Retrogradation Behavior Research Articles

Shear scission through extrusion diminishes inter-molecular interactions of starch molecules during storage

The starch retrogradation behavior of native and extruded maize, wheat and rice flours were compared to better understand the efficacy of extrusion to decrease the propensity of different starches to form inter-molecular interactions. In all flour pastes, the increase of the storage modulus (G′) during a 7-day storage (representing inter-molecular interactions) was diminished with extrusion, albeit this effect was not detectable in rice due to the low gel consistency. Furthermore, thermo-rheological analyses revealed two distinct mechanisms depending on the cereal source. In maize and wheat flours, AM fragmentation through extrusion (detected through HPSEC) decreased the residual G′ at 85 °C of 7-day stored gels, which represents AM-AM physical junction zones that build gel structure. On the other hand, the extrusion of rice flour, which contains starch with lower AM ratio, resulted in a marked AP fragmentation that decreased the relative G′ drop, representing inter-molecular interactions involving AP.

Slowly digestible starch in fully gelatinized material is structurally driven by molecular size and A and B1 chain lengths

The objective of this study was to obtain structure-digestion relationships of fully gelatinized starch. Twelve starch samples with marked fine structural differences (HPLC-SEC) were studied for their retrogradation behavior (thermal and rheological properties of starch gels) and in vitro digestibility. A reduction in the digestion rate during storage for 7 days was observed in all samples and, interestingly, this reduction was particularly evident in sago (64.7%), potato (57.3%), pea (55.1%) and acid-converted maize (ACM, 51.6–51.8 %) starches. Results indicated two potential interactions that may result in slowly digestible supramolecular structures: 1) double helices between external A and B1 chains of DP at peak maximum ≥ 15.5 Glucose Units (perhaps involving internal long chains) that also are prone to forming intermolecular associations [high relative drop in the storage modulus (G’) during heating of 7 days-stored gels] and; 2) interactions of small molecular size acid-hydrolyzed starch molecules that may be more mobile and easily aligned.

Short-term retrogradation behaviour of corn starch is inhibited by the addition of porcine plasma protein hydrolysates

The potential inhibition of porcine plasma protein hydrolysates (PPPH) on the short-term retrogradation of corn starch (CS) was investigated. Compared with native CS, PPPH significantly enhanced breakdown and decreased the total setback in a rapid visco analyser (RVA) measurement (P < 0.05). Dynamic time sweep analysis of pre-prepared gelatinized samples showed a decrease in the storage modulus (G′) and increase in the loss tangent (tan δ) in the presence of PPPH. Differential scanning calorimetry results showed that PPPH significantly reduced the gelatinization enthalpies (ΔHg) and retrogradation enthalpies (ΔHr) of CS (P < 0.05). Fourier transform infrared spectroscopy analysis indicated that the addition of PPPH decreased the amount of hydrogen bonds within starch. Low field nuclear magnetic resonance results showed that the addition of PPPH has an important role in increasing the mobility of water molecules and blocking the short-term retrogradation of CS. X-ray diffraction results showed that the peaks at 2θ close to 17–18° were progressively decreased to smaller angles with increasing PPPH concentrations. This phenomenon indicated that PPPH could interact with amylose and cause lattice distortion, which reduced the starch retrogradation. The results demonstrate that the addition of PPPH plays a crucial role in interfering with short-term retrogradation of CS.

Impact of different structural types of amylopectin on retrogradation

Retrogradation is the re-association and recrystallization process of glucan chains in gelatinized starch. The objective of the study was to investigate the effect of amylopectin structure on re-association of glucan chains during retrogradation. Amylopectin retrogradation of 17 starches from four different structural types was examined by differential scanning calorimetry (DSC). Gelatinized starches were stored for 10 days at 4 °C and then scanned from 10–120 °C at 10 °C/min. The structural type of amylopectin influenced the transition temperatures (Tm and Tc), melting temperature range (Tc–To) and enthalpy change of transition (ΔH). Correlation analysis between different chain length categories and the melting parameters of recrystallized amylopectin revealed a strong correlation of the external chain length (ECL) with Tm (r = 0.90, p < 0.01), Tc (r = 0.95, p < 0.01), Tc–To (r = 0.89 p < 0.01), and ΔH (r = 0.89, p < 0.01) showing the importance of the external chains of amylopectin in the recrystallization process. Chains with very short external length (ECL 6–8) showed negative relationship with retrogradation behavior. However, also the inter-block chain length (IB-CL; distance between tightly branched units) showed positive correlation with transition temperatures (Tc: r = 0.96, p < 0.01, Tc–To: r = 0.97, p < 0.01), and ΔH (r = 0.91, p < 0.01) suggesting that longer internal chain segments also play an important role, possibly by contributing to a flexible amylopectin structure. The retrogradation behavior of amylopectin types can be systematically interpreted with the backbone model of amylopectin.

Mixolab, retrogradation and digestibility behavior of chapatti made from hulless barley flours

Barley flours can be utilized for preparation of chapatti after blending with 7% vital wheat gluten. Mixolab analysis revealed a significant role of non-starchy polysaccharides in increasing dough consistency after mixing (C1) and heating (C3). A significant negative correlation (R = −0.63) of mixolab retrogradation (%) was observed with soluble arabinoxylan contents of flours indicating their positive effects on chapatti quality. Soluble arabinoxylans also exerted beneficial effects by promoting lower rate of shrinkage (R = −0.69) and bake loss (R = −0.77) in chapatti, however β-glucans and insoluble arabinoxylans increased the chapatti shrinkage (p ≤ 0.05). Fresh barley chapatti displayed lower soluble starch contents (1.8–2.6%) as compared to wheat chapatti, which may indicate an inhibitory effect of barley β-glucans on starch swelling, leading to lower retrogradation (R = −0.62). Reduced rapidly digestible starch contents were observed for barley chapatti. Presence of higher levels of total β-glucans in barley flours also promoted the formation of slowly digestible starches in retrograded chapatti (R = 0.61). Upon storage of chapatti for 48 h, both soluble amylose and soluble amylopectin content decreased and starch crystallinity increased. These factors were significantly affected by the presence of β-glucans and arabinoxylans.

Effects of different emulsifiers on the bonding performance, freeze-thaw stability and retrogradation behavior of the resulting high amylose starch-based wood adhesive

High performance of starch-based wood adhesive is essentially important for its application in the versatile material science field. This study was carried out to evaluate the effect of different emulsifiers on the bonding performance, freeze-thaw (F/T) stability and retrogradation behavior of starch molecule in the adhesive system. The improved F/T stability and bonding performance was supported by the stability of viscosity after repeated F/T cycles and enhanced shear strength and grafting parameters. ζ- potential analysis revealed enhanced stability of the emulsion droplets through addition of emulsifiers. Furthermore, time sweep experiment, low-field nuclear magnetic resonance (LF-NMR), and x-ray diffraction (XRD) analysis showed that the retrogradation of starch molecule in the adhesive system was inhibited by addition of emulsifiers. Sodium dodecyl sulfate (SDS) showed the best improvement in the properties of high amylose starch-based wood adhesive (HASWA) among all the emulsifiers tested. These results offer a major step forward to prepare high performance bio-based wood adhesive in order to make them compete with less environment friendly wood adhesives.

Determination of Retrogradation Degree in Starch by Mid-infrared and Raman Spectroscopy during Storage

Retrogradation behavior is an important physicochemical property of starch during storage. A fast and sensitive method was developed for determining the retrogradation degree (RD) in corn starch by mid-infrared (MIR), Raman spectroscopy, and combination of MIR and Raman. MIR and Raman spectra were collected from different retrogradation starch and then processed by partial least squares (PLS), interval PLS (iPLS), synergy interval PLS (siPLS), and backward interval PLS (biPLS). Two different levels of fusion data extracted from MIR and Raman spectra were analyzed by PLS. The developed models demonstrated that both MIR and Raman techniques combined with chemometrics can be used to determine the RD in starch. The PLS model built by medium-level fusion approach achieved the most satisfied performance with a correlation coefficient of 0.9658. Integrating MIR and Raman technique combined with chemometrics improved the prediction performance of RD in comparison with a single technique.

The Impact of Heat-Moisture Treatment on Physicochemical Properties and Retrogradation Behavior of Sweet Potato Starch

Abstract Starch isolated from sweet potato was subjected to different levels of HMT at 15, 20, 25, 30, and 35 %. HMT showed negligible effect on the swelling power of starch. The swelling power was decreased with the increasing of the initial moisture content of the starch. The apparent amylose contents of HMT starches decreased from 24.11 % to 20.56 % with the initial moisture content increasing from 15 % to 35 %. The pasting temperatures enhanced from 73.1 to 81°C (p &lt; 0.05) with the rapidly digestible starch (RDS) contents decreasing from 86.97 to 70.24 % (p &lt; 0.05). Avrami equation analysis showed that HMT reduced the rate of starch retrogradation. The Avrami exponents of native and HMT-35 starches were 0.70 and 0.98 with the recrystallization rates 0.22 and 0.10, respectively. HMT could restrain the starch retrogradation and these results could provide theoretical guidance on sweet potato starch modification.

The effect of lamellar structure ordering on the retrogradation properties of canna starch subjected to thermal and enzymatic degradation

The starch retrogradation is the main cause of quality deterioration in starchy food during storage. The current work evaluates the retrogradation properties of degraded canna starches with the aim of probing the retrogradation mechanism. Degraded canna starches were prepared thermally (TDCS) and enzymatically (EDCS) with or without α-amylase (Bacillus subtilis) at increasing temperatures. The retrogradation behavior was assessed by morphology, transmittance, syneresis, and texture changes. At earlier stage of retrogradation, the starch gel has a smooth surface, with the time progressed, a coarse surface was formed, finally changed to hollow network structure. This process lead to a decrease of transmittance, and an increase of syneresis rate (SR) and hardness. Among the degraded starches, TDCS has a lower retrogradation tendency than native canna starch (NCS) and EDCS. Overall, the higher the lamellar structure ordering has, the easier the starch retrograde, therefore thermal and enzymatic degradation possess the potential capacity to reduce the degree of retrogradation by decreasing the lamellar structure ordering.

Retrogradation of Maize Starch after High Hydrostatic Pressure Gelation: Effect of Amylose Content and Depressurization Rate.

High hydrostatic pressure (HHP) has been employed to gelatinize or physically modify starch dispersions. In this study, waxy maize starch, normal maize starch, and two high amylose content starch were processed by a HHP of the order of 600 MPa, at 25°C for 15min. The effect of HHP processing on the crystallization of maize starches with various amylose content during storage at 4°C was investigated. Crystallization kinetics of HHP treated starch gels were investigated using rheology and FTIR. The effect of crystallization on the mechanical properties of starch gel network were evaluated in terms of dynamic complex modulus (G*). The crystallization induced increase of short-range helices structures were investigated using FTIR. The pressure releasing rate does not affect the starch retrogradation behaviour. The rate and extent of retrogradation depends on the amylose content of amylose starch. The least retrogradation was observed in HHP treated waxy maize starch. The rate of retrogradation is higher for HHP treated high amylose maize starch than that of normal maize starch. A linear relationship between the extent of retrogradation (phase distribution) measured by FTIR and G* is proposed.

Retrogradation enthalpy does not always reflect the retrogradation behavior of gelatinized starch.

Starch retrogradation is a term used to define the process in which gelatinized starch undergoes a disorder-to-order transition. A thorough understanding of starch retrogradation behavior plays an important role in maintaining the quality of starchy foods during storage. By means of DSC, we have demonstrated for the first time that at low water contents, the enthalpy change of retrograded starch is higher than that of native starch. In terms of FTIR and Raman spectroscopic results, we showed that the molecular order of reheated retrograded starch samples is lower than that of DSC gelatinized starch. These findings have led us to conclude that enthalpy change of retrograded starch at low water contents involves the melting of recrystallized starch during storage and residual starch crystallites after DSC gelatinization, and that the endothermic transition of retrograded starch gels at low water contents does not fully represent the retrogradation behavior of starch. Very low or high water contents do not favor the occurrence of starch retrogradation.

Retrogradation behavior of corn starch treated with 1,4-α-glucan branching enzyme

The retrogradation behavior of corn starch treated with 1,4-α-glucan branching enzyme (GBE) was investigated using rheometry, pulsed nuclear magnetic resonance (PNMR), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). Dynamic time sweep analysis confirmed that the storage modulus (G′) of corn starch stored at 4°C decreased with increasing GBE treatment time. PNMR analysis demonstrated that the transverse relaxation times (T2) of corn starches treated with GBE were higher than that of control during the storage at 4°C. DSC results demonstrated that the retrogradation enthalpy (ΔHr) of corn starch was reduced by 22.3% after GBE treatment for 10h. Avrami equation analysis showed that GBE treatment reduced the rate of starch retrogradation. FTIR analysis revealed that GBE treatment led to a decrease in hydrogen bonds within the starch. Overall, these results demonstrate that both short- and long-term retrogradation of corn starch were retarded by GBE treatment.

Retrogradation property of starch nanoparticles prepared by pullulanase and recrystallization

Retrogradation behavior of starch nanoparticles (SNPs) prepared by the recrystallization of short‐chain amylose (SCA) debranched from amylopectin‐rich waxy proso millet starch was investigated. In differential scanning calorimetry thermograms, the SCA: water ratio of 1:2 (w/w) led to a remarkable increase in enthalpy at 4 or 25°C compared with that corresponding to the ratios of 1:1 and 1:5, indicating better recrystallization and higher crystallinity of SCA. Morphology analysis showed that nanoparticles measuring 10–30 nm in diameter were formed when SCA solution (1:5, w/v) was retrograded for 15, 30, and 60 min. As the retrogradation duration was increased to 120 and 240 min, larger SNPs appeared. X‐ray diffraction patterns of all SNPs were of the B‐type, and the degree of crystallinity increased when retrogradation time was prolonged.

Effect of low temperature on the retrogradation behavior of rice gels with different milling degrees

The retrogradation properties of rice gels with different milling degrees (0, 3, 6, and 9%) stored at 4°C and −20°C were investigated. Results showed that rice gels with the same degrees of milling (DOM) stored at 4°C retrograde faster than those stored at −20°C. Moreover, higher milling degree leads to a faster retrogradation in the same temperature. Texture profile analysis demonstrated that samples showed a lower hardness but higher adhesiveness during storage at −20°C. Differential scanning calorimetry (DSC) revealed that the higher the milling degree, the higher retrogradation index (ΔHr/ΔHg) obtained at 4°C or −20°C. X‐Ray diffraction (XRD) analysis indicated that samples stored at −20°C had a lower degree of crystallinity compared with those stored at 4°C, which was also confirmed by Fourier Transform infrared spectroscopy (FTIR) analysis. Scanning electron microscopy (SEM) analysis showed that samples stored at −20°C presented a more shrinkable appearance with more pores. The results are expected to provide some theoretical guidance for retarding the retrogradation of rice in processing and preservation industry.

Retrogradation behavior of rice flour/starch gel using response surface methodology

Effects of moisture content (40, 50, and 60%), the percent ratio of rice flour to rice starch (0, 50, and 100%), and heating-end temperature (100, 120, and 140°C) on the retrogradation degree of rice flour/starch gels were investigated using a response surface methodology (RSM). The rice flour/starch samples gelatinized under different conditions were stored at 4°C for 48 h, and their retrogradation enthalpy was measured by differential scanning calorimetry. The rice flour/starch gels with 50% moisture content had higher retrogradation degree than those with 40 or 60% moisture content. The retrogradation degree of rice flour/ starch gel increased as the heating-end temperature decreased. The retrogradation degree of rice flour/starch gel was higher in 1:1 mixture samples than 100% rice starch samples or 100% rice flour samples. The moisture content among three independent variables played the most critical role in the retrogradation of the rice flour/starch gel.

Microstructure changes of on the extruded high-amylose bionanocomposites as affected by moisture content via synchrotron radiation studies

The crystalline domain changes and lamellar structure observations of sorbitol-plasticized starch nanocomposite had been investigated via synchrotron. Strong interactions were found between amylose–sorbitol, resulting in reduced inter-helix spacing of the starch polymer. Achievable dspacing of nanoclay was confirmed to be correlated to the moisture content (mc) within the nanocomposites. SAXS diffraction patterns changed from circular (high mc samples) to elliptical (low mc samples), indicating the formation of long periodic structure and increased heterogeneities of the electron density within the samples. Two different domains sized at around 90Å and 350Å were found for the low mc samples. However, only the ~90Å domain was observed in high mc samples. Formation of the 380Å domain is attributed to the retrogradation behaviour in the absence of water molecules. Meanwhile, the nucleation effect of nanoclay is another factor leading to the emergence of the larger crystalline domain.

Retrogradation behaviour of high-amylose rice starch prepared by improved extrusion cooking technology

Native rice starch (NRS, amylose/28.9%) was gelatinized by improved extrusion cooking technology (IECT) and retrograded (RRS) after low temperature storage (4°C). The retrogradation behaviour of RRS was changed to low retrogradation percentage and low retrogradation rate. The retrogradation resulted in a high compact morphology. The melt enthalpy change and percentage of retrogradation of RRS was 3.68J/g and 37.7%, respectively, compared to those of NRS (9.75J/g, 100%). The retrogradation percentage for RRS was low during storage as shown as a low retrogradation rate (0.21d−1) and a high Avrami exponent (0.89). The pattern of rice starch changed from A-type to amorphous and B-type. Both the relative crystallinity of RRS (12.7%) by the X-ray diffractograms and the ratio of the band height (0.63) in the FTIR spectra were low. The analysis of retrogradation structure and short-range molecular order further confirmed the retrogradation behaviour of rice starch after IECT treatment.

Long-term stability of waxy maize starch/xanthan gum mixtures prepared at a temperature within the gelatinization range

The retrogradation behavior of waxy maize starch pastes with added xanthan gum was investigated. The pastes were prepared with or without added xanthan gum at two starch concentrations (5:100 and 7:100), at two temperatures within the gelatinization range (70°C or 72°C) and at acid or neutral pH. The evolution of the macrostructure (texture, flow behavior and syneresis), microstructure (oscillation rheology) and molecular aggregation (pulsed-field NMR) of the pastes was followed up in an 8week period during cold storage (7°C). Heating temperature was found to have a profound effect on the long-term stability of the pastes. Pastes prepared at 70°C behaved as flocculated dispersions of largely intact, swollen granules which resulted in stable structural properties during the preservation period. At 72°C, a higher degree of gelatinization and degradation was observed, resulting in structurally unstable systems due to association and crystallization of amylopectin. Especially for these systems, xanthan gum was found to enhance the gelation process, probably due to phase separation. Although xanthan gum may restrict the granule disruption during preparation, this beneficial effect on the freshly prepared pastes did not result in an improved stability during storage.

Understanding the role of plasticisers in spray-dried starch

Amorphous thermoplastic starch (TPS) films were produced by compression moulding of solution spray-dried TPS powder and by direct solution casting. Oxidised potato starch was used as a feedstock for production of plasticised formulations containing glycerol or urea, or their combinations with maltodextrin (DE=19.1) as processing aid.The crystallinity index of freshly moulded films made from solution spray-dried powder was significantly lower than that for casted films. FTIR analysis showed that starch interacted in hydrogen bond formation with glycerol and urea plasticisers, reducing the glass transition temperature to 136°C and 106°C, respectively. Formulations containing maltodextrin did not show a Tg. Glycerol-plasticised and co-plasticised films immediately started to retrogradate in the presence of moisture, while urea based systems only showed slow recrystallization at the highest moisture exposure. In line with retrogradation behaviour, urea plasticised and co-plasticised films exhibited a more ductile behaviour, whereas glycerol based ones showed more brittle behaviour.

The effect of three gums on the retrogradation of indica rice starch.

Retrograded starch (RS3) was produced from indica rice starch with three kinds of gums (konjac glucomannan, KGM; carrageenan, CA, USA; and gellan, GA, USA) by autoclaving, respectively, and the effect of the gums on the retrogradation behavior of starch was estimated. The influences of polysaccharide concentration, sodium chloride concentration, autoclaving time, refrigerated time, and pH value on RS3 formation were discussed. Except for sodium chloride’s persistent restraint on RS3, the others all forced RS3 yields higher at first, but lowered it after the peak value. The influencing sequence of these impact factors was: sodium chloride concentration > polysaccharide concentration > autoclaving time > refrigerated time > pH value. The results also proved that in the three gums, KGM plays the most significant role in RS3 changing. It was concluded that the incorporation of each of these three gums into starch, especially KGM, results in an increase or decrease of RS3 under different conditions. This phenomenon could be taken into consideration when developing starchy food with appropriate amount of RS3.