Aggregation Of Amylose Research Articles

Unraveling the mechanisms of pea protein isolate in modulating retrogradation behavior of pea starch

The study investigated the impact of pea protein isolate (PPI) on the short-term and long-term retrogradation behavior of pea starch (PS). Dynamic time scanning and water migration analysis revealed that the presence of PPI enhanced water mobility within the PS gel during short-term storage (4 °C, 8 h) and impeded amylose gelation, effectively suppressing the short-term retrogradation of amylose. Over long-term storage (4 °C, 14 d), PPI reduced the retrogradation enthalpy and the ordered structure of starch molecules. The relative crystallinity and retrogradation degree reduced by 40.6% and 29.9%, respectively, as the PPI content increased from 0 to 12%. Textural profile analysis showed PPI decreased the gel hardness and induced the formation of a weak gel of PS, thereby delaying the long-term retrogradation of amylopectin. Scanning electron microscopy analysis further confirmed that the PS-PPI mixed gel exhibited a more disordered and loose structure compared to the PS gel, which resulted from PPI inhibiting the rearrangement and aggregation of amylose and amylopectin molecules. These findings suggested that PPI exhibited the potential to inhibit the short-term and long-term retrogradation of PS, thus providing valuable theoretical evidence for enhancing the development and research of pea-based products.

Physicochemical properties and structure of modified potato starch granules and their complex with tea polyphenols

The physicochemical, rheological properties and structure of potato starch and starch-tea polyphenols (TPs) complex modified by enzyme and alcohol was investigated in this study. Cavities on the modified starch granules and morphology change could be investigated by SEM, while significant birefringence observed in complete granules by polarizing light microscope, but disappeared in crashed starch. TPs inhibited the aggregation of amylose and retrogradation of starch-TPs complex, resulting in the decrease of gel strength, and the increase of viscosity and gelatinization stability of starch granules. Fourier transform infrared (FT-IR) spectra showed that intramolecular hydrogen bond could be formed between TPs with modified starch, and the hydrogen bond force formed by starch and TPs was stronger than that between starch molecules. X-ray diffraction (XRD) analysis revealed that three modification methods did not change the crystalline structure of starch, but new diffraction peaks appeared in the four starch-TPs complex, suggesting that the hydrogen bond was incurred by interaction between TPs and amylose to form V-type crystalline. These results demonstrated that the complex formed by TPs and native/modified potato starch could be used in food industrial applications due to the inhibition of starch retrogradation.

Roles of dextran, weak acidification and their combination in the quality of wheat bread

Dextran-containing sourdoughs have been widely employed in baking, obtaining products with higher quality instead of adding additives. This study investigated effects of dextran of a high weight-average molecular weight (Mw) and linear structure, sourdough and their combination on wheat bread quality. The underlying mechanism was explored from properties of pasting, amylopectin retrogradation and water distributions of starch systems. Bread characteristic analyses showed that both dextran and weak acidification due to addition of sourdough improved bread quality, especially crumb softness. Dextran decreased moisture migration due to high water-binding capacity. Enhancements of amylose aggregation by weak acidification contributed to retardation of amylopectin recrystallization. A synergy existed between dextran and weak acidification. Dough rheology demonstrated that weak acidification was fundamental for dextran-induced positive dough viscoelasticity. This study indicates a combined anti-firming performance of high Mw dextran and weak acidification, possibly being a promising strategy to prolong shelf life of wheat bread.

Study on the retrogradation behavior of starch by asymmetrical flow field-flow fractionation coupled with multiple detectors.

In this study, the capacity of asymmetrical flow field-flow fractionation (AF4) coupled with multiangle light scattering (MALS) and differential refractive index (dRI) detectors, to monitor starch retrogradation behavior in situ was evaluated. Meanwhile, the starch samples were characterized by differential scanning calorimetry (DSC) and fourier transform infrared spectroscopy (FTIR). The effect of the botanical origin, amylose/amylopectin ratio, storage conditions (i.e., temperature and time), and salt on starch retrogradation was systematically investigated. The starch aggregation and disassociation is a kinetic equilibrium process that is dependent on the storage conditions and the content of amylose. Moreover, it was found that nitrate ions retarded starch retrogradation behavior by inhibiting the formation of hydrogen bonds between amylose molecules. The results suggest that the formation of the small amylose aggregates plays an important role in starch retrogradation and maize amylopectin degradation. The information obtained by AF4-MALS-dRI is valuable for understanding the starch retrogradation mechanism.

Improved material properties of solution-cast starch films: Effect of varying amylopectin structure and amylose content of starch from genetically modified potatoes

High-amylose potato starches were produced through genetic modification resulting in changed granule morphology and composition, with higher amylose content and increased chain length of amylopectin. The increased amylose content and structural changes in amylopectin enhanced film-forming behavior and improved barrier and tensile properties in starch films. The molecular structure in these starches was related to film-forming properties. Solution-cast films of high-amylose starch revealed a homogeneous structure with increasing surface roughness at higher amylose content, possibly due to amylose aggregation. Films exhibited significantly higher stress and strain at break compared with films of wild-type starch, which could be attributable to the longer chains of amylopectin being involved in the interconnected network and more interaction between chains, as shown using transmission electron microscopy. The oxygen permeability of high-amylose starch films was significantly decreased compared with wild-type starch. The nature of the modified starches makes them an interesting candidate for replacement of non-renewable oxygen and grease barrier polymers used today.

Effect of heating time and temperature on partially gelatinized starch-fatty acid interactions

A series of samples of aqueous dispersions of high amylose (70%) maize starch were prepared in the presence of fatty acid potassium salts. The samples were heated at either 75 or 80 or 85 °C for 30 or 60 or 90 min. The fatty acids used were myristic, palmitic and stearic and they were added to starch dispersions either before the commencement of heating or after the heating was completed at the predetermined temperature and heating time. Flow behavior studies revealed that the temperature of heating but not the time of heating affected the flow properties of the samples. X-ray diffraction studies showed that at temperatures below 85 °C the degree of amylose–fatty acid complexation was fatty acid chain length dependent i.e. the shorter the fatty acid chain length the more the available amylose interacted with the fatty acid when the addition of the acid was done prior to heating. Scanning Electron Microscopy revealed that spherulites were formed on the surface of the thermally treated starch granules, at temperatures as low as 75 °C, which could be due not necessarily only to the amylose-fatty acid complexes but to retrograded amylose aggregates as well.

In situ SAXS under shear unveils the gelation of aqueous starch suspensions and the impact of added amylose–lipid complexes

The gelation of heat-treated, aqueous starch suspensions has been explained either in terms of a nanoscopic amylose aggregation or a fractal-like phase separation. These concepts, as well as the supporting experimental evidence, at first sight seem incompatible. The present study exploits rheometry in combination with in situ small angle X-ray scattering and clearly points to creation of finely dispersed, elongated nano-objects when a starch gel is formed in the presence of shear forces. These objects are interpreted as aggregated amylose double helices that provide the system with physical, intermolecular crosslinks. Increasing the aggregate size and concentration increases the gel storage modulus. The gelation process is enhanced in the presence of amylose–lipid complexes as, during heating, short amylose fragments are liberated from these complexes that, upon cooling, promote amylose aggregation and thus gel formation. When shearing is stopped, the aggregates promptly grow and agglomerate into larger fractal objects resulting in an increased gel stiffness. The present work thus suggests that small scale amylose aggregation and the formation of fractal phases have to be considered as subsequent events rather than as mutually exclusive concepts. Finally, it is argued that size-induced polymorphic changes may also contribute to the starch gel stiffness.

Functions of iota-carrageenan on the gelatinization and retrogradation behaviors of corn starch in the presence or absence of various salts

Gelatinization and retrogradation behaviors of the aqueous starch/iota-carrageenan composite system (0.5 w/v% starch and 0.2% carrageenan) were investigated. Purified iota-carrageenan in sodium form was mixed with corn starch in the presence or absence of various salts. Functions of iota-carrageenan on starch depended on salts added. During gelatinization, the addition of iota-carrageenan lowered the incipient swelling temperature of the composite system with decreased peak viscosity in the absence of added salts and in the presence of monovalent cations, while the temperature increased in the presence of divalent cations. It also increased the rate constant for short-term (<24 h) retrogradation of the composite system with depressed gel-like characters in the presence or absence of salts. The effect of iota-carrageenan to increase the rate constant was the greatest in the absence of added salts and was greater in the presence of monovalent cations than divalent cations. The effect of the polysaccharide to depress gel-like characters was the greatest in the presence of LiCl and NaCl. The molecular mechanism was deduced from microscopy to explain these rheological behaviors mainly from the structural similarity between iota-carrageenan and amylose. Thermodynamic incompatibility between these two substances may explain the early onset of viscosity increase during gelatinization (i.e., upon heating) and the acceleration of subsequent short-term retrogradation due to increased effective concentration of starch or amylose, whereas physical interactions (both molecular complexes and steric hindrance) between the substances may explain the retardation of structural ordering during retrogradation (i.e., upon cooling) due to inhibited amylose aggregation.

Interaction between starch and aroma compounds as measured by proton transfer reaction mass spectrometry (PTR-MS)

The interaction between starch and the complexing aroma compounds hexanal and menthone was investigated by headspace analysis using proton transfer reaction mass spectrometry (PTR-MS). Starch systems with non-modified and modified tapioca starch were prepared containing single aroma compounds (hexanal, menthone) or a blend of the two aroma compounds at low aroma concentrations (6 × 10 −3 mg/100 g). The headspace intensity of starch–aroma systems was slightly reduced due to starch–aroma interactions compared to aroma water-systems. The combination of hexanal and menthone did not lead to competitive aroma release effects, but hexanal retention increased by increasing the equilibration time from 48 to 96 h. Non-modified and chemically modified starch showed similar aroma release behaviour. It is concluded that the formation of starch–aroma complexes influences aroma release, but that at low aroma concentration the dissociation of the complex is not hindered by the aggregation of amylose–aroma complexes.

Phase and rheological behaviors of xanthan/amylose and xanthan/starch mixed systems

Phase separation and rheological properties of wheat starch (2 wt%) or amylose (0.3 wt%) with xanthan (0.1 or 0.5 wt%) mixtures were investigated at two salt levels (less than 0.01 M equivalent NaCl and 0.1 M NaCl). Mixed systems were prepared with pre-heated solutions and/or dispersions. Appearance of two or more phases upon time, followed using a technique based on multiple light scattering, occurred at both salt concentrations. However, it was faster and more pronounced at higher salt concentration. Generally, a transparent upper phase, an intermediate diffuse turbid zone (amylose aggregates) and an opaque down phase (granules and/or aggregated amylose sedimentation) were observed. According to their dynamic rheological properties, xanthan and mixed systems behave like viscoelastic fluids with xanthan dominating the overall behavior. Spectra obtained at various xanthan concentrations may be shifted along modulus and frequency axis for both salt conditions and the shift factors dependence on xanthan concentration is discussed.

Differences in amylose aggregation and starch gel formation with emulsifiers

The effects of different kinds of emulsifiers, polyglycerol ester and glycerol monostearate, and the surface-active lignosulfonate, on network formation and aggregation of amylose and starch in gels were studied. Pastes with emulsifier and 5% amylose or different starches were heated to between 90 and 150 °C, cooled and studied by means of transmission electron microscopy. The fine-stranded amylose network aggregated into thicker strands when emulsifiers were added. At high emulsifier concentrations, spherical aggregates without internal structure formed, and the network disappeared. In wheat starch gels, a lower concentration of emulsifier was needed for amylose aggregation than in pure amylose gels. At high temperatures (>140 °C), aggregation was more ordered, and long, needle-like threads or brush-like aggregates were achieved. The amylose aggregated similarly with the complexing emulsifiers used in this work as with the non-complexing surfactant, which showed that amylose–lipid complex formation was not the primary explanation for aggregation.

Rheological investigation of the interaction between amylose and κ-carrageenan

By combining rheological and turbidity measurements, the interaction and viscoelastic properties of amylose–κ-carrageenan mixtures were investigated under conditions allowing gelation of the former and gelation or non-gelation of the latter. Amylose concentration was kept constant (1.34 wt%) and carrageenan content was varied from 0.093 to 1.38 wt%. Amylose was dispersed in water at 150°C and its gelation was induced by quenching aqueous solutions from 80 to 25°C. When desired, carrageenan gelation was also induced by addition of 20 mM KCl. Absorbance and gel-cure profiles were highly dependent on carrageenan concentration and presence of salt. The storage modulus at 15 h depended strongly on carrageenan concentration; for concentrations <0.2%, amylose aggregation occurred rapidly and the rigidity of gels was reinforced as a result of phase separation between amylose and κ-carrageenan. Further addition of carrageenan, either without or with KCl, resulted in a maximum G′ occurring at about 0.2 and 0.3%, respectively. Beyond such values a sharp decrease was observed suggesting phase inversion with carrageenan forming the continuous phase. Above 0.5%, G′ increased steadily showing a predominance of carrageenan gel properties. Results support the existence of at least two different conditions in which amylose and carrageenan form the continuous and disperse phase alternately.

Partial hydrolysis of gelatinized barley and waxy barley starches by alpha-amylase

The hydrolysis of gelatinized commercial barley starch by Bacillus licheniformis alpha-amylase began by rapid depolymerization of amylopectin in two stages. The formation of low molecular weight hydrolysis products, as indicated by an increase in reducing power, was only observed when all the original high molecular weight amylopectin had degraded further. The hydrolysis of waxy barley starch followed a similar pattern. Hydrolysis had a big influence on the microstructure of the starch dispersion: first the degradation of the amylopectin rich granule residues (‘ghosts’) was observed, and later amylose aggregates were formed.

Gelation process of amylose‐DMSO‐water system

AbstractAmylose gel is obtained by cooling amylose aqueous solution at a certain cooling rate. In order to clarify the gelation process of amylose in the mixed solvent of water and DMSO, the characteristics of turbidity and dynamic viscoelasticity of the solution as a function of temperature have been studied by optical and rheological methods, respectively. Accordingly, cloud temperature (Tc) at which the aggregation of amylose occurs, and gelation temperature (Tgel) at which the elasticity began to appear were obtained. Tc and Tgel were strongly dependent on cooling rate, and these values shifted to higher temperatures with decreasing cooling rate. However, there was difference between Tc and Tgel, and Tc was higher than Tgel, indicating the gelation process occurs in two stages.

Heat-induced Changes in Native and Acid-modified Oat Starch Pastes

Abstract Light microscopy and viscoelastic measurements were used to study the heat-induced changes in low-sheared native and acid-modified oat starch dispersions. A significant structural change occurred in the native oat starch dispersion between 90 and 95°C: the granule structure broke down and, at 95°C, the amylopectin formed a continuous phase in which amylose was dispersed. During cooling, oat starch dispersions, pre-heated to 95 and 98°C, underwent two transitions in viscoelastic behaviour: one below 85°C, the other below 40°C. The former is related to phase separation of amylose and amylopectin, the latter to aggregation of amylose. Both cooling and storage at 4°C enhanced separation into amylose- and amylopectin-rich domains. Most of the acid-modified oat starch was solubilized when pre-heating was to 95°C, and the viscosity of the hot paste was substantially lower than that of native oat starch dispersion. During cooling, the acid-modified oat starch underwent a transition in viscoelastic behaviour; below 40°C storage modulus increased and phase angle decreased. This partly hydrolysed gel, although less rigid, was more elastic than the corresponding native starch gel. Microstructural studies showed that amylose was responsible for the gel structure of the acid-modified oat starch.

Aggregation of amylose in aqueous systems: the effect of chain length on phase behavior and aggregation kinetics

Nearly monodisperse amyloses having a wide range of chain lengths have been enzymically synthesized in vitro. The rate of aggregation from aqueous 0.2-5.0% solution and the physical form of extensively aggregated material have been studied as a function of chain length. Aggregation (monitored by turbidity) is found to be most rapid for chain lengths of ∼100 residues in agreement with previous results (Pfannemuller, B.; Mayerhofer, H.; Schulz, R. C. Biopolymers 1971, 10, 243-261) for initial aggregation rates in 0.1% solution. Amyloses having chain lengths of 1100 residues) gelation is found to predominate over precipitation. The variation of phase behavior and aggregation rate with chain length is rationalized on the basis of ordered polymer-polymer associations involving chain segments of typically less than 100 residues.

Molecular mechanisms underlying amylose aggregation and gelation

The molecular origin of the aqueous aggregation and gelation behavior of amylose is shown to lie in the formation of interchain double helices. Gelation is shown to be possible from nonentangled amylose solutions, and no correlation is found between critical gelling concentrations and coil overlap concentrations for a range of amylose chain lengths. NMR and X-ray diffraction experiments show that amyloses precipitated from dilute aqueous solution contain only B-type aggregated double helices and that amylose gels contain rigid double-helical junction zones interconnected by more mobile amorphous single-chain segments. Optical rotation results suggest that the double-helix structure underlying amylose aggregation and gelation may have a left-handed conformation.

Kinetics of amylose retrogradation

AbstractThis article deals with the kinetics of the retrogradation of amylose in aqueous solutions of pH 4.0, 9.2, and 11.9. The course of the retrogradation is followed by means of light‐scattering measurements. From our interpretation of the light‐scattering data we conclude that the retrogradation mechanism appears to be in qualitative agreement with von Smoluchowski's theory on coagulation. From the rate of retrogradation one may tentatively conclude that only a small fraction of the collisions between the amylose aggregates leads to permanent coagulation. In order to explain this phenomenon, additional conditions are suggested for permanent attachment of two colliding aggregates. The relevant fraction is smaller at pH 11.9 than at the lower pH's, a fact which is ascribed to the mutual repulsions of the aggregates due to their negative charges.

カマボコの顕微鏡観察

“Kamaboko”, one of the most favorite fish meat products in Japan, is a sort of jelly which is prepared by grinding fish meat with some salt into a paste, and then steaming or broiling it. Sometimes starch is added to the meat in order to enhance jelly strength. Some 60 samples of the products with high jelly strength were examined under a microscope. The majority of them were observed to possess porous or network structures (Figs. 1 and 2). This has led us to an opinion that network structure not only of colloidal dimension, but also of microscopical one may have something to do with the elastic property of “Kamaboko”, though an assumption that elasticity of gel is due to the presence of network structure of colloidal dimension has been accepted in general. No significiant difference in the microscopical structures was evident among the jelly products prepared from various kinds of fish, nor seemed to be dependent on heating methods. When starch had been added to starting materials, the greater portion of it was found existing in the jelly as granules, despite their being gelatinized (Figs. 4 and 5), while the minor part was found here and there as amylose aggregates (Fig. 9). Though starch granules in the jelly were seen gelatinized, they were but a little greater than those of native starch and much smaller than those gelatinized in water (Figs. 6 and 7).

An investigation by light scattering of the state of aggregation of amylose in aqueous solutions

AbstractAqueous alkali has been assumed to be a good solvent for amylose, and has been used as a medium for physicochemical studies on this polymer. It is shown that there is a slow but substantial reduction in the turbidity of normal KOH solutions of amylose, even in the almost total absence of oxygen. More significantly there is a corresponding, but much more rapid, drop in turbidity in neutral solutions (pH 6.5–7.0). At pH 4.0 the turbidities are, in general, constant for up to at least 30 days. The results are interpreted on the basis of aggregates, which evidently must be of a very special type and are termed “native” aggregates. It is suggested that these may consist of amylose in essentially the helical configuration. The properties of these aggregates are in strong contrast to those of the retrograded aggregates. In the form of the first type of aggregate the amylose will not retrograde, at room temperature, without undergoing first a drop in turbidity suggesting that the transition from the “native” to the retrograded aggregate passes through the molecular state. The native aggregates are stabilized toward both disaggregation and retrogradation by pretreatment with iodine. Disaggregation is accompanied by a drop in relative viscosity. Some of the implications of these unexpected observations are pointed out.