Retrogradation Behavior Research Articles

Effect of polysaccharides on gelatinization and retrogradation of wheat starch

We employed differential scanning calorimetry and X-ray powder diffraction to determine the effect of tea polysaccharide (TPS) and carboxymethyl cellulose (CMC) on the gelatinization and retrogradation behavior of wheat starch (WS) gels. The total WS concentration of the gels was 35 wt%; WS/polysaccharide mixing ratios were 10/0, 9.9/0.1, 9.8/0.2, 9.7/0.3, 9.6/0.4, and 9.5/0.5. As the polysaccharide level was increased, the onset temperature, conclusion temperature and enthalpy of starch melting also increased. Samples blended with CMC exhibited higher gelatinization parameters than TPS mixtures at the same concentration. Upon reheating the starch samples after storage at 4 °C, we found that the glass transition temperature and retrogradation ratio decreased with increasing polysaccharide ratio and increased with the duration of storage. As the concentration of polysaccharide was increased, the endothermic enthalpy gradually decreased for the WS/TPS system and slightly increased for WS/CMC. After 20 days of storage at 4 °C, the degree of crystallization in the WS/TPS system was significantly lower than in the WS/CMC system. Avrima equation analysis revealed that the retrogradation rate of the control was eight times higher than samples containing 5% TPS and two times higher than samples containing 5% CMC. The overall results demonstrated that the inhibitory effect of TPS was greater than that of CMC under the same conditions.

Urea and ethanolamine as a mixed plasticizer for thermoplastic starch

Mixtures of urea and ethanolamine were used as plasticizers for preparing thermoplastic starch (TPS) in a single-screw extruder. The interaction between urea/ethanolamine and starch was investigated using Fourier Transform Infrared (FT-IR). Glass transition temperature of TPS was tested by Differential scanning calorimetry (DSC). Both FT-IR and DSC proved that the mixture of urea and ethanolamine could form more stable and strong hydrogen bonds with starch molecules than the conventional plasticizer, glycerol. By Scanning Electron Microscope (SEM) native starch granules were proved to transfer to a continuous phase. The thermal stability, mechanical properties and starch retrogradation behavior were also studied by TG (Thermal Gross), tensile testing and X-ray Diffraction (XRD), respectively. TPS plasticized by urea (15 wt/wt%) and ethanolamine (15 wt/wt%) showed a better thermal stability and mechanical properties than conventional TPS plasticized by glycerol. Moreover, the tensile stress, strain and Energy Break, respectively, reached 9.00 MPa, 34.4% and 1.34 N m. At the same time, this mixed plasticizer could effectively restrain the retrogradation of starch and urea.

Food hydrocolloids control the gelatinization and retrogradation behavior of starch. 2b. Functions of guar gums with different molecular weights on the retrogradation behavior of corn starch

Retrogradation behavior of corn starch in an aqueous system was studied in the presence or absence of various guar gum samples with different molecular weights. Dynamic mechanical loss tangent for starch system with 26% amylose (5 w/v%) was increased by the addition of guar (0.5%) after storage at 4 °C for 24 h, which indicated the reduction of gelled fraction in the system, leading to the retardation of short-term retrogradation of starch. This rheological change of the system related to the amount of amylose leached out the starch granules during gelatinization. The higher the molecular weight of guar, the lower the amount of amylose leached, but this effect of guar became less dependent on its molecular weight at above 15.0×10 5 g/mol. The rate constant determined from the relationship between storage time (for 14 days at 4 °C) and creep compliance for the starch system (15% starch) was decreased in the presence of guar (0.5%), suggesting the retardation of long-term retrogradation of starch. This effect of guar became marked at above 30.0×10 5 g/mol, which was apparently higher than the critical molecular weight value determined from short-term retrogradation. Syneresis for the starch system (5% starch) was increased adversely by the addition of guar (0.5%) with relatively low molecular weight values (e.g. <5.0×10 5 g/mol) after storage at 4 °C for 14 days, suggesting the promotion of long-term retrogradation. Functions of guar on the retrogradation behavior of starch were hypothesized considering interactions between guar and starch components; amylose and amylopectin.

Food hydrocolloids control the gelatinization and retrogradation behavior of starch. 2a. Functions of guar gums with different molecular weights on the gelatinization behavior of corn starch

Gelatinization behavior of starch in an aqueous system was studied in the presence or absence of various guar gum samples with different molecular weights in order to clarify the difference in functions of each guar to starch. Some native corn starches with different amylose/amylopectin ratios were used to clarify which fraction of starch the gums act on. Weight-average molecular weight M w of the guar samples ranged from 4.7×10 5 to 34.6×10 5 g/mol, whereas z-average root-mean-square radius of gyration R g ranged between 82 and 233 nm from static light-scattering technique. Relationship between M w and R g was expressed by the Flory exponent of 0.503. Also, intrinsic viscosity [ η] of the guar samples in aqueous solution was in good agreement with M w determined, and relationship between M w and [ η] was expressed by the Mark–Houwink–Sakurada exponent of 0.517. Gelatinization behavior of starch/guar system was investigated from its viscosity profiles. Guars with M w values higher than 12.2×10 5 g/mol shifted the onset of viscosity increase for the system to lower temperatures and increased its peak viscosity upon heating at a relatively low starch concentration (e.g. 5 w/v%). The earlier onset of viscosity increase was independent of M w of guar, while the increase in peak viscosity was dependent on its M w. These guars shifted the onset of viscosity increase for the system upward, on the contrary, at a relatively high starch concentration (e.g. 15%). Interaction between guar and starch components, amylose and amylopectin, was hypothesized as one of the factors to govern the gelatinization behavior of starch.

Effects of non-ionic polysaccharides on the gelatinization and retrogradation behavior of wheat starch ☆

Gelatinization and retrogradation behavior of wheat starch in an aqueous system was studied by rheological and thermal techniques in the presence or absence of non-ionic polysaccharides, including guar gum, tara gum, locust bean gum, and konjac glucomannan. Macromolecular characteristics of each polysaccharide, including weight-average molecular weight M w and radius of gyration R g, were determined by static light-scattering, resulting in (1.0–3.2)×10 6 g/mol for M w and 104-217 nm for R g, respectively. During gelatinization, addition of each polysaccharide (0.5–1% w/v) increased peak viscosity for the starch system (13%): 163–231 unit larger than the control at 0.5%, whereas 230–437 unit larger at 1%. Among the galactomannans tested, the order of this effect (locust>tara>guar) was contrary to that of the molecular size (guar>tara>locust). During short-term retrogradation, addition of each polysaccharide (0.5%) increased dynamic mechanical loss tangent ( tan δ) for the starch system (5%) after storage at 4 °C for 24 h: (16.5–26.9)×10 −2 unit larger than the control. Among the galactomannans tested, the larger the molecular size, the greater the effect to increase tan δ, and this effect of polysaccharide was not explained simply by the difference in the amount of amylose leached during gelatinization. During long-term retrogradation, addition of each polysaccharide (0.5%) decreased the rate constant expressing the relationship between storage time (for 14 days at 4 °C) and creep compliance for the starch system (15%): (0.9–1.5)×10 −2 unit smaller than the control. Among the galactomannans tested, the larger the molecular size, the greater the effect to decrease the rate constant. Functions of polysaccharide to starch were hypothesized considering structural compatibility and molecular interactions between polysaccharide and starch components; amylose and amylopectin.

Urea and formamide as a mixed plasticizer for thermoplastic starch

AbstractMixtures of urea and formamide were tested as plasticizers for thermoplastic starch (TPS). The hydrogen bonding interactions between urea/formamide and starch were investigated by using Fourier‐transform infrared spectroscopy (FT‐IR). The thermal stability, mechanical properties and starch retrogradation behavior were also studied by thermogravimetric analysis (TGA), tensile testing and X‐ray diffraction (XRD), respectively. TPS plasticized by urea (20 wt%) and formamide (10 wt%) showed better thermal stability and water resistance than conventional TPS plasticized by glycerol. Moreover, the tensile stress, strain and energy at break, respectively, reached 4.83 MPa, 104.6 % and 2.17 N m after storing in an atmosphere of relative humidity (RH) of 33 % for one week. At the same time, this mixed plasticizer could effectively restrain the retrogradation of starch. Copyright © 2004 Society of Chemical Industry

Functional properties and retrogradation behaviour of native and chemically modified starch of mucuna bean (Mucuna pruriens)

AbstractMucuna bean (Mucuna pruriens) starch was isolated and subjected to chemical modification by oxidation and acetylation. The proximate analysis of the non‐starch components of the native starch on a dry weight basis was 92 g kg−1 moisture, 5 g kg−1 ash, 2 g kg−1 fat, 7 g kg−1 crude fibre and 19 g kg−1 protein. Chemical modification reduced the values for all the non‐starch components except the moisture level. For all the samples, swelling power and solubility increased as the temperature increased in the range 50–90 °C. The swelling power of mucuna native starch (MNS) and mucuna acetylated starch (MAS) increased with increasing acidity and alkalinity, while that of mucuna oxidised starch (MOS) only increased with increasing pH in the acidic range. The maximal solubility of all the starches was observed at pH 12. All the starch samples absorbed more oil than water. The lowest gelation concentration followed the trend MAS &lt; MNS &lt; MOS. Chemical modification reduced the gelatinisation temperature (Tp), while peak viscosity (Pv), hot paste viscosity (Hv) and cold paste viscosity (Cv) decreased after oxidation but increased following acetylation. The setback tendency of the native starch was reduced significantly after chemical modification. However, the breakdown value of MNS, 65 BU (Brabender units), was lower than that of MOS (78 BU) but higher than that of MAS (40 BU). Differential scanning calorimetry studies of gelatinisation and retrogradation revealed that chemical modification reduced the onset temperature (To), peak temperature (Tp) and conclusion temperature (Tc). Oxidation and acetylation reduced the gelatinisation and retrogradation enthalpies of the native starch. The enthalpy of retrogradation of the starches increased as the length of storage increased. Copyright © 2003 Society of Chemical Industry

Rice starches. III. Structural aspects provide insight in amylopectin retrogradation properties and gel texture

Abstract The long term amylopectin retrogradation behaviour of five waxy (low peak gelatinisation temperature ( T p )) and 10 normal (low (three), intermediate (four) and high (three) T p )) rice starches was investigated by differential scanning calorimetry (DSC) rescan following gelatinisation in excess water (1:2 w/w starch/water). Textural attributes of rice starch gels (stored during 2 days or 2 weeks at 6 °C) were studied following gelatinisation (8% dry matter starch) in a Brabender visco-amylograph. Both amylopectin retrogradation and gel textural characteristics were related to absolute (AAM), free (FAM) and lipid-complexed (LAM) amylose contents and amylopectin chain length distributions. Upon storage at ambient temperature (2 and 4 weeks), retrograded amylopectin DSC conclusion temperatures were not related to AAM and FAM contents. Upon 4 weeks storage at 6 °C, however, retrograded amylopectin conclusion temperatures and enthalpies of the investigated normal intermediate and high T p rice starches were negatively related to both AAM and FAM contents. LAM was positively correlated with retrograded amylopectin conclusion temperatures and enthalpies in the case of 4 weeks at ambient temperature and 6 °C, suggesting heterogeneous nucleation. Relative amounts of amylopectin chains with DP 6-9 and DP>25 decreased amylopectin retrogradation conclusion temperatures and enthalpies, whereas opposite results were observed for chains of DP 12-22. Higher correlations were found with increasing storage temperatures and times. Firmness and force after relaxation increased and elasticity (2 days of storage at 6 °C) decreased with increasing AAM and FAM contents, whereas no correlations with LAM were observed. No significant correlations between amylopectin chain length distribution and gel texture were observed.

Retrogradation of Starch Mixtures Containing Rice Starch

ABSTRACT: Different starches often coexist in food systems. Starch retrogradation is the primary reason for quality deterioration of a food system during storage. This article addresses the retrogradation behaviors of several starch mixtures containing normal rice starch (NRS). Potato starch, tapioca starch, waxy corn starch, hydroxypropylated potato starch, hydroxypropylated tapioca starch, and acetylated tapioca starch were mixed with NRS. Starch suspensions were gelatinized and the relative solid content, (S′) measured by pulsed nuclear magnetic resonance, was used to characterize the retrogradation behavior of starch systems. The retrogradation behaviors of starch mixtures can be divided into two categories according to the additive or non‐additive nature of S′, for which the concept “regional moisture content” was introduced.

Structure-retrogradation relationship of rice starch in purified starches and cooked rice grains: a statistical investigation.

Amylose content and amylopectin chain length distribution, the two most commonly used structural parameters of starch, have significant effects on starch retrogradation. In the present work, starches were separated and purified from 18 rice cultivars. The amylopectin was purified from each starch. Amylopectin chain length distribution was analyzed by high-performance size-exclusion chromatography after debranched using isoamylase. The blue value was used to measure the amylose content before and after the defatting of starch. The amount of amylose associated with lipid was calculated. Pulsed nuclear magnetic resonance was used to follow the retrogradation of starch both in cooked rice grains and in the purified form. The Avrami equation was employed to describe the retrogradation kinetics of rice starch. To look into the relationship between the starch structure and retrogradation behavior, the structural parameters were correlated with retrogradation kinetics parameters using both Pearson and partial correlations. The results indicated the following: first, the retrogradation behavior of rice starch remains similar in both the purified form and cooked rice grains; second, the peak value of amylopectin short-chain length has a significant positive relationship with the amylopectin crystallization rate constant k; third, the amylose content after defatting has a significant positive relationship with the parameter k and a negative relationship with the Avrami exponent n; and fourth, the amount of amylose associated with lipid has a negative relationship with the parameter k.

Effect of fatty acids on the rheological properties of corn and potato starch

Effects of fatty acids (myristic and stearic acid) on the rheological properties of corn and potato starch during heating and cooling were investigated using a Carri-Med CSL 2 dynamic rheometer. Potato starch showed a lower gelatinization temperature ( TG ′) as compared to corn starch. Potato starch had a TG ′ of 61.2°C against 71.5°C for corn starch. The addition of both the fatty acids inhibited the swelling of the starch granules in both corn and potato starch and consequently, increased the TG ′. The storage modulus ( G ′) increased to a maximum and then dropped during heating of both the starches. Potato starch showed a higher peak G ′ value as compared to corn starch. Addition of stearic acid decreased the peak G ′ in corn starch and increased the same in potato starch, while the addition of myristic acid resulted in a decrease in peak G ′ in both the starches. The extent of breakdown in G ′ during heating was higher for potato starch as compared to corn starch which confirmed the more rigid structure of corn starch granules. During cooling, the G ′ values increased with decrease in temperature and with the addition of fatty acids. Corn starch showed higher peak loss tangent (tan δ) values than potato starch during heating. Tan δ values decreased during the cooling of corn and potato starch. Retrogradation (synersis) behaviour of both the starches heated in the presence of stearic and myristic acid during storage was also studied. The rate of synersis was more in potato starch than in corn starch. Synersis increased with the increase in storage duration and decreased with the addition of both the fatty acids.

Gelatinisation and Retrogradation Behaviour of Some Starch Mixtures

Differential scanning calorimetry (DSC) and dynamic rheological measurements were used to characterise the behaviour of potato-waxy maize, potato-barley and waxy maize-barley starch mixtures. Gelatinisation and retrogradation were studied at two starch concentrations, 20% (w/w) and 50% (w/w). In the DSC gelatinisation thermograms of the mixtures it was possible to recognise features of the thermograms of the individual components, indicating that each starch gelatinised independently of the other starch in the mixture. The retrogradation enthalpy was measured in the DSC after four and seven days of storage at 6 °C. The lowest values of retrogradation enthalpy for the mixtures were found for the waxy maize-barley and potato-barley mixtures, particularly at 20% starch concentrations and in the ratios 25:75 and 50:50, correspondingly. The retrogradation enthalpy measured for most starch mixtures corresponded to the calculated value, assuming that each starch contributed to the enthalpy according to its proportion in the mixture. Storage and loss moduli were measured for gelatinised starch suspensions during cooling from 90 to 6 °C, and then during a holding period at 6 °C for up to 6 h. The moduli for the mixtures were in most cases in between the values obtained for the individual starches.

Effects of concentration dependence of retrogradation behaviour of dispersions for native and chemically modified potato starch

The effects of concentration on the retrogradation behaviour and effects of concentration for native potato starch (NPS) and hydroxypropylated and phosphate cross-linked potato starch (HPS) were studied by heating differential scanning calorimetry (DSC), transparency, granule size distribution and dynamic viscoelasticity measurements. DSC and dynamic viscoelasticity measurements showed that the retrogradation of NPS dispersions was far more conspicuous than that of HPS dispersions. Concentration and time dependence of the storage shear modulus G′ for NPS dispersions heated at 60 and 95°C were different, because NPS granules were disintegrated after being heated at 95°C, whilst some of them remained when heated at 60°C. The rate of retrogradation for NPS dispersion heated at 60°C was faster than that heated at 95°C. The concentration dependence of the storage shear modulus G′ at low concentration range was stronger than that at high concentration range because starch granules were fully swollen to fill the space completely above a certain concentration if the starch granules were not ruptured after being heated. On the other hand, the retrogradation phenomena of HPS were scarcely observed by DSC measurements. The granule size, transparency and storage and loss shear moduli of heated HPS dispersions had not changed much during storage at 5°C. Even a slight modification retarded the retrogradation remarkably. The viscoelasticity of starch dispersions was primarily governed by a combination of the volume fraction of the granule and concentration, if the granules of starch were not ruptured after being heated.

Molecular Characteristics Influencing Retrogradation Kinetics of Rice Amylopectins

ABSTRACTThe enthalpy changes (ΔH) for melting of crystallites formed during retrogradation of 60% (w/w) amylopectins (AP) aged at 4°C were investigated using AP from 13 rice cultivars with well‐known structural properties. According to the Avrami equation, the resultant kinetic parameters for AP retrogradation were obtained in relation to structural factors. Generally, the AP systems studied showed two stages of retrogradation behavior during early (≤7 days) and late (≥7 days) storage. The Avrami exponent for early‐stage kinetics (n1, 1.04–5.54) was greater than the corresponding value for late‐stage kinetics (n2, 0.28–1.52). While the Avrami K constant of the early‐stage kinetics (K1, 1.0×10‐5 to 2.3×10‐1 day‐n) was lower than the corresponding value of late‐stage kinetics (K2, 4.4×10‐2 to 1.4 day‐n). The ΔH values for late and infinite retrogradation stages showed a significantly positive correlation with the proportions of short chain (chain length [CL] ≤ 15 glucose units) and long chain (CL = 16–100 glucose units) fractions, respectively. Retrogradation of AP with a higher number‐average degree of polymerization, greater proportion of short chain fractions, and shorter average chain lengths revealed significantly greater n1 values and smaller K1 values. Values for n2 and K2 showed little influence from the molecular properties except for the proportion of extra long (CL&gt;100 glucose units) and long chain fractions on K2. The negatively linear relationships between log K and n suggest the importance of some nonstructural factors for AP retrogradation mechanisms in various starch systems.

On the roles of protein and starch in the aging of non-waxy rice flour

Changes in pasting and thermal properties of non-waxy rice flour and its isolated starch during storage at 25, 35 and 45°C were compared. Aging had no apparent effect on the pasting behaviour of the isolated starch, but markedly affected that of the flour. Peak viscosity ( V p) of rice flour pastes generally increased with both temperature and time of storage, but reached a plateau within 4 weeks of storage at 45°C. Fresh flour paste exhibited lower V p, a slower rise in apparent viscosity, and much better stability than an isolated starch paste. The addition of isolated oryzenin to isolated rice starch resulted in pasting behaviour which more closely approximated that of an extensively aged flour. DSC scans of fresh flour at ∼13% moisture revealed a weak heat-irreversible endothermic event over the temperature range from 47 to 66°C which was attributed to the denaturation of oryzenin. This transition was shifted to higher temperatures with increasing storage temperature and time. It also became increasingly skewed and broadened until it was no longer detectable after the flour had been stored at 45°C for 8 weeks. Starch gelatinization characteristics of both flour and isolated starch, as determined by DSC, were apparently unaffected by aging. However, rice flour exhibited significantly higher onset temperature of gelatinization, but lower gelatinization enthalpy, than isolated rice starch. Similarly, pulsed NMR studies showed no apparent effect of aging on retrogradation behaviour of rice flour or starch gels. These results suggest that modification of the protein component, rather than starch, was primarily responsible for rheological changes associated with aging of rice flour.

Rheological and Thermal Properties of Aged Starch Pastes from Three Waxy Maize Genotypes

ABSTRACTThe rheological and thermal properties of aged starch gels (15:85 starch‐water) from three waxy maize genotypes (wx, wx sh1, and du wx) during storage (4°C for up to 25 days) were studied. After storage, changes of storage modulus (G′) and phase angle (δ) of the gels as a function of temperature were measured using oscillatory rheometry. For the du wx samples, G′ at 25°C increased rapidly during the first four days of storage at 4°C, compared to the gradual increases over the 25‐day storage period for the wx and wx sh1 samples. A peak in G′ at 45°C was observed during heating for the du wx samples after 10 days of storage and for the wx sample stored for 25 days. The G′ peak may have been due to syneresis in the gels. Retrogradation of amylopectin of the aged starch samples was examined using differential scanning calorimetry. The du wx starch had greater retrogradation enthalpies than the other two samples (which showed similar retrogradation behavior) throughout the storage. The retrogradation enthalpy of the du wx samples increased rapidly during the first seven days, followed by a slower increase through the rest of storage. For the wx and wx sh1 samples, no endotherm was observed during the first four days of storage, after which the enthalpy increased steadily as a function of storage time. Addition of sucrose delayed the formation of gel networks for all three starches. The greater tendency for gelling and retrogradation of the du wx starch might be attributed to the greater proportion of DP20–30 chains of the amylopectin.

Retrogradation Behavior of Wheat Starch Gels with Differing Molecular Profiles

ABSTRACTDiffering molecular profiles of starches were developed by acid treatment of native wheat starch. Molecular weight distribution, branching, and linear chain length distribution was characterized. Starches with fewer large size amylopectin fragments, increased smaller size amylopectin fragments, decreased branch points, decreased overall sizes, and narrower linear chain length distributions, had higher initial retrogradation rates. However, all aged starch gels had similar final crystalline enthalpy levels. Different retrogradation behaviors were due to smaller size amylopectin fragments, narrowed linear chain length distribution, and decreased branching. Retrogradation behavior was modeled using classical Avrami kinetics to allow comparison with other retrogradation studies.

The retrogradation and gelation of amylopectins from various botanical sources

The distribution of the chain lengths of amylopectins from wheat, barley, maize, pea, canna, and potato starches were characterized by size-exclusion chromatography. The cereal amylopectins had the shorter average chain-length. The gelation and retrogradation behaviour of the amylopectins, examined using measurements of shear modulus and differential scanning calorimetry, together with studies of the structure of the associated regions in amylopectin gels, indicated that association of the chains in cereal amylopectin gels occurred over shorter segment lengths. The cereal amylopectins have a reduced rate of retrogradation which is linked to their shorter average chain-lengths.