A novel triple‐wavelength colorimetric method for measuring amylose and amylopectin contents

A novel triple‐wavelength colorimetry based on the principle of iodine binding was developed to determine amylose and amylopectin contents. Detection wavelengths of different starch material were different for each method. Comparative trials were carried out by both single‐ and dual‐wavelength colorimetry. We found that single‐wavelength colorimetry could only be used to evaluate amylose content. Correlation coefficient of standard curves for amylopectin content determination was improved by increase of detection wavelength numbers. The precision and recovery coefficient was also improved by triple‐wavelength colorimetry compared to single‐ and dual‐wavelength colorimetry. Percent amylose of cassava, potato, and high‐amylose maize determined by triple‐wavelength were 19.3, 21.8, and 42.3%, respectively, and percent amylopectin were 78.9, 76.9, and 54.5%, respectively. This developed triple‐wavelength colorimetry could provide accurate data for evaluating amylose content and have potential for amylopectin content detection.     

双波长分光光度法测定烟草中的直链淀粉和支链淀粉

根据双波长比色原理,选择直链淀粉的测定波长为512和596 nm,支链淀粉的测定波长为560和695 nm,依据回归方程求出直链和支链淀粉的含量。结果表明:用双波长分光光度法测定直链淀粉和支链淀粉的含量结果准确,适用于批量分析。     

The importance of amylose and amylopectin fine structures for starch digestibility in cooked rice grains

Statistically and causally meaningful relationships are established between starch molecular structures (obtained by size-exclusion chromatography, proton NMR and multiple-angle laser light scattering) and digestibility of cooked rice grains (measured by in vitro digestion). Significant correlations are observed between starch digestion rate and molecular structural characteristics, including fine structures of the distributions of branch (chain) lengths in both amylose and amylopectin. The in vitro digestion rate tends to increase with longer amylose branches and smaller ratios of long amylopectin and long amylose branches to short amylopectin branches, although the statistical analyses show that further data are needed to establish this unambiguously. These new relationships between fine starch structural features and digestibility of cooked rice grains are mechanistically reasonable, but suggestive rather than statistically definitive.     

Textural properties and morphology of soy 7S globulin-corn starch (amylose,amylopectin)

The texture properties (hardness, adhesiveness, cohesion, elasticity) of composite gels with different ratios (0:100, 6:94, 8:92, 10:90, 12:88, and 14:86, respectively) of soy 7S globulin to corn starch (amylose, amylopectin) were studied. Furthermore, the morphology and crystal structure of the mixed gels were investigated. The results showed: the addition of soy 7S globulin could weaken the hardness of corn starch (amylose, amylopectin) and increased the adhesiveness of corn amylose significantly (p < 0.05). Generally, when the additive amount of soy 7S globulin was 10%, the composite gels of soy 7S globulin and corn starch (amylose, amylopectin) appeared to have the best consistency, cohesion, and elasticity.     

双波长法测定绿豆中的直链和支链淀粉

建立绿豆中直链淀粉和支链淀粉含量同时测定的双波长分光光度法,研究光度测定的影响因素,并对方法精密度和加标回收率进行考察。直链淀粉的测定波长和参比波长分别为610nm和498nm,支链淀粉为553nm和709nm。方法精密度良好,直链和支链淀粉平均回收率分别为94.10%和90.94%。建立回归方程并求得3种绿豆的直链淀粉含量为11.70%~12.67%,支链淀粉含量为32.70%~34.22%。     

葛根淀粉提取及直链、支链淀粉的双波长测定

以淀粉提取率为指标,采用正交实验研究了葛根淀粉的加工工艺,并确定了最佳工艺参数为:料水比为2:17,浸泡液的pH为8.5,浸泡时间为1h;同时采用双波长分光光度法对葛根中直链淀粉和支链淀粉的显色反应和光度测定的最佳条件进行了详细的考察,根据吸收光谱,确定直链淀粉的测定波长为617nm和476nm,支链淀粉的测定波长为415nm和532nm,建立回归方程并求得葛根淀粉中直链淀粉的含量为18.29%,支链淀粉的含量为77.24%。      

Some physical and nutritional characteristics of genetically modified potatoes varying in amylose/amylopectin ratios

Transgenically modified potatoes with a large spread in amylose/amylopectin ratios were analysed both as tubers and in the form of isolated starch. Different microscopic techniques were used to study starch granules and tuber tissue. Starch gelatinisation properties and recrystallisation of amylopectin and amylose were studied by differential scanning calorimetry. Starch bioavailability and resistant starch (RS) were evaluated using enzymatic in vitro procedures. Glycaemic indices (GI) were predicted from low molecular weight carbohydrates (LMWC) contents and the in vitro hydrolysis rate of the starch moiety. For many of the examined parameters, differences of varying magnitude were found between the potato lines, especially for high amylose lines. High amylose starch granules had irregular shapes and showed only a limited swelling. Moreover, contents of RS and recrystallised amylose were elevated. GI’s for the starch moiety were reduced, though elevated contents of LMWC caused a high over-all predicted GI.     

马铃薯中直链淀粉和支链淀粉含量测定方法的优化

本文以马铃薯为原料,优化马铃薯淀粉预处理方法,改善直链淀粉和支链淀粉的测定波长,完善淀粉的测定方法。采用直链淀粉和支链淀粉标准品绘制标准曲线,以未经过脱糖脱脂、脱脂、脱糖、先脱糖后脱脂、先脱脂后脱糖为样品预处理方法,分析不同预处理方法对直链淀粉和支链淀粉含量的影响。结果表明,直链淀粉和支链淀粉的最大吸收波长分别为609 nm和546 nm,参比波长分别为473 nm和734 nm。标准方程回归系数均大于0.999。先脱脂后脱糖样品颗粒溶解性好,支链淀粉含量为70.27%,直链淀粉含量为12.38%。因此,采用先脱脂后脱糖处理样品,在双波长法条件下可以准确测定马铃薯中直链淀粉和支链淀粉含量。      

Effects of molecular characteristics of tea polysaccharide in green tea on glass transitions of potato amylose,amylopectin and their mixtures

Tea polysaccharide (TPS) is attracting more attention gradually in many fields due to its particular biological properties. To further elucidate the functions of TPS to starch-based foods, experiments were carried out using mixed amylose/amylopectin/TPS system as a model. The effects of TPS in green tea on the glass transition temperatures (Tgs) of the mixtures with different amylose/amylopectin ratios at low water contents were investigated using high-speed differential scanning calorimetry (Hyper-DSC). The results showed that the Tgs of amylose, amylopectin and their mixtures decrease with increasing concentration of TPS. It is suggested that the addition of TPS has plasticizing effects on the structures of amylose and amylopectin on the molecular level. Based on the molecular characteristics of TPS, the results in this study indicated that TPS is a homogeneous and spherical polymer with branch in solution, which can increase free volume and molecular movement of amylose and amylopectin chains. TPS can also produce greater electrostatic repulsion and decrease association among macromolecules, thereby resulting in the decrease of the Tgs of amylose, amylopectin and their mixtures.     

Amylose and amylopectin molecular fractions and chain length distribution of amylopectin in 12 varieties of Ghanaian sweet potato (Ipomoea batatas) flours

Sweet potato (Ipomoea batatas) is a commonly cultivated root crop in tropical and subtropical regions, including Ghana. Different varieties of sweet potato have been bred, in order to expand its utilisation within the food and industrial sector. This study analysed flours made from 12 recently developed Ghanaian sweet potato varieties in terms of their amylose and amylopectin molecular fractions and amylopectin chain length distribution. Starch content of the sweet potato flours ranged from 49 to 77 g/100 g dry matter, with 11 of the varieties containing above 60 g/100 g dry matter. An orange-fleshed variety, Apomuden, had the lowest amount of starch (48.9 g/100 g dry matter), while the cream-fleshed variety Histarch had the highest (77.3 g/100 g dry matter). The flours from the 12 sweet potato varieties had intermediate amounts of amylose, within the range 10–30 g/100 g dry matter, and showed typical molecular distribution according to size-exclusion chromatography (SEC). The fine structures of amylopectin, as revealed by anion-exchange chromatography, contained features common for starches of C-type X-ray pattern, but some structural differences were also observed.     

双波长法测定籼米中直链淀粉和支链淀粉含量

建立了双波长法测定籼米中直链淀粉和支链淀粉含量的方法.按照双波长测定的等吸收点波长法确定两种淀粉的测定波长和参比波长,直链淀粉的分别为596 nm和449 nm,支链淀粉的分别为533 nm和705 nm.直链淀粉浓度在20～60 mg/L线性良好,R=0.999 8;支链淀粉浓度在100～200 mg/L线性良好,R=0.999 7.籼米中直链淀粉和支链淀粉质量分数分别为24.2％和50.5％.     

双波长分光光度法测定新鲜怀山药中直链与支链淀粉的含量

以新鲜怀山药为原料制备山药粉,通过石灰水浸泡工艺提取山药淀粉。以碘为显色剂,扫描直链淀粉和支链淀粉与碘形成复合物的全波长吸收光谱。利用不同浓度的直链与支链淀粉标准品分别与碘形成复合物从而得到淀粉含量与吸光度差值之间的线性关系制作出标准曲线,根据标准曲线计算出样品中直链淀粉与支链淀粉的含量。根据双波长选择原理和扫描光图谱,确定直链淀粉的测定波长为 560nm,参比波长为 659nm; 支链淀粉的测定波长为600nm,参比波长 532nm。实验说明直链淀粉与支链淀粉的测定相对标准偏差分别为 0.27% 与 0.63% 、回收率也分别达到了96.18%与97.89%,检出限分别为0.09mg/L 与 1.58mg/L,再经准确性分析验证了用双波长法测定山药淀粉中直链淀粉与支链淀粉的含量的检测方法具有较为准确的效果。     

磷酸酯化直/支链淀粉的性能测试与比较

为了研制应用性能可以在一定范围内定量调整的磷酸酯化淀粉,采用干法制备了磷酸酯化直链淀粉和磷酸酯化支链淀粉,并用IR光谱、X-衍射光谱进行了表征;测定和比较了质量比分别为3∶1、1∶1、1∶3的磷酸酯化直/支链淀粉的透光率、抗凝沉性、冻融稳定性、吸水性、吸油性、黏度及黏度热稳定性等应用性能。试验结果表明:磷酸酯化直/支链淀粉的透光率、抗凝沉性、冻融稳定性、吸水性、黏度及黏度热稳定性随着磷酸酯化支链淀粉比例的增加而逐渐增大,吸油性则逐渐减小。     

Relationship between the structure,physicochemical properties and in vitro digestibility of rice starches with different amylose contents

The in vitro digestibility and molecular and crystalline structures of rice starches (Long-grain, Arborio, Calrose, and Glutinous) differing in amylose content were investigated and the relationship between the structure and in vitro digestibility of starch was studied. Long-grain showed the highest amylose content (27.2%), whereas Glutinous showed the lowest amylose content (4.2%). Long-grain had the highest average amylopectin branch chain length (18.8) and proportion (8.7%) of long branch chains (DP ≥ 37), and the lowest proportion (26.9%) of short branch chains (DP 6–12). Among the non-waxy rice starches (Long-grain, Arborio, and Calrose), Calrose had the lowest average chain length (17.7) and the lowest proportion (7.1%) of long branch chains (DP ≥ 37). The relative crystallinity of rice starch followed the order: Glutinous (33.5%) > Calrose (31.4%) > Arborio (31.0%) > Long-grain (29.9%). Long-grain had the highest gelatinization temperature and the lowest gelatinization temperature range, whereas Glutinous showed the highest gelatinization temperature range and gelatinization enthalpy. Arborio had the highest melting enthalpy for amylose–lipid complex among the tested rice starches. Pasting temperature, setback, and final viscosity increased with increasing amylose content, whereas the peak viscosity and breakdown showed negative correlations with amylose content. The rapidly digestible starch (RDS) content of the tested rice starches followed the order: Glutinous (71.4%) > Calrose (52.2%) > Arborio (48.4%) > Long-grain (39.4%). Contrary to this, the slowly digestible starch (SDS) and resistant starch (RS) contents showed an opposite trend compared to RDS. Digestibility (RDS, SDS, and RS) of the rice starches was significantly correlated (p ≤ 0.05) with amylose content, proportions of DP 6–12 and DP 13–24, relative crystallinity, intensity ratio (of 1047 cm⁻¹ to 1022 cm⁻¹ from Fourier transform infrared spectroscopy), swelling factor, amylose leaching, onset temperature of gelatinization, gelatinization temperature range, gelatinization enthalpy, pasting temperature, peak viscosity, breakdown, setback, and final viscosity.     

双波长分光光度法测定新鲜怀山药中直链与支链淀粉的含量

以新鲜怀山药为原料制备山药粉,通过石灰水浸泡工艺提取山药淀粉。以碘为显色剂,扫描直链淀粉和支链淀粉与碘形成复合物的全波长吸收光谱。利用不同浓度的直链与支链淀粉标准品分别与碘形成复合物从而得到淀粉含量与吸光度差值之间的线性关系制作出标准曲线,根据标准曲线计算出样品中直链淀粉与支链淀粉的含量。根据双波长选择原理和扫描光图谱,确定直链淀粉的测定波长为 600nm,参比波长为 532nm; 支链淀粉的测定波长为560nm,参比波长 659nm。实验说明直链淀粉与支链淀粉的测定相对标准偏差分别为 0.27% 与 0.63% 、回收率也分别达到了96.18%与97.89%,检出限分别为0.09mg/L 与 1.58mg/L,再经准确性分析验证了用双波长法测定山药淀粉中直链淀粉与支链淀粉的含量的检测方法具有较为准确的效果。      

Effects of cross-linking and low molecular amylose on pasting characteristics of waxy corn starch

The action of amylose within the granule of normal corn starch is investigated by changes in pasting characteristics of waxy corn starch in a Rapid Visco Analyzer (RVA), using addition of soluble amylose (DP = 18) and cross-linking with epichlorohydrin. Although waxy corn starch, containing no amylose, did not show an effect of addition of amylose on pasting characteristics, by cross-linking with epichlorohydrin, the pasting peak viscosity and breakdown were greatly enhanced and set-back (viscosity increased in the cooling process after gelatinization) was generated. The cross-linking depressed the disintegration of starch granules in the swelling process, with amylose interaction, resulting in RVA pasting characteristics similar to those seen with normal corn starch containing amylose. Set-back was essentially caused by rearrangement among modified amylopectins. Addition of sodium dodecyl sulfate (SDS) to the RVA more efficiently enhanced the effect. This indicated that amylose in normal corn starch interacts with amylopectin through locally strong linkages.     

甘薯块根膨大过程中质构特性和淀粉直/支比的研究

甘薯块根膨大过程中质构特性和淀粉组分的变化对甘薯的品质和用途有着重要影响。本研究选取3种甘薯类型和4个时期,通过质地多面分析法(TPA)和双波长碘比色法,分析其质构特性和淀粉直链淀粉和支链淀粉比值(淀粉直/支比)随块根膨大的变化规律。结果表明,甘薯淀粉直/支比在扦插后80天开始下降,至扦插后110天达到谷值,之后小幅回升;整体上,甘薯扦插后的天数与淀粉直/支比、内聚性和弹性呈显著负相关(r =-0.390, r= -0.367, P <0.05;r= -0.634, P <0.01);与硬度呈显著正相关(r= 0.590, P <0.01)。淀粉直/支比与块根的内聚性、弹性和咀嚼性呈显著正相关(r =0.368, P <0.05; r= 0.463, r= 0.642, P <0.01);综合分析发现,扦插后80~110天（块根膨大高峰期至膨大后期）收获的甘薯适合水果型(生食型)甘薯的开发。     

Rheological properties and phase transition of cornstarches with different amylose/amylopectin ratios under shear stress

The rheological properties and phase transition of cornstarch with low moisture content under shear stress was investigated using a mixer with twin‐roller rotors by the variation of torque as functions of temperature and time. Cornstarches with different AM/AP ratios (wx: 4:96, maize: 29:71, Gelose 50: 62:38, and Gelose 80: 77:23) were used as model materials in the experimental work. The results showed that, as the AM content increased from 0 to 77%, the maximum torque increased from about 54 to 66 N/m and the final torque increased from about 27 to 47 N/m, respectively, and a longer mixing time was required to achieve a stable state (constant torque value). Microscopic and differential scanning calorimetry (DSC) studies showed that the phase transition reflected by changes of birefringence and endotherms could well be associated with the torque curve measured by the mixer. The higher gelatinization temperatures of the starches with higher AM content, and especially the existence of multi‐phase transitions at high temperatures, could explain the rheological behaviors detected by the mixer. The technique can be used to study the starch melting and destructuration under shear stress with low moisture content (<45%), which represents the most of extrusion conditions for starch‐based materials.