrins average number of end-groups decreases in molecules from 11 to 4 and the number of branchings from 10 to 3.     

Alkalizahlen thermisch dispergierter Stärken

Alkali Numbers of Thermically Dispersed Starches. The alkali numbers of six native starches and their pastes were determined by a potentiometric method. Analogous experiments were carried out with thermically dispersed starches. All investigated native starches showed higher alkali numbers than their pastes. Prolonged thermical dispersion lead to different increasing of the alkali numbers, probably due to a different velocity of thermic degradation in the starch molecules. A good correlation was observed between the reciprocal alkali numbers of thermically dispersed starches and their molecular weights.     

Zum thermischen Verhalten von Glucanen. Teil 1: Thermoanalytische Untersuchungen an Stärken und stärkehaltigen Systemen

On the Thermal Behaviour of Glucanes. Part I: Thermoanalytic Studies with Starches and Starch Containing Systems. The thermal behaviour up to 300°C of native and pregelatinized starches as well as of amylose and amylopectin was studied by means of derivatography both under exclusion of interactions with non-carbohydrate components. Thermolysis (>200°C), which was run under anaerobic and aerobic conditions, is characterized by dominating endothermic characteristics in case of pure carbohydrates. Native starches, amylose, and amylopectin differ from eachother by onset temperature of thermolysis, loss in weight and heat of reaction. The botanical origin of the starches is without specifical significance. The differing thermal behaviour of the pregelatinized starch samples is attributed to principal differences in the super molecular structures. In contrast to the pure native starches starch-protein systems as well as cereal flours exhibit distinctly exothermic characteristics in the main destruction phase. Obviously a cooperative interaction between protein and starch will take place during thermolysis.     

Modifizierte Stärken als Bestandteile von Lebensmitteln

Modified Starches as Ingredients of Food. During the past ten years the starch industry has made considerable progress in the improvement of the properties of modified food starches. Modified starches with a relatively low degree of substitution were found to have certain properties valuable to modern food technology which are not present in native starches. To prove that they are safe and pose no hazards to health the experts of the european starch industry in a yoint effort prepared for the Joint FAO/WHO Expert Committee on Food Additives (JEC) comprehensive monographies on modified food starches which are of particular interest to food manufacturers. On the basis of the biological and toxicological findings obtained from these tests, the JEC recently announced for all major modified food starches that they are toxicologically safe and may be used in foods without limitation by ADI values and without quantity restrictions.     

Stufenweise Elutionsanalyse thermisch dispergierter Stärken

Stepwise Elution Analysis of Thermically Dispersed Starches. Qualitative changes of kernels of sorghum, wheat, maize and potato starch and decomposition of their pastes during thermic dispersing at 120°C were observed by elution analysis. After thermic dispersing potato and sorghum starch were the most decomposed. The chromatograms of their pastes showed after thermic dispersing in water at smaller concentrations of perchloric acid new zones of the iodine starch complex. Due to the molecular decomposition the intensity of the coloured zones decreased in the lower and middle part of the chromatogram, while new zones with increased colour intensity appear in the upper parts. The chromatograms of all native starches showed more coloured zones than their pastes. This is in good correlation with previous determinations where all investigated native starches showed smaller average molecular weights than their corresponding pastes.     

Hafer,Gerste und Triticale — Eigenschaften und Chancen für die technische Stärkegewinnung

Oats, Barley and Triticale — Properties and Chances for the Industrial Starch Production. Process development for the recovery of novel materials from agriculture for chemical and technical utilization has become a main point in the research program „Renewable Resources”︁ of the Federal Ministry of Nutrition, Agriculture and Forestry. In preliminary investigations oats, barley and triticale were tested for the development of starch manufacturing processes. Cereal milling techniques and methods for separation of starch, protein and fibre were predominant with water extraction, screening and centrifugation techniques which can be realized in technical scale. Process water recycling, acid treatment and separation of proteins reduced COD values to 50%. Starches with high percentage of small granules will get more importance for the production of novel technical and chemical derivatives. Methods for concentration and isolation of fine fractions were studied and controlled by electron microscopy. The starches showed differences in stability to alkali treatment and in viscosity characteristics.     

Molekulargewichtsbestimmungen von Carboxymethylstärken

Molecular Weight Determinations of Carboxymethyl Starches. At the synthesis of carbomethylated starches of different degrees of substitution (DS) by monochloracetic acid on starch in alkali solution reacting in the presence of acetone for different periods of reaction time a partial decomposition of the macromolecules takes place. It could be stated that with increasing the substitution degrees the molecular weight of the ethers decreased relatively the most rapidly in the samples of lower substitution degrees. The mean values M_n of the carboxymethylated ethers were determined by a chemical method of work which has been applied also for the determination of molecular weight of native starches. In order to determine the reducing capacities the factor f in dependence of the degree of substitution of the carboxymethyl starches has been calculated.     

Bestimmung der Substitutionsmuster von chemisch modifizierten Stärken

Determination of the Substitution Pattern of Chemical Modified Starches. Methods for the investigation of oxidized starches, starch ethers and starch esters with respect to their degree and position of substitution are described. Oxidized starches were directly hydrolyzed and the hydrolysis products analized as trimethylsilylderivatives. The classical methylation analysis was applied for starch ethers; alternatively the permethylated starch was submitted to reductive depolymerization. Methylation of starch esters proceeded with methyltriflate under retention of acyl groups and hydrolytic or reductive degradation. All degradation products were acetylated and investigated by combined gaschromatography-masspectrometry.     

Potentiometrische Molekulargewichtsbestimmungen von Stärken

Potentiometric Determination of Molecular Weights of Starches. The volumetric method of Hassid for sugar determination in plant materials, which is based on the oxidation of sugars by means of alkaline potassium hexacynoferrate (III) solution and retitration of the Fe²⁺ ions with cerium sulphate solution, was modified to determine the molecular weights M_n of native starches. Potentiometric titrations yielded well reproducible results. There was a good correlation between the molecular weights of six native starches and their alkali numbers.     

Eigenschaften von Gießfilmen aus nativen und chemisch modifizierten Stärken

Properties of Casting Films from Native and Chemically Modified Starches. Starch acetates and hexanoates were prepared from potato, wrinkled pea, and amylomaize starch of low and high degrees of substitution (DS=0.1-2.8). These products were used as raw materials for film casting in a laboratory scale. The objective of this work was to study the influence of starch types and derivatisations on film properties, i.e. tensile strength and elongation as well as water absorption and solubility. After the addition of softeners transparent, flexible, and water soluble films were obtained from unsubstituted and partially substituted starches, while totally substituted starch derivatives (triacetates and hexanoates) resulted in films insoluble in water. The well-known amylose advantage of film casting was found only after derivatisation. In the case of wrinkled pea and amylomaize starch considerable improvements of mechanical film properties, both tensile strength and elongation, were achieved even at low degrees of substitution.     

Absolute und relative Verkleisterungscharakteristik von Stärken. Teil I. Absolute Viskositätsmessung nach dem Searle-Prinzip

The Absolute and the Relative Gelatinization Characteristics of Starches. Part 1. Absolute Viscosity Measurings (Searle Principle). The rheometric conditions for executing absolute measurings of gelatinization characteristics of potato, maize and wheat starches without change of the preparation container are explained, and the results of coaxial cylinder measurings by “Rotovisko” at the absolute viscograms of the starch pastes are discussed. For absolute measurings of starch viscosities the preparation of the starch dispersions from the suspension of starch granules from the beginning of the swelling process to the formation of the homogeneous phase in turbulent current conditions is necessary; relative viscosities of the preparation phase show the swelling characteristics of the starches. By comparing different instruments of the same type their accuracy of measuring is traced at the absolute viscograms throughout the whole gelatinization range as a function of the rate of shear, and a comparison of starch viscosities by the gelatinization maxima of the absolute viscograms is proposed.     

Thermisches Dispergieren von nativen Stärken

Thermic Dispersing of Native Starches . Pastes of six native starches were prepared in a Brabender viscograph and then thermically treated at exactly defined conditions at 120°C in an autoclave for different periods of reaction time. The colloidal solutions, obtained in this way, were additionally treated with NaOH-solutions. It could be stated that at longer periods of reaction time at thermic dispersing the molecular weights and the pH values decreased much more than in the case of high amylose starch. Addition of alkali to the pastes and thermic dispersing caused further decrease of the molecular weights of the investigated starches. The results of our investigations indicate that in the first phase of heating in the autoclave to 120°C mainly a desaggregation of the associated molecules took place; at further thermic dispersing at 120°C a thermic degradation of the macromolecules and hydrolytic action of the formed products with acid properties – mainly in the amylopectin component of the starch – were stated.     

Verfahren zur Herstellung von Stärke,Protein und Fasern aus Hafer

Process Technology for the Production of Starch, Protein and Fiber from Oats. Novel raw materials for starch manufacturing processes have gained greater importance since by-products of high value became more and more decisive for the economy of the entire production process. Oat as raw material does not only contain small granule starch with novel technically suitable properties but also proteins, lipids, fibers, β-glucans and other valuable by-products for modern human nutrition and various industrial utilization purposes. Small granule starches with a narrow range of particle size distribution are of particular interest for the production of fine printing paper, biodegradable synthetic material and plastic sheets as well as technical and cosmetic powders. A process for the fractionation of oats developed from laboratory scale results and a series of pilot plant tests runs up to 30 t of oats will be presented.     

Influence of prior acid treatment on physicochemical and structural properties of acetylated sorghum starch

Influence of prior acid treatment on acetylation of starch isolated from an Indian sorghum cultivar was investigated. The starch was acid thinned (AT) using 0.1, 0.5, and 1 M HCl for 1.5 h and then acetylated (Ac) with acetic anhydride (8% w/w). The acid thinning and subsequent acetylation appeared to reduce the percentage acetylation as indicated by degree of substitution. Ac‐AT starches exhibited significantly different physicochemical, thermal, pasting, and gel textural properties from those of AT and Ac starches. Starches after dual modification showed higher solubility, lower AM content, gelatinization temperatures, retrogradation, peak viscosity, and gel hardness than native starch. Enthalpy and range of gelatinization were observed to be higher in dual modified starches than native starch. However, no significant changes in granule morphology or crystalline pattern of Ac‐AT starches were observed compared with native starch.     

Neuere Untersuchungen über die Lipide der Getreidestärken. Teil II. Die Lipide verschiedener Stärkearten und ihre Bindung an die Amylose

Recent Studies on Lipids of Cereal Starches. Part 2. Lipids of Various Types of Starch and their Bond to Amylose. By means of butanol/water (65 : 35) the lipids have been extracted from various cereal starches at 70°C. 1.0 respectively 1.3 %. lipids could be obtained from barley resp. oat starch. In every case lysolecithine was the main part (50–60 %). Apart from that, other lysophosphatides as well as free fatty acids were isolated and identified. The lipids bound to starch remain unchanged for a longer term. Apparently, the inclusion into the amylose helix acts as a protection against autoxidation. The amylose-lysolecithine-inclusion compound was prepared in pure form with a lysolecithine content of 10.2%. Processes for the determination of amylose so far proposed do not take into consideration the special bonding circumstances of lipids in cereal starches. Thus, amylose contents having been determined by these processes are too low.     

Die Wechselwirkung zwischen Stärke und Reaktivfarbstoffen. Eine neue Untersuchungsmethode in der Stärkeforschung. Teil I. Handelsübliche Farbstoffe,ihre Wechselwirkung mit Stärken und ihre Anwendung in der Stärke-Mikroskopie

Reaction of Starches with Reactive Dyes. A New Technique for the Investigation of Starches. Part I Reactive dyes can be used for the microscopical detection of damaged or structurally altered starch granules. Stainings of high intensity and contrast can be obtained. The dyes, e. g. of the Levafix E-type, are chemically bonded to the starch granules and therefore the stainings are permanent. In contrast to the chemical reaction with starches the sorption properties of reactive dyes are similar to those dyes used up until now in starch staining.     

Zur Reduktion von Schwefeldioxid-Restmengen in Getreidestärken

On the Reduction of Residual Amounts of Sulfur Dioxide in Cereal Starches. New economically applicable methods for considerable elimination of sulfur dioxide from starch products are described. Extraction experiments show that a part of the sulfur dioxide is chemically bounded. The SO₂-content of corn starches can be decreased below 20 ppm by application of less than the stoichiometrically calculated amount of sodium hydroxide or hydrogen peroxide in aqueous solution. Because of the more favourable process conditions the hydrogen peroxide-method is preferred to the others.     

DSC-Untersuchungen an Stärken. Teil II. Untersuchungen an Stärke-Lipid-Komplexen

DSC Investigations of Starches. Part II. Investigations on Starch-Lipid-Complexes. Starch-lipid-complexes are present in native starches, especially in cereal starches. Such complexes as well as those formed with added emulsifiers play an important role during application of starches and flours, e.g. within baking. Starch-lipid-complexes or amylose-lipid-complexes can be well characterized by Differential-Scanning-Calorimetry (DSC), while amylopectin-lipid-complexes could not yet be detected. The formation and the thermal stability of complexes with fatty acids depend on the chain length and the degree of unsaturation. The thermal stability increases with increasing chain length for saturated fatty acids and decreases with increasing degree of unsaturation for the unsaturated acids. Within a temperature range between 70–100°C a characteristical reorganization can occur which is described in detail.     

Kernresonanz-Untersuchungen zum Mechanismus der Wasserbeweglichkeit in verschiedenen Stärken

Nuclear Magnetic Resonance Investigations on the Mechanism of Water Mobility in Different Starches. From the temperature behaviour of the proton relaxation times of different starches can be concluded, that the water molecules at the starch structure carry out an anisotropic motion. Above room temperature exchange processes of the water protons with the OH-protons of the starch structure are observed. For potato starch the anisotropic motion results in a distinct splitting of the deuteron resonance, which can be used for studies of structural changes during the heat treatment of the starch at different moisture contents. Below 20% water content above 100°C changes in the spectrum can be observed indicating a hydrolytic attack of the starch structure. These damages partially heal at higher water contents. Irreversible changes at temperatures below 90°C can be obtained at water contents above 41%.     

Erfahrungen mit der NIR-Reflexionsspektroskopie bei der Routine-Analyse von Stärken,Stärkederivaten und Stärkeverzuckerungsprodukten

Experiences with NIR-Reflectance Spectroscopy in Routine Analysis of Starches, Starch Derivatives and Starch Saccharification Products . Application of reflectance-techniques in the Near Infrared is possible without any sample pretreatment in most cases. For routine-use the development of microcomputers was necessary because no distinct absorptions are measured between 900 and 2 500 nm. Therefore identification of absorption bands is rather complicated. A new generation of instruments based on this principle enables a rapid analysis of many products consisting of several components. The electronically stored calibration curves are activated by pressing a push-button and the instrument is ready for the next sample. Analysis time including sampling is one minute. Experiences with this technique in analysis of corn, starches, starch derivatives and starch saccharification products as well as their components water, protein, starch, and degree of substitution (acetate, hydroxypropyl, cyanoethyl, cationic groups) and degree of degradation (dextrose-equivalent, carbonyl and carboxyl groups) are given in the lecture. Broad application is possible because of the flexibility of this technique. Simple handling is important for use by untrained people. Estimated pay-back-period therefore is one year at maximum.