Rheological Properties of Starch Gels from Wheat Mutants with Reduced Amylose Content (original) (raw)
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).
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. ©
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 glucose concentration on the rheological properties of wheat-starch dispersions
Food Hydrocolloids, 2000
The effect of glucose addition and time of constant temperature heating (t CTH ) on the rheological properties of starch dispersion systems was examined. A fixed starch mixture of 5% (w/v), and glucose concentrations of 0-6% (w/v) were used. The starch dispersion was heated up to 80ЊC, then was kept, at this temperature, for a period of 0, 10, 20, or 30 min. The apparent viscosity was then measured as a function of shear rate. In addition, the apparent viscosity was measured, at constant shear rate of 106 s Ϫ1 , as a function of shearing time. The Herschel-Bulkley model t t 0 ϩ m _ g n was used to fit the flow behavior of starch dispersions. It was found that the flow behavior index, n, approaches unity (Bingham model) for most of the data. It was also found that as t CTH was increased, for a given glucose concentration, both yield stress, t 0 , and consistency coefficient, m, increased. The presence of glucose also resulted in an increase of both t 0 and m. At 6% glucose concentration, samples with t CTH of 30 min showed the highest anti-thixotropic behavior. The apparent viscosity of starch dispersions at t CTH of 0 min had the lowest value at all levels of glucose concentrations. In general, the presence of glucose resulted in an increase in the apparent viscosity compared to that of glucose-free starch dispersions. ᭧
Rheological Properties of Pastes Obtained from Starches Derived from Immature Cereal Kernels
Starch - Stärke, 2004
The results presented in this work concern the starches of three basic varieties of cereal cultivated in Poland-wheat, rye and barley-harvested at different stages of maturity in 1997 and 1998. Starches from these kernels were isolated by a laboratory method. The flow curves and thixotropic properties of 5% starch pastes at 507C and controlled shear rates between 0 and 600 s 21 were obtained. All the investigated starch pastes were non-Newtonian, plastic and thixotropic fluids, that differed in their values of yield stress. The pastes from immature cereal starches were characterised by a higher plasticity because they needed a higher shear stress (t) to achieve the yield stress (t 01) in comparison with the pastes from the mature cereal starches. At applied shear stress the pastes from the "immature" starches had a higher thixotropy in comparison with the "mature" ones. Pastes from immature starch were more susceptible towards shearing forces but at the same time they exhibited a better ability to rebuild their structure. The description of the flow curves by the Ostwald-de Waele equation allows the conclusion that pastes from the immature starches have a higher structural viscosity. In addition, the application of the Casson model allows to describe the flow curves and determine the yield stress and the plasticity properties of the investigated pastes. However, the viscosity values calculated from the Casson model do not reflect differences in viscosity among the samples.
The Journal of Microbiology, Biotechnology and Food Sciences, 2017
During production of β-glucans preparations from oat a large amount of so called residual oat flour is manufactured. It contains all compounds of oat, only amount of dietary fiber is decreased. Such flour could be possibly used in baked goods, or as a thickening agent. In order to evaluate its possible application as thickening agent the rheological investigations of system containing residual oat starch were carried out. They involved performing of pasting profiles and texture profile analysis of flour pastes and gels in the presence of starch hydrolyzate, which recently played a increasing role in food industry as alternative for sucrose. Also commercial wheat and oat flours were investigated as reference material It was observed differences in pasting profile and texture of gel caused by introduction of starch hydrolyzate into systems containing cereal flours. Obtained results allow to draw conclusion, that such systems can be successfully used as thickeners
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.
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.