A Differential Scanning Calorimetry Study on the Effect of Annealing on Gelatinization Behavior of Corn Starch

Gelatinization characteristics of laboratory-isolated and commercial corn starch were compared by differential scanning calorimetry (DSC) before and after being annealed at subgelatinization temperatures in excess water. Prior to annealing, commercial corn starch has a relatively narrow gelatinization range, with a peak temperature at 71°C. Starches isolated in the laboratory have wide gelatinization ranges and lower peak temperatures. After annealing, commercial starch showed little change in gelatinization characteristics, whereas laboratory starches all had narrowed gelatinization ranges, higher peak temperatures, and increased gelatinization enthalpy, indicating changes in the internal structure of the starch granules. This demonstrates that the wet-milling process anneals corn starch during the isolation procedure.     

Application of Differential Scanning Calorimetry to Starch Gelatinization. I. Commercial Native and Modified Starches

Differential scanning calorimetry has been used to examine the gelatinization behaviour of native starches and modified wheat starches. The results indicated that the shape of the endotherms varied between native starches and also between modified wheat starches. Substitution appeared to decrease both the gelatinization energy and gelatinization peak temperature while the cross-linked starches also displayed lower gelatinization energies but slightly higher peak temperatures. Oxidation, dextrinisation and acid cut wheat starches all posses lower gelatinization energies but higher peak temperatures than unmodified wheat starch.     

Gelatinization of Low Water Content Wheat Starch — Water Mixtures. A Combined Study by Differential Scanning Calorimetry and Light Microscopy

The effect of heating starch-water mixtures of low water content (between 50% and 1.5% water) has been observed by the techniques of both birefringence measurement and differential scanning calorimetry. The temperature at which gelatinization was complete, i. e. at which complete loss of birefringence occurred, increased as the water content was reduced. Complete loss of birefringence occurred over the whole of this range of water content. A correlation was established between the loss of birefringence and passage through the M1 DSC endotherm, assigned to the melting of starch crystallites.     

Application of Differential Scanning Calorimetry to Starch Gelatinization. III. Effect of Sucrose and Sodium Chloride

The influence of sucrose and salt on the gelatinization endotherm of wheat starch was examined using differential scanning calorimetry. Sucrose was found to decrease gelatinization energy (– ΔH_G) and to increase peak temperature (T_p) as its concentration was increased. Onset and conclusion temperatures (T₀ and T_c) were not affected by sucrose level. The effect of salt on the endotherm was more complex. A decrease in – ΔH_G occurred as the level of this solute in the aqueous phase was raised to 6% but further increases in salt caused it to rise again. Salt levels up to 9% caused increases in T₀ and T_p. With further rises in solute level, T₀ then decreased and T_p remained relatively constant. T_c rose slowly as salt concentration increased.     

Enzymatic Hydrolysis of Amaranth Flour — Differential Scanning Calorimetry and Scanning Electron Microscopy Studies

High-protein amaranth flour (HPAF) and carbohydrate rich fraction (CRF) were produced from raw flour in a single-step process using a heat-stable α-amylase preparation. Protein content of flour increased from 15 to about 30 or 39% at liquefaction temperatures of 70 or 90°C, respectively, and 30 min hydrolysis time. CRF exhibited 14–22 DE. Enzymatic action at 70°C increased endotherm temperatures and gelatinization enthalpy of HPAF, in relation to gelatinized flour, as assessed by differential scanning calorimetry (DSC). Hydrolysis at 90°C did not affect significantly (P > 0.05) DSC peak temperature. It is suggested that these changes in DSC performance might result from differences in amount and type of low-molecular weight carbohydrates and residual starch. Scanning electron microscopy (SEM) demonstrated that hydrolysis temperature changed substantially the structural appearance of flour particles. HPAF and CRF might find applications as dry milk extender and sweetener, respectively.     

Application of Differential Scanning Calorimetry to Starch Gelatinization. II. Effect of Heating Rate and Moisture Level

The influence of heating rate on the gelatinization of wheat starch and starch/water ratio on the gelatinization of wheat, maize, waxy maize and amylomaize starches was examined. More rapid heating resulted in a lowering of the onset temperature of gelatinization for wheat starch from 52 °C at 8°C/min to 46 °C at 32 °C/min. A linear relationship was observed between moisture content and gelatinization energy for starch/water ratios between 1 :2 and 2:1. This allowed calculation of the minimum level of water necessary to initiate gelatinization of each starch. These levels were in excess of the water binding capacity for each starch and were 0.45, 0.45, 0.47 and 0.52 g water/g of wheat, maize, waxy maize and amylomaize starches respectively.     

Prediction of Degradability of Starch by Gelatinization Enthalpy as Measured by Differential Scanning Calorimetry

It was investigated whether the degradability of starch could be predicted by differential scanning calorimetry (DSC). Degradation of potato starch with a varying degree of gelatinization. of isolated starch of different origins, and of raw materials differing in origin and technological treatment was determined with α-amylase and bovine ruminal fluid. Gelatinization enthalpy and the gelatinization temperature of starch were determined by DSC. There was a good correlation between gelatinization enthalpy measured by DSC and degradation with α-amylase and ruminal fluid for potato starches with varying degrees of gelatinization and for isolated starch granules of different origins. For raw materials of different origins there was a good correlation between gelatinization enthalpy and degradation with α-amylase, whereas the correlation between gelatinization enthalpy and degradation with ruminal fluid was poor. There was a good correlation between gelatinization enthalpy and degradation with both α-amylase and ruminal fluid for (technologically treated) raw materials of one and the same origin. There was no relation between starch degradation and gelatinization temperature.     

Gelatinization Properties of Different Size Classes of Wheat Starch Granules Measured with Differential Scanning Calorimetry

The particle size distributions of wheat starch fractions, obtained after a sedimentation procedure, were characterized with a Coulter Counter. DSC-measurements of the starch samples showed that the small granules gelatinized within a broader temperature interval than the large granules. The gelatinization onset temperature of the small granules was lower, whereas the gelatinization peak temperature was higher compared to the large granules. The gelatinization enthalpy was independent of the particle size distribution. The enthalpy of the endothermic transition due to the amylose-lipid complex was found to be greatest for the small granules.     

Differential Scanning Calorimetry of Mung Bean Starch

Mung bean starch-water mixtures at water content between 13.6% and 90.2% (volume fraction of water V₁ 0.20 and 0.94) were studied by differential scanning calorimetry (DSC) and subjected to microscopic examinations afterwards. Only a monophasic endotherm appeared for water contents above 67% while for water contents between 67% and 37.3% a biphasic endotherm was found by DSC. No endothermic transition was observed for water levels below 37.3%. The melting temperature of the most perfect crystallites was correlated to the volumetric fraction of water, thus, enthalpy, entropy and extrapolated melting temperature of the transition were calculated.     

Gelatinization Transitions of Acid‐modified Tapioca Starches by Differential Scanning Calorimetry (DSC)

Tapioca starch was partially hydrolyzed by 6 % and 12 % hydrochloric acid (w/v) at room temperature for various length of time. The gelatinization transitions of the acid‐modified tapioca starches were studied using Differential Scanning Calorimetry. Starch suspensions (67 % moisture) were heated at 5 °C/min to follow melting transition of amylopectin. As the hydrolysis time increased, onset (T_o), peak (T_p) and conclusion (T_c) temperatures of gelatinization have been observed to increase, in the same order of relative crystallinity, until reaching some critical values, then decreased with the large broadening of the endotherms. The increasing of the transition temperatures corresponded to the retrogradation of the remaining partially hydrolyzed amylose followed by a decrease of these parameters corresponding to the reduction of the length of the chains of double helices amylopectin.     

Differential Scanning Calorimetry Properties and Paper-Strength Improvement of Cationic Wheat Starch

Cationic derivatives of normal corn and wheat starch were produced and investigated. Differential scanning calorimetry showed that substitution lowered the starch gelatinization temperature, the gelatinization endotherm, and the temperature of amylose-lipid V-complex dissociation. Substitution lowered the starch-iodine color and inhibited precipitation of the amylose-alcohol complex by standard fractionation techniques. Cationic derivatives of normal corn and wheat starch gave similar improvements in dry strength of paper when added at the wet-end.     

利用差示扫描量热仪研究小米淀粉及小米粉的糊化特性

采用差示扫描量热仪（differential scanning calorimeter,DSC）研究NaCl添加量、蔗糖添加量及pH值对小米淀粉和小米粉糊化特性的影响,并用SPSS软件进行相关性及显著性分析,将小米淀粉和小米粉的糊化特性进行对比。结果表明：相同测试条件下,小米淀粉的糊化温度（包括糊化起始温度T0、峰值温度Tp、糊化终止温度Tc）比小米粉糊化温度低（2.65±0.87） ℃;糊化热焓值（ΔH）比小米粉高（2.51±0.32） J/g;添加NaCl的小米淀粉及小米粉的糊化温度比添加蔗糖的糊化温度高（4.30±1.24） ℃。酸性条件抑制小米淀粉的糊化作用,碱的存在则促进体系糊化。     

Differential Scanning Calorimetry Studies on the Crystallinity of Ageing Wheat Starch Gels

The ageing of wheat starch gels stored at 4°C, 21°C and 30°C was examined by differential scanning calorimetry. Kinetics of the crystallisation process were studied using the Avrami model where it was found that the experimental data fitted the model more satisfactorily when the Avrami exponent was less than unity. At higher storage temperature the starch crystals appeared more symmetrically perfect. Addition of wheat flour pentosans to 50% starch gels did not significantly affect the kinetics of ageing. The extent of crystallisation during the ageing process depends on the moisture content of the starch gel. Crystallinity of the starch gel, measured in the temperature range 306–346°K does not occur if the solids content is below 10% or above 80% and a bell shaped curve is obtained. Reduction of the moisture content of the starch fraction of baked goods either directly or indirectly using materials competing for water, might therefore reduce the staling problem.     

DSC法研究6种莲子淀粉糊化和老化特性

利用差示扫描量热仪(DSC)结合Avrami 方程研究在4℃、储存两周的条件下,6种莲子淀粉的糊化和老化特性,探讨直链淀粉以及贮存时间对其热力学行为产生的影响,并用SPSS软件计算其相关性。结果表明：6种莲子淀粉的糊化温度、ΔH、老化焓、老化度以及老化速率存在着一定的差异,老化速率的大小顺序为太空莲＞美人红＞大紫红＞武植2号＞鄂莲＞洪湖莲,太空莲淀粉的老化速率是洪湖莲淀粉的1.36 倍;6种莲子淀粉的成核方式均为瞬间成核;4℃条件下贮存两周的莲子淀粉的老化度随着贮存时间的增加而增大;直链淀粉含量与Avrami 指数n值呈负相关,与速率常数k值、ΔH、老化焓以及冰融溶焓呈正相关。     

An Investigation of Starch/Surfactant Interactions Using Viscosimetry and Differential Scanning Calorimetry

Viscosity measurements at 60°C and differential scanning calorimetry were used to investigate the behaviour of starch/surfactant mixtures. Preparation temperature proved to dramatically modify the rheological effects observed with wheat starch and the amylose-complexing emulsifiers but was a less important variable with the more hydrophilic detergent species examined. The latter also caused quite large viscosity enhancements with waxy maize starch, effects not observed, or expected, with the emulsifiers. When 0.2-M sodium chloride was present, however, the derergents were found to behave like the emulsifiers. To account for these differences it is suggested that the detergent species are able to complex with amylopectin molecules as well as with amylose, unlike the emulsifiers which, as previously thought, only seem to complex with amylose. Calorimetry experiments did not give direct evidence, in terms of observable transitions, for the occurence of amylopectin/surfactant complexes with any of the examined surfactants. Analysis of the enthalpies associated with the several transitions observed however did provide substantial support for the suggested hypothesis.     

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.     

Differential Scanning Calorimetry of Air-Classified Starch and Protein Fractions from Eight Legume Species

The thermodynamic parameters of eight legume flours were interpreted following differential scanning calorimetry (DSC) of their air-classified starch and protein fractions. Samples of legumes from different sources, and their air-classified fractions, showed consistent peak gelatinization (T_G) and peak denaturation/aggregation temperatures for each legume species. However, enthalpies of gelatinization and denaturation/aggregation were highly variable, were not specific to species, and appeared to be determined primarily by environmental conditions during seed development. The T_G values for the starch fractions were closely correlated to the initial pasting temperatures but the viscosity characteristics of the starch slurries were not associated with DSC parameters or the amylose contents of the starch fractions. The amylograph viscosity curves lacked a distinct pasting peak and showed stable viscosities during the heating cycle.     

Scanning Electron Microscope Study on Gelatinization of Starch Granules in Excess Water

Morphological changes of starch granules from potato and corn were studied by scanning electron microscopy after they were heated progressively to different temperatures in an excess of water. A honeycomb-like structure was observed within the granules at the gelatinization temperature. It was believed that formation of this structure caused the irreversible, profound swelling and loss of the polarization crosses. Higher temperatures resulted in further swelling and melting which led to strong deformation of the granules, and ultimately the molten granules connected with each other to form a spongelike structure.     

Effects of Heating Rate and Sample Size on Differential Scanning Calorimetry Traces of Starch Gelatinized at Intermediate Water Levels

A study was made of the effects of heating rate and sample size on differential scanning calorimetry traces of aqueous suspensions containing 50% (w/w) rice starch. The variation in the thermal profiles so obtained was due to changes in the resolution of the instrument. Thus, the biphasic traces that characterise the gelatinization of starch at intermediate water levels are not due to polymer recrystallization as has been suggested elsewhere.     

Influence of Annealing on Gelatinization Properties,Retrogradation and Susceptibility of Breadfruit Starch (Artocarpus Communis)

Breadfruit starch samples were prepared after annealing at 45–60°C for 24 h and the relationship between the thermal properties and the retrogradation of starch was investigated using differential scanning calorimetry. The peak temperature (T_p) increased with increasing annealing temperature but enthalpy value was decreased with increasing annealing temperature. Twelve days after storage, according to the Avrami equation, the retrogradation rate of annealed breadfruit starch that estimated by the change of re-gelatinization enthalpy of starch was slowed when compared with the control. Furthermore, annealing treatments strongly affected the susceptibility of starch to enzymatic hydrolysis. These results showed that the increasing of T_p breadfruit starch by differences of annealing treatments could retard the retrogradation and resistant of breadfruit starch to enzymatic hydrolysis.