Phase and State Transitions in Granular Starches Studied by Dynamic Differential Scanning Calorimetry

Phase and state transitions of granular starches heated in water are studied by dynamic differential scanning calorimetry (DDSC). The DDSC results of various granular starches show a stepwise heat capacity (C_p) change in the storage C_p curve, which starts at the beginning of melting or immediately preceding gelatinization and ends before the melting reaches its peak temperature. Annealing reduces the magnitude of this stepwise change in storage C_p. After the amorphous phase is selectively removed by acid, the stepwise storage C_p is greatly reduced. The stepwise storage C_p increase is not observed when recrystallized linear short chains from enzyme‐debranched waxy maize starch are heated in water. The results show that the stepwise change in C_p observed on the granular starch is a unique property associated with the phase transition of granular structure and reflects a glass transition of the rigid amorphous regions in starch granules. The glass transition of the mobile amorphous phase in granular starch is believed to extend over a broad range of temperatures before gelatinization. A small glass transition below 0°C is directly detected by DDSC and is attributed to part of the mobile amorphous fraction in granular starch.     

Amylose Chain Association Based On Differential Scanning Calorimetry

Amylose and lipid depleted starches from amylomaize, pea, maize, wheat, potato, and waxy maize were heated from 20°C to 180°C, cooled to 4°C, and then reheated to 180°C in a differential scanning calorimeter (DSC) in excess water. Cooling curves of the amylose and starch melts showed exothermic transitions (< 70°C) attributed to the mechanism of amylose chain association. Amylose/amylopectin mixtures covering the range 0–95% amylose were similarly heated and cooled. The association of linear amylose chains was restricted by amylopectin.     

Determination of Amylose by Differential Scanning Calorimetry

A differential scanning calorimetry (DSC) method for the determination of amylose as its amylose-L-α-lysophosphatidylcholine (LPC) complex is described. Potato amylose/amylopectin mixtures covering the range of 0–95% amylose were heated in the presence of LPC, cooled and then reheated to follow melting of the amylose-LPC complexes formed during the cooling phase. A linear relationship (r = 0.98) was obtained between the amylose content of the mixtures and the enthalpies of the amylose-lipid complexes. This linear calibration was used to predict the amylose content of various native starches, rice flours, wheat flour, durum wheat semolina, and lyophilized raw potato on the basis of the melting enthalpy of their amylose-LPC complexes. Except for the potato samples, amylose contents determined by the DSC method were in good agreement with those obtained from a colorimetric assay.     

Morphology and Microstructure of Maize Starches with Different Amylose/Amylopectin Content

The morphology and microstructure of maize starches with different amylose/amylopectin ratios (waxy: 0/100; normal maize: 23/77; Gelose 50: 50/50; Gelose 80: 80/20) were studied by microscopy with ordinary and polarized light, scanning electron microscopy (SEM) and X‐ray diffraction (XRD). Generally, the granules of the amylopectin‐rich starches were more regular in shape than those of the amylose‐rich starches, but the surfaces of the amylose‐rich starches were smoother than those of the amylopectin‐rich starches. The birefringence and particle size of the granules were waxy > normal maize > G50 > G80, which also corresponds with the trend of molecular weight. Waxy and normal maize starches showed typical A‐type patterns, while G50 and G80 show B‐type patterns. Crystallinity increases with increasing the amylopectin content.     

Measurement of Food Thermal Conductivity Using Differential Scanning Calorimetry

To measure thermal conductivity of foods, an attachment to a differential scanning calorimeter was constructed. A needle probe with a 40 gauge type-T thermocouple was used to measure the temperature of a cylindrical food sample. The DSC heating pan temperature was maintained at 40°C, and then raised to 50°C. The average thermal conductivities of rutabagas, radish, parsnip, turnip, potato, green apple, and carrot were 0.447, 0.499, 0.392, 0.480, 0.552, 0.405, and 0.564 W/m°C, respectively, for a temperature range between 40–50°C. The DSC method was reliable, precise, and a relatively rapid technique for determining thermal conductivity of foods.     

Crystallization Kinetics of Amorphous Lactose as a Function of Moisture Content Using Isothermal Differential Scanning Calorimetry

Isothermal differential scanning calorimetry (DSC) was used to study the crystallization kinetics of amorphous lactose at 3 moisture contents. Each sample was heated to several temperatures between Tg and Tm. After subtraction of an induction time, the Avrami equation was used to model the data and a Lauritzen-Hoffman like expression used to fit the crystallization rates between Tg and Tm. The highest Tm/Tg ratio and crystallization rate were observed for the sample containing the most moisture. Conversely the lowest Tm/Tg ratio and crystallization rate were observed for the sample containing the least moisture. Evidence for multiple transitions was seen. The Avrami equation may not be the best way to model such data.     

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.     

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。     

Screening Potato Starch for Novel Properties Using Differential Scanning Calorimetry

Thermal and other physicochemical properties of starch from 42 potato genotypes were studied to find those with unique properties for food use, and to analyze relationships between thermal and other physicochemical properties. Onset and peak transition temperatures and gelatinization enthalpy intercorrelated. Transition temperatures intercorrelated with pasting temperature using a Brabender Visco-amylograph. Gelatinization entbalpy correlated with Brabender pasting temperature and peak paste viscosity, and onset temperature correlated with phosphorus content. Genotype E55–3.5 with highest onset and peak transition temperatures also had highest phosphorus and peak Brabender viscosity. DSC might be useful for rapidly screening samples of <1g starch for such. Potato starch DSC characteristics did not correlate with amylose, intrinsic viscosity, or water-binding. For 10 genotypes from successive years, correlations were observed for pasting temperature (r = 0.83), phosphorus content (r = 0.80), and stability ratio (r = 0.66). Direct comparison between samples from consecutive years showed good reproducibility for amylose, but not for phosphorus or pasting.     

Analysis of Variations in the Amylose Content of Grains Located at Different Positions in the Rice Panicle and the Effect of Milling

The results of the presented study indicated that the amylose content (AC) of individual rice kernels varied among grains in the same panicle and even in outer and inner layers of the same grain. The differences among the grains in panicles were 19.1% in the Indica variety “Zhenong 5” and 22.8% in the Japonica variety “Zhehu 9827”. The amylose content of the grains in the upper position or the first branches of panicles and of the early flowering grains or heavier grains was higher than that of others. Amylose content increases by 1.36% in Japonica rice variety “Zhehu 9827” and 1.92% in Indica rice variety “Zhenong 5”, when the degree of milling increases by 10%. The tendency of changes in AC was the same for grains of the Japonica and the Indica rice variety. Furthermore, for analyzing AC the grains in a panicle should carefully be selected. Errors coming from sampling could be decreased by using a multiplicity of grains rather than single‐grain samples.     

A Rapid Method for the Determination of Amylose Content by Using Differential-Scanning Calorimetry

A calorimetric procedure to measure amylose content of various starchy raw materials has been developed. It is based on the measurement by Differential Scanning Calorimetry (DSC) of the enthalpy change of the formation of complexes between amylose and add phospholipid (L -α-lysophosphatidylcholine from egg yolk) observed during cooling. Contrasting to the colorimetric determination of amylose, the DSC procedure is not influenced by the presence of amylopectin or indigenous lipids. For rice and maize flours, the amylose content determinations are very similar for both colorimetric and DSC methodologies whether the starchy material was raw or pre-cooked. But the DSC methodology is more repeatable and time saving; in particular, the defatting and starch determination steps can be omitted.     

热处理对不同直链淀粉含量的玉米淀粉理化性质的影响

采用快速黏度分析法、离心法、差示扫描量热分析法、动态流变仪分析法等,研究了干热与湿热处理对3种不同直链淀粉含量的玉米淀粉糊化性质、膨润性质、热力学性质、流变性质的影响,为淀粉的物理改性研究和加工应用提供理论依据。结果表明,干热处理使淀粉更易糊化,表现为3种玉米淀粉糊化温度降低,溶解度、膨胀度增加。湿热处理加大糊化难度,使3种玉米淀粉的糊化温度升高,膨胀度降低。热处理使玉米淀粉糊稠度、糊化焓值降低。蜡质玉米淀粉经热处理后,溶解度和老化率增加。流变性质测定结果表明,湿热处理不利于高直链玉米淀粉黏弹性凝胶的形成。     

Investigation of Cornmeal Components Using Dynamic Vapor Sorption and Differential Scanning Calorimetry

Degermed cornmeal, native starch, and corn gluten meal were individually extruded. DVS technology was used to produce isotherms and to condition extrudates to a constant moisture for Tg analysis. The DVS method results are compared to a PEC method. DSC was used to determine Tg. Isotherm and Tg data for starch and corn gluten meal were used to predict cornmeal snack sorption and Tg behavior. The Tg for extruded cornmeal, dent starch, and corn gluten meal at 18.5%db moisture content were 46.2, 49.4, and 12.7 °C, respectively. This suggests that the polymeric fractions of cornmeal (starch, protein) contribute to the Tg of cornmeal approximately based on the weight fraction of each polymer.     

State Diagram of Freeze-dried Garlic Powder by Differential Scanning Calorimetry and Cooling Curve Methods

ABSTRACT: The state diagram of freeze-dried garlic powder was developed using freezing curve, glass transition line, and maximal-freeze-concentration condition. Freezing points of garlic powder were measured by differential scanning calorimetry (DSC) and the cooling curve method, whereas glass transitions were measured by DSC. The freezing curve and glass transition line were modeled using the Clausius-Clapeyron equation, adjusted with unfreezable water, and the Gordon-Taylor model, respectively. Maximal-freeze-concentrated condition was found as X '_s (characteristic water content) = 0.82 [ X '_g (characteristic solids content) = 0.18] with the characteristic temperature of glass formation being T '_m (characteristic glass transition) =−38.6°C and T '_m (characteristic end point of freezing) =−26.0°C. Other characteristic glass transitions T "_g and T ‴_g equal to −29.3°C and −48.6°C, respectively.     

Effects of Na2CO3 and NaOH on Retrogradation of Selected Native Cereal Starches Studied by Differential Scanning Calorimetry and Nuclear Magnetic Resonance

ABSTRACT: Using differential scanning calorimetry and pulsed nuclear magnetic resonance (NMR), it was found that the presence of Na2CO3 and NaOH retarded retrogradation of aged starch (wheat, corn, waxy corn, rice, and waxy rice) gels during storage at 4°C. At the same level of addition (based on a fixed starch/water ratio), the effect of NaOH was observed to be more pronounced than that of Na2CO3. Kinetic studies using pulsed NMR showed a progressive reduction in rate of starch retrogradation with increasing concentration of alkali (up to a level of 1 g/100 starch).     

Effect of Amylose Content on Gelatinization,Retrogradation and Pasting Properties of Flours from Different Cultivars of Thai Rice

Presently, rice cultivars are categorized according to amylose content into three groups: low, medium and high amylose content cultivars. The correlation of amylose content with gelatinization properties, retrogradation, and pasting properties of eleven cultivars of Thai rice were investigated. Rice flour was prepared from milled rice by the wet grinding process. Onset (T_o), peak (T_p) and conclusion (T_c) temperatures of gelatinization, (determined by DSC) were found to be highly positively correlated with amylose levels. This correlation could be used for prediction of amylose content of rice flour. Low amylose starch could also be characterized by low degree of retrogradation (%R). The data obtained from RVA‐viscograms (peak viscosity, breakdown, setback, and pasting temperature) can be used only for characterization of the group of low amylose starches (waxy rice). It was demonstrated that low amylose rice starch provided the highest peak viscosity and breakdown and the lowest setback and pasting temperature among the groups investigated.     

Crystallization Kinetics of Lactose and Sucrose Based On Isothermal Differential Scanning Calorimetry

Isothermal Differential Scanning Calorimetry (DSC) was used to study the crystallization kinetics of freeze-dried samples of lactose and sucrose at several temperatures between Tg and Tm. The sample was rapidly heated to the required temperature. After subtraction of an induction time, the Avrami equation was used to model the data and a Lauritzen-Hoffman like expression used to fit the derived rates of crystallization over the temperature range Tg相似文献   

用差示扫描量热法测定调温针织物的热性能

介绍了差示扫描量热法（DSC）的原理、用途及用法,测定了罗纹空气层织物的相变温度和相变焓,得到了其DSC曲线图。结果表明该织物具有良好的温度调节功能。     

Detection of Animal Fat Contaminations in Sunflower Oil By Differential Scanning Calorimetry

In this study, the use of differential scanning calorimetric heating thermograms was investigated to detect the presence of lard, beef tallow, and chicken fat as contaminants in sunflower oil. Sunflower oil samples spiked separately with lard, beef tallow, and chicken fat in levels ranging from 1 to 20% (w/w) were analyzed using high performance liquid chromatography to get triacyl-glycerol profiles and differential scanning calorimetric to obtain their heating profiles. The results showed that below 20% (w/w) level of contamination, both lard and beef tallow in sunflower oil can be detected using characteristic contaminant peaks appearing in the higher temperature region (0–50°C) of differential scanning calorimetric curve. However, chicken fat contamination in sunflower oil did not show any characteristic peaks in this region, but caused changes only in the exiting thermal transitions in the low temperature region of the differential scanning calorimetric curve. Based on the characteristic differences in the peak size, shape, and position, it was also possible to make a distinction between lard and beef tallow contaminations in sunflower oil.     

用差示量热扫描方法研究米粉糊的老化

采用差示量热扫描方法研究米粉糊在低温贮存时的老化情况 ,比较了不同水分含量 (质量分数 )和添加剂对米粉糊抗老化能力的影响 .结果显示 :米粉糊在 4℃下贮存较在 2 5℃下贮存易于老化 .在米粉糊中添加 1 .0 %的蔗糖酯和 1 .0 %的CaCl2 能有效地提高米粉糊在贮存期间的抗老化性能 .