Rheological Properties of Starch Gels from Wheat Mutants with Reduced Amylose Content (original) (raw)
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Starches from nine Indian wheat lines were evaluated to study the relationships between physicochemical and rheological properties. Large granules (>15 lm) were present in the highest proportion followed by medium (5-15 lm) and small granules (<5 lm). Amylose content ranged between 27.4 and 37.2%. Starch with the highest proportion of large granules (68.9%) showed higher values of G¢ peak (576 Pa) and G¢ final (432 Pa). Amylose content showed positive relationships with retrogradation, gel firmness, gumminess and adhesiveness while negative with springiness. Cooked starch pastes with the highest amylose content (37.2%) had higher DH ret (0.88 J g )1 ), G¢ ret (361 Pa), adhesiveness (1.48 Ns), firmness (0.45 N) gumminess (0.22 N) and the lowest springiness (0.88). Amylose-lipid complex (AML) dissociation showed negative relations with swelling power, G¢ peak , G¢ breakdown and breakdown viscosity (r = )0.779, )0.66, )0.771 & )0.775, respectively, P < 0.05) while positive relationship with pasting temperature (r = 0.775, P < 0.05).
Thermal and viscoelastic properties of starch gels from maize varieties
The aim of this work was to determine the thermal, functional and rheological properties of maize (Zea mays) starch isolated from seven varieties. Chemical analysis was undertaken in all starch samples. The gelatinization and retrogradation temperature at different storage times, as well as the enthalpy of the isolated starches, were determined using differential scanning calorimetry (DSC). Swelling and solubility were also measured in individual samples. Dynamic oscillatory tests (amplitude and frequency sweeps) were undertaken on starch samples with 10% (w/v) of total solids during a cycle of three stages (kinetics) of heating/cooling, using a strain-controlled rheometer. The samples presented an amylose content which ranged from 22% to 29%, typical in normal starches, the lipid values were under 1%, while the protein contents were just over 1%. The calorimetric profile for the studied starches showed a peak temperature (gelatinization) over the temperature range from 72.5 to 75.7 • C and enthalpy values between 13.68 and 17.58 J g −1. Four starches presented enthalpy values of the retrogradation transition that increased with the storage time, showing differences among the starches analysed. Maximum swelling and solubility were usually found at the second stage of the above-mentioned cycle. The rheological profile showed that the gels formed during the first stage of the above-mentioned kinetics presented the behaviour of weak viscoelastic gels with the storage or elastic modulus (G) higher than the loss or viscous modulus (G) over the applied strain and frequency ranges. All samples showed a more elastic character as the kinetics progressed. Starches isolated from diverse maize varieties showed differences in their characteristics studied, and might produce different functional properties in the products where they are used.
Combined rheological and optical investigation of maize, barley and wheat starch gelatinisation
Carbohydrate Polymers, 2008
Microstructural and rheological changes during gelatinisation are important indicators of starch functionality. A combined rheometer and optical microscope system (Rheoscope 1, Thermo Haake) was used to monitor the gelatinisation of different starches (maize starch containing 0%, 24%, 55% and 85% amylose; wheat starch and barley starch) suspended in a 0.1% guar solution (to minimise settling during the initial stages of gelatinisation). The 0.1% guar solution was selected after Rapid Visco Analyser, Modulated DSC and settling studies indicated that it minimised any effect on starch gelatinisation compared to carboxy methyl cellulose and xanthan. The Rheoscope study demonstrated that the viscosity of the starch during gelatinisation is related to changes in starch granules as a result of swelling. There was a two to threefold increase in starch granule size during the gelatinisation for all starches except for high amylose maize starches. Viscosity development during the gelatinisation was affected by the presence of B-type granules, whose presence tended to reduce the overall viscosity increase, indicating the importance of starch granules size and their distribution in determining the rheological responses of starch during gelatinisation.
Effect of Amaranthus and buckwheat proteins on the rheological properties of maize starch
Food Chemistry, 1999
The relationship between pasting properties (determined with a Rapid Visco-Analyser) of maize starch and the texture of the resulting gel was examined after addition of Amaranthus and buckwheat proteins. An increase in the peak viscosity due to the addition of protein concentrates was observed, and a lesser increase from the addition of protein hydrolysates. The increase in starch pasting viscosity was related to protein solubility, and could be attributed to the starch granule stabilizing action of proteins. The interactions between starch and proteins were further investigated using oscillation and creep/recovery rheological tests. Generally, the proteins weakened starch gel structure, shown by the lower elastic modulus (G′) and higher phase degree (δ) compared to gels without any proteins added. The same results were obtained from creep/recovery experiments. It seemed that, since native proteins interact more with the granules, they act as a barrier to the release of amylose molecules; hence the resulting gels became weak. If desired, such effects could be lessened by partially hydrolyzing the proteins. ©
Relationship between Viscoelastic Properties and Starch Structure in Rice from Thailand
Starch - Stärke, 2005
This study continues the studies of Noosuk et al. to investigate the properties of four Thai rice starches with different amylose content published in Starch/Stärke (2003,(337)(338)(339)(340)(341)(342)(343)(344). The composition, gelatinisation behaviour and paste viscosity of these starches has been discussed previously. Here the amylopectin fine structure, amounts and size of the amylose are reported and discussed with reference to the viscoelastic behavior of the gels. The viscoelastic response was measured for 6 to 15% (w/w) pastes (607C) and gels (257C) by oscillation (pastes and gels) and creep (gels). Viscoelasticity was shown by all gels at concentrations .6% and the creep compliance could be represented by a four element Burger model. G' from oscillation, the instantaneous elastic modulus and Newtonian viscosity from creep, increased strongly with both starch and amylose concentration. Starch gels (30%, w/w) were monitored over 100 h, by Fourier Transform Infra Red spectroscopy (FTIR) and dynamic oscillatory rheology on storage at 257C. Changes were seen at similar rates, using the Avrami model, for the two high-amylose (.20%) samples, but not for the other starches. Development of crystallinity, at both 25 and 57C, was monitored by X-ray diffraction. Both the kinetics of retrogradation and extent of crystallinity suggest that amylopectin retrogradation is occurring in the high-amylose starch gels on storage but not in the lower amylose samples. It is suggested that amylopectin retrogradation is promoted by retrograded amylose. The fine structure of amylopectin may also be important, because samples that showed no retrogradation on storage had an amylopectin with a high proportion of amylopectin chains of DP 3-10 and a lower portion of chains of DP 11-22. In gels from waxy wheat it has been reported that retrogradation does occur, which may be related to the lower proportion of the shorter amylopectin chains in this material compared with low amylose rice.
International Journal of Food Properties, 2017
Starches isolated from eight oat cultivars were tested for their physicochemical, structural, and rheological properties. The isolated starches had low levels of ash and nitrogen contents with amylose ranging from 21.8 to 32.3 g/100 g. The amount of water released from starch gels decreased significantly (p < 0.05) with increase in freeze thaw cycle. The scanning electron micrographs revealed the presence of polygonal to irregularly shaped starch granules. All the starches exhibited A-type X-Ray diffraction pattern typically characteristic of cereal starches. The rheological properties of pastes were well described by the Herschel-Bulkley model at a shear rate of 0-100 s −1 (R 2 > 0.99). The starch pastes behaved like a pseudoplastic fluid and exhibited shear thinning fluid characteristics with values of flow behaviour index considerably less than 1. Both the storage and loss moduli of the pastes increased sharply initially and then dropped after reaching the gelatinization peak. The magnitude of the dynamic rheological parameters varied significantly (p < 0.05) between the cultivars. All the starch pastes were highly elastic than viscous as evidenced by the lower tan δ values. Structure property relationships were established between starches using principal component analysis.
Cereal Chemistry, 2001
In this study, 3% aqueous high-amylose maize starch (Hylon VII) dispersions were heated to temperatures of 140-165°C. The onset and rate of gel formation was observed using a small-strain oscillation rheometer as a function of temperature from 90 to 25°C. The gel formation clearly began earlier in high-amylose starch paste preheated at lower temperatures, but the rate of gelation was slower and the resulting gel was weaker in comparison with starch pastes preheated at higher temperatures. In addition, the structure of the final gels was studied using large deformation compression measurements. The most rigid gel structure on the basis of small and large deformation tests was obtained for high-amylose starch gel preheated to 150-152°C, depending on the type of measurement. The rate of gelation was also fastest in that temperature range. High-amylose gels heated to higher temperatures lost their rigidity. The molecular weight distribution of starch molecules was measured by size-exclusion chromatography. Heating caused extensive degradation of amylopectin, which had a great effect on amylose gel formation and the final gel properties of high-amylose maize starch. Micrographs of Hylon VII gels showed that phase separation of starch components visible in light microscopy occurred on heating to higher temperatures.
Starch - Stärke, 2015
Molecular parameters and gel properties of systematically prepared acid-thinned starch products (wheat, potato, and pea) were investigated. The impacts of acid type (HCl, H 2 SO 4), acid concentration (0.36 and 0.72 N), and hydrolysis time (4 and 24 h) were found to be statistically significant on weight-average molar mass (M w) of the starch as revealed by analysis of variance (ANOVA). Especially for potato starch samples, the blue value (BV) was found to increase after short-time hydrolysis and decrease after longer modification, indicating a reduced amount of polysaccharide chains able to complex with iodine, which was found for all products. Simultaneously, the wavelength of the absorption maximum (l max) decreased systematically with an increasing degree of modification, giving evidence for decreasing length of linear polymer chains. Enzymatic debranching of amylopectin and dextrins and molecular characterization by means of size exclusion chromatography-multi angle laser light scattering (SEC-MALS) enabled the detection of M w and the amount of amylose fraction. Generally, declining M w of amylose was accompanied by a mass-specific loss. Starch pastes with very good solution states were prepared in general. Pastes of the acid-thinned starches showed dominant viscous behavior, whereat storage and loss modulus decreased with increasing degradation. Additionally, a significant reduction of the sol-to-gel-transition temperature was found applying oscillation measurements. Increasing gel strength of the starch samples was detected due to acid-thinning up to a certain degree of modification and optimal molecular parameters of the starch as well as the amylose fraction were determined resulting best strength properties. The gel clarity was reduced due to acid modification in general.