A Novel Copolymer: Starch‐g‐Polyvinylpyrrolidone

In this study, graft copolymerization of N‐vinylpyrrolidone (N‐VP) onto starch was carried out in an aqueous medium using azobisisobutyronitrile (AIBN) as initiator. The variables affecting the graft copolymerization, such as monomer and initiator concentrations, reaction time and temperature, were thoroughly examined. In general, grafting of N‐vinylpyrrolidone onto starch increased with the increase in time and monomer concentration up to a certain value and then leveled off. Similarly, increase both in initiator concentration and temperature first favored and than impeded the grafting reaction. Optimum conditions established for grafting were as follows: N‐VP = 0.7 M, AIBN = 1.5×10^‐3 M, T = 70°C and t = 5 h. Structural changes of the grafted starch were followed by FTIR, intrinsic viscosity and water absorption capacity studies.     

低取代度阳离子淀粉-丙烯酰胺接枝共聚物的制备及应用

以低取代度的阳离子淀粉为原料,硝酸铈铵为引发剂,制备了低取代度阳离子淀粉-丙烯酰胺接枝共聚物。研究了丙烯酰胺与阳离子淀粉质量比、反应温度、反应时间和引发剂浓度对接枝率和接枝效率的影响。结果表明:接枝率和接枝效率最高的条件为:m(丙烯酰胺)∶m(阳离子淀粉)=2.5∶1,反应温度为55℃,反应时间为3 h,c(引发剂)=2 mmol/L。将合成的聚合物用于纸张增强,当低取代度阳离子淀粉-丙烯酰胺接枝共聚物的用量为1.0%时,对纸张的增强效果最好,可使纸张抗张指数增加23.0%,撕裂指数增加12.7%,耐破指数增加63.7%,耐折度增加115.1%。     

Synthesis,characterization and swelling behaviour of superabsorbent polymers from cassava starch‐graft‐poly(acrylamide)

Superabsorbent polymers (SAPs) were prepared from cassava starch by graft copolymerization of acrylamide on to starch using ceric ammonium nitrate (CAN) as free radical initiator, followed by alkali saponification. The reaction parameters such as concentration of acrylamide, concentration of CAN, temperature, and duration of polymerization reaction were optimized for maximum water absorbency using a 4‐factor 3‐level Box‐Behnken design. The highest values of percentage grafting and absorbency obtained were 174.8% and 425.2 g/g, respectively. The polymers were characterized by determination of grafting efficiency, N‐content, acrylamide content, FTIR analysis, SEM and XRD analyses. Thermogravimetric analysis (TG) showed that the SAP has higher thermal stability. The rate of water absorbency and the swelling behaviour of the SAP under different conditions of pH, and different salts were determined. The de‐swelling pattern of the hydrogels over different time durations was also determined.     

Response Surface Methodology for the Optimization and Characterization of Cassava Starch‐graft‐Poly(acrylamide)

Response surface methodology (RSM) was employed for the synthesis of cassava starch‐graft‐poly(acrylamide) using ceric ammonium nitrate as free radical initiator. Concentration of acrylamide, concentration of ceric ammonium nitrate, reaction temperature and duration of reaction were optimized using a 4‐factor 3‐level Box‐Behnken design. The dependent variables were percentage grafting (%G) and grafting efficiency (GE). Second order polynomial relationships were obtained for %G and GE, which explained the main, quadratic and interaction effects of factors. The highest%G and GE obtained were 174.8% and 90.7%, respectively. The optimum values of parameters predicted through RSM were 20 g acrylamide/10 g dry starch, 3.3 g/L ceric ammonium nitrate, 180 min reaction duration and 45ºC temperature with a %G of 190.0. For GE, the predicted levels of factors for the optimum value of 90.8% were 17.5 g acrylamide/10 g dry starch, 4.1 g/L ceric ammonium nitrate, 180 min reaction duration and 55ºC temperature. The graft reaction was confirmed by FTIR analysis, where the absorption bands corresponding to the C=O stretching and N‐H bending of the –CONH₂ group were observed. Scanning electron microscopic studies on grafted starches revealed that the granular structure of the starch was affected by the reaction. X‐ray diffraction analysis showed that the crystallinity of starch was decreased as a result of grafting and the reduction was higher for the grafted starches with higher percentage grafting.     

Preparation,characterization, and water resistance of cationic acetylated starch‐g‐poly(styrene‐butyl acrylate) surfactant‐free emulsion

Cationic acetylated starch‐g‐poly(styrene‐butyl acrylate) surfactant‐free emulsion (CAS‐g‐poly(St‐BA)) was synthesized by graft copolymerization of styrene (St) and butyl acrylate (BA) onto CAS using FeSO₄–H₂O₂ redox initiator. The maximum graft of 55.68% was derived when H₂O₂ concentration, monomer concentration, and St/BA ratio were 9%, 130%, and 1:1, respectively. The results obtained from FTIR, NMR (H¹ NMR and C¹³ NMR), XRD, SEM, and thermogravimetric analysis (TGA‐DTG) confirmed graft copolymerization of St and BA onto CAS. And it was demonstrated that film‐forming properties of starch were greatly improved via grafting St and BA onto starch. It was also found that paper sized with CAS‐g‐poly(St‐BA) exhibited higher ring crush index and bursting strength than paper sized with cationic potato starch (CS) and CAS, as well as much lower water absorption, which is further verified by contact angles results.     

反相乳液聚合制备阳离子改性接枝淀粉

本实验以淀粉、丙烯酰胺、阳离子单体(二甲基二烯丙基氯化铵)为原料,采用过硫酸铵-尿素氧化还原引发体系,以油酸失水山梨醇酯为乳化剂,通过反相乳液聚合技术,合成阳离子改性淀粉接枝共聚物.分析讨论了单体配比、乳化剂用量、引发剂用量及油水体积比等合成条件对共聚物性能的影响,并采用正交实验方法对合成条件进行了优化.     

反相乳液聚合制备阳离子改性接枝淀粉

本实验以淀粉、丙烯酰胺、阳离子单体(二甲基二烯丙基氯化铵)为原料,采用过硫酸铵--尿素氧化还原引发体系,以油酸失水山梨醇酯为乳化剂,通过反相乳液聚合技术,合成阳离子改性淀粉接枝共聚物.分析讨论了单体配比、乳化剂用量、引发剂用量及油水体积比等合成条件对共聚物性能的影响,并采用正交实验方法对合成条件进行了优化.     

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.     

Effects of cationization on DSC thermal profiles,pasting and emulsifying properties of sago starch

Cationic sago starches were prepared using an aqueous alkaline process with different levels of cationic reagent 3‐chloro‐2‐hydroxypropyltrimethylammonium chloride (0.01–0.10 M ), sodium hydroxide (0.03–0.86 M ) and reaction temperature (30–62 °C). The degree of substitution (DS), reaction efficiency, thermal and pasting properties of cationic sago starches were analysed. Emulsifying and fat binding properties of native sago starch, cationized sago starch and commercial chitosan were compared at two different pH values (4 and 7). Degree of substitution increased with an increase in concentration of cationic reagent or NaOH, or reaction temperature. The reaction efficiency was proportional to the concentration of NaOH and reaction temperature but inversely proportional to the cationic reagent concentration. The highest DS and reaction efficiency achieved was 0.06 and 79%, respectively. The pasting temperature and gelatinization enthalpy of cationic starch (DS 0.06) were lower compared with native sago starch. Cationization increased the peak viscosity and breakdown of the starch paste but decreased the setback. The presence of cationic groups significantly increased emulsion stability, emulsion viscosity and fat binding capacity of sago starch. However, the cationic sago starch was still inferior to chitosan, which showed the highest emulsion stability, emulsion viscosity and fat binding capacity. There was no significant difference between the surface tension values of native and cationic sago starch and chitosan. The influence of pH on emulsifying properties was not significant. The emulsion stability of the cationic sago starch improved due to an increase in viscosity and fat binding capacity but not its surface active property. Copyright © 2004 Society of Chemical Industry     

Microwave‐accelerated Synthesis and Characterization of Potato Starch‐g‐poly(acrylamide)

Using a very low concentration of potassium persulfate as initiator, acrylamide could be efficiently grafted onto potato starch under microwave irradiation and for the grafting O₂ removal from the reaction vessel was not required. Under optimal conditions, grafting and efficiency observed were 160% and 89%, respectively. Grafted starch was characterized by using Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD) and thermogravimetric analysis (TGA). It was observed that the microwave irradiation could significantly accelerate the synthesis of starch‐graft‐poly(acrylamide), because under identical conditions no grafting was observed in a conventional procedure. Viscosity, shear stability and water/saline solution retention of the microwave‐synthesized grafted starch were studied and compared with that of the parent starch.     

Construction of cold‐triggered/heat‐destroyed emulsions for use as a practical cold‐storage thermal history indicator

BACKGROUND: To provide a record of the occurrence of a high‐temperature event during a cold‐chain system in the range from 1 to 10 °C, an indicator material that undergoes an irreversible temperature‐related visual change in response to high temperatures is needed. RESULTS: In order to obtain the required indicator, we attempted to construct highly thermo‐sensitive cold‐triggering and heat‐destructive emulsions that could start monitoring a high‐temperature event just by cooling, and after triggering provide an irreversible visual change over the upper limitation of the monitoring temperature. Emulsions composed of oil mixtures of triacylglycerols and fatty acid esters provided a 1 °C triggering and 10 °C destructive emulsion. The effect of the oil‐phase composition was studied by differential scanning calorimetry, nuclear magnetic resonance and microscopy with a cooling/heating system. CONCLUSION: The emulsion was triggered by cooling at 1 °C and was immediately destroyed by heating to 10 °C, with clear visible phase separation. For cold‐triggering, crystalline structures of frozen oils should work to destroy the interfaces of the emulsion droplets. This could be used as a thermal indicator that would trigger in cold‐chain distribution systems and be destroyed in these systems. Copyright © 2009 Society of Chemical Industry     

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.     

Water‐Soluble Grafted Starches for Hydration Suppression of Swellable Clay

The study was undertaken to investigate the hydration suppression of swellable clay by water‐soluble graft terpolymers of potato starch with the mixed monomer system of acrylamide and 2‐(dimethylamino)ethyl methacrylate. It was found that the grafted starches investigated suppress the clay hydration‐swelling more effectively than a partially hydrolyzed polyacrylamide with a degree of hydrolysis of 16 %, a typical inhibitive polymer used in current drilling fluids. Besides, an increase in the grafting extent or concentration of the grafted starches results in enhanced hydration‐suppression efficiency. The starch graft terpolymer with a grafting extent of 120 %, applied at a concentration of 0.6 % (w/w) gives a suppression efficiency of 64.8 % toward the swelling of clay that had been hydrated for 24 h. The interaction of the terpolymer with the clay particles was discussed with the help of SEM observation.     

Effects of starch alkenylsuccinylation on the grafting efficiency,paste viscosity,and film properties of alkenylsuccinylated starch‐g‐poly(acrylic acid)

Commercial cornstarch was alkenylsuccinylated with alkenylsuccinic anhydride to different degrees of substitution (DS) and then the products were graft‐copolymerized with acrylic acid for investigating the effects of starch alkenylsuccinylation on the graft copolymerization with vinyl monomer, as well as on paste viscosity and film properties of alkenylsuccinylated starch‐g‐poly(acrylic acid) (ASS‐g‐PAA). The number of carbon atom of alkenyl in alkenylsuccinates considered was 8 and 12, corresponding to octenylsuccinylation and dodecenylsuccinylation of starch, respectively. The graft copolymerization was accessed by grafting efficiency, grafting ratio, and conversion of monomer to polymer, and the film properties of ASS‐g‐PAA considered included tensile strength, breaking elongation, and work‐to‐break. Experimental results demonstrated that the alkenylsuccinylation showed marked effects on the copolymerization, paste viscosity, and film properties. It resulted in increased grafting efficiency, stable paste viscosity, and strong starch film. Carbon‐chain length of the alkenyl and DS value of the alkenylsuccinates also exhibited evident effects on the copolymerization and film properties. Octenylsuccinylation of starch before the copolymerization was superior to dodecenylsuccinylation in improving the efficiency and film properties. Low levels of octenylsuccinylation could be utilized to increase the efficiency of the copolymerization and improve the properties of starch film.     

Purification of α‐amylase from human saliva by superparamagnetic particles

BACKGROUND: Several studies of magnetic carrier technology have focused on the application of separation technology, because the magnetic support can separate the target from the reaction medium by application of a magnetic field and because the magnetic carrier can be easily recovered. In the present study, superparamagnetic iron oxide (SPIO) modified by epichlorohydrin was employed as a support whose surface could be coated with starch. The starch‐coated support was used for isolating human salivary amylases. RESULTS: The results showed that the starch‐SPIO support could isolate amylases from human saliva with 91.1% recovery and 3.5‐fold purification to high specific activity. Sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed that the purifed amylase comprised two isoamylases with estimated molecular weights of 55 and 59 kDa. The activities of crude and purified amylases showed optimal pH values of 6–7 and 7 and optimal temperatures of 40 and 30 °C respectively. The thermal stability range for both crude and purified amylases was between 20 and 40 °C. CONCLUSION: The attachment of substrates to SPIO could offer a novel and efficient method for purifying enzymes either as an initial step prior to further purification or as a final step for diagnostic usage. Copyright © 2009 Society of Chemical Industry     

有机硅-阳离子聚丙烯酰胺接枝共聚物的合成及增强作用

首先以乳液聚合法合成水包水型CPAM乳液,然后对CPAM与有机硅的接枝共聚反应进行了研究,讨论了反应条件如反应单体配比、反应时间、反应温度等对合成产品性能及对草浆成纸增强效果的影响,并对产物进行了表征。     

Starch Modification,Destructuration and Hydrolysis during O‐Formylation

The mixing of dry starch with 40 or 99% (v/v) formic acid (FA) produces an O‐formylation reaction which causes a combination of acid hydrolysis and starch destructuration. Moreover, this esterification reaction is highly exothermic in the presence of pure FA. When O‐formylation is performed at temperatures higher than 20°C, starch formate content is high (degree of substitution, DS, of 2.15 after 60 min at 105°C) but then molecular weight decreases (η_red ≶ 10 mL/g). Under thermally‐controlled conditions at 20°C in formic acid, degrees of substitution reach 1.5–1.6 after 6 h reaction times and polymer degradation seems to be limited (η_red = 110 to 140 mL/g). The degrees of substitution obtained in water/formic acid mixtures are below those in formic acid alone. The level of destructuration of starch in formic acid and water/formic acid mixtures was also evidenced by dynamic rheological measurements and optical microscopy. Plots of storage modulus (G’) versus frequency (ω) was used to characterize both the gelatinization and the gel destruction processes as a function of reaction temperature (T_r) and FA concentration.     

Cold‐triggered/heat‐destroyed emulsions composed of phospholipids and triacylglycerols as thermal history indicators for cold‐chain distribution systems

BACKGROUND: Recently, cold‐chain distribution systems have come to play important roles in worldwide food processing/storage/transportation networks. To ensure the maintenance of the quality and safety of foods, it is necessary to develop thermal history indicators for products involved in cold‐chain distribution systems. To provide a record of the occurrence of a high‐temperature event during a cold‐chain system, a temperature‐related phase change in a material within the indicator is needed to indicate that the high‐temperature event occurred. Preferentially, for safety, the materials of the indicators should be edible and easy to handle. It should be possible to store the indicators at ambient temperature before use, and they should be triggered automatically just by cooling at the start of a cold‐chain system. Furthermore, if the indicator is heated even once during the cold‐chain distribution system, its appearance must be irreversibly altered to provide evidence of the high‐temperature experience. RESULTS: Based on the edible materials composed of lyso‐lecithin (15 g), lecithin (2 g), triacylglycerol (150 g), and water, we successfully constructed a stable emulsion that could be triggered just by cooling to 4 °C or lower for more than 12 h. After triggering, it was immediately destroyed by heating up to 20 °C or higher. Furthermore, the mechanism of cold‐triggering and heat‐destruction has been studied by nuclear magnetic resonance. CONCLUSION: The cold‐triggered/heat‐destroyed emulsion should be applied as a new thermal history indicator that can be automatically triggered just by cooling down and irreversibly change its appearance after a high‐temperature experience in cold‐chain distribution systems. Copyright © 2008 Society of Chemical Industry     

Study on Preparation and Thickening Efficiency of an Inverse Emulsion of Anionic Starch‐graft‐Polyacrylamide

A series of graft copolymers of starch with polyacrylamide was made by using a K₂S₂O₈ initiation system in inverse emulsion. The corresponding anionic graft copolymers, which have a different hydrolysis degree, are prepared by alkaline hydrolysis of the uncharged graft copolymers. Adequate hydrolytic conditions including type and amount of hydrolyzing agent, temperature, and time were studied. These graft copolymers have been tested for their temperature sensitivity, salt tolerance and shear stability, and a comparison has been made with ungrafted polyacrylamide (PAM). Experiments showed that a high hydrolysis degree can be obtained in a shorter time when NaOH and Na₂CO₃ were used together as hydrolyzing agents, and the highest solution viscosity was observed when the hydrolysis degree of the graft copolymers was approximately 30%, . In addition, the shear stability, temperature sensitivity and salt tolerance in the graft copolymers were also investigated.     

Production and characterization of digestion‐resistant starch by the reaction of Neisseria polysaccharea amylosucrase

Recombinant amylosucrase (200 U/mL) from Neisseria polysaccharea was used to produce digestion‐resistant starch (RS) using 1–3% (w/v) corn starches and 0.1–0.5 M sucrose incubated at 35°C for 24 h. Characterization of the obtained enzyme‐modified starches was investigated. Results show that the yields of the enzyme‐modified starches were inversely proportional to the original amylose contents of corn starches. After enzymatic reaction, insoluble RS contents increased by 22.3 and 20.7% from 6.9% of waxy and 7.7% of normal corn starches, respectively, using 3.0% starch as acceptor and 0.3 M sucrose as donor, while amylomaize VII showed the lowest increase (8.5%) in RS content. The crystalline polymorph of these enzyme‐modified starches resulted in the B‐type immediately after enzymatic reaction. The enzyme‐modified starches displayed higher melting peak temperatures (85.6–100.6°C) compared to their native starch counterparts (70.1–78.4°C). After enzymatic reaction, pasting temperature increased in waxy (71.9 → 77.6°C) and normal corn starches (75.3 → 80.6°C), and the peak viscosity of waxy corn starches increased from 264 to 349 RVU, whereas that of normal corn starches decreased from 235 to 66 RVU.