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Native and modified starches are important raw materials used in the industry. Gelatinization and rheological properties of starch are primary physicochemical properties to determine its applications. Starch gelatinization refers to a process that starch loses the native order and crystalline structure of the granules and becomes amorphous. Key rheological properties of starch include pasting property, viscosity of starch paste, and rheological features of starch gel. In this review, gelatinization and rheological properties of native starches from different botanical sources are compared and impacts of other ingredients, including sugars, salts, and lipids, on the properties are summarized. The review also covers current understandings of the gelatinization and rheological properties of modified starches with different structures. The information provided will be useful for the applications of starch in the industry as well as fundamental research in this field.

The effect of concentration and temperature on viscoelastic properties of chestnut starch is discussed in the paper. The starch structure was estimated using the fractional standard linear solid model FSLSM. Rheological parameters of the FSLSM model were determined and their changes for different concentrations and temperatures of chestnut starch paste were discussed. High values of the viscoelastic modulus of plateau allow us to state that in all the analyzed cases, the medium with a structure typical of viscoelastic quasi-solid bodies is formed. The values of the rheological parameters of FSLSM model provide useful information concerning the structure of chestnut starch paste, such as the total elasticity of the networks, network oscillations, gel stiffness, and structure of cross-linking. The proposed method of discussion of the results of rheological measurements allow to present a comprehensive evaluation of the analyzed medium structure.

Antiaris africana seeds yielded 29.6% starch which showed appreciable high contents of ash, protein, and fat. The average diameter of A. africana starch granules was 3.98 µm compared to 8.93 µm for maize starch. A. africana starch had a C-type XRD pattern and crystallinity of 41.5%. A. africana starch had higher AM content (24.1%) than maize starch (20.9%). The gelatinization onset temperature of A. africana starch (66.7°C) was higher than maize starch (63.1°C), but its gelatinization temperature range (8.57°C) and enthalpy (13.97 J/g) were lower than the values for maize starch (14.02°C, 14.65 J/g). The pasting temperature (Pt) and setback (Vs) were lower and breakdown (Vb) higher for A. africana starch (Pt = 82.5°C, Vs = 173.8 RVU, and Vb = 121.42 RVU) than for maize starch (Pt = 84.9°C, Vs = 183.73 RVU, and Vb = 78.58 RVU). The GPC analysis gave Mw of 2.18 × 107 g/mol and radius of gyration of 95.1 nm for Antiaris starch. Antiaris starch paste exhibited poor freeze-thaw stability but its small granule size indicates potential for application as dusting starch.

Acid-thinned cornstarch was monophosphorylated by reaction with orthophosphates to obtain an agent for sizing heat-sensitive viscose warp yarns under reduced temperature. Influences of the modification and sizing temperature on paste behavior, adhesion to viscose fibers, and properties of sized viscose yarns were studied for a range of substitution of 0.021-0.082 and temperatures from 60°C to 95°C. The modification resulted in an increase in viscosity stability of the starch paste, enhancement of the adhesion to the viscose fibers, improvement of mechanical properties of the sized viscose yarns, and a decrease in hairiness of sized yarns even if the temperature of the starch paste was lowered to 60°C. The modification is capable of improving the sizing properties of starch for viscose yarns at 60-80°C when the degree of substitution with phosphate groups is about 0.05.

Alternative sources from different botanical origin were used for starch isolation. Chemical analysis and functional properties were studied in amaranth seed and banana fruit starches. Chemical composition in both starches was different; banana starch presented higher protein, fat and ash levels than that from amaranth. Botanical origin of these starches contributes notably in their chemical composition. Blue value and λmax gave information on starch components: amaranth starch is classified as waxy type and banana starch as normal. Functional properties were evaluated; amaranth starch was more soluble than banana starch, but at higher temperatures amaranth showed lower swelling values than banana starch. The results of freeze-thaw stability suggest that amaranth starch can be used in frozen products. Apparent viscosity studies showed that amaranth starch paste has higher viscosity than banana starch, but the former starch presented higher stability during the 30-min test.

The lysine rich high protein seeds of A. paniculatas (Rajgeera) are reported to contain 50–60% of waxy starch, concentrated in the endosperm. However its food related properties are comparatively unknown. In the present work, paste viscosity, paste clarity, freeze-thaw stability and effect of shear on the viscosity of A. paniculatas starch paste have been studied and compared to corn starch. Also included are the stability of Rajgeera starch paste under pressure cooking (30 min, 15 lb pressure) and acidic conditions (pH 6.98—1.76). Rajgeera starch was found to have a higher paste viscosity, lower paste clarity and high freeze-thaw stability than corn starch. Both Rajgeera and corn starch underwent thinning on being subjected to mechanical shear. Rajgeera starch withstood pressure cooking conditions admirably, but was found to be sensitive to acidic conditions. Einige Eigenschaften der Pasten von Amaranthus paniculatas-Starken (Rajgeera). Es wird berichtet, das die eiweisreichen und lysinreichen Samen von A. paniculatas (Rajgeera) 50–60% wachsige, im Endosperm konzentrierte Starke enthalten. Ihre lebensmittelbezogenen Eigenschaften sind dagegen vergleichsweise unbekannt. In der vorliegenden Arbeit wurden die Pastenviskositat, die Pastenklarheit und die Wirkung von Scherung auf die Viskositat der Starkepasten untersucht und mit denen von Maisstarke verglichen. Auch die Stabilitat von Rajgeera-Starkepasten unter Druckkochung (30 min, 25 lb Druck) und sauren Bedingungen (pH 6,98—1,76) wurde mit eingeschlossen. Es wurde gefunden, das Rajgeera-Starke hohere Pastenviskositat, geringere Pastenklarheit und hohere Gefrier-Tau-Stabilitat als Maisstarke besitzt. Sowohl Rajgeera- als auch Maisstarke zeigten Verdunnung bei mechanischer Scherung. Rajgeera-Starke widerstand den Bedingungen der Druckkochung beachtlich, zeigte sich jedoch empfindlich gegenuber sauren Bedingungen.

On Determination of Shearing Stability of Starch Pastes. Test conditions for the shearing stability test of starch pastes are not sufficiently outlined in existing publications. In the present paper, first of all a determination of optimum parameters (type of paste production, type of stirrer, stirring time, stirrer revolutions, viscosity measurement etc.) for a shearing stability test was attempted. It became apparent that shearing treatment of 5 min by means of a blade stirrer at a number of stirrer revolutions of 1800 r.p.m. with a 5% paste concentration is sufficient to determine shearing stability of a starch paste. For viscosity measurement which as well as pasting and shearing stress is carried out a 95 °C, a Brookfield viscosimeter is used. Provided measuring conditions (type of spindle, spindle revolutions) are kept constant before and after shearing stress, shearing stability can be expressed as remaining viscosity as a percentage of the initial viscosity. Furthermore, reproducibility of paste production as well as that of the whole shearing stability test were determined. Finally, a test was carried out as to wether there is a connection between shearing and heat stability of paste. Values obtained from 11 commercial products made such a connection between the two criteria apparent.

Mit der stufenweisen Elutionsanalyse wurden die durch thermisches Disperieren hervorgerufenen Veranderungen in den Sol- und Gelfraktionen von Wachsmais- und Amylosestarke verfolgt. Die Sol- und Gelfraktionen wurden durch Elektrodialyse der Kleister bzw. der Dispersionen, die im Autoklaven bei 120°C hergestellt worden waren, gewonnen. Es wurde festgestellt, das beim thermischen Dispergieren die Sol- und Gelfraktionen des Kleisters der Wachsmaisstarke stark abgebaut werden, zum Unterschied der analogen Fraktionen der Amylosestarke. Laugenzusatz zu den Solfraktionen hat praktisch keinen Einflus auf das Aussehen der Chromatogramme. Besonders in der Gelfraktion des Amylosestarkekleisters und teilweise auch in der Gelfraktion des Wachsmaisstarkekleisters sind Fragmente zu beobachten, die nach Laugenzusatz desaggregieren. In der Solfraktion des Kleisters der Wachsmaisstarke konnten nur 9% Starke gefunden werden, wahrend in der Solfraktion nach 3stundigem Dispergieren im Autoklaven ungefahr 45% Starke vorlagen. In den analogen Solfraktionen der Amylosestarke war kein Anstieg des Starkegehaltes festzustellen. Stepwise Elution Analysis of Electrodialysed Fractions of Waxy Corn- and Amylose Starch. Changes in the sol and gel fractions of waxy corn- and amylose starch during thermic dispersing were observed by stepwise elution analysis. The sol- and gel fractions were separated from pastes and dispersions, after being treated in an autoclave at 120°C, by electrodialysis. It was found that during the thermic dispersing the sol- and gel fractions of waxy corn paste decompose more intensively than the analogous fractions of amylose starch. Addition of alkali to the sol fraction of waxy corn- and amylose starch has no influence on the chromatograms. Especially in the gel fraction of amylose starch paste and partially also in the gel fraction of waxy corn starch paste fragments can be observed which after addition of alkali disaggregate. In the sol fraction of the paste of waxy corn starch only 9% of starch could be detected, in the sol fraction, isolated after 3 h of dispersing in an autoclave, however, 45% approx. were determined. In the analogous fractions of amylose starch no increase of the starch contents was observed.

Isolation and some of the important physicochemical properties of starch from rajgeera grains have been investigated. The yield of starch was about 61.2%, on whole grain basis. The results on physicochemical properties revealed that it exhibited moderate swelling and higher solubility (55.5%) in water, as compared to other millet starches. An extensive solubility in dimethylsulphoxid (72.5%) of the starch indicated easy penetration of solvent in a granular matrix, may be due to labile and heterogenous bonding forces within the granules. Brabender viscoamylographic data on pasting characteristics revealed that it yielded low viscosity (448 B. U.) at concentration of 10% (w/v) and showed very little tendency to retrograde during cooling of the starch paste. The amylopectin content was 88.5% indicating the starch of rajgeera is probably waxy in nature. Amylolytic digestibility of native and gelatinized starch of rajgeera by human salivary α-amylase and glucoamylase was investigated. Untersuchungen zur Isolierung und Charakterisierung der Starke aus Rajgeera-Konern (Amaranthus paniculatus Lin.). Die Isolierung und einige der wichtigen physikalisch-chemischen Eigenschaften der Starke aus Rajgeera-Kornern wurden untersucht. Die Ausbeute an Starke betrug 61,2%, bezogen auf das Ganzkorn. Die Bestimmung der physikalisch-chemischen Eigenschaften zeigte mittlere Quellung und hohere Loslichkeit in Wasser (55,5%) im Vergleich zu anderen Millet (Hirse)-Starken. Eine starke Loslichkeit der Starke in Dimethylsulfoxid (72,5%) wies auf leichtes Eindringen des Losungsmittels in die Kornmatrix hin, moglicherweise infolge von labilen und heterogenen Bindungskraften innerhalb der Korner. Brabender-viskoamylographische Daten zur Verkleisterungscharakteristik zeigten geringe Viskositat (448 BE) bei einer Konzentration von 10% (w/v) sowie geringe Retrogradationstendenz wahrend der Abkuhlung der Starkepaste. Der Amylopektingehalt betrug 88,5% und zeigte, das die Starke aus Rajgeera offenbar wachsige Natur besitzt. Die amylolytische Abbaubarkeit nativer und verkleisterter Starke von Rajgeera durch menschliche Speichel-α-Amylase und Glucoamylase wurde untersucht.

Observations on Viscosity Properties of Low-Substituted Starch Acetates. It was shown that with low-substituted starches dispersibility in water increases with increasing content of acetyl groups and increasing temperature. This fact becomes evident in lower temperatures at the beginning of pasting and at maximum of „viscosity”-graph. This has confirmed and extended earlier observations. Viscosity of starch acetate pastes is lower in cold as well as in hot state as that of native starch paste. Viscosity decreases down to an acetyl content of 2.36% and it changes only unnoticeably above that point. The decreasing gel forming ability can be expressed by the ratio of paste viscosities in cold and hot state. The rotation viscosimeter Rheotest proved well applicable for studies of viscosity and rheological properties of starch and of low-substituted acetates.

Starch from six clonal selections of Dioscorea rotundata was isolated by standard procedure. The yield was between 20–24%. Various properties of these starches were compared. Granule size, 2% viscosity, peak viscosity, clarity, sol stability, total and soluble amylose contents were studied and only small variations were observed in the properties except paste viscosities among the clonal selections. The phosphorus content of Dioscorea starch was found to be three times as much as cassava starch, but low compared to potato starch. The higher gel strength of D. rotundata starch paste compared to cassava gel may be attributed to the phosphate linkages among the starch molecules in the granules. Untersuchungen uber die Eigenschaften der Starke von Dioscorea rotundata. Die Starke von sechs klonalen Auswahlen von Dioscorea rotundata wurde mittels eines Standard-Verfahrens isoliert Die Ausbeute betrug 20–24%. Verschiedene Eigenschaften der Starken wurden verglichen. Korngrose, Viskositat 2%iger Suspensionen. Spitzenviskositat, Klarheit. Solstabilitat, gesamte und losliche Amylose wurden untersucht und nur geringe Abweichungen in den Eigenschaften beobachtet, abgesehen von den Kleisterviskositaten unter den klonalen Auswahlen. Der Phosphorgehalt von Dioscorea-Starke war dreimal so hoch wie der von Cassavastarke, aber niedrig im Vergleich zu Kartoffelstarke. Die hohere Gelstarke von D. rotundata-Starkekleister im Vergleich zu Cassava-Gelen durfte den Phosphatbindungen zwischen den Starkemolekulen in den Kornern zuzuschreiben sein.

In this paper the viscosity increase of the starch paste during gelatinization is examined. Upon heating, raw starch granules gelatinize and the paste viscosity of the starch adhesive increases dramatically. Bonding develops further through the dehydration of the gelatinized starch by the board. Bond setting of carrier-type (mixture of dissolved and raw) starch on paperboard in the corrugated board operation is thought to result from a combination of thermal gelatinization and dehydration by the board. Veranderung der Rheologie von Starkeklebstoff wahrend der Verkleisterung. In dieser Arbeit wird die Erhohung der Viskositat der Starkepaste wahrend der Gelatinisierung untersucht. Durch Erhitzen gelatinieren die Rohstarkekorner, und die Pastenviskositat steigt drastisch an. Die Bindung entwickelt sich weiter durch die Dehydratation der gelatinierten Starke durch die Pappe. Man nimmt an, das die Hartung der Bindung vom Trager-Starketyp (Mischung aus gekoster und roher Starke) aus der Kombination von thermischer Gelatinisierung und Dehydratation durch die Pappe in der Wellpappe resultiert.