Ultra high pressure (UHP)-assisted acetylation of corn starch

Potential roles of ultra high pressure (UHP) in starch granule reactivity and properties of acetylated starch were investigated. Corn starch was substituted with acetic anhydride at pressure range of 0.1–400 MPa for 15 min; also, conventional reaction (30 °C, 60 min) was conducted as reaction control. Native and acetylated corn starches were assessed with respect to degree of substitution (DS), X-ray diffraction pattern/relative crystallinity, starch solubility/swelling power, gelatinization, and pasting behavior. For the UHP-assisted acetylated starches, DS values increased along with increasing pressure levels from 200 to 400 MPa, and reaction at 400 MPa exhibited maximum reactivity (though lower than the DS value of the reaction control). Both UHP-assisted and conventional acetylation of starch likely occurred predominantly at amorphous regions within granules. Gelatinization and pasting properties of the UHP-assisted acetylated starches may be less influenced by UHP treatment in acetylation reaction, though restricted starch solubility/swelling were observed.     

Optimization of the synthesis of 1-allyloxy-2-hydroxy-propyl-starch through statistical experimental design

The synthesis of 1-allyloxy-2-hydroxy-propyl starches was studied using a statistical experimental design approach. The etherification of two different granular maize starches with allyl glycidyl ether (AGE) in a heterogeneous alkaline suspension was investigated. The optimal reaction conditions were found via experimental design and the obtained response factor, e.g. the degree of substitution (DS) of the starch hydroxyl group, was statistically evaluated. The effects of six process factors on DS, namely the starch concentration, the reaction time, the temperature, and the amount of NaOH, Na₂SO₄ and AGE were investigated. The statistical analysis showed significant impact of the temperature, the amount of NaOH and the amount of AGE on the DS for both starches. Optimum conditions for the highest DS for waxy maize starch were: 0.0166% AGE (based on dry starch (ds)) and 1.0% NaOH (ds) at 34 °C in 4 h; on dent maize starch, these were 0.0099% AGE (ds) and 1.0% NaOH (ds) at 37 °C in 16 h.     

Process optimization for the synthesis of octenyl succinyl derivative of waxy corn and amaranth starches

Modification of starch by dicarboxylic acid anhydrides to starch esters, containing both hydrophilic and hydrophobic groups are known to improve its emulsification properties, and can also be used for encapsulation after hydrolysis. Reports on the effect of process conditions on the extent of modification of starches by using n-octenyl succinic anhydride (n-OSA) are not readily available. In the present study, the process of manufacturing of OSA starches from waxy corn and amaranth starch were studied with respect to the OSA/starch ratio, pH, temperature and time of the reaction. The effects of these parameters were evaluated on the basis of degree of substitution (DS). The concluding conditions for amaranth-OSA starches was a reaction time of 6 h at 3% OSA/starch ratio at 30 °C and pH 8.0 at 25% starch concentration. For waxy corn-OSA starch, all parameters were identical except for the reaction time of 24 h. The maximum DS achieved for both the starches was 0.02. Emulsification capacity and oil absorption capacity of the OSA-modified starches were more or less similar within the parameter chosen and also independent of starch type.     

Physicochemical and functional properties of starches from sorghum cultivated in the Sahara of Algeria

Pure starches were isolated from white and red sorghum cultivated in Tidikelt, a hyper arid region situated in south Algeria. Amylose content, X-ray pattern and rheological properties of starches were examined. The amylose content in white sorghum starch (27.1%) was slightly higher than that in red sorghum (24.8%). The swelling power and the solubility behavior of both starches were nearly similar below 65 °C. At higher temperatures, starch isolated from the white sorghum cultivar showed higher swelling power and lower solubility index than pigmented sorghum starch. The pasting properties of starches determined by RVA, Rapid Visco Analyser showed different viscosity peaks. Red sorghum starch had a higher value (4731 cP) than white sorghum starch (4093 cP). For both sorghum, X-ray diffractograms exhibit an A-type diffraction pattern, typical of cereal starches and the relative degrees of crystallinity were estimated at 22.72% and 28.91%, respectively, for local white and red sorghum starch. DSC analysis revealed that sorghum starches present higher temperatures at the peak (70.60 and 72.28 °C for white and red sorghum starches, respectively) and lower gelatinization enthalpies (9.087 and 8.270 J/g for white and red sorghum starches, respectively) than other cereal starches.The results showed that physicochemical and functional properties of sorghum cultivar starches were influenced by the genotype and the environment.     

Resistant glutarate starch from adlay: Preparation and properties

Reaction conditions were optimized to increase the content of resistant starch in adlay starch using esterification with glutaric acid, and the physicochemical properties of the prepared glutarate starches were investigated. Different amounts of glutaric acid (0.1–0.5 g/g starch, dry weight basis) were reacted with adlay starch at various temperatures (70–130 °C) and reaction times (3–9 h). The resistant starch levels increased with increased glutaric acid content, reaction temperature, and reaction time. The color difference was mainly affected by reaction time. The highest resistant starch content (RS 66%) was obtained using conditions of 0.4 g glutaric acid/g starch, 115 °C, and 7.5 h, with a color difference of 10.24. After digestion with α-amylase and amyloglucosidase, the water-soluble fraction of glutarate starch had more oligosaccharides than high-amylose maize starch (RS 43%). FT-IR and solid-state NMR detected carbonyl groups in the glutarate starch, indicating the formation of cross-linkages through esterification. The granular structure of the glutarate starches was not destroyed and they retained birefringence. After heating with an excess of water, the granules kept their shape but lost their birefringence. The glutarate starches had low solubility in both cold and hot water, and the resistant starch contents were unchanged after heating due to the restriction of swelling by cross-linking. The glutarate starches had a similar chain-length distribution to raw starch, indicating that acid hydrolysis took place at branching points in the amorphous region. Furthermore, the glutarate starches possessed a weaker crystalline region, more diverse double helical chains, and lower enthalpy than raw starch.     

Flocculation of kaolin by waxy maize starch phosphates

Waxy maize starch phosphates were tested as flocculants in order to determine if they have the potential to replace petroleum-based polymer flocculants currently used commercially. Phosphorylation was carried out by dry heating of starches and sodium orthophosphates at 140 °C for 4 h. Native and phosphorylated waxy maize starches were ineffective as flocculants for kaolin in deionized water. However, in the presence of small amounts of Ca²⁺ (1–4 mM), starch phosphates were effective flocculants of kaolin at concentrations as low at 3–4 ppm. The optimal degree of substitution (DS) for flocculation was 0.024 but the effect of DS was rather small over the range DS 0.007–0.08. Although a common synthetic polymer flocculant (polyacrylamide-co-acrylic acid) was effective at 1 ppm, the lower cost of starches should make them economically competitive.     

Structural and physicochemical properties of starch gels prepared from partially modified starches using Thermus aquaticus 4-α-glucanotransferase

The modified starch gels prepared from partial enzyme treatments (1, 3, and 6 U/g starch; 2-h incubation) of the corn and rice starch pastes using Thermus aquaticus 4-α-glucanotransferase (TAαGT) were investigated for their molecular characteristics, microstructures, and physicochemical properties. Unlike the native and partially modified normal starches, the native and partially modified waxy starches could not form gels strong enough for textural analysis after 24 h for gel setting. Features of the partially modified normal starches were the specific apparent amylose contents and maximum iodine absorption wavelength (λ_max, ∼567 nm), as well as the tri-modal molecular weight profiles and flatter side-chain distributions. Also, the partially modified normal starch gels possessed fractured surfaces with discontinuous crystalline fibrous assembly that differed from the native starch gels’ porous continuous network, which resulted in more brittle, rigid, and resilient gels compared with the native gels.     

Acetylation of α-chitin in ionic liquids

Acetylation of α-chitin using acetic anhydride in an ionic liquid, 1-allyl-3-methylimidazolium bromide (AMIMBr), was performed. First, a mixture of chitin and AMIMBr (2% w/w) was heated at 100 °C for 24 h for dissolution. Then, acetic anhydride (5–20 equiv) was added to the solution and the mixture was heated with stirring at desired temperatures for 24 h. The product was precipitated by the addition of the reaction mixture into methanol. The IR spectrum of the product indicated the progress of acetylation. The degrees of substitution (DS), which were determined from the IR spectra, increased with increasing the amounts of acetic anhydride used for the reaction. The highest DS was 1.86, which was obtained by the reaction using 20 equiv of acetic anhydride at 100 °C. The product with this DS value was soluble in DMSO, and thus the structure of the product was further confirmed by ¹H NMR spectroscopy in DMSO-d₆. The DS value estimated by the integrated ratio of signals due to acetyl protons to a signal due to anomeric protons was in good agreement with that determined from the IR spectrum.     

Susceptibility of annealed starches to hydrolysis by α-amylase and glucoamylase

The objective of this work was to determine if annealing altered the susceptibility of different starches to enzyme hydrolysis. Five commercial starches, including waxy corn, common corn, Hylon V, Hylon VII, and potato, were annealed by a multiple-step process, and their susceptibility to α-amylase and glucoamylase and the physicochemical properties of the hydrolyzed native and annealed starches were determined. During 36 h of enzyme hydrolysis, significant differences were noted between annealed starch and its native counterpart in the extent of α-amylolysis for Hylon V, Hylon VII, and potato, and in the extent of glucoamylolysis for potato. Waxy and common corn starches were hydrolyzed to a greater degree by both enzymes when compared with the other starches. The apparent amylose content of both native and annealed starches decreased during α-amylolysis for all starches, but increased for Hylon V, VII, and potato starches during glucoamylolysis. Most native and annealed starches exhibited comparable or increased peak gelatinization temperatures and comparable or decreased gelatinization enthalpy on hydrolysis with the exception of annealed potato starch, which showed a significant decrease in peak gelatinization temperature on hydrolysis. Annealed starches displayed significant higher peak gelatinization temperatures than their native counterparts. The intensity of main X-ray diffraction peaks of all starches decreased upon hydrolysis, and the changes were more evident for glucoamylase-hydrolyzed starches. The annealing process allowed for a greater accessibility of both enzymes to the amorphous as well as the crystalline regions to effect significant changes in gelatinization properties during enzyme hydrolysis.     

Debranching enzyme concentration effected on physicochemical properties and α-amylase hydrolysis rate of resistant starch type III from amylose rice starch

The effect of debranching enzyme concentration on physicochemical properties and α-amylase hydrolysis rate of resistant starch type III from high amylose rice starch were studied. The pullulanase enzyme (8, 10, 12, 14 and 16 U/g starch) was introduced to modify amylopectin molecules of 15% (w/w) gelatinized rice starches at 55 °C for 16 h. The debranched starches with different degrees of hydrolysis (0.14–5.27%), and having 66.60–98.82% β-amylolysis limit were then induced at 4 °C for 16 h, afterward a one cycle of freeze–thaw process (?10/30 °C) was applied. The results showed that a pullulanase hydrolysis improved the degree of syneresis (51.64–54.85% from 8 to 16 U/g starch). Resistant starch content increased sharply as the amount of the enzyme increased, reaching the highest (19.81%) for a 12 U/g starch and decreased to 13.16% by 16 U/g starch. α-Amylase hydrolysis rate showed that incompletely-debranched had a lower estimated glycemic index than completely debranched rice starches. Microstructure of the selected RS III samples using X-ray diffraction and scanning electron microscopy revealed a crystal pattern change from A- to V-type pattern and formed a coarse honeycomb-like and a filamentous network structure.     

Influence of Drying Procedure and of Low Degree of Substitution on the Structural and Drug Release Properties of Carboxymethyl Starch

The aim of this study was to investigate the influence of drying methods and low range of degrees of substitution (DS) on the structural, physicochemical, and drug-release properties of carboxymethyl high-amylose starch (CMS). CMS with three DS of 0.03, 0.14, and 0.25 was synthesized and dried by either solvent precipitation (SP), spray drying (SD), or lyophilization (Ly). DS had an influence on the crystalline structure of CMS. It was found that a DS of 0.14 or higher induced a modification of polymorphism. The drying method and the DS had both an impact on the physical properties of the CMS powder which can further influence the formulation characteristics and drug-release properties from monolithic tablets. The CMS with DS of 0.14 and 0.25 dried by SP or SD presented good excipient properties in terms of compressibility. With acetaminophen (20%) as tracer, the monolithic CMS tablets showed controlled drug release over 17 h for DS of 0.14 and 10 h for DS of 0.25, almost independent of pH, suggesting interesting properties for sustained release applications.     

Starch modification by iterated syneresis

Potato, tapioca, corn and wheat starches were solubilised in water and isolated from the solution by iterated syneresis and the effect of this physical modification on the physicochemical properties and structure was studied. The experimental starches were examined by chemical analysis, the Brabender rheological method, scanning electron or light microscopy, X-ray diffractometry, infrared spectroscopy, and differential scanning calorimetry. Physical modification was evidenced to the change starch–water interaction and the structure of starches. Pasting temperature shifted to lower values and the gelatinisation mechanism changed. All modified starches had a B-type of X-ray diffraction pattern. The melting temperature of starch crystallites was typical of retrograded starch, but the enthalpy change was higher. The correlation between the resistant starch content of modified starches and their crystal structure was discussed together with the thermal properties.     

Effect of heat–moisture treatment on the structure and physicochemical properties of tuber and root starches

Starch from tubers potato (Solanum tuberosum), taro (Alocassia indica), new cocoyam (Xanthosoma sagitifolium), true yam (Dioscorea alata), and root cassava, (Manihot esculenta) crops was isolated and its morphology, composition and physicochemical properties were investigated before and after heat–moisture treatment (HMT) (100 °C, for 10 h at a moisture content of 30%). Native starch granules were round to oval to polygonal with smooth surfaces. The granule size (diameter) ranged from 3.0 to 110 μm.The total amylose content ranged from 22.4 to 29.3%, of which 10.1–15.5% was complexed by native lipid. The phosphorus content ranged from 0.01 to 0.1%. The X-ray pattern of potato and true yam was of the ‘B’-type. Whereas, that of new cocoyam and taro was of the ‘A’-type. Cassava exhibited a mixed ‘A+B’-type X-ray pattern. The relative crystallinity, swelling factor (SF), amylose leaching (AML), gelatinization temperature range and the enthalpy of gelatinization of the native starches ranged from 30 to 46, 22 to 54, 5 to 23%, 13 to 19 °C and 12 to 18 J/g, respectively. Susceptibility of native starches towards hydrolysis by 2.2N HCl and porcine pancreatic -amylase were 60–86% (after 12 days), and 4–62% (after 72 h), respectively. Retrogradation was most pronounced in the B-type starches. Granule morphology remained unchanged after HMT. The X-ray pattern of the B-type starches was altered (B→A+B) on HMT. However, that of the other starches remained unchanged. HMT decreased SF, AML, gelatinization enthalpy and susceptibility towards acid hydrolysis, but increased gelatinization temperatures and enzyme susceptibility. Extent of retrogradation and relative crystallinity decreased on HMT of true yam and potato starches, but remained unchanged in the other starches. The foregoing data showed that changes in physicochemical properties on HMT are influenced by the interplay of crystallite disruption, starch chain associations and disruption of double helices in the amorphous regions.     

Production, characterization and evaluation of methylcellulose from sugarcane bagasse for applications as viscosity enhancing admixture for cement based material

In previous works, methylcellulose (MC) was prepared from sugarcane bagasse cellulose in heterogeneous medium using dimethyl sulfate (DMS) as etherification agent. MC was produced in a range of degrees of substitution (DS) from 0.70 to 1.40 and the materials showed low water solubility. In this work methylcellulose was prepared with 5 h (MC5h) of reaction with reagent substitution at each hour. MC5h showed a DS of 1.89 ± 0.04. An aqueous viscous suspension was produced with MC5h for application as viscosity enhancing admixture of cimentitious adhesive mortars. It was observed a 40.37% increase on the consistency index (CI) and a 27.70% increase on the Potential Tensile Adhesion Strength. Such characteristics show the potential of this material for the utilization in situations that require good workability, improve viscosity and adhesive properties such as for tile setting in civil engineering.     

Physicochemical characteristics and fine structure of high-amylose wheat starches isolated from Australian wheat cultivars

High-amylose starch is a source of resistant starch (RS) which have great impact on human health like dietary fiber. Nowadays, high-amylose wheat has been produced by genetic backcrossing, which enhances apparent amylose content and generates altered amylopectin. In this study, the high-amylose wheat starches isolated from various high-amylose wheat cultivars grown in Australia were characterized for understanding their physicochemical properties and fine structure of starch. The physicochemical characteristics of the high-amylose wheat starches are significantly different among the cultivars. Amylose contents of these cultivars were in a range of 28.0–36.9%, which is significantly higher than that of the normal wheat starch (25.6%). The high-amylose wheat starches also had higher blue value but lower λ_max than the normal wheat starch. Gelatinization temperature of the high-amylose wheat starches is higher than that of the normal wheat starch but transition enthalpy is lower. X-ray diffraction showed that the high-amylose wheat starch had C-type crystals close to A-type crystal. Pasting properties of the high-amylose wheat starches were varying depending on the cultivars. However, almost high-amylose wheat starches had lower peak and final viscosities and higher setback viscosity than did the normal wheat starch. Fine structure of amylose and amylopectin was different among the high-amylose wheat cultivars and related to the physicochemical properties of starch. These results help to understand well the characteristics of the high-amylose wheat starches before application for food processing.     

Preparation and properties of oxidized starch with high degree of oxidation

A highly efficient method for preparing oxidized starches with a high degree of oxidation (DO) was developed, using CuSO₄ and H₂O₂ respectively as a catalyst and an oxidant. The effect of different parameters including starch origin, oxidant content, temperature, catalyst content, and reaction time on the DO was investigated systematically. In the present study, only 0.5% of catalyst was added, and the reaction time could be reduced to 1 h, while in the previous study the reaction time of 72 h was necessary to achieve almost the same DO without a catalyst. The structures and properties of oxidized starches were characterized by FT-IR, DSC, TGA, XRD, and transmittance light testing. The oxidation reduced the intrinsic viscosity and thermal stability of the oxidized starches, and could change the crystalline structures into amorphous states when the DO reached 56.3%. When temperature and/or DO increased, the transmittance of suspended solution of oxidized starch increased correspondingly.     

Preparation and Application of Carboxymethyl Yam (Dioscorea esculenta) Starch

Yam (Dioscorea esculenta) starch was modified by carboxymethylation. The effect of reaction parameters, amount of sodium hydroxide (NaOH), amount of sodium monochloroacetate (SMCA), and reaction time on the degree of substitution (DS) of carboxymethyl yam starch (CMS), was studied using the Box–Behnken experimental design. Physicochemical and potency to be a tablet disintegrant of CMS were evaluated. CMS with DS in the range of 0.08–0.19 were obtained. The results from regression analysis indicated that the most important factor in controlling DS was the amount of NaOH followed by SMCA content and reaction time. However, high concentration of NaOH and SMCA lowered the DS. The optimal conditions to achieve the highest DS (0.19) were found to be at molar ratios of NaOH and SMCA to anhydroglucose unit of 1.80 and 2.35, respectively, and with the reaction time of 4.8 h. The swelling power and viscosity of CMS increased with an increase in the degree of modification. CMS showed satisfying tablet disintegrant properties. The tablets containing 1.0–4.0 % CMS disintegrated faster than 5 min. Hence carboxymethyl yam starch can be used as an excellent tablet disintegrant in low concentration.     

Microstructure and aggregation behavior of methylcelluloses prepared in NaOH/urea aqueous solutions

Three water-soluble methylcelluloses (MCs) were prepared through homogeneous reaction in NaOH/urea aqueous solution, using dimethyl sulfate as a methylation reagent. The microstructure of the MC samples was characterized by IR, GC/MS, NMR, while dilute solution properties were measured by SEC–LLS, DLS and viscometer. The total degrees of substitution (DS) of the MC samples were 1.09, 1.42 and 1.56, respectively. However, we found that the relative DS value varies with the position of the hydroxyl group, i.e., C-2 > C-3 ≈ C-6, indicating the difference of reaction activity of different hydroxyl groups. In aqueous solution, MC has a trendency to form aggregates and hard to form actual solution, even at low concentration and low temperature, which was confirmed by the SEC–LLS and DLS result that isolated MC chains and large aggregates coexisted in the dilute aqueous solution. MC aqueous solutions showed two-stage temperature dependence of hydrodynamic radius. In the first stage, i.e., the temperature ranges from 20 to 65 °C, the hydrodynamic radius of MC displayed bimodal distribution, corresponding to the single chains and large aggregates. While in the second stage, i.e., the temperature higher than 70 °C, only large aggregates appeared. The results also proved that the microstructure of MC had a great influence on its physical properties.     

Effect of acid–alcohol treatment on the molecular structure and physicochemical properties of maize and potato starches

The molecular structure and physicochemical properties of acid–alcohol treated maize and potato starches (0.36% HCl in methanol at 25 °C for 1–15 days) were investigated. The yields of the modified starches were ranging from 91 to 100%. The average granule size of modified starches decreased slightly. The solubility of starches increased with the increase of treatment time, and the pasting properties confirmed the high solubility of modified starches. The gelatinization temperatures and range of gelatinization increased with the increase of treatment time except T_o (onset temperature) of maize starch. Molecular structures of modified starches suggested the degradation of starches occurred mostly within the first 5 days of treatment, and degradation rate of potato starch was higher than maize starch both in amylopectin and in amylose. Maize starch was found less susceptible to acid–alcohol degradation than potato starch.     

Physicochemical property-driven optimization of diarylaniline compounds as potent HIV-1 non-nucleoside reverse transcriptase inhibitors

Using physicochemical property-driven optimization, twelve new diarylaniline compounds (DAANs) (7a–h, 11a–b and 12a–b) were designed and synthesized. Among them, compounds 12a–b not only showed high potency (EC₅₀ 0.96–4.92 nM) against both wild-type and drug-resistant viral strains with the lowest fold change (FC 0.91 and 5.13), but also displayed acceptable drug-like properties based on aqueous solubility and lipophilicity (LE > 0.3, LLE > 5, LELP < 10). The correlations between potency and physicochemical properties of these DAAN analogues are also described. Compounds 12a–b merit further development as potent clinical trial candidates against AIDS.