Carboxymethyl Cocoyam Starch: Synthesis,Characterisation and Influence of Reaction Parameters

Twenty carboxymethyl starch derivatives of cocoyam starch were synthesized under different reaction conditions. The influences of sodium hydroxide concentration, sodium monochloroacetate concentration, water, type of organic solvent, reaction time and temperature were evaluated for degree of substitution (DS) and reaction efficiency (RE). The optimal ratio of moles of NaOH per mole anhydroglucose unit (AGU), n_NaOH/n_AGU was 1.62. Increases in ratio of moles of monochloroacetate (n_SMCA) to mole of AGU (n_AGU) increased the DS progressively. The ratio of water to solvent (isopropanol, IPA) in the reaction media was optimal at H₂O/IPA 0.16. Both RE and the DS increased with increase in reaction time within the studied time range (1‐4 h). Increases in temperature enhanced both reaction efficiency and DS. Among the solvents studied, an isopropanol – water medium produced the optimal result. The starch paste clarity improved remarkably after carboxymethylation. Wide angle X‐ray diffractometry revealed that starch crystallinity was reduced after carboxymethylation. ¹³C‐NMR showed peaks at δ = 180.42 ppm, 80.35 ppm, 77.77 ppm, and 71.96 ppm, which were assigned to C‐O, substituted C‐2, C‐3 and C‐6, respectively. In addition, three signals appeared at δ = 74.16 ppm, 73.42 ppm and 72.59 ppm and they were assigned to the CH₂ in the carboxylate substituents.     

Influence of Soluble Polymer Residues in Crosslinked Carboxymethyl Starch on some Physical Properties of its Hydrogels

Crosslinked carboxymethyl starch (CMS) was synthesized from potato starch in a single‐step procedure with mono‐ (MCA) and dichloroacetic acid (DCA), using the well‐known Williamson reaction. The products varied in their degree of substitution DS (average number of carboxymethyl groups per monomer unit) and crosslinker ratio F_z (number of crosslinker molecules offered per monomer unit). After neutralizing and removal of the formed salt, one part of the synthesized CMS networks was pre‐swollen in water in an additional purification step in order to wash out unlinked, soluble polymer chains. The rest of the product remained unwashed. Different swelling experiments were performed with the two samples, before being dried and ground. Both, the Free Swelling Capacity (FSC) and the Absorption Capacity Under Mechanical Load (AUL) of the hydrogels were strongly influenced by chemically unlinked CMS chains that were only physically entangled in the network structure. These mobile polymer segments were responsible for a significant weight loss of the swollen, unwashed hydrogels over the course of time. Rheological oscillatory experiments showed that, in order to achieve comparable values for the storage and loss moduli (G′ and G′′), the polymer content of an unwashed hydrogel had to be more than twice as high as that of the corresponding purified product. By using a special rheological test procedure with a cyclic temperature program, the long‐term stability of CMS gels could be measured and verified.     

槲皮素-羧甲基甘薯淀粉酯的合成

以甘薯淀粉为原料,依次经过羧甲基化、槲皮素共价修饰两步改性,得到槲皮素-羧甲基甘薯淀粉酯,并采用单因素及响应面试验考察制备工艺条件对产物取代度的影响。单因素试验结果表明,其取代度随反应底物配比（N槲皮素/AGU）（X1）的增加而增加,随活化试剂与羧甲基甘薯淀粉脱水葡萄糖基的物质的量比（NEDC/AGU）（X2）及反应体系pH值（X3）的增加呈先增加后降低的趋势;响应面试验结果表明,NEDC/AGU及反应体系pH值对取代度有极显著影响（P＜0.01）,而N槲皮素/AGU以及二次项和交互项对取代度的影响不显著（P＞0.05）。得到最佳工艺条件为羧甲基甘薯淀粉质量浓度51?g/L、N槲皮素/AGU?2∶1,NEDC/AGU?1.8∶1、反应体系pH?7.4,可制得最大取代度（0.114?9）的槲皮素-羧甲基甘薯淀粉酯。通过检测槲皮素从产物的水解释放确认产物的合成。     

Influence of the Cross‐linking Agent on the Gel Structure of Starch Derivatives

Hydrogels were synthesized through cross‐linking of carboxymethyl starch (CMS; Degree of Substitution DS = 0.45) using polyfunctional carboxylic acids (malic, tartaric, citric, malonic, succinic, glutaric and adipic acid). The syntheses used a cross‐linking agent ratio (ratio of the number of cross‐linking agent molecules to the number of monomer units constituting the polymer) of F_Z = 0.05. After cross‐linking the gels were dried, ground and then hydrogels of a polymer concentration of 4 mass‐% were produced. These CMS‐hydrogels were then rheologically characterized using dynamic oscillatory measurements. From measurements of the plateau region storage modulus G'_P, the network parameters molar mass between two entanglement points M_e (M_e ranging from 9.318 (citric acid) to 281.397 g/mol (tartaric acid)), the cross‐link density ν_e and the distance between two entanglement points ξ were calculated. Using carboxylic acids without other functional groups, a maximum in gel sturdiness is found at a spacer length of two CH₂‐groups. The evaluation of the loss factor tan δ for the CMS‐hydrogels showed that values of tan δ = 0.2 varied only slightly with the frequency ω. Flow curves showed a pseudopIastic flow behavior for all CMS‐hydrogels (the shear viscosity η declining over five decades in the range of the shear rate γ of 10⁻³ to 10³ s⁻¹) The different polyfunctional carboxylic acids have a strong influence on the sturdiness of the synthesized CMS‐hydrogels.     

Starch Functionalized by Chloroacetate Groups: Coupling of Bioactive Salicylic Acid

Starch partially functionalized with chloroacetate groups was obtained by reaction of starch with chloroacetyl chloride using the N,N‐dimethylacetamide/5%lithium chloride system as solvent and pyridine as catalyst. The coupling of salicylic acid to starch functionalized with chloroacetate groups was carried out by reaction with the sodium salt of salicylic acid. The structures of chloroacetylated starch and starch‐salicylic acid adducts were determined by means of FTIR, ¹H‐NMR and ¹³C‐NMR spectra. The degree of substitution per anhydroglucose unit (AGU) of chloroacetylated starch was calculated from the chloride content and ranged from 0.52 to 2.34, depending on the ratio of chloroacetyl chloride to starch. The hydrolysis of starch‐salicylic acid adducts in a heterogeneous phase showed that the release of sodium salicylate from tablets is dependent on the hydrophilic character of the adduct and on the pH value of the medium.     

The Role of Reaction Parameters on the Preparation and Properties of Carboxymethyl Cassava Starch

The role of reaction variables on carboxymethylation of cassava starch was investigated using a statistically experimental design approach. The reaction was carried out in an isopropanol‐water mixture at 40°C for 3 h. The reaction parameters under investigation included water fraction in the reaction medium, the ratio of sodium hydroxide to anhydroglucose unit (AGU) and the ratio of sodium monochloroacetate (SMCA) to AGU. The dependent responses were degree of substitution (DS) of CMS and the reaction efficiency (RE) of the carboxymethylation. Carboxymethyl cassava starches with DS in the range of 0.01 to 0.86 were prepared. The result from regression analysis indicated that the most important factors in controlling the DS of CMS were sodium hydroxide and SMCA contents followed by water content. Response surface plots suggested that the optimal levels of sodium hydroxide and water content to achieve CMS with high DS were at the intermediate values. Similar effects of sodium hydroxide and water content were also observed on the RE while SMCA content had a negative effect; increasing SMCA content resulted in lower RE. The optimal conditions to achieve the highest DS and RE were found to be at a water content of 17–19% with a molar ratio of sodium hydroxide to AGU of 1.8–1.9 and a molar ratio of SMCA to AGU between 1.1–1.5. Carboxymethyl cassava starch with various DS was also prepared. The properties of CMS as affected by the degree of modification were also discussed.     

Octenylsuccinate Derivatives of Carboxymethyl Starch – Synthesis and Properties

Carboxymethyl starch (CMS, DS_CM 0.1) was modified with octenylsuccinic anhydride in various solvent systems. Using the dimethyl sulphoxide (DMSO)/p‐toluenesulphonic acid (p‐Ts‐OH) system, carboxymethyl starch octenylsuccinates (OS‐CMS) were obtained with degrees of substitution (DS) ranging from 0.03 to 0.53 at high reaction efficiency, and characterized with regard to their molecular structure, their rheological and surface active properties. The water‐soluble OS‐CMS derivatives showed a pseudoplastic behavior dependent on both the DS and polymer concentration (c_p). The thickening power displayed a maximum at DS 0.14 at higher c_p (2.5 and 5.0%). In spite of the only moderate surface‐tension decreasing effect of the OS‐CMS derivatives, most of them exhibited excellent emulsifying, foaming and antiredeposition effects. They represent novel polysaccharide‐based biosurfactants with a broad application potential.     

Homogeneous synthesis and characterization of starch acetates in ionic liquid without catalysts

Homogeneous modification of corn starch with acetic anhydride was performed in ionic liquids 1‐butyl‐3‐methylimidazolium chloride (BMIMCl) without catalysts. The results indicated that the pretreatment of starch, which starch was dissolved in BMIMCl at 105°C for 2 h before reaction, provided feasible reaction environment for starch functionalization. Optimum modification conditions for maximum degree of substitute (DS 2.11) were shown as following: acetic anhydride/anhydroglucose units (AGU) molar ratio 5:1, reaction temperature 105°C and reaction time 2 h. The pretence of acetyl groups in starch products was confirmed by FTIR and ¹H NMR spectroscopy. SEM and XRD data showed that the crystalline structure of native starch was disrupted and new structure was formed during the dissolution and modification processes. The higher DS due to acetylation had a beneficial effect on the thermal stability of samples.     

Synthesis of Carboxymethyl Starch

Carboxymethyl starch (CMS) was obtained under heterogeneous conditions as a product of the reaction of starch and monochloroacetic acid (MCA) in the presence of sodium hydroxide. The influence of the composition of the reaction mixture, the reaction time and temperature and the type of starch being carboxymethylated on the degree of substitution, DS, and limiting viscosity number, [η], was studied. The reaction temperature influenced the DS values, the highest values of the DS being obtained when the carboxymethylation was performed at 58 °C. Increase of the molar ratio of NaOH to anhydroglycose units leads to an increase in DS, but only to certain extent. The values of the DS and [η] of CMS increased almost linearly with increasing MCA amount in the reaction mixture. The reaction mixture changes caused by adding water to ethanol influenced the DS values of the obtained CMS samples, the maximum DS value being obtained for CMS sample synthesized in ethanol with 25% (v/v) water.     

Synthesis,characterisation and in vitro digestibility of carboxymethyl potato starch rapidly prepared with microwave-assistance

Carboxymethyl potato starch was synthesised with the aid of microwave. Optimal degree of substitution (DS) of 0.32 was obtained at 45 °C in 25 min using aqueous ethanol media with water/solvent of 0.15 at 200 W. The molar ratio of sodium hydroxide and monochloroacetic acid to anhydroglucose unit for optimal DS were 2.5 and 1.0, respectively. FT-IR spectrometry revealed the carboxymethyl starch to show new bands at ν = 1614 cm⁻¹ and ν = 1429 cm⁻¹. Wide angle X-ray diffractometry and DSC revealed a remarkable reduction in starch crystallinity after carboxymethylation, which was consistent with destroyed surface observed in SEM. The digestibility of carboxymethyl starch (CMS) was lower than that of native starch. With similar DS, there was no difference in digestibility of carboxymethyl starch prepared with and without microwave. As DS increased from 0.05 to 0.32, the amount of resistant starch in microwave-assisted carboxymethyl starch was elevated from 14.6% to 20.0%, which was much higher than that of native starch (10.8%).     

Synthesis and Application of Starch 3, 5‐Dinitrobenzoate

A novel starch ester was prepared by the reaction of starch and 3, 5‐dinitrobenzoyl chloride (DNBZ‐Cl). The product (starch 3, 5‐dinitrobenzoate, DNBZ‐ST) was characterized by means of elemental analysis, Fourier Transform Infrared (FTIR) and ¹³C NMR spectroscopy. The influences of molar ratio of DNBZ‐Cl to anhydroglucose (AGU), reaction temperature and time, and amount of pyridine on the degree of substitution (DS) were studied. The esterification reaction is essentially complete after 2 h. Increase in the molar ratio of DNBZ‐Cl to AGU leads to an increase in DS when the former varies from 2:1 to 5:1. DS increases with the reaction temperature when the latter is varied from 70 to 100 °C. DS first increases and then decreases with amount of pyridine, the highest DS was obtained when V(pyridine)/m(starch) was 53 mL/g. The thermal stability of DNBZ‐ST increases when the DS increases, and the degradation starts at 353 °C for the sample of DS 2.14. Creatinine is a toxin accumulated in the blood of chronic renal failure (CRF) patients and a special adsorbent for creatinine is not reported in literature. DNBZ‐ST displayed specific adsorption ability for creatinine, the adsorption equilibrium is reached after 4 h. The adsorption capacity increases with the DS of adsorbent and creatinine concentration. When the creatinine concentration is higher than 300 mg/L, concentration has no apparent effect on the adsorption capacity. As the temperature of the solution is varied from 19 to 49 °C, adsorption capacity first decreases and then increases, being lowest at 37 °C. The adsorption capacity first increases and then decreases as the pH value increases, and is highest at pH 8.The highest adsorption capacity obtained was 25 mg of creatinine per gram of adsorbent at 37 °C, pH 7 and a creatinine concentration of 100 mg/L. The study on the FTIR and UV‐VIS spectra suggested that some chemical reaction took place between the DNBZ‐ST and creatinine in buffer solution.     

Synthesis and Optimization of the Reaction Conditions of Starch Sulfates in Aqueous Solution

Starch sulfate was prepared by chemical modification of potato starch with trisulfonated sodium amine (N(SO₃Na)₃), which was synthesized by reaction of sodium bisulfite and sodium nitrite in aqueous solution. The factors that could affect the degree of substitution (DS) of potato starch were investigated in detail, which included reaction temperature and time of preparing the sulfating agent, reaction temperature and time of synthesizing the starch sulfate, dosage of sulfating agent and potato starch, pH of sulfation reaction medium, and the ratio of liquid volume to starch mass. A starch sulfate with DS of 2.14 was obtained under optimal conditions. FTIR spectra showed the characteristic absorptions of sulfate ester bonds at 1236 cm⁻¹ and 821 cm⁻¹.     

Synthesis and Characterization of Cross‐linked Carboxymethyl Potato Starch Ether Gels

Hydrogels were synthesized by cross‐linking of potato starch (PS) with dichloroacetic acid (DCA) in the presence of monochloroacetic acid (MCA) to form etherified carboxymethyl starch (CMS) gels, to be used for ultrasonic medical examinations. By etherification cross‐linked CMS‐hydrogels can be produced, that are stable in contrast to the in the long‐term unstable esterified gels, that were presented in the last paper. The rheological benchmarks for the CMS‐hydrogels were set in comparison with synthetic ultrasonic gels. Gels with potato starch contents in the reaction batch ranging from 12.5% to 20% showed the best compliance with the benchmark parameters. The DS values of these CMS‐hydrogels vary from 0.42 to 0.49, increasing with decreasing amount of starch in the reaction mixture. The free swelling capacities (FSC) vary between 77 g/g for the 12.5% PS‐gel and 34 g/g for 20% PS‐gel, the turbidities of the samples being in the range from 14.5 NTU (Nephelometric Turbidity Units) (12.5% PS) up to 20.5 NTU (20% PS). The variation of the PS fraction in the reaction mixture showed that with an increased amount of PS in the reaction batch the number of cross‐links of the CMS‐gels increases, too. At a higher number of cross‐links the swelling capacity is reduced and the concentration needed to form stable hydrogels is greatly increased. Thus a hydrogel of a polymer concentration of 5 mass‐% from a 12.5% PS batch was produced, that showed the best accordance with the rheological benchmark parameters such as gelatinization time, visco‐elastic and pseudoplastic properties and long‐term stability. The ultrasonic pictures taken with this CMS‐gel were not different from those taken with the synthetic gels. This hydrogel was then subjected to long‐term‐stability measurements performed over one year and to rheological temperature cycle tests. The tests showed that the long‐term stability of the gels is sufficient for their use as ultrasonic gel.     

Carboxymethyl Starch Octenylsuccinate: Microwave‐ and Ultrasound‐assisted Synthesis and Properties

The synthesis of water‐soluble octenylsuccinates of carboxymethyl starch (OS‐CMS) was performed with octenylsuccinic anhydride by assistance of microwave and ultrasound irradiation using the dimethyl sulphoxide/p‐toluenesulphonic acid system and DMSO as solvents for activation of CMS as well as reaction medium of the following esterification. The prepared OS‐CMS derivatives were characterized with regard to their structural, surface‐active and performance properties. The application of both microwave and ultrasound irradiation as energy sources permitted to shorten the esterification time to several minutes from 24 h of the previously reported conventional heating [33], whereby the reaction efficiencies were high and the water‐soluble derivatives exhibited excellent emulsifying efficiency as well as surfactant performance properties tested by washing power and antiredeposition efficiency. The results indicate also the high potential of both microwave and ultrasound energy sources to innovate and increase the efficiency of technological polysaccharide esterification processes.     

非晶颗粒态玉米淀粉制备羧甲基淀粉的研究

以原玉米淀粉、氯乙酸为主要原料,先用乙醇制备非晶颗粒态玉米淀粉,然后将氢氧化钠和氯乙酸加入反应瓶中制备羧甲基淀粉.研究了氯乙酸用量、氢氧化钠用量、反应体系水分含量、反应温度、时间对样品取代度(DS)的影响.结果表明:在m(氯乙酸)/m(淀粉)为0.2,n(氢氧化钠)/n(淀粉)为0.4,反应体系水分25%条件下,温度55℃反应4 h得到较高取代度的羧甲基淀粉CMS.     

Influence of drying conditions on colour,betacyanin content and antioxidant capacities in dried red-fleshed dragon fruit (Hylocereus polyrhizus)

In this study, drying of red-fleshed dragon fruit at different temperatures (40, 50, 60, 70 and 80 °C) and air velocities (1.0 and 1.5 m s⁻¹) was conducted under the specific humidity of 25 g H₂O kg⁻¹ dry air. The results showed that drying at higher temperatures resulted in shorter drying times. However, temperature and air velocity did not significantly affect the total betacyanin contents and antioxidant capacities in dried products. Seven betacyanins identified by LC-MS were betanin, isobetanin, phyllocactin, isophyllocactin, betanidin 5 –O-(6′O-3-hydroxybutyryl)-β-glucoside, isobetanidin 5 –O-(6′O-3-hydroxybutyryl)-β-glucoside and decarboxylated phyllocactin. In addition, the temperature increased the isomerisation of betacyanins. The most preferable condition for preserving the colour and betacyanin contents of red-fleshed dragon fruit was the drying at a temperature of 80 °C and air velocity of 1.5 m s⁻¹ since it could shorten the drying time and give a bright red colour to the dried product as well as it had no significant impact on the betacyanins.     

制备荞麦羧甲基淀粉的研究

研究了以荞麦淀粉为原料，用乙醇溶剂法制备荞麦羧甲基淀粉(CMs)。探讨了淀粉乳浓度、一氯乙酸用量、氢氧化钠用量、反应体系水分含量、反应温度和反应时间对荞麦羧甲基淀粉取代度(Ds)的影响，通过正交试验，确定制备荞麦羧甲基淀粉最优工艺条件。     

Synthesis of high fatty acid starch esters with 1‐butyl‐3‐methylimidazolium chloride as a reaction medium

In this work, high fatty acid esters of corn starch were synthesized by reacting the starch with fatty acid methyl ester using 1‐butyl‐3‐methylimidazolium chloride (BMIMCl) ionic liquid (IL) as reaction media. The effect of reaction variables such as the catalyst amount, molar ratio of fatty acid methyl ester/anhydroglucose unit (AGU) in starch, pyridine/AGU molar ratio, reaction temperature, as well as reaction time on the degree of substitution (DS) of starch esters was investigated. The experimental results showed that the DS value of the obtained starch esters could be varied depending on the process conditions. In the optimum reaction condition, the achieved maximum DS of starch laurate and starch stearate was 0.37 and 0.28, respectively, at a reaction temperature of 110°C for starch laurate and 120°C for starch stearate for a reaction duration of 2 h. Furthermore, the starch esters were characterized by FTIR, SEM, and X‐ray diffractometry (XRD) techniques, respectively. Results from FT‐IR spectroscopy suggested that the hydroxyl groups in the starch molecules were converted into ester groups. SEM and XRD studies showed that the morphology and crystallinity of starch esters were disrupted largely in the IL medium under the reaction conditions.     

Effect of storage on resistant starch content and in vitro starch digestibility of some pressure‐cooked cereals and legumes commonly used in India

Resistant starch (RS) is that fraction of starch, which escapes enzymic hydrolysis in the small intestine and passes in the colon. Effect of storage time (12 and 24 h) and temperature (4 °C and 25 °C) was studied on RS content of the pressure‐cooked cereal and legume grains/seeds and their flours. RS content was observed to increase in the stored cereals and legumes, with more enhanced increase in the flour samples stored at refrigeration temperature for longer duration (41.4% in wheat flour and 85.4% in pea flour). Significant positive correlations were observed between RS content (4 °C, 24 h) and amylose (y = 0.388 × –5.948, r = 0.840, P ≤ 0.05, n = 7) as well as between % increase in insoluble dietary fibre content (4 °⁰C, 24 h) and amylose (y = 2.257 × –27.724, r = 0.971, P ≤ 0.05, n = 7). Reduced in vitro starch digestibility of the cooked/stored samples (4 °C, 24 h) was observed when compared to freshly cooked samples.     

木薯羧甲基淀粉的机械活化固相化学法制备、表征及其特性

以木薯淀粉为原料,氯乙酸钠为醚化剂,氢氧化钠为催化剂,采用机械活化固相化学反应法制备羧甲基淀粉。以取代度为评价指标,通过单因素和正交试验设计优化确定最佳制备工艺,采用傅里叶红外光谱（Fourier transform infrared spectroscopy,FTIR）、X-射线衍射（x-ray diffraction,XRD）、扫描电镜（scanning electron microscope,SEM）对羧甲基淀粉的结构进行表征,并考察羧甲基淀粉的理化特性。结果表明,最佳工艺参数为淀粉与氯乙酸钠物质的量比1∶1、反应温度50?℃、反应时间1.5?h、氢氧化钠溶液质量分数18.8%、搅拌速率380?r/min、球磨介质堆体积500?mL,在此条件下制备的羧甲基淀粉取代度为0.540?1。FTIR、XRD、SEM检测进一步证实木薯淀粉发生了羧甲基化反应。理化特性结果显示,羧甲基淀粉的黏度升高,溶解度增大,吸水性、保水性、冻融稳定性、抗酸碱性、抗酶解性等均得到较好的提高。