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Starch retrogradation is a process in which disaggregated amylose and amylopectin chains in a gelatinized starch paste reassociate to form more ordered structures. Starch retrogradation has been the subject of intensive research over the last 50 years, mainly due to its detrimental effect on the sensory and storage qualities of many starchy foods. However, starch retrogadation is desirable for some starchy food products in terms of textural and nutritional properties. To better understand the effect of starch retrogradation on the quality of starchy foods, measurement methods of starch retrogradation and factors that influence starch retrogradation have been studied extensively. This article provides a comprehensive review of starch retrogradation including the definition of the process, molecular mechanisms of how it occurs, and measurement methods and factors that influence starch retrogradation. The review also discusses the effect of retrogradation on the in vitro enzyme digestibility of starch. Spectroscopic methods such as FTIR and Raman are considered to be very promising in characterizing starch retrogradation at a molecular level, although more studies are needed in the future.

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.

BACKGROUND Functional properties of wheat starches with different particle size distribution were investigated. RESULTS A-granules displayed a disc shape and B-granules displayed a spherical shape. A-granules had the highest conclusion temperature (Tc, 80.28 °C) and gelatinisation enthalpy (3.268 J g−1) and B-granules had the highest peak temperature (Tp, 66.00 °C) and the lowest gelatinisation enthalpy (2.237 J g−1). The gelatinisation onset temperature (To), the peak temperature (Tp), Tc and retrogradation of mixed starches increased with the increase of the ratio of B-granules, while the enthalpy, all the viscosity parameters and syneresis of mixed starches decreased with the increase of the ratio of B granules. B-granules had a higher pasting temperature. The sample of B/A = 0.5/10 had the highest peak, breakdown and final viscosity. The percentage of water separated from B-granule gels was minimal, indicated that B-type gels were more stable than other samples. The ΔH2 of A-granules was obviously higher than that of B-granules. However, during storage, the ΔH2 of the starch paste was dramatically increased and the ΔH2 of B-granules was obviously higher than that of A-granules. CONCLUSION B-granules were easier to age than A-granules and most of the properties of wheat starches varied significantly with the ratio of B-granules. The relationship between structure and functionality of wheat starch received further verification. © 2013 Society of Chemical Industry

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.

Native starch from waxy mutant wheat Tanikei A6599-4 is known to exhibit more stable hot paste viscosity than a typical waxy wheat (Tanikei H1881) and waxy corn. The objective of this study was to investigate the starch paste properties of Tanikei A6599-4 after cross-linking and compare with Tanikei H1881 and waxy corn. As an example of cross-linking, the reaction (at 30, 60, 120, and 360 min) with sodium trimetaphosphate was used. In Rapid Visco Analyser (RVA) measurement, the unique characteristic was maintained in Tanikei A6599-4 starch cross-linked at low reaction time (

A model for dough is proposed in which the distribution of water between hydrated gluten and starch paste explains a number of practical observations such as 1) the extreme sensitivity of the consistency of dough to the amount of water in the recipe, and 2) the fact that working of the material results in an increase in consistency. The model assumes dough to be a composite material consisting of a starch paste and gluten filaments. During kneading, the starch granule paste in dough dries to become a phase with a yield stress as a result of the uptake of water by the stretching gluten filaments. This study focused on one particular aspect of this model: the osmotic properties of gluten during stretching. The results suggest that gluten can be hydrated more efficiently in the stretched state than in an unstretched conformation. Gluten hydration tends to change slowly over a period of weeks, which is accompanied by water expulsion or uptake, depending on the osmotic properties of the solvent. The r...

The factors involved in the baking expansion of native and sour cassava starch doughs were compared with those of native corn starch. Unlike corn starch dough, native and sour cassava starch doughs showed expansion properties during baking. The storage modulus E ′ decreased for cassava starch doughs before baking expansion, but remained unchanged for corn starch dough. Expansion during the baking of sour cassava starch was attributed to water vaporisation and the fluidity of starch paste. The fact that temperature and weight loss variations at adequate water contents were significantly greater for cassava than corn starch dough is indicative of the important role played by starch melting in expansion. Expansion ability could be correlated with changes in dough–crumb thermomechanical properties when close to the starch melting temperature. © 2001 Society of Chemical Industry

The mechanical behavior of cowpea starch gels (10%, w/v) at small and large deformations were investigated in comparison with acorn, corn, and potato starches in storage at 4°C for seven days. The rapid viscograms of starch paste (7%, w/v) revealed that cowpea starch had a larger setback (1,135 cP) than other starches (465–830 cP), although peak viscosity (1,723 cP) and pasting temperature (76°C) were between those of corn and potato starches. Texture profile analysis of cowpea starch gel showed exceptionally higher values for hardness, gumminess, chewiness and initial modulus than other starch gels. Cowpea starch gel also exhibited higher G′ and smaller tan δ compared with other starch gels, regardless of the storage time. A creep test revealed that the cowpea starch gel could remain highly resistant to stress, showing the least deformation among the tested starch gels during storage up to seven days. The overall results disclosed that cowpea starch was capable of forming exceptionally strong an...

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.

In a study of pungency in food systems, three carriers (water, cheese sauce, starch paste) with varying fat levels (none, low, medium, high), synthetic capsaicin concentrations (0.0, 0.4, 0.8, 1.3 ppm), and serving temperatures (25 and 38C) were formulated. Panelists evaluated sensory heat intensity over a 3-min interval. Time-intensity parameters (maximum intensity-MAX, time to maximum intensity-TMAX and rate of release-RATE) were evaluated. Overall, intensity scores increased as capsaicin concentration increased. The increase was related to carrier andfat level. Water samples (0. 4, 0. 8, and 1.3 ppm) were perceived as more intense than cheese or starch samples at the same capsaicin level. Generally, increasing the fat level resulted in lower intensity scores. Warming samples increased RATE, the only parameter affected by temperature. The training method was effective when water was the carrier. However, physical or chemical interactions that occur in simple food systems may influence perceived pungency.

The dynamic viscoelasticity and stress relaxation often types of starch pastes were measured. The dynamic moduli increased with increasing frequency, and were different for each starch paste, changes in tan δ for cassava and potato starch pastes being about 0.5-0. 6. The stress relaxation behaviour of all the samples tested could be represented by a four-element mechanical model. The relationship between spinnability and stress relaxation was determined, the spinning distance increasing with increased relaxation time (T 2 ). No satisfactory linear relationship between spinning distance and relaxation time (T 2 ) was apparent with the 10 starch paste samples.

A fundamental rheological method was used to study the freeze-thaw stability of hydroxypropyl potato starch pastes. The effect of the number of freeze-thaw cycles on the changes in complex modulus (G*) and phase angle (δ) during heating of the thawed starch pastes was evaluated by comparing the rheological measurements with the measurements of syneresis at different centrifugal forces. The centrifugal forces influenced the detection of the first syneresis as well as the extent of syneresis, with regard to the number of freeze-thaw cycles. When starch pastes exhibited syneresis, the G* formed a distinctive peak during heating at 52.5–53.8C. The magnitude of the peak became bigger with number of freeze-thaw cycles. Furthermore, the results of this rheological method give information on the destabilization process and provide a simple method for detection and prediction of the extent of freeze-thaw stability of starch paste. With this method, the effect of the storage period at –20C, and the freezing rate, on the extent of freeze-damage of starch pastes could be investigated successfully.

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.

Unmodified cassava starch paste was characterized on the basis of its paste viscosity as affected by drying, cooking, and paste temperatures at different paste concentrations The paste exhibited plastic fluid flow with high hot-paste peak viscosity. The temperature of the peak viscosity decreased with increasing concentration. Drying temperature had statistically significant effects on the paste viscosity; the higher the temperature at which the starch was dried, the lower was the paste viscosity over the levels of concentration and cooking temperature. Starch drying temperature and paste concentration significantly affected the paste stability as measured by freeze-thaw tests and paste retrogradation tendencies.

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.

Some aspects of mechanical finishing processes for cotton textiles, mainly calendering, have been examined, and the influences of heat, pressure, moisture content, and starch content on the resultant finish investigated. An increase in moisture content of the fabric during calendering produces the following effects on the finished samplesndashincrease in stiffness and lustre, decrease in thickness, loss in textile qualities, and increase in resistance to abrasion. On storage, both the stiffness and the lustre of the calendered fabric show a gradual fall, With softening agents, the stage at which they are added to the starch paste determines the viscosity of the paste and the stiffness of the fabric. Studies on soluble starches show that for pastes of the same viscosity the stiffness of the fabric depends on the amount of the starch taken up and on the concentration of the starch.

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.