Effects of Preparation Temperature on Gelation Properties and Molecular Structure of High-Amylose Maize Starch (original) (raw)
Related papers
Gelation and crystallisation of maize starch after pasting, drum-drying or extrusion cooking
Journal of Cereal Science, 1988
The structure of the starchy gels (33 % dry matter) obtainedfrom normal maize starchby different treatments(pasting,drum-dryingor extrusioncooking) havebeen studied with various physicochemicaltechniques: X-ray diffraction, differential scanning calorimetry, birefringence, mild acid hydrolysis and gel permeation chromatography. After pastingor drum-drying,amylosecrystallisesindependentlyfrom amylopectin by complex formation and retrogradation.This phenomenonis explained by the leachingof amyloseduring thermal treatmentand the subsequent phaseseparation, and crystallisationwithin the amylosevolume fraction. Thesecrystallites,composed of linear chainswith degreeof polymerisation(DP) of 35-40, are acid-resistant and exhibit a high fusion temperature(above 100 0q. On the contrary, after extrusioncooking, amylose and amylopectin co-crystallise in the same manner as pure amylopectin.Thesecrystallitesarethin (composed mainly of linear chainsof DP IS), acid labile and melt at 50°C.
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.
Carbohydrate Polymers, 2009
Corn starches with different amylose/amylopectin ratios (waxy 0/100, normal corn 23/77, Gelose 50 50/50, Gelose 80 80/20) were annealed at below their gelatinization temperatures in excess water. The effects of annealing on the gelatinization and microstructures of the starches were studied using DSC, XRD and a microscope equipped with both normal and polarized light. In addition, a high-pressure DSC pan was used to study the effects of high-temperature annealing on the multiphase transitions of starches with different water contents. The granular size of the starches increased after the annealing process, but the size variation rates were different, with higher amylopectin contents resulting in a higher diameter growth rates and final accretion ratios. DSC results showed that annealing increased the gelatinization enthalpy of the amyloserich starches. The increased enthalpy was mainly attributed to endotherm G -there were no significant changes to endotherms M1, M2 or Z -indicating that annealing mainly affected the helical length of shorter or sub-optional amylopectins, in particular the amylopectin in amylose-rich starches. The XRD traces of all starches after annealing remained unchanged.
The roles of amylose and amylopectin in the gelation and retrogradation of starch
Carbohydrate Research, 1985
The retrogradation of starch gels has been studied by using X-ray diffraction, differential scanning calorimetry, and measurements of the shear modulus. Starch gels were considered as composites containing gelatinised granules embedded in an amylose matrix. The short-term development of gel structure and crystallinity in starch gels was found to be dominated by irreversible (T ~100") gelation and crystallisation within the amylose matrix. Long-term increases in the modulus of starch gels were linked to a reversible crystallisation, involving amylopectin, within the granules on storage. It was considered that the crystallisation resulted in an increase in the rigidity of the granules and thus enhanced their reinforcement of the amylose matrix. opaque starch-gel quickly develops, which becomes firmer on storage over several weeks',*. These changes have a profound effect on the texture, and hence accepta-*All percentages are w/w.
Gel formation in mixtures of high amylopectin potato starch and potato starch
Carbohydrate Polymers, 2004
The effects of starch granules on the rheological behaviour of gels of native potato and high amylopectin potato (HAPP) starches have been studied with small deformation oscillatory rheometry. The influence of granule remnants on the rheological properties of samples treated at 90 8C was evident when compared with samples treated at 140 8C, where no granule remnants were found. The presence of amylose in native potato starch gave to stronger network formation since potato starch gave higher moduli values than HAPP, after both 90 and 140 8C treatments. In addition, amylose may have strengthened the network of HAPP because higher moduli values were obtained when native potato starch was added to the system. The moduli values of the mixtures also increased with increasing polysaccharide concentration in the system, which is due to an increment in the polysaccharide chain contacts and entanglements. Finally, it was found that a mixture of commercial amylose from potato starch and HAPP resulted in lower values of G 0 compared to native potato starch. This indicates that the source of amylose is important for the properties in a blend with native amylopectin. q
Properties of Starch Subjected to Partial Gelatinization and β-Amylolysis
Journal of Agricultural and Food Chemistry, 2009
The overall objective of this research is to understand the impact of partial gelatinization and -amylase hydrolysis ( -amylolysis) on the physicochemical properties of starch. Three starches (normal corn, waxy corn, and wheat) were chosen as test examples and thermally treated at 40% moisture content to up to 95°C and then subjected to -amylolysis. The enzyme treatment resulted in over 10% maltose yield. Subsequent debranching analysis showed the production of chain stubs as short as having the degree of polymerization of 2 and 3, suggesting a thorough -amylolysis at certain branch locations. For starch samples subjected to partial gelatinization, polarized light microscopy shows reduced intensity of birefringence and differential scanning calorimetry shows reduced enthalpy change associated with gelatinization. Both indicate the reduced chain organization due to the treatment. Further, a substantial transformation of initial A-type crystalline structure to B-and V-types upon treatments is noticed from X-ray powder diffraction measurements. In addition, the rapid viscosity analysis (RVA) indicated a drastic viscosity reduction, increased peak temperature, and improved stability of pasting behavior due to hydrothermal treatments and -amylolysis. Overall, our results point out the possibility of obtaining modified starches having desirable stable pasting behavior by using a combined partial gelatinization and -amylolysis approach.
Journal of Agricultural and Food Chemistry, 2005
Five cassava genotypes were investigated to identify the fine amylopectin structures and granule chemical compositions, which differentiated the starches into high (T o ) 63.7°C on average) and low (57.3°C on average) gelatinization temperatures. The amylose contents (15.9-22.4%) and granular dimensions (12.9-17.2 µm) significantly differed among the starches. Diverse amylopectin structural elements resulted in significant swelling power, viscoelastic properties, and gel firmness. Debranched starches revealed a trimodal amylopectin distribution of three fractions: FIII (DP 12), FII (DP 24.31), and FI (DP 63) and FIII (DP 12), FII (DP 24.69), and FI (DP 67) for the low and high gelatinization starch groups, respectively. The higher proportion of FI long chain entanglement with amylose chain lengths to form longer helical structures was confirmed in the high gelatinization starch group, which developed "true" gels with better shear resistance, frequency independence, and higher gel firmness. Significant amounts of resistant starch fractions revealed the potential for application of these genotype starches in diverse foods.
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.
Food Chemistry, 1995
A comparative study was undertaken to examine the effect of sugars on the thermal and mechanical properties of ageing waxy maize, wheat, potato and pea starch gels. The addition of sugars, at a ratio of 1 : 0.5 : 1.5 (w/w) for starch-sugar-water mixtures, inhibited chain reorganization in starch gels, as followed by differential scanning calorimetry and dynamic rheometry in the order, ribose > sucrose > maltotriose > water alone, glucose > fructose. Kinetic experiments on the evolution of storage modulus (G) at 8°C indicated a progressive transition from a sigmoid curve (waxy maize) to a hyperbolic G' -time relationship (potato and pea starches), consistent with an increasing proportion of amylose in the composite gels. The effects of sugars on the development of the retrogradation endotherm (AH) and gel rigidity (0) were less pronounced for potato and pea starches than for waxy maize or wheat starches, presumably because of their higher amylose content, which dominates the gel network properties.