The Modification of Starch by High Pressure. Part I: Air- and Oven-dried Potato Starch

Air and oven-dried potato starch was compressed at 0.8–1.2 × 10⁹ Pa for 60 to 600s. Structural studies have shown that observed changes are both pressure and time dependent. The amylopectin shell of starch grains is the component which suffers most essential but rather random damage. The high pressure of 1 × 10⁹ Pa seems to cause some repolymerization of dextrin formed first under compression. The 1.2 × 10⁹ Pa pressure causes further damage of the structure with ordering of the molecules into more crystal-like matter. The compression of the air-dried starch provide the formation of hard solid gels.     

Studies on Rye Starch Properties and Modification. Part II: Swelling and Solubility Behaviour of Rye Starch Granules

Rye starch shows the typical inhibited swelling behaviour of triticeae starches with an onset of swelling at rather low temperature (50–55°C). Swollen rye starch granules exist as individuals even after swelling at 100°C. The total dispersion of rye starch needs temperatures above 120°C with pressure cooking. On heating of the rye starch suspension preferentially amylose is leached. Defatting of rye starch exhibits no influence on swelling power but results in higher solubility and in increased amylose leaching. The drying procedures applied here resulted in stronger assoziation of the polymer molecules in the starch granule leading to higher swelling temperatures and a reduced solubility. Shiftings of the crystalline/ amorphous-ratio of the starch granules as caused by different drying procedures, had no influence on the results of swelling power investigation but the highest swelling enthalpy as well as Brabender viscosity were exhibited by a sample dried at room temperature. It is proved to be possible to change the swelling behaviour of rye starch to “potato starch type” by slight chemical modification like succination.     

Depolymerization of Starch by High Pressure Extrusion

High pressure extrusion (13,00–40,000 psi), using a French Pressure Cell and hydraulic press, was evaluated for the degradation of potato starch. Rapid decreases in both relative and intrinsic viscosities of starch colloidal solutions (0.5–2.5%, w/v) were evident, particularly following the first extrusion. However, maximum reducing powers formed (1.15 dextrose equivalents) were negligible even after 5 consecutive extrusions of a 0.5% starch solution. The significant decreases in viscosities of starch solutions were due to depolymerization of the starch molecules into smaller fractions with little reducing power. However, the use of high pressure extrusion combined with heat (97°C) and 3N HCI significantly enhanced degradation of a 2.5% starch solution to yield 52.1 dextrose equivalents.     

高压对淀粉糊化特性的影响

差示扫描热分析法等,对小麦、玉米、绿豆、藕、木薯、甘薯、土豆淀粉经４０ＭＰａ以下的高压处理后,其糊化温度、糊化焓等糊化物的变化进行了研究。     

高压对淀粉粒结晶结构的影响

对7种淀粉分别进行100－450MPa的高压处理,采用X－射线衍射等方法研究其结晶结构。结果表明：压力对淀粉颗粒结晶结构的影响与淀粉结晶类型有关,对A－型淀粉影响最大,超过2000MPa遭到破坏,并有B－型结构出现;对B－型淀粉影响较小,结晶度稍有加强;对C－型淀粉影响介于A－型和B－型之间。     

Chemical Modification of Proteins Part 6. Further Studies on Gelation of Casein after Modification by Dialdehyde Starch

The physical and chemical changes in casein during the gelation owing to the chemical modification by dialdehyde starch (DAS) in 8–10% solution were studied using electron-microscopy, measuring the mechanical properties (shear deformation), turbidimetric titration, and determination of amino groups. The gelation which proceeds during a storage time of 2 weeks is accomplished by the formation of a super-molecular network structure. Depending on the conditions of modification (pH, percentage of DAS, protein concentration) a more or less dense network is formed. An increase of pH (in the range of pH 6,3–9,7) leads to an increase of gelation speed, which favours the formation of irregular network structures. The denser the network formed the smaller is the shear deformation measured by the device of Tolstoi. During the storage of the gels the plastic component of compliance decreases to a greater amount than the elastic one. Therefore the relative amount of elastic component increases. During the reaction with DAS the maximum of turbidity of the protein (solubility minimum) shifted to lower pH owing to a blockage of positively charged groups. On the contrary to the changes measured by physical methods, this shift is complete soon after a 1 day storage. Similarly the blockage of amino groups is finished in the most cases this time too.     

Compression of gellan gels. Part II: Effect of sugars

The effect of sucrose, glucose, fructose and their mixtures on the gelation of 0.5 wt% low acyl gellan in the presence of potassium chloride (100 mM) was investigated by large deformation compression experiments. The sugar concentration varied from 0 to 15 wt% whereas all their combinations at a final concentration of 15 wt% were also studied. Stress at failure and strain at failure along with Young's modulus were calculated from each compression curve. Samples prior to compression were refrigerated at 5 °C for 1, 2 and 24 h. Glucose showed no contribution to the gellan network strength but decreased the firmness of the gels. On the other hand, fructose and sucrose enhanced the strength of the network, with sucrose being slightly more effective, but had no effect on firmness. This behaviour depended solely on the presence of each sugar and not in their concentration. The elasticity of the gels was not significantly altered by the addition of sugars or their mixtures. Strength and firmness shared similar profiles when mixtures of sugars were used to promote gelation. Sugars, when in mixtures, showed no synergistic interactions whereas their type seems to affect the properties of the resulting gels.     

Studies on Rye Starch Properties and Modification. Part I: Composition and Properties of Rye Starch Granules

Rye is considered as a potential raw material for starch industry. Starting from a survey of technical procedures of isolating starches from rye-flour and -grits investigations will be reported, which were performed on pilot plant- and laboratory-isolated rye starches. The present paper deals with its granule appearance and composition. A distribution of granule size between small granules (⩽ 10 μ − 15%) and large granules (⩾ 11 … ⩽ 40 μ − 85%) is typical for the totality of the starches. Differing distributions depend on the conditions of isolation: the entity of starch containing samples resulted from the laboratory procedures under investigation. Large-granule starch preparations were isolated in the pilot plant: the centrifuge-overflow contains the small-granule fraction which is high in impurities. Granule crystallinity amounts to 16%. The crystalline component - like in wheat and triticale starches - consists predominatly of A-polymorph - with up to 9% of the B-type. The isotherms of water exchange are of the cereal type. The contents of minor constituents largely relate to the small granule fraction which assembles the majority of crude protein, pentosans and lipids, which are difficult to remove

1 Large granule samples may be produced in high purity (⩽ 0,2% crude protein)

. Lipid components in all fractions influence the results of linear chain-iodine interactions and they must be removed to proceed from apparent to absolute polysac-charide indices. The absolute amylose contents amount to ∼ 25% for large granule samples and to 20–21% for small granule samples. The average chain-length of iodine binding helical regions was determined with 220–240 AGU.     

The Measurement of Resistance to Compression Part II: Precision of Measurement

Confidence limits are estimated for the precision of measurements of resistance to compression made according to the Australian Standard AS 3535–1988.     

Reaction of Epichlorhydrin with Carbohydrate Polymers. Part II. Starch Reaction Mechanism and Physicochemical Properties of Modified Starch

Detailed mechanistic pathways are described for starch-epichlorohydrin (ECH) reaction. The mature and extent of side reactions accompanying the cross-linking reaction as well as the influence of reaction conditions on these have been demonstrated. The influence of degree of crosslinking of starch on its various physicochemical properties such as swelling, solubility, gelatinization, viscosity, iodine complex, crystallinity and granular structure are discussed.     

Studies on Starches of High Amylose-Content. Part 14. The Fractionation of Amylomaize Starch by Aqueous Leaching

Amylomaize starch is known to contain an anomalous material which does not conform to the classical definitions of either amylose or amylopectin. A detailed study of this polysaccharide has not yet been carried out, principally because of the difficulty of obtaining it in sufficient quantity. This paper presents a rapid and simple method by which the isolation may be achieved.     

Lipids and Rheological Properties of Starch. Part II: The Effect of Granule Surface Material on Viscosity of Wheat Starch

The extraction of wheat starch with ethanol reduced the protein content from 0.4 to 0.3%. Wheat starch extracted with 1% SDS containing 1% 2-ME or with 1% SDS gave no staining with amido black, indicating that most of starch surface protein has been separated. TLC of lipids extracted from starch without gelatinization showed that ethanol extracted considerable amounts of starch lipids such as lysophosphatidyl choline, lysophosphatidyl ethanolamine and free fatty acids. After extraction with SDS and especially with SDS + 1% 2-ME only some starch granules were deformed. In this starch some changes have been observed also on the granules surface by REM. The extraction resulted also in considerable changes in rheological properties of extracted starches. The starch samples were characterized thermodynamically also.     

Studies on Sweet Potatoes. Part II: Isolation and Characterization of Starch

By differential sedimentation and centrifugation steps four starch isolates were recovered from sun dried sweet potato flour. The granules in these isolates were of different size, shape and population characteristics, and were anionic in nature. They showed a single stage swelling with 30 to 35% solubility in water and only ∼30% solubility in DMSO even after 72h. Their starch content varied from ∼48 to 88%. The presence of thermostable amylases in sweet potato resulted in considerable decrease in Brabender viscosity values as amylographic studies in the presence of H_gCl₂ showed significant increase in peak (PV) and setback (SBV) viscosities. The starch isolate I had 25% higher PV as compared to the isolate II but retrogradation was much low in this. Susceptibility to glucoamylase digestion showed a decreasing trend from the isolate I to the IV on solid basis, but comparable on starch basis.     

超高压对马铃薯淀粉糊化作用的研究

采用偏光显微镜对超高压处理后的马铃薯淀粉偏光十字进行了观察,结果表明5%的马铃薯淀粉乳液在300、400、500 MPa下处理5 min后,马铃薯淀粉的偏光十字没有消失,在600 MPa下,少数淀粉颗粒的偏光十字开始消失,在700 MPa的超高压下处理5 min后,偏光十字全部消失,说明马铃薯淀粉糊化压力在600～700 MPa.     

Cereal- and Root Starch Modification by Heat-Moisture Treatment. II. Functional Properties and Baking Potential

Functional baking properties of heat-moisture treated starches (barley, triticale, red millet, arrowroot, cassava) described in preceding paper* are given. The bread and cake baking potential of cereal starches was adversely affected by the treatment. Although the quality of breads and cakes failed to match that of untreated wheat starch, the treatment improved tuber starches, suggesting that the molecular order of starches is an important factor in starch baking quality. Thickening properties tested with pie fillings demonstrated adverse effects of the treatment on this starch property.     

A Study of Hydroxyethyl Starch. Part II. Degradation-Sites of Hydroxyethyl Starch by Pig Pancreas α-Amylase

The degradation sites of hydroxyethyl starch (HES) by pig pancreas α-amylase were determined by gas liquid chromatography. As a result, it was confirmed that HES could be hydrolyzed by α-amylase only at the glucosidic bond of unsubstituted glucose residues, but not at the bond of 2-0-, 3-0-, and 6-0-hydroxyethylglucose residues. Furthermore, it was suggested that the enzymic degradation rate of HES could be well determined by measuring the reducing power.     

Investigations on High Amylose Corn Starch Films. Part 3: Stress Strain Behaviour

By autoclaving a watery high amylose corn starch suspension, homogenous and isotrope films were obtained with different processing parameters. The films were used for investigations on the stress strain behavior. A systematical dependence on the water content and the relationship between native lipids and the starch chains was observed. Especially for films obtained from defatted corn starch, a clear transition was obtained, depending on the water content, from a brittle behavior far below the glass transition temperature T_G with a very high Youngsmodulus to a ductile failure behavior above T_G. The results led to a microscopical model for the native high amylose corn starch films, which in addition outlines the very interesting possibility of controlling in detail changes of the macroscopic stress strain behavior through variations on a molecular scale.     

Studies on Rye Starch Properties and Modification. Part III: Viscograph Pasting Characteristics of Rye Starches

Pasting characteristics of native as well as of physically and chemically modified rye starches have been characterized and compared with the other triticeae starches and starches from maize and potatoes. Normal and pressure viscograph techniques were applied. Additional, ridgelimetry investigation were performed with the gels formed from the viscographically prepared pastes. Rye as well as wheat and triticale starches exhibit unique, typical gelatinization behaviour, late onset of consistency gain, low but highly stable cooking consistency, consistency gain of the two-threefold on cooling. Gels are of statistically lower firmness as those of maize starch. Higher degrees of consitency, good cooking stability and high consistency gain on cooling were achieved after treatment in the pressure viscograph (max. temp. 120°C). Physical treatment like annealing, heat-moisture treatment, extraction by aqueous solvents, drying procedures result in different but in each case typical change of properties: shift of onset consistency gain, lower maximum consistency values, lower consistency gain on cooling. Gelfirmness will be enhanced in every case. The pasting characteristics of heat-moisture treated wheat starch differ from this by remarkably higher consistency values. Possible reasons for this are discussed. Succination (0.7-2.1%) changes the pasting characteristics towards the potato starch type, lower onset temperatures of consistency gain, very high values in maximum consistency, diminished cooking stability. The gels formed are smooth and turbid. Acetylation (0.7-2.3%) changes the pasting characteristics towards the maize starch type, maximum consistencies are lower compared with succinated triticeae starches. Ac contents of 0.7% inhibit the formation of rigid gels.