Molecular Structure of Starch from Pueraria lobata (Willd.) Ohwi Relative to Kuzu Starch

The molecular structures of starches from Pueraria lobata (Willd.) Ohwi were examined and compared with those of other tuberous and root starches. The fresh tubers were collected from three Chinese main Pueraria lobata (Willd.) Ohwi growing regions. The chain distributions of the amylopectins as determined by gel permeation chromatography were similar to those of the amylopectins of other starches. Among the three amylopectins studied, the respective β‐amylolysis limits were 55%, 56% and 58% which were similar to that of kuzu amylopectin. The number average degree of polymerization ( ) values of the amylopectins were 8.7‐9.7×10³, lower than those of sweet potato and potato amylopectins (9.9×10³ and 11.2×10³, respectively). The number of branch chains per amylose molecule was 5.0. The average chain length ( ) of the Pueraria lobata (Willd.) Ohwi amyloses was similar to those of kuzu (310), sweet potato (310) and tapioca amyloses (340), but lower than those of lily (475) and potato (670).     

Physicochemical,crystalline, and thermal properties of native and enzyme hydrolyzed Pueraria lobata (Willd.) Ohwi and Pueraria thomsonii Benth. starches

Starches isolated from the bulbs of Pueraria lobata (Willd.) Ohwi (PLO) and Pueraria thomsonii Benth. (PTB) were hydrolysed by glucoamylase for different lengths of time (2, 4, 8, 12, and 24 h). The hydrolysis results were compared by scanning electron microscope (SEM), X‐ray power diffractometer (XRD), and differential scanning calorimetry (DSC). The SEM results revealed that both of the PLO and PTB starches showed the same hydrolysis mechanism, which indicated that the glucoamylase primarily attacking the exterior of starch granules and then the interior. The results of XRD revealed the crystalline type of PTB starch changed from C‐type to A‐type with crystallinity reducing from 43.5 to 20.9% during the hydrolysis. Unlike PTB starch, the PLO starch did not show marked changes in crystalline style but lower degree of crystallinity was obtained from 32.4 to 13.7% during the hydrolysis. All the XRD results demonstrated that B‐type polymorph was preferentially degraded than A‐type polymorph in the C‐type starch. The DSC results revealed that both of the PLO and PTB starches showed decreased enthalpy of gelatinization (ΔH_gel) and gelatinization temperature range (R)‐value after hydrolysis, while the gelatinization temperature (T_p) indicated different tendency, initially ranging from 68.6 to 64.3°C and then increasing to 67.8°C for PLO starch. While for PTB starch, the T_p‐value showed progressive reduction from 85.4 to 74.3°C during the whole process.     

野生葛根保健醋发酵工艺研究

介绍了以野生葛根为主要原料,利用黑曲霉、酵母菌、醋酸菌对葛根进行发酵,将葛根中的淀粉转化为醋的工艺,该工艺保留了葛根中的功能性成分,所制出的醋有较高的黄酮含量,使其有较好的保健功能。     

The effect of starch gelatinization and solute concentrations on T g′ of starch model system

The effect of starch gelatinization on glass transitions in a starch/water model system and how the concentrations of added solutes (sucrose and sodium chloride) affect the glass transition temperatures of the gelatinized starch solution was investigated. The starch suspension samples were heat treated in a Differential Scanning Calorimeter (DSC) under different time and temperature regimes to achieve different degrees of gelatinization. The gelatinization characteristics (onset, peak and end temperatures and enthalpy) and the glass transition values of a potato starch were determined using the DSC. The results showed that the starch concentrations had no effect on gelatinization characteristics and the T_g′ of the gelatinized potato starch but had clearly increased their ΔC_p in the T_g′ region. Annealing at a temperature slightly below the T_g′ of −5 °C, led to maximal freeze‐concentration in the total/partial gelatinized starch and a higher T_g′ value at about −3 °C was obtained. The T_g′ values of the totally gelatinized starch samples were slightly lower than those of partially gelatinized samples. The T_g′ of the gelatinized starch decreased with increasing concentrations of sucrose or sodium chloride. Sodium chloride had a stronger depressing effect on T_g′ than sucrose. © 2000 Society of Chemical Industry     

Annealing of Granular Rice Starches — Interpretation of the Effect on Phase Transitions Associated with Gelatinization

The effects of annealing on phase transitions associated with gelatinization at different moisture contents of an atypical non-waxy rice starch exhibiting a clearer-than-usual glass transition were studied by differential scanning calorimetry. Consistent with observations on synthetic glassy polymers, annealing at temperatures below the glass transition for limited periods caused an elevation of T_g which is attributed to the slow relaxation of the amorphous regions of the starch granules to their equilibrium glassy states. The crystalline regions were significantly affected only after annealing at temperatures above the glass transition, the resulting increase in crystallite melting temperatures and narrowing of the gelatinization range being ascribed to crystal growth and/or perfection. Passage through the glass transition (which precedes crystallite melting) appears to give rise to an apparent endotherm which becomes even more prominent on sub-T_g annealing of samples at low moisture contents. Annealing of an ordinary rice starch (with no clearly discernible glass transition) at a temperature below its onset gelatinization temperature (T₀) produced effects which paralleled those observed after sub-T_g annealing of the atypical rice starch. The conclusion drawn is that a glass transition is superposed on the crystalline melt at the leading edge of the single endothermic peak observed at high moisture contents. Where biphasic endotherms at intermediate moisture levels are concerned, however, the present results suggest that the first or G endotherm very likely arises from a glassy-to-rubbery state transformation while the second or M₁ endotherm is associated with crystallite melting.     

葛根淀粉生产工艺的研究

采用Ｃａ（ＯＨ）２水溶液代替清水作为浸泡剂，可以有效地提高淀粉的现提率及淀粉的品质，也使功能性保健因子葛根总黄酮在淀粉中的保留量大为提高。正交试验研究的结果表明，葛根淀粉生产的最优工艺条件为：料液比１：４，浆料ｐＨ８．５，浸泡时间３ｈ，浸泡温度３０℃。     

Thermo‐rheological and functional properties of gamma‐irradiated wholewheat flour

The effects of different doses (0, 0.5, 1, 2.5, 5 and 10 kGy) of gamma irradiation on the thermal, rheological and functional properties of the wholewheat flour were evaluated. Water and oil absorption capacity of the flour increased from 85.92% to 91.44% and 1.10 to 1.91 g g^?1 of flour, respectively, with increase in irradiation dose. The dough development time decreased with dose from 4.0 to 3.0 min. The transition temperatures (T_o, T_p and T_c) decreased as the dose increased; enthalpy of gelatinisation (?H) decreased from 5.18 to 4.27 J g^?1 with dose. The flow behaviour showed a shear‐thinning behaviour, and the hysteresis area decreased with dose. The structural recovery decreased with dose. FTIR did not show formation of any new chemical groups.     

Comparative NMR relaxometry of gels of amylomaltase-modified starch and gelatin

With the aim of generating gelatin-like starch gel functionality, starches extracted from normal potato, high amylose potato, maize, waxy maize, wheat and pea and oxidized potato starch were modified with amylomaltase (AM) (4-α-glucanotransferase; E.C. 2.4.1.25) from Thermus thermophilus. Gel characteristics after storage for 1 and 10 days at 20 °C of 12.0% gels were assessed by monitoring proton relaxation for the resulting 51 enzyme-modified starches and two gelatins using low-field ¹H nuclear magnetic resonance (LF NMR) relaxometry. Discrete and distributed exponential analysis of the Carr–Purcell–Meiboom–Gill (CPMG) LF NMR relaxation data revealed that the pastes and gels contained one water component and that the spin–spin relaxation time constants (T₂) and distributions differed with respect to starch type and enzyme modification. Typically, AM modification resulted in starches with decreased T₂ relaxation time and a more narrow T₂ distribution indicating a more homogeneous water population. In contrast, treatment with a branching enzyme (BE) (EC 2.4.1.18) combined with AM increased T₂ relaxation time and a broadened T₂ distribution. As evaluated by the principal component analysis (PCA), long chains of amylopectin generated hard gels and decreased T₂ relaxation time at both day 1 and day 10. Especially at day 10, T₂ relaxation time could be predicted from the amylopectin chain length (CL) distribution. Reconstructed amylopectin CL distribution required to emulate gelatin LF NMR data suggest the importance of combined fractions of long (DP 60–80) and short (DP 10–25) amylopectin chains.     

Effect of dual modification of banana starch and storage time on thermal and crystallinity characteristics of its films

Banana starch was oxidized at three different levels and subsequently acetylated. This double modified banana starch was used for film preparation with the addition of glycerol. Thermal and crystallinity properties were evaluated. Acetylation decreased the peak temperature and enthalpy of double modified banana starch. When the oxidation level and storage time increased in films elaborated with the double modified banana starch, both thermal parameters increased as well. The T_g showed slight changes in films prepared with the double modified banana starch compared to its oxidized counterpart, and similar patterns were found when oxidation levels increased in double modified films. However, a decrease in the T_g was determined with the storage time in films prepared with oxidized and double modified starches. Films prepared with the double modified banana starch presented lower percentage of crystallinity than its oxidized counterpart, nevertheless at higher storage periods, crystallinity levels increased. Thermal and crystallinity properties of films prepared with double modified banana starch could be used to understand the behavior during their application.     

Material Properties and Glass Transition Temperatures of Different Thermoplastic Starches After Extrusion Processing

Four different starch sources, namely waxy maize, wheat, potato and pea starch were extruded with the plasticizer glycerol, the latter in concentrations of 15, 20 and 25% (w/w). The glass transition temperatures of the resulting thermoplastic products were measured by Dynamic Mechanical Thermal Analysis (DMTA). Beside mechanical and structural properties also the transition temperatures of the materials were evaluated during tensile and impact tests. Above certain glycerol contents, dependent on the starch source, a lower glass transition temperature T_g resulted in decreased modulus and tensile strengths and increased elongations. Lowering the T_g at different glycerol contents did not influence the impact strength. When the amylose/amylopectin ratio increased a decrease in T_g was found. For pea, wheat, potato and waxy maize starch the T_g was 75 °C, 143 °C, 152 °C and 158 °C, respectively. Therefore products with higher percentages of amylose are more flexible. The shrinkage of the specimens made by injection molding was considerable compared to the specimens made by pressing.     

葛根及葛根素脑保护作用的研究进展

葛根为我国传统的药食两用植物,葛根素为其主要药效成分之一。依据中医药理论,葛根具有解表退热、生津止渴的功效。现代药理学研究表明,葛根及葛根素均具有显著的脑保护活性,对阿尔茨海默病、帕金森病及脑卒中等模型动物或细胞产生保护作用,其机制与调节GSK-3β/Nrf2、PI3K/Akt、cAMP/PKA等神经细胞凋亡信号转导通路有关。提示葛根具备开发为抗神经系统疾病保健食品的潜在价值。     

INFLUENCE OF GLASS TRANSITION TEMPERATURE ON RATE OF RICE STARCH RETROGRADATION DURING LOW-TEMPERATURE STORAGE

An increasing amount of research suggests a relationship between the glass‐transition temperature (T_g) and the optimum storage temperature for a frozen food. In addition, the T_g for a frozen food is related to the cooling rate through the temperature range of phase transition for water. The objectives of this study were to investigate the influence of T_gon the rate of starch retrogradation during low‐temperature storage. Rice starch with 65% w/w water content was heated to obtain starch gel as a model food. The influences of cooling rate, storage temperature and time on rate of retrogradation were evaluated. Differential scanning calorimetry was used to measure the T_gand the enthalpy during retrogradation. Results indicated that the retrogradation rate during storage was reduced at a slower cooling rate. The retrogradation rates at storage temperatures above T_gwere higher than at storage temperatures below T_g.     

Physical aging of glassy normal and waxy rice starches: effect of aging time on glass transition and enthalpy relaxation

Physical aging and glass transition characteristics of amorphous normal and waxy rice starches (11 and 15% moisture contents) were investigated under differential scanning calorimetry as function of aging time. Normal rice starch showed higher T_g than waxy rice starch. The T_g and ΔC_p at glass transition gradually increased with aging time, whereas fictive temperature was slightly reduced regardless of moisture content and starch type. The relaxation enthalpy and relaxation peak temperature increased with aging time until structural equilibrium was reached. Enthalpy increase was more significant in the early stage of aging whereas temperature increase was constant during the aging period tested (120 h). Aging kinetic analysis using Cowie and Ferguson model revealed that the amorphous normal and waxy rice starches behaved in different modes for the physical aging. Relaxation distribution parameter (β) of both starches was in a range of 0.3<β<0.7, but higher at a lower moisture content, and for normal starch than for waxy starch. Maximum relaxation enthalpy for normal starch (1.10 and 2.69 J/g, respectively, at 11 and 15% moistures) was higher than those of waxy starch (0.77 and 2.48 J/g). Based on the characteristic time (t_c), normal starch has slower progression toward an equilibrium than waxy starch. Overall results proved that physical aging kinetics were highly dependent on starch structure and composition.     

New insights on the characteristics of starch network

This study investigated the roles of granule-associated proteins (0.16% w/w d.b.) in mungbean starch (MBS, Vigna radiata (L) Wilczec) on the microstructural and thermo-mechanical properties of MBS gel and thermoplastic. Gelatinization at high water content (9–13% w/w) and intermediate water content (40–60% w/w) ranges generated microscopic multi-phase structure of swollen MBS granules, separated starch-rich phase and separated protein-rich phase. The presence of 50 mM calcium lactate plus 25 mM cysteine lowered the compressive stress of MBS gels at high water content range, increased T_o, T_p and T_e of MBS slurries at intermediate water contents, and lowered the storage modulus of the protein-rich phase in thermoplastic MBS at its T_g (P < 0.05). This study revealed the new insights on the significance of granule-associated proteins in the regulation of the envelope permeability, the leaching of starch and the thermo-mechanical characteristics of starch network over a wide range of water contents.     

Effect of gluten content on recrystallisation kinetics and water mobility in wheat starch gels

The effect of gluten on starch retrogradation at 5 °C was studied using ¹H NMR relaxometry. Gels were made from gluten and starch at 27.8 and 38.5% total solids and with gluten comprising either 10, 15 or 20% of the solids. Changes in the transverse relaxation time constant (T₂) were related to water mobility. Mono‐exponential analysis of relaxation curves showed that, in general, gluten retarded starch retrogradation. T₂ values in gluten gels also decreased during storage, but to a much lesser extent. Distributed exponential analysis showed that two distinct regions of T₂ were observed in all samples. During aging, the peak values of both regions shifted to lower values for all gels. Starch gel samples showed the most significant shift, and gluten gels showed the least. The three levels of gluten addition in starch/gluten gels produced similar shifts. For all samples the signal intensity of the less mobile region decreased more dramatically than that of the more mobile region during storage. It was suggested that gluten retards water loss in the granule remnants. Copyright © 2004 Society of Chemical Industry     

1H NMR studies of molecular mobility in wheat starch

Pulsed ¹H NMR was used to determine moisture content and molecular mobility of wheat starch suspensions at water activity (a_w) values between 0 and 0.93. Moisture determination by NMR agreed well with gravimetric determinations (R²=0.99). Transverse proton relaxation (T₂) of the systems were identified using single pulse and CPMG experiments. T₂ associated with starch molecules increased linearly from 7.1 to 10.1 μs as a_w increased from 0 to 0.93, due to plasticizing effects of water. T₂ associated with water molecules showed a linear increase up to a_w of 0.69. Results indicated that ¹H NMR could be employed to determine moisture content of starch suspension and to identify and quantify the molecular motion of starch chains and water molecules of starch suspensions at low moisture levels.     

Preparation,characterization, and water resistance of cationic acetylated starch‐g‐poly(styrene‐butyl acrylate) surfactant‐free emulsion

Cationic acetylated starch‐g‐poly(styrene‐butyl acrylate) surfactant‐free emulsion (CAS‐g‐poly(St‐BA)) was synthesized by graft copolymerization of styrene (St) and butyl acrylate (BA) onto CAS using FeSO₄–H₂O₂ redox initiator. The maximum graft of 55.68% was derived when H₂O₂ concentration, monomer concentration, and St/BA ratio were 9%, 130%, and 1:1, respectively. The results obtained from FTIR, NMR (H¹ NMR and C¹³ NMR), XRD, SEM, and thermogravimetric analysis (TGA‐DTG) confirmed graft copolymerization of St and BA onto CAS. And it was demonstrated that film‐forming properties of starch were greatly improved via grafting St and BA onto starch. It was also found that paper sized with CAS‐g‐poly(St‐BA) exhibited higher ring crush index and bursting strength than paper sized with cationic potato starch (CS) and CAS, as well as much lower water absorption, which is further verified by contact angles results.     

Subzero Glass Transition of Waxy Maize Starch Studied by Differential Scanning Calorimetry

A mixture of waxy maize starch and water (1:2, w/w) was heated in a differential scanning calorimeter (DSC) pan to different temperatures to obtain different degrees of gelatinization. Each pan was then quenched to ‐30°C and rescanned, and the subzero glass transition temperature (T_g′) of the content was determined. A three‐phase model of a starch granule—a mobile amorphous phase, a rigid amorphous phase, and a crystalline phase—was used to interpret results and explain the glass transitions in starch. Waxy maize starch had an onset gelatinization temperature (T_o) of 61.5°C, peak temperature (T_p) of 70.3°C, and completion temperature (T_c) of 81.7°C. The T_g′ was clearly noted after the starch and water mixture was heated to T_p and T_c, but was small and barely observable when the mixture was heated up to T_o and immediately cooled to ‐30°C. When the starch and water mixture was heated to 55°C, which was 6°C below the T_o, and held for 2 h, a T_g′ was observed. Moreover, T_g′ began to appear and was observable if the starch and water mixture was heated to 10°C below gelatinization onset temperature (51°C) and annealed for 2 h without any gelatinization. Further holding at ‐7°C showed a clear subzero glass transition of annealed native starch granules.     

Impact of Annealing on the Physicochemical Properties of Unfermented Cassava Starch (“Polvilho Doce”)

Unfermented cassava starch (“polvilho doce”) was subject to annealing treatment at 50°C for 24, 48, 96, 120, 168 and 192 h, in 1:5 starch to water ratio. The annealing treatment changed the internal structure of “polvilho doce” at increasing treatment time. Peak viscosities decreased significantly, denoting that there was a decrease in leaching of amylose from the granules. The pasting temperatures were increased, setback and breakdown were reduced while hold and final viscosities increased, showing an improvement of the stability of the paste. Swelling power and solubility were reduced at all temperatures and the solubility at 55°C was zero after 120 h of treatment. The DSC data for T_o, T_p, T_c and ΔH increased and the gelatinization range was narrowed. The X‐ray diffractograms changed from C_A to A pattern (samples annealed for 48, 96, 120, 168 and 192 h), denoting an increase in organization of double helices of amylopectin. Annealing imparts to the samples some waxy starches characteristics which can be very useful in the food industry.     

Molecular and physicochemical characterisation of starches from yam,cocoyam, cassava,sweet potato and ginger produced in the Ivory Coast

Granule sizes, macromolecular features and thermal and pasting properties of starches from seven tropical sources (Florido, Kponan and Esculenta yams, cocoyam, cassava, sweet potato and ginger) were compared with those of several well‐known cereal, legume and tuber starches. The aim of the study was to characterise some non‐conventional starches with a view to possibly marketing them. Amylose content varied from 148 mg g^?1 in Esculenta starch to 354 mg g^?1 in smooth pea starch. For total starches, weight‐average molar mass (M?_w) ranged between 0.94 × 10⁸ and 1.80 × 10⁸ g mol^?1 for potato and normal maize starches respectively. Gyration radius (R?_G) varied from 157 nm for ginger starch to 209 nm for normal maize starch. Gelatinisation enthalpy (ΔH) ranged between 9.8 and 20.7 J g^?1 for wheat and Florido starches respectively. Gelatinisation peak temperature (T_g) varied from 58.1 °C for wheat starch to 87.3 °C for ginger starch. Native starch granule mean diameter ranged between 5.1 and 44.5 µm for Esculenta and potato starches respectively. Cassava and potato starches had the highest swelling power and dispersed volume fraction at all treatment temperatures, while ginger starch had the lowest. Cocoyam starch had the highest and ginger starch the lowest solubility at 85 and 95 °C. Cassava starch was the most stable under cold storage conditions. Roots and tubers such as ginger and cassava produced in the Ivory Coast are new sources of starches with very interesting properties. Thus these starches could be isolated on an industrial level in order to market them. Copyright © 2007 Society of Chemical Industry