百合淀粉糊化特性的研究

以自制的卷丹百合淀粉为材料,运用差示扫描量热仪对百合淀粉糊化特性进行了研究。结果表明,百合淀粉具有糊化温度低、糊化热焓小、易糊化等特点。整个糊化过程可分为两个阶段,低温(<63.79℃)糊化的特点是速率低,而且不能彻底糊化;高温(>63.79℃)糊化的特点是速率高,可瞬间完成,类似于高活化能的鸡蛋蛋白变性作用。      

蕨根淀粉颗粒形貌与糊化黏度特性

以马铃薯淀粉和红薯淀粉为对照,研究了蕨根淀粉的颗粒形貌及糊化黏度特性。蕨根淀粉颗粒多为圆形或椭圆形,少数呈棒状,颗粒表面光滑。颗粒大小差异较大,粒径为5~31μm。蕨根淀粉颗粒具有可见偏光十字,偏光十字位于颗粒一端,呈"Ⅹ"。蕨根淀粉的起糊温度明显低于红薯淀粉,与马铃薯淀粉相当。蕨根淀粉糊具有较好的热稳定性,较高的回生值,适宜加工粉丝类产品。蔗糖、NaCl、碱面和明矾的添加及pH值对蕨根淀粉糊化特性有影响。蔗糖使蕨根淀粉糊黏度增大;NaCl可提高蕨根淀粉糊的热稳定性,延缓体系老化;碱面、明矾的添加使蕨根淀粉糊的热稳定性下降;蕨根淀粉糊耐酸性差,在酸性条件下,蕨根淀粉发生明显水解作用,体系黏度降低。     

蕨根淀粉的颗粒形态与糊化特性研究

为探讨蕨根淀粉的糊化性能,以蕨根为原料,采用湿法提取淀粉,并进行提纯,对蕨根淀粉的颗粒形态、糊黏度曲线、糊冷热黏度、糊透明度、抗剪切性、冻融稳定性、凝沉性及抗老化性等特性进行了研究,并与玉米淀粉进行了比较。结果表明:扫描电镜观察蕨根淀粉颗粒表面光滑,大小均匀,呈椭圆或鹅卵石形,粒径范围10.23~26.14μm,长轴平均粒径19.09μm,稍大于玉米淀粉;布拉班德糊黏度曲线表明蕨根淀粉糊化温度为68.9~89.4℃,低于玉米淀粉糊,而峰值黏度为611 mPa·s,高于玉米淀粉;与玉米淀粉相比,蕨根淀粉稳定性好、透光性好、冻融稳定性好、抗老化性强,而凝沉性较弱、抗剪切性较差。蕨根淀粉较适于速溶、快餐、冷冻食品加工。     

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。     

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。     

稻米糊化温度DSC试验条件的优化及相关分析

差示扫描量热仪是目前米粉糊化温度测定中最为准确的一种方法,而目前研究中所使用的样品量、加水量和升温速率有着较大差异,利用正交设计方法确定了TAQ20型差示扫描量热仪的最小相对标准偏差试验条件。结果表明样品量、加水量和升温速率等3个因素的变化对糊化温度结果有一定的影响。比较各个组合的相对标准偏差值,选出3个因素的最佳组合为14μL水、3.0 mg米粉和10℃/min升温速率。应用这一测定条件,测定了21份籼稻米粉的糊化温度。相关分析表明,糊化温度与碱消值和直链淀粉含量的相关系数分别为r=-0.75***和r=0.51*,说明糊化温度与碱消值之间存在极显著负相关、与直链淀粉含量则表现为显著正相关。     

抗性淀粉糊化规律的研究

采用差示扫描量热分析技术(DSC)对原淀粉及各抗性淀粉样品的糊化温度及糊化热效应进行了测试和研究。DSC吸热曲线显示,经处理过的样品晶体完全不同于原淀粉晶体。抗性淀粉的吸热曲线除了在85℃左右出现一个小峰外,在125℃左右又开始出现吸热峰,相变高峰温度约在155℃。随着样品中抗性淀粉含量的升高,曲线中第二吸热峰的相变焓逐渐升高,相变高峰温度也遵循同样的规律。     

莲藕淀粉糊化温度的测定

对莲藕糊化温度的三种测定方法展开比较,得出偏光十字消失法测得莲藕淀粉的糊化温度为63.8～71.8℃,差示扫描量热分析法(DSC)测得糊化温度为63.5～74.7℃,动态流变仪法测得糊化温度为60.1～66.2℃。得出结论:在一般的实验室里,品种相同的情况下,应用偏光十字消失法是较为准确且经济的测定方法;如果条件允许,动态流变仪法是相对精确的方法。     

莲藕淀粉糊化温度的测定

对莲藕糊化温度的三种测定方法展开比较,得出偏光十字消失法测得莲藕淀粉的糊化温度为63.8～71.8℃,差示扫描量热分析法(DSC)测得糊化温度为63.5～74.7℃,动态流变仪法测得糊化温度为60.1～66.2℃。得出结论:在一般的实验室里,品种相同的情况下,应用偏光十字消失法是较为准确且经济的测定方法;如果条件允许,动态流变仪法是相对精确的方法。      

饲料含水率对淀粉糊化及蛋白变性温度的影响

在过量水的条件下,用DSC测定了小麦淀粉、小麦面粉、大豆粕、鱼粉,以及用这些组分配合而成的对虾饲料等试样加热时的吸热曲线,并以此辩认了这些原料中所含淀粉及蛋白质的吸热峰值。在不同的水分含量条件下,测定了这些峰值的变化,其结果被引用于解释常用制粒条件(水分17%,温度93℃)下所得颗粒饲料的糊化度仅为35%左右的原因。     

蕨根淀粉糊的老化特性及影响因素

实验研究了蕨根淀粉糊的老化特性及影响因素。结果表明:蕨根淀粉糊静置贮藏过程中会发生老化现象,在4℃下老化比常温下快;常温下贮藏蕨根淀粉比马铃薯淀粉和玉米淀粉粘度变化稍大,4℃下贮藏24h内蕨根淀粉糊比马铃薯淀粉和玉米淀粉糊的粘度变化小,但24h后稀化比马铃薯快;不同浓度蕨根淀粉糊的老化现象有一些差别;加入蔗糖和葡萄糖能减弱粘度变化趋势,葡萄糖和蔗糖对透光率的减小有一定的阻止能力,浓度达20%时效果明显;pH和盐类也对老化有影响。     

Effect of Sodium Dodecyl Sulphate on the Physicochemical,Thermal and Pasting Properties of Cassava Starch

The effect of different concentrations of sodium dodecyl sulphate (SDS) on cassava starch properties after complexation and in situ addition were studied. The swelling volume of the starch‐SDS complexes increased to a maximum of 100 mL/g with increase in concentration of SDS (even at 0.004 mol SDS) with a corresponding decrease in solubility. During in situ addition also, a similar but gradual behaviour was observed for swelling volume and solubility. The apparent and total amylose contents showed an irregular trend. The soluble amylose content decreased with increase in concentration of SDS. In vitro enzyme digestibility of starch‐SDS complexes was significantly lowered compared to that of native starch. The water‐binding capacity showed an initial decrease followed by a significant increase at higher concentrations of SDS. DSC studies showed that in addition to the gelatinisation endotherm, a peak corresponding to the melting of the starch‐SDS complex was obtained in the case of in situ addition of the surfactant. The peak viscosity of starch during in situ addition of SDS exhibited a rapid increase except at the highest concentration. The peak viscosity of starch‐SDS complexes underwent an initial reduction followed by a gradual increase at higher concentrations. The breakdown, setback and pasting temperature were also affected.     

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.     

The effect of electrostatic interactions on pasting properties of potato starch/xanthan gum combinations

The effects of electrostatic interactions on pasting properties of potato starch (PS)/xanthan gum (XG) combinations were investigated. The RVA peak viscosity of combinations was decreased firstly and then increased with the adding of XG. The analysis and regression model performance of RVA measurement showed that there was the relationship between pasting properties of combinations and XG concentrations. Electrostatic repulsions between native potato starch or anionic modified potato starches (AP) and XG could be present by decreasing peak viscosity, but the pasting temperatures showed increasing trend. However, electrostatic attractions between cationic modified potato starch (CP) and XG showed the opposite effect. Negative zeta potential determination for combinations (− 54.6 mv) was higher than PS (− 35.2 mv) illustrated that combinations had more electronegativity and stability, in addition a phase-separated microstructure was exhibited in the combinations determined by Zeta potential results. SEM micrographs presented that XG film attached to the surface of PS granules, which inhibited the starch granules destruction and leaching of amylase. The electrostatic repulsion leaded to more stability of the three dimensional network structures of combinations. The strong electrostatic interactions between PS and XG were found to play an important role on the pasting properties of the combinations.     

花果山野生蕨菜多糖和黄酮的提取及含量测定

以连云港花果山野生蕨菜干粉为原料,通过正交试验选择最佳提取条件,用分光光度法测定总黄酮和多糖的含量。结果表明：蕨菜中多糖提取的最优条件为蕨菜与水料液比1:20(g/mL)、提取温度90℃、提取时间1.5h、提取次数2 次。新鲜蕨菜干粉中多糖含量为1.39%,三月枯蕨菜干粉中多糖含量为7.08%;提取蕨菜中黄酮类物质的最优条件为蕨菜与70% 乙醇比1:10(g/mL)、提取温度90℃、提取时间2h、提取次数2 次,测得新鲜蕨菜干粉中总黄酮含量为4.90%,三月枯蕨菜干粉中总黄酮含量为3.11%。     

差示扫描量热法及其发展趋势

差示扫描量热仪可以测定多种热力学和动力学参数,如比热容、反应热、转变热、相图、反应速率、结晶速率、高聚物结晶度及样品纯度等。该仪器具有使用温度范围宽(-175~500℃)、分辨率高和试样用量少的优点。本文论述了差示扫描量热仪的特点、目前我国与差示扫描量热法相关的标准以及方法的未来发展趋势。未来在聚合物的结晶性研究和相变材料的热焓变化测量方面,差示扫描量热法(differential scanning calorimetry,DSC)会有更广泛的应用。在物质的鉴别方面,熔点的精确测量也会起到很重要的辅助作用。未来期待温度范围更宽的DSC仪器的出现,同时,红外-气相-差式扫描联用技术及热重-差式扫描量热联用仪器的更进一步发展会使得联用技术在未来得到更多的重视。     

Physicochemical and pasting properties of maize as affected by storage temperature

Maize grains are used as raw material in various food products. In countries where the production is seasonal, the grains must be stored throughout the year in order to provide sufficient maize supply for the food industries and consumers. During storage, the environmental temperature is considered as one of the most critical variables that affects grain quality. This study aimed to evaluate the effects of various storage temperatures (5, 15, 25 and 35 °C) on the proximate composition, pH, fat acidity, percentage of grains infected by molds, grain color, protein solubility and pasting properties of maize stored for 12 months. Grains stored at 35 °C during the 12 months period showed the greatest decrease in grain yellowness, pH, protein solubility and breakdown viscosity. An increase in disulfide bonds within the protein structure and interaction between starch and non-starch components seems to be responsible for the changes in protein solubility and pasting properties determined in maize during the storage period. Fat acidity and the percentage of grains infected by visible molds were concluded to be very dependent of moisture content. The result of this study demonstrated that the minimum temperature of 5 °C was able to maintain the quality of maize stored for up 12 months.     

Isolation,composition, morphological and pasting properties of starches from rice cultivars grown in Nigeria

The isolation, composition, morphology and pasting properties of rice starches from different rice cultivars (N2R, Nerica II rice; IGR, Igbemo rice; ILR, Ilaje rice; and EAR, Efon Alaye rice) were studied. The starches were isolated from their flours by using a modified deproteination method in 0.1% NaOH. The highest starch yield of 65% was obtained from EAR with a residual protein of 0.41% and lowest starch yield of 45.70% from IGR with a residual protein of 0.42%. The AAM concentration of rice starches ranged from 21.88 to 26.04%. The sizes of the starch granules obtained from SEM were between 3 and 8 µm, some of the granules were individual (single) while others were fused (compound granules). The starch granules were small, polygonal and irregular in shape. The pasting parameters were evaluated using rapid visco analyser (RVA). Significant differences were observed in individual pasting parameters such as peak viscosity (PV), breakdown viscosity (BV), final viscosity (FV) and setback viscosity (SV). Cooked ILR starch had the highest PV (279.69 RVU; rapid viscosity units) and BV (52.50 RVU) when compared to the other starches. In contrast, N2R showed the highest FV (329.92 RVU) and SV (102.50 RVU), the latter due to the high concentration of AAM. The results revealed that cultivar has an effect on composition and pasting properties of rice starch.     

Gelatinization and retrogradation of native starch from cherimoya fruit during ripening, using differential scanning calorimetry

The aim of this work was to determine the physicochemical characteristics of non-conventional starch from cherimoya fruit in order to suggest possible applications of these polymers in various food systems. The influence of the stage of ripening on thermal behaviour of cherimoya fruit starch was also analysed. Starch was visualized by cryo-SEM, and gelatinization and retrogradation properties were studied by differential scanning calorimetry (DSC). DSC was also used for accurate determination of the starch content of cherimoya dry matter. The calorimetric profile for cherimoya fruit starch showed a peak temperature (gelatinization) over a range from 63.7 to 65.2 °C and enthalpy values between 14.8 and 15.9 J g⁻¹ during ripening. Neither temperatures nor melting enthalpy of recrystallized amylopectin differed over the ripening period. The recrystallization rate, as measured by changes in melting enthalpy with time according to the Avrami model, showed a very slight retrograde tendency. It is suggested that these characteristics could be useful in products where good quality and long shelf-life are required.