Starch-water System Research Articles

Unravelling temperature-dependent molecular changes in hydrated wheat and maize starches using 1H time-domain NMR

This study proved that time-domain NMR (TD-NMR) experiments can accurately demonstrate the interaction between starch (wheat and maize) and water and the distribution of water molecules in starch-water systems during heating. Molecular properties in starch-water systems at 50% moisture content were monitored by Rhim and Kessemeier – Radiofrequency Optimized Solid-Echo (RK-ROSE) and Carr-Purcell-Meiboom-Gill (CPMG) pulse sequences at frequent (2 °C intervals) measurements during heating (55–80 °C). Starch-like and water-like phases were obtained by RK-ROSE and CPMG pulse sequences, respectively. The second moment, M2, along with the relaxation times of the populations, associated with fast-decaying protons, provided information on the crystal structure state during heating and the extent of gelatinisation. The relaxation times of the most abundant population from the CPMG signal decreased during heating due to strong interactions between starch and water. Temperature of stabilisation of this population aligned with the associated findings from the differential scanning calorimetry and rheological measurements.

Modeling the gelatinization-melting transition of the starch-water system in pulses (lentil, bean and chickpea)

Cooking-induced conversion of starch, the major carbohydrate in pulses, is crucial for the digestibility of the seed. The gelatinization-melting transition of lentil, bean and chickpea starches was studied using Differential Scanning Calorimetry at different temperatures (T values ranged from 20 to 160 °C) and water contents (X from 0.2 to 3 kg kg−1 db). Gelatinization and melting endotherms were successfully modeled as two desummed Gaussian functions. This modeling enabled to generate the degree of starch conversion for any T and X conditions, a valuable indicator that could be used in predictive cooking models. As previously reported for melting, the temperature of gelatinization was found to depend on moisture in a way that can be modeled using the Flory-Huggins equation. The results suggest that starch undergoes melting transition irrespective of water content. The similar starch conversion diagram for the three pulses suggest that starches have similar thermal behavior.

Effect of molecular structure on phase transition behavior of rice starch with different amylose contents

Phase transition behaviors in starch-water system and molecular structures of rice starches isolated from four Korean cultivars with different amylose contents were investigated and the importance of structural features affecting starch phase transitions was also explored. The Dodam starch with the highest average chain length of amylopectin (26.1), the highest proportion (24.3 %) of long chains (DP ≥ 37), and the lowest proportion (17.5 %) of short chains (DP 6-12) displayed the highest gelatinization and retrogradation temperatures. Enthalpies of ice freezing and melting, and glass transition temperature (Tg′) of rice starches increased with increasing amylose content and decreasing proportion of short amylopectin chains because these structural features are related to a higher thermal stability of the starches. Ice melting temperature was also influenced by amylopectin chain structures. The results suggest that the phase transition behaviors of rice starches were highly influenced by their amylose content and amylopectin chain length distribution.

Starch properties of high and low amylose proso millet (Panicum miliaceum L.) genotypes are differentially affected by varying salt and pH

Variation in salt content and in pH are common in starch-based foods and can affect starch properties and final product texture. Fifteen accessions of proso millet starch with diverse amylose content were selected to investigate single factor and interaction effects of pH and NaCl on thermal, pasting, and textural properties. Pasting properties and gelatinization temperatures were markedly altered by salt addition. Changes in pH only had substantial effects on ΔH, but other properties were generally stable under different pH conditions. From two-way ANOVA, interactive effects of salt and pH were found to affect ΔH. The response of starch of different genotypes in terms of thermal and pasting properties differed under the same pH and salinity conditions. The reason is likely that ions in the starch–water system performed the roles of both reducing water activity and building of hydrogen bonds, which will have opposite effects on starch gelatinization.

Removal of uranium (VI) from water by the action of microwave-rapid green synthesized carbon quantum dots from starch-water system and supported onto polymeric matrix

Carbon quantum dots (CQDs) are a new class of carbon nanoparticles with superior advantages as small particle size, excellent biocompatibility and low toxicity which advance their recent applications in biotechnology, bioimaging and biosensing. The use of free CQDs in water treatment is greatly rendered by their high solubility in water. Therefore, this work is aimed to rapidly synthesize CQDs in only 10 min via microwave irradiation pyrolysis of starch-water system. The maximum fluorescence emission of CQDs was detected at 526 nm throughout the excitation wavelength (390 nm). The CQDs have been targeted to occupy the surface and pores of a polymeric material based on poly(anthranilic acid-formaldehyde-phthalic acid) (PAFP) to produce a novel CQDs@PAFP nanobiosorbent. The surface area of CQDs@PAFP was detected (28.79 m2 g−1 BET) and the nanoparticle size was confirmed (TEM). The highest removals of U(VI) by CQDs@PAFP nanobiosorbent were 95.5–98.0 % for 30−90 mg L-1. The sorption mechanism was designated to the pseudo-second-order model and closely tailored with Freundlich model. CQDs@PAFP was emerged as an excellent nanobiosorbent for U(VI) removal from wastewater (97.3 %) and sea water (96.0 %). CQDs@PAFP confirmed its excellent reusablity for efficient multi- recovery of U(VI) from different water samples.

Enthalpy of sorption by glassy polymers

Thermodynamics and molecular mechanisms of sorption of gases and liquids by glassy polymers and are still not fully understood. In particular, the enthalpy of sorption (or mixing) in the glassy state – a parameter crucial for understanding the thermodynamics of sorption is not properly described by existing approaches. In this work, we propose a thermodynamic theory that describes the effect of the glass transition on the enthalpy of sorption. Firstly, a rigorous thermodynamic expression for the sorption enthalpy is presented, and then equations applicable for practical calculations are derived using certain approximations. The theory presented here is tested on the experimental water sorption data on starch and cellulose. The equations describing the hydration enthalpy are in excellent agreement with experimental data. Remarkably, the glass transition-induced apparent heat capacity change for water in carbohydrate polymers turned out to be negative. Being counterintuitive, this result can however be supported by re-evaluation of the literature data on heat capacities of the starch-water system.

The effect of heating rates on functional properties of wheat and potato starch-water systems

The effect of heating rate on structural and functional properties of wheat and potato starch-water systems were analyzed in term of gelatinization, swelling and pasting behavior as well as in terms of textural and flow characteristics of gels recovered. Gelatinization temperatures and enthalpy of starch increased with increasing heating rate. Viscosities measured during the pasting procedure increased with the heating rate as a consequence of granule swelling. Slower heating rates resulted in smaller breakdown of viscosity during the pasting procedure. Both wheat and potato starch gels showed shear thinning behaviours, with a consistency index decreasing when the heating rate increased. The hardness of wheat starch gels slightly decreased when the heating rate increased while the hardness and gumminess of potato starch gels increased with the heating rate.

The effect of Ca2+ ions on the pasting, morphological, structural, vibrational, and mechanical properties of corn starch–water system

This work focuses on the effects of different concentrations of Ca2+ ions 0, 0.10, 0.15, 0.25, and 0.35% w/w and the steeping time in corn starch-water system with and without heating, as well as the influence of the Ca2+ concentrations on the pasting profile, regarding the physicochemical changes that take place along the thermal process. The first and second derivatives of the pasting profiles were calculated to identify the main changes originated in the heating and cooling regions. The inclusion of Ca2+ ions has a strong effect at the end of the pasting profile; below the gelatinization temperature starch grains exhibit a semi-crystalline structure and were still integer, at the peak viscosity, the samples were amorphous as a result of the gelatinization, at the final viscosity the structure was complete amorphous observed in the X-ray patterns. Micrographs of the starch-water system with Ca2+ show that the morphology changed rapidly and depends on the Ca2+ concentrations. IR spectroscopy shows that Ca2+ions did not form any new chemical bonds, yet only the van der Waals interaction occurred. We demonstrate for the first time the effect of calcium ions on the elastic and plastic regions of the custard and hydrogels.

Non-additive response of starch systems in different hydration states: A study of microwave-absorbing properties

Abstract In the food industry, microwave-based curing and modification represent green, low-energy-consumption techniques for food processing, offering significant advantages. Water, a representative high-dielectric material, can react with many food components; however, few studies on microwave absorption to these components have been reported. In this study, commercially available potato starch and rice starch (the latter a representative cereal starch) were selected as the research materials. Based on vector network analysis of these materials, the bow coaxial probe and improved arch methods were used to study the dielectric properties and microwave reflection loss of the potato starch and rice starch systems, with different hydration levels, at 2.45 GHz. Their absorption behaviour was compared with the classical model to study the absorption properties of the starch systems under different hydration conditions. The results showed that at ambient temperature, potato starch and rice starch had similar dielectric responses, which both showed a steady rise with increasing water content. Therefore, because of their similar dielectric properties, the two systems behaved similarly in the microwave field. However, further experiments found that the microwave absorption properties of both starches differed significantly from that of water: starch–water systems with different compositions varied nonlinearly in their microwave absorption performance, consistently with the “true single layer of water” theory.

Multi-scale NMR and MRI approaches to characterize starchy products

This review deals with the use of Nuclear Magnetic Resonance techniques to monitor the behavior of starch as well as the migration and distribution of water during the processing or storage of starchy matrices. The aim is to emphasize the potentials of NMR techniques for the quantitative characterization of water transfers in starch-water systems on different length scales. Relaxation and self-diffusion experiments using low-field NMR spectrometry provided important information on the relationship between water dynamics and the microscopic organization of starch granules at various temperatures and water contents. Some works dealt with the botanical origin of starch but also the impact of possible additives. Indeed, the investigation on model starch-based systems was recently expanded to more complex real systems, including dough, bread, cakes, spaghetti and lasagna. Two-dimensional (2D) cross correlation methods have also been developed to elucidate chemical and diffusional proton exchange phenomena, and to improve the interpretation of results obtained in 1D. Finally, magnetic resonance micro-imaging methods were developed to study or to quantify water intake into starch-based matrices.

Hydrothermal Changes of Starch Monitored by Combined NMR and DSC Methods

The thermal, dynamic, and structural properties of wheat starch–water systems with different levels of water content (11, 35, 40, 42, 45, and 50%, wet basis) were investigated. 1H time domain nuclear magnetic resonance (TD-NMR) spectroscopy was used to interpret and quantify the water transfer and starch transformations in terms of water uptake, granule swelling, amylose leaching, and melting of starch polymers in relation to the different levels of water content. Complementary differential scanning calorimetry (DSC) experiments were performed to study the effects of water content on the degree of starch gelatinization. In particular, this twofold approach was applied to the first endotherm to study the mechanisms of gelatinization with a common heating range both in NMR and DSC. It was shown that the trend of the enthalpy changes in the first phase transition in starch–water (SW) mixtures was strongly correlated with the loss of solid content measured by NMR in the corresponding temperature range (55–70 °C). Based on the evolution of the relative amplitudes of T 2, structural transformations of starch were shown to occur in both crystalline and amorphous regions within SW samples, supporting the fact that the amorphous phase of starch also plays a significant role in the phase transition of granules during gelatinization. This dynamic and hydrothermal approach provided the first NMR-based interpretation of the first endotherm measured by DSC.

Structural and physicochemical characterization of Sphenostylis stenocarpa (Hochst. ex A. Rich.) Harms tuber starch

Several characteristics of African Yam Bean tuber starch (AYB) were studied and compared with that of a well-known native potato starch (P). The diameter of AYB granules ranged from 5.7μ to 49μ with a median at 19.5μ. During its pasting, AYB exhibited a low peak of viscosity in accordance with its low granules swelling and disintegration capacity. The gelatinization temperature of AYB was 75.2°C while that of P was 60.4°C. AYB was observed to be more stable during thermo-gravimetrical Analysis. Its degradation peak was observed at 308°C while that of P was 303°C. The X-ray diffraction analysis revealed that AYB belongs to the A-type crystalline group instead of C-type as claimed for several legumes starches. The stability of AYB and its capacity to structure starch-water systems make this resource an interesting ingredient for new food and non-food products.

Understanding starch gelatinization: The phase diagram approach

By constructing a detailed phase diagram for the potato starch–water system based on data from optical microscopy, synchrotron X-ray scattering and differential scanning calorimetry, we show that gelatinization can be interpreted in analogy with a eutectic transition. The phase rule explains why the temperature of the gelatinization transition (G) is independent on water content. Furthermore, the melting (M1) endotherm observed in DSC represents a liquidus line; the temperature for this event increases with increasing starch concentration. Both the lamellar spacing and the inter-helix distance were observed to decrease with increasing starch content for starch concentrations between approximately 65wt% and 75wt%, while the inter-helix distance continued decreasing upon further dehydration. Understanding starch gelatinization has been a longstanding challenge. The novel approach presented here shows interpretation of this phenomenon from a phase equilibria perspective.

The impact of microwave heating on the granule state and thermal properties of potato starch

Microwave energy is widely used in the field of starchy food processing and heating. To date, research on microwave heating has focused predominantly on gelatinization. In order to investigate the mechanism of microwave heating, we selected potato starch, which has a typical B‐type crystalline structure of regular shape that is used and consumed widely. Based on the characteristics of the microwave heating process, we established a control heating model and evaluated this with both standard and polarizing light microscopy, laser particle size distribution analysis, and differential scanning calorimetry to probe the destruction of birefringence, the effects on the granule state, and the enthalpy involved. The results showed that thermal‐ and microwave‐specific effects applied to the different stage of gelatinization. Microwave‐specific effects dominated initially, but thermal effects began to dominate during and after gelatinization. The starch–water system was affected by microwave radiation throughout the heating process.

Effects of High Hydrostatic Pressure on Rheological Properties of Rice Starch

The effect of high hydrostatic pressure-750 on rheological properties of rice starch-water system was examined. The starch dispersions (20% w/v) were pressurized at 120, 240, 360, 480, and 600 MPa for 30 min. The storage modulus and loss modulus increased with the pressure increase. A yield stress was generated at a low shear rate. The high hydrostatic pressure-treated starch gels performed shear thinning and the apparent viscosity dropped sharply at 480 MPa. Hysteresis loop area increased with the pressure increased and reached the maximum at 600 MPa. High hydrostatic pressure-treated starch gels were found to be weak gels and thixotropic.

Effects of Fatty Acid Addition on the Physicochemical Properties of Corn Starch

The effect of addition of six fatty acids (stearic, palmitic, myristic, oleic, palmitoleic, and myristoleic acid) on the gelatinization, glass transition, and retrogradation properties of corn starch as well as their complexing abilities with amylose were determined. Differential scanning calorimeter studies reflected that addition of fatty acids caused a 73–89% decrease in the gelatinization enthalpy compared to that of the native starch. Besides amylose-lipid formation, exotherm was determined at the same temperature range with the gelatinization endotherm. As a result, it was suggested that fatty acids complexed with amylose during gelatinization. Fatty acid addition significantly increased the glass transition temperature of starch gel. This was attributed to two reasons: the first is due to the physical cross-linking action of amylose–lipid complexes in starch-water system; the second may be due to the effect of uncomplexed fatty acids on water distribution in the gel structure as a result of their amphiphilic character. Thermal properties of amylose-lipid complexes were compared in order to determine the effect of fatty acid properties. It was found that the shorter chain length and unsaturation favored the complex formation but the complexes formed by longer and saturated fatty acids were more heat stable. Addition of fatty acids resulted in 73–90% and 47–71% reduction in the retrogradation enthalpy compared to native starch gels at 5°C and 21°C, respectively. The reduction in the retrogradation enthalpy was inversely related to the amylose-lipid complexing abilities of the fatty acids and it might be explained by the hindrance effect of uncomplexed fatty acids to the water distribution in the starch gel matrix.

デンプン‐水系における凍結水の熱分析による解析

含水量の異なるポテトおよびうるち米デンプン-水系について－30～120℃の温度範囲でDSC測定を行った．凍結水の融解挙動を解析することにより，自由水と束縛水の量および融解熱を求めた．含水量によって自由水と束縛水との存在割合が変化することが示された．自由水が存在する含水量では自由水の融解熱は332～337 J/gWと求まり，通常の水の融解熱と一致した．それに対して，束縛水の融解熱は225～246 J/gWであり，自由水の約2/3と求まった．生デンプン-水系および糊化デンプン-水系いずれにおいても含水量0.6 gW/gDM以上では自由水の融解が確認でき，乾燥物重量当たり一定量の束縛水が存在することが示され，束縛水量は生デンプン-水系が0.09～0.10 gW/gDMで，糊化デンプン-水系が0.18～0.23 gW/gDMだった．自由水が存在しない含水量は，糊化デンプン-水系が0.54～0.57 gW/gDM以下で，生デンプン-水系は0.39～0.50 gW/gDM以下であると推定できた．得られた結果から，束縛水の融解熱は自由水の融解熱の2/3程度であり，両者に差があることが明らかになった．これまでは，自由水と同じ融解熱であると仮定して凍結水量を見積もっていたが，算出した束縛水の融解熱から，測定した系において0.30～0.40 gW/gDMの不凍水量を見積もることができた．

State of water in starch–water systems in the gelatinization temperature range as investigated using dielectric relaxation spectroscopy

The dielectric response of native wheat starch–water slurries containing 5–60% starch (w/w) was measured in the frequency range of 0.2–20GHz after heating the slurries to 7 different temperatures between 25 and 90°C for 30min. Three relaxations, with relaxation time range of 4–9ps, 20–25ps and 230–620ps at 25°C, were identified from the dielectric spectra of starch slurries. The fastest relaxation process (4–9ps) was attributed to bulk water while the two slower relaxations were attributed to the confined water molecules present in the starch–water system. The amount of water exhibiting the slowest relaxation (230–620ps) was calculated to be 0.08–0.16gwater/g starch, which was close to the monolayer water associated with wheat starch. Mobility of bulk water was significantly reduced (P<0.001) upon gelatinization at low starch concentration (10% starch), but remained unaffected at higher starch concentrations. The mobility of two slower relaxing water species was not significantly influenced (P>0.19) by gelatinization at all starch concentrations.

Comparison of State of Water in Various Starch-water Systems after High Pressure Treatment or Heat Treatment

Comparison of State of Water in Various Starch-water Systems after High Pressure Treatment or Heat Treatment

EFFECT OF SUGAR AND GUMS ON THE PASTING PROPERTIES OF CASSAVA STARCH

ABSTRACT Pasting properties of cassava starch solutions were prepared with different types of sugars (glucose, sucrose and fructose) at different levels as 10.71, 19.35, 32.43% and gums (gum acacia, guar gum and gum tragacanth) at 0.1, 0.2, 0.3, 0.4% levels, respectively, were analyzed using the Rapid Visco Analyzer. The pasting temperature increased with increase in the sugar concentration in cassava starch–water system and the maximum 78.27C at 32.43% sucrose solution. The peak viscosity (PV) and breakdown viscosity (BD) decreased with increase in the sugar concentration. Hot paste viscosity and cold paste viscosity decreased progressively with increase in sugar concentration in fructose and glucose solution. The PV and BD increased with increase in guar gum concentration and was maximum 5,704 and 3,773 mPa·s at 0.4% concentration, respectively. PRACTICAL APPLICATIONS Cassava starch performs most of the functions where maize, rice and wheat starch are currently used. In food industry, cassava starch is used in extruded snacks for improved expansion, as a thickener in foods, in processed baby foods as a filler material and bonding agent in biscuit and confectionary, textile, pharmaceutical, paper and cosmetic industries. Cassava starch can be converted to maltotriose, maltose, and glucose as well as to other modified sugars and organic acids. Starch from cassava can be used to make gelatin capsules. Starches and gums are often used together in food systems to provide texture, control moisture, water mobility, improve overall product quality and stability, reduce cost and facilitate processing. Cassava starch, due to its high swelling power, is reported to yield better quality instant noodles.