大米中直链淀粉含量快速测定方法的探讨

建立一种快速、准确的测定大米中直链淀粉含量的方法.在GB/T 15683-2008方法的基础上,脱脂后样品与标准品,采用130℃恒温干燥3 h的水分校准法制备试样,再经碱液分散后与碘试剂呈显色反应,于720 nm处测吸光度.该方法显色液的吸光度值与直链淀粉含量具有良好的线性关系,相关系数R2为0.999 9,相对标准偏差小于2.0%,具有良好的稳定性,并可节省检测时间40 h.与国标水分平衡法制备样品测得的结果对比分析,水分校准法具有分析速度快、准确度高、重现性好等特点,适于大批量大米直链淀粉含量分析检测.     

早籼稻中直链淀粉含量及糊化温度的测定

采用2mol/L的KOH溶液对4粒早籼稻米进行糊化,其糊化温度与标准方法测定结果相比,两者相关系数为0. 944,达极显著水平;糊化后经I2-KI显色,在620nm处测吸光度,所测样品直链淀粉含量与标准方法测定直链淀粉含量之间的相关系数为0. 966,达极显著水平。该方法具有简便及相对准确的特点,非常适合小样品早籼稻的直链淀粉含量和糊化温度的测定。     

双波长法测定山药中直链和支链淀粉含量

使用双波长分光光度法测定不同品种山药中直链淀粉和支链淀粉的含量,根据双波长法的测定原理,确定山药直链及支链淀粉的测定波长和参比波长,直链淀粉分别为624 nm和410 nm,支链淀粉分别为538 nm和758 nm。试验结果表明,该测定方法标准曲线良好。直链淀粉在0~50μg/mL质量浓度范围内其碘复合物与吸光度呈线性关系(R~2=0.999 7),支链淀粉在0~250μg/mL质量浓度范围内其碘复合物与吸光度呈线性关系(R~2=0.998 4)。山药中直链淀粉含量为0.026 mg/mL,回收率在96.72%~98.73%之间;支链淀粉的含量为0.072 mg/mL,回收率在95.74%~97.87%之间,RSD均小于1.5%。     

采用分光光度法分析酱香型白酒生产用糯高粱中淀粉的研究

样品经粉碎脱脂、干燥、分散、加入碘试剂显色定容,采用分光光度计测定吸光度.通过不同浓度的测定,得出直链淀粉在0.006～0.026 mg/mL,标准品与吸光度值有较好的线性关系,支链淀粉浓度在0.05～0.10 mg/mL,标准品与吸光度值有较好的线性关系.该方法的精密度和回收率都比较良好.     

碘显色法测定烟草中的淀粉含量

淀粉是较难测定的烟草组分之一。为了快速准确地测定烟草中的淀粉含量,借鉴食品中淀粉的测定,建立了碘显色法测定烟样中淀粉含量的方法。即在600nm处测定淀粉-碘反应液的吸光度,再根据淀粉标准曲线计算出烟草中的淀粉含量。该方法的平均回收率96 8%,CV=0 97%。与传统的酸解法和酶解法进行了比较,并采用该方法测定了18种烤烟烟叶和15种市售卷烟的淀粉含量。     

糖粉产品中淀粉抗结剂的含量测定

国家食品标准中测定淀粉的方法主要是酶水解法和酸水解法,都不适于测定糖粉中作为抗结剂使用的淀粉含量。本文采用碘显色可见分光光度法测定糖粉中抗结剂含量,将糖粉直接溶解、加热糊化、碘液显色,采用标准曲线法,基于在590 nm波长处的吸光度测定计算出抗结剂的含量。由于糖粉抗结剂淀粉和用来制作标准曲线的淀粉标样是不同来源的玉米淀粉,分子结构有所差别,其碘复合物的吸收光谱虽形状变化相同,但存在差异。本文利用它们的淀粉-碘复合物的最大吸光值之比值作为校正系数,解决待测样品与标准品的玉米淀粉不同所产生的系统偏差,测得样品抗结剂含量为3.96%。     

湘西葛根淀粉与几种植物淀粉特性比较

取葛根、土豆、玉米、水稻、糯米、白莲等植物淀粉进行特性比较,研究各种淀粉的差异,旨在快速鉴定葛根淀粉及其他淀粉。结果表明,淀粉颗粒形态因作物种类不同而有差别。直链淀粉含量以红腰豆淀粉最高为57.25%,糯米淀粉最低为5.15%;葛根的直链淀粉含量仅为16.04%。各植物淀粉的吸光度在30～60℃时无明显差异,60℃后呈现不同,葛根在85℃时吸光度为0.452,其吸光度和玉米淀粉在60℃时的吸光度相近,但在85℃时吸光度差变大。葛根的糊化温度为66～85℃。     

NaN02-Al(N03)3显色分光光度法测定香椿叶总黄酮的含量

采用NaNO2-Al(NO3)3显色分光光度法测定香椿叶提取液中总黄酮含量,并对测定条件进行研究.结果表明:以芦丁为标样,以NaN02-Al(NO3)3为显色剂,碱性条件下在510 nm处测定显色液的吸光度确定总黄酮的含量,黄酮含量在12.032 mg/L～96.256 mg/L范围内,服从比耳定律,回归方程A=0.011 9C-0.008 4,相关系数R2=0.999 8,方法的回收率为96.33%～101.20%,相对标准偏差(RSD)为1.26%;本方法简便、快速.     

双波长法测定木薯淀粉中直链和支链淀粉的含量

目的：分离纯化木薯淀粉中的直链和支链淀粉,建立同时测定木薯淀粉中直链与支链淀粉含量的双波长法。方法：采用正丁醇结晶法分离纯化直链和支链淀粉,蓝值比较法表征直链与支链淀粉的纯度;根据双波长法原理,分别在测定波长624、538nm,参比波长440、750nm处测定木薯淀粉中直链与支链淀粉含量。结果：分离纯化得到的直链与支链淀粉蓝值分别为0.979和0.144,分别落在0.8～1.2与0.08～0.22范围内,表明纯化后木薯直链与支链淀粉的纯度较高;直链淀粉在0～80mg/L质量浓度范围内其碘复合物与吸光度呈线性关系(r＝0.9992),支链淀粉在0～220mg/L质量浓度范围内其碘复合物与吸光度呈线性关系(r＝0.9995)。结论：正丁醇结晶法能有效地分离木薯直链与支链淀粉;双波长法操作快速、准确,无需分离即可同时测定木薯淀粉样品中直链和支链淀粉含量。     

铁氰化钾-紫外分光光度法检测玉米中粗淀粉含量的探讨

建立了一种快速、准确的测定玉米粮食中粗淀粉含量的方法。在碱性介质中,淀粉水解液在沸水浴条件下与铁氰化钾发生氧化还原反应生成亚铁氰化钾,于418 nm处测反应液吸光度。该方法反应液的吸光度值与直链淀粉含量具有良好的线性反比关系,相关系数为0.9996,相对标准偏差小于0.5%。铁氰化钾-紫外分光光度法具有分析速度快、准确度高、重现性好等特点,适于大批量玉米粗淀粉含量的分析检测。     

A Simple and Rapid Colorimetric Method for the Determination of Amylose in Starch Products

A method for the determination of the amylose content in starch has been developed which is based on the colorimetric measurement of the iodine complexes formed with amylose and amylopectin. The method requires measurement at only one wavelength and avoids the use of harsh dispersants for the starch. Dimethyl sulphoxide is used as the dispersant and a wavelength of 600 nm can be used for measurement of the amylose content of starches from different botanical sources. A linear relationship was obtained between absorbance and amylose concentration for mixtures of amylose and amylopectin standards, and this forms the basis of the determination. The method is rapid, simple, accurate and does not require the use of multi-component analysis of spectra, since a wavelength is chosen that suits the particular starch being analysed. It can be adapted to a micro-scale method if necessary.     

Variation in Faba Bean Amylose Content

Standard methods of amylose content determination by iodine colorimetry were adapted for use on Vicia faba. Samples of 100 mg of flour from dehulled and milled faba bean seeds were soaked overnight in a weak ammonia solution and ground in NaCl solution. The starch slurry was washed through CsCl, sodium dodecyl sulphate, water and ethanol, then dried. Amylose content was determined by iodine staining and optical absorbance at 535 and 620 nm. In a germplasm survey of 72 accessions, amylose content ranged from 17 % and 29 % of starch. Larger-seeded varieties tended to have lower amylose contents (r = 0.397, p<0.01). Variation within a cultivar, in 100 seeds of Icarus, was 15 to 26 %, almost as wide as that between cultivars. Induced mutation may be an appropriate method for enhancing variation in amylose content in this species.     

四种测定直链淀粉和支链淀粉方法的比较

对常用的直链和支链淀粉的四种测定方法进行比较分析,筛选出更适宜的方法。对单标单波长法(方法1)、单标双波长法(方法2)、双标单波长法(方法3)、双标双波长法(方法4)进行验证、精密度、回收率及样品测定试验。结果表明,根据直、支链淀粉-碘复合物吸收光谱分别确定测量波长(638、536 nm)及参比波长(430、768 nm)建立四种方法,得到回归方程,其在各浓度范围内符合比尔定律。直链淀粉中方法2、3、4较精确,方法4的相对标准偏差0.29%,回收率103.25%~103.48%;支链淀粉中方法2、3较精确,方法3的相对标准偏差最小(1.54%),回收率94.52%~94.85%。由此选择混合标准溶液,直链淀粉测定波长638、430 nm,支链淀粉测定波长536 nm,依据回归方程可求出直、支链淀粉及总含量。     

Wx基因对小麦淀粉生物合成和积累的影响

为研究Wx基因的缺失对小麦淀粉生物合成的影响,本研究以8个Wx小麦近等基因系为材料,在灌浆期的10、20、30和40 d取籽粒测定直链淀粉、支链淀粉、总淀粉的含量及合成速度。结果表明:直链淀粉、支链淀粉和总淀粉含量及积累速率在花后逐渐增加,以花后10~20 d最大,此后逐渐降低。3个Wx基因对直链淀粉的含量及积累速率的影响依次为Wx-B1Wx-A1Wx-D1;小麦Wx基因型对直链淀粉的合成及积累速率影响较大,而对支链淀粉的影响较小,其对总淀粉含量及其积累的影响主要通过直链淀粉进行。     

Mechanical Properties of White Salted Noodles from Near‐isogenic Wheat Lines with Different wx Protein‐Deficiency

Flour with a low amylose content produces a desirable texture in white salted noodles (WSN). In order to understand the impact of amylose content on noodle texture, flours of similar quality but different starch characteristics must be compared and analyzed because the characteristics of the protein contained in the flour also affect the mechanical properties of WSN. In this study, eight genotypes of near‐isogenic wheat with different compositions of the Wx‐proteins involved in amylose synthesis were used to study the relationship between the mechanical properties of WSN and their amylose content in starch. Results of the study indicated that the breaking force/breaking deformation value of WSN made from the eight lines decreased and that softer noodles were obtained when the amylose content was lower. The gels made from flours and starches of the eight lines decreased in maximum compression stress, in line with the lowering of amylose content. These results show that the mechanical properties of WSN are determined primarily by the amylose content of the flour and the properties of the starch gel. Sensory evaluations of the WSN indicated that the noodles from the flours of single‐null types, which lack either the Wx‐B1 or Wx‐D1 proteins, and doublenull types, which lack the Wx‐A1 and Wx‐D1 proteins, especially the latter, had desirable textures.     

Variability in starch physicochemical and functional properties of yam (Dioscorea sp) cultivated in Ivory Coast

An Erratum has been published for this article in Journal Of the Science of Food and Agriculture 85(5), 889 (2005). Native starches were extracted from 21 cultivars of four yam species representative of the yam population of Ivory Coast. They were first characterized for their proximate composition, starch physico‐chemical properties (amylose content, particle size distribution, crystallinity, thermal properties and intrinsic viscosity). Some functional properties (swelling, solubility and pasting behaviour and paste clarity) were then determined. Analysis of variance and principal component analysis showed that three homogenous groups could be distinguished, mainly based on starch physico‐chemical properties. The first group contained all yam starches of the D alata and the D cayenensis‐rotundata complex species. It was characterized by a large diameter grain (approximately 25 µm), a high amylose content (around 25% db), a high intrinsic viscosity (mean of 190 cm³ g^?1), and a high apparent viscosity and clarity of the paste. The second group contained the D esculenta varieties, characterized by a small granule size (diameter 6 µm), a low intrinsic viscosity (121 cm³ g^?1), a high gelatinization enthalpy change (19 J g^?1) and a low paste viscosity. The D dumetorum sample differed from the D esculenta group by having a pure A‐type crystalline form and an opaque paste. A multiple regression showed that the volume fraction of the dispersed phase and native granule size (or amylose content) could account for close to 80% of the variability of paste apparent viscosity. Gel clarity appeared mainly linked to granule size, small granules from D dumetorum and D esculenta giving the most opaque gels. Copyright © 2004 Society of Chemical Industry     

Kritische Situationen bei der Bestimmung des Substitutionsgrades von Amyloseverbindungen über ihren Kohlenstoffgehalt

Critical Situations at the Determination of the Degree of Substitution for Amylose Compounds via Their Carbon Content. The degree of substitution (DS) of amylose compounds is not always ascertainable via their carbon content. Critical situations arise for derivatives with one substitute, if the carbon contents in the latter and in pure amylose (4/9 = 0,444) are equal. In practice, one encounters that scarcely. Disubstituted amylose compounds exhibit a large number of critical situations. That depends on the DS of the determined substituent and is possible only, if the substitute that is to determine is the smaller one. the critical DS(1)=DS_kr may become every value between 0 and 3. At trisubstituted compounds critical situations arise rarely. It is a size between the both known substituents. The sum DS=DS(1)+ DS(2) of the latter is, obviously, always greater than 2. All pairs DS(1) and DS(2) are connected by linear equations. Special and common formulae were derived for prediction of critical situations for all amylose compounds.     

Determination of Amylose in Cereal and Non-Cereal Starches by a Colorimetric Assay: Collaborative Study

An improved colorimetric method, based on the well-known reaction between amylose and iodine, is described. Native starch is dissolved in ureadimethylsulfoxide and the resulting solution defatted with ethanol. An aliquot of the lipid-free solution is then reacted with iodine and the absorbance of the blue-coloured amylose-iodine complex measured, thus determining the iodine-binding capacity of starch (Blue Value). A collaborative study was conducted, according to official guidelines, to determine the method's repeatability and reproducibility: 8 participants were each sent 8 starch samples from different botanic origin for duplicate analysis. Statistical evaluation of the results gave good precision results, with an average repeatability relative standard deviation of 2.1% and an average reproducibility relative standard deviation of 5.6%. The method is, therefore, suitable to determine precisely the amylose content of native starch.     

Milling and flour pasting properties of waxy endosperm mutant lines of bread wheat (Triticum aestivum L)

Two waxy endosperm mutant lines, K107Wx1 and K107Wx2, derived from a bread wheat cultivar, Kanto 107, had a lower flour yield in test milling and a lower peak temperature in flour pasting measurement than their parent. Starch content in the kernel of waxy mutants was low, while fat and (1→3),(1→4)‐β‐D‐glucan content was high compared with cv Kanto 107, but protein content was similar for all of them. Waxy mutants had less α‐amylase activity than their non‐waxy parent, and had lower peak viscosity of flour paste in the pasting medium of water. A pasting test in silver nitrate solution increased peak viscosity in both waxy and non‐waxy flours. The viscosity of waxy flour paste rapidly increased above 60°C, while that of non‐waxy flour paste increased gradually at 60–80°C. The difference in pasting behaviour was attributed to the presence of amylose in starch granules. © 1999 Society of Chemical Industry