Starch Esters Research Articles

Scandium triflate catalyzed acetylation of starch at low to moderate temperatures

Scandium (III) trifluoromethane sulfonate (Sc(OTf) 3) was investigated as a catalyst for the acetylation of starch in order to determine the potential for preparing new types of starch esters under mild (low to moderate temperature) conditions. At room temperature, dry granular corn starch reacts with acetic anhydride in the presence of Sc(OTf) 3 to form starches highly acetylated on the granular surface only. At higher temperatures (80 °C), starch acetates of degree of substitution (DS) 1.2 and 0.40 were obtained by reaction of granular starch with acetic anhydride or acetic acid, respectively. When starch was gelatinized in acetic acid prior to reaction, acetylation with acetic anhydride was much more rapid with DS reaching 3 after 1 h at 80 °C. Acetylation was rapid at levels of Sc(OTf) 3 down to 0.1 mol%. These data suggest that powerful Lewis acid catalysts such as Sc(OTf) 3 may be useful in preparing novel starch esters using either carboxylic acids or anhydrides.

Enzymatic modification of cassava starch by fungal lipase

Esterification of starch was carried out to expand the usefulness of starch for a myriad of industrial applications. Lipase obtained from Candida rugosa (lipase AYS) was used for starch esterification by two methods: liquid state and microwave oven. The esterification of cassava starch with recovered coconut oil (lauric acid) using microwave heating gave a degree of substitution of 55.28% with degree of substitution (DS) 1.1 and liquid state esterification with palmitic acid gave a degree of substitution of 65.86% with DS 1.04. Esterification was confirmed by IR spectroscopy studies. Thermal gravimetric analysis (TGA) showed that the higher DS attributed to the thermostability, since onset of decomposition is at a higher temperature (390 °C) than the unmodified (280 °C) and was stable above 600 °C. α-Amylase digestibility was found to be reduced for modified starch compared to the control (76.5–4.6%). Viscosity differed with the acyl donor used, palmitic acid increased viscosity while hydrolysed coconut oil reduced viscosity of modified starch ester. Esterification of starch with long chain fatty acids like palmitic acid gives thermoplastic starch which has got wide use in plastic industry, pharmaceutical industries, and in biomedical applications such as materials for bone fixation and replacements, carriers for controlled release of drugs and other bioactive agents. Unlike chemical esterification, enzymatic esterification is ecofriendly and avoids the use of nasty solvents.

Effect of acetylation on the properties of corn starch

Acetylated corn starches with different degrees of substitution (DS 0.85, DS 1.78, DS 2.89) were synthesized by the reaction of corn starch with acetic anhydride in the presence of acetic acid under varying reaction temperatures. The product was characterized by FTIR spectroscopy, 1H NMR, X-ray diffraction and contact angle measurement. Acid-base titration and 1H NMR methods were employed to determine the degree of substitution of product. FTIR spectroscopic analysis showed that the characteristic absorption intensities of esterified starch increased with increase in the degree of substitution, and the characterized peak of hydroxyl group almost disappeared in the spectrum of DS 2.89 acetylated starch. The detailed chemical microstructure of native starch and acetylated starch was confirmed by 1H NMR, 13C NMR and 13C– 1H COSY spectra. Analysis of 1H NMR spectra of acetylated starches was assigned accurately. Strong peaks in X-ray diffraction of acetylated starch revealed that new crystalline regions were formed. Compared with native starch, the hydrophobic performance of acetylated starch esters was increased. The contact angle of acetylated starch with DS 2.89 was 68.2°.

Physico-chemical characterization of starch ferulates of different degrees of substitution

Starch ferulates were prepared by reacting potato starch with ferulic acid chloride, using pyridine as a catalyst in dimethyl sulfoxide. Starch ferulates of different degrees of substitution (DS) were prepared and their formation was confirmed by the presence of the carbonyl signal around 1726 cm −1 in the FT-IR spectra. The thermal characteristics of the native starch and starch ferulates of different degrees of substitution were studied using TGA, DTG and DSC and the studies revealed the starch ferulates to be thermally more stable than the native starch. The starch esters exhibited 50% weight loss at temperatures from 332 to 375 °C while the native starch underwent 50% weight loss at 321 °C. The 1H and 13C NMR studies confirmed the structure of the modified starch. X-ray diffraction studies revealed the loss of the ordered B-type crystalline structure, characteristic of potato starch. The microstructural imaging of the starch esters exhibited a networking which was enhanced with increasing degree of substitution. The starch ferulates also exhibited DPPH radical and ABTS radical cation-scavenging activity.

Surface properties of water soluble maltodextrin, starch acetates and starch acetates/alkenylsuccinates

Surface and interfacial tensions with hexadecane were measured for water soluble maltodextrin and starch ester solutions in order to determine their potential as stabilizers or emulsifiers. The surface tension for an acid hydrolysed starch (maltodextrin) initially declined with concentration and then reached an equilibrium value of 56 mN/m at 20–40 wt.%, suggesting that hydrated starch has this surface energy. Surface and interfacial tensions of starch acetates decreased more rapidly with concentration reaching values of 41–44 and 11–13 mN/m, respectively, at 40 wt.%. There was little dependence of surface or interfacial tensions on degree of substitution between 0.3 and 0.8 and amylose content of starch acetates. Surface and interfacial tensions for starch acetate/alkenylsuccinates were lower than those for starch acetates, particularly at low concentrations. Emulsions of soybean oil/water mixtures were stabilized for >1 day by waxy starch acetate/octenylsuccinate and acetate/dodecenylsuccinate but not starch acetates. In summary, these starch esters may represent biodegradable, economical alternatives to some emulsifiers and coating polymers currently in use.

Esterification of starch with sodium selenite and selenate

Granular potato starch was esterified with selenous and selenic acid sodium salts in the microwave assisted solid state reaction. Degree of esterification (DE) in both cases did not exceed 3.01 × 10 −2. Reaction with selenite provided higher DE. DE increased with the applied power of the microwave oven but increased amount of admixed selenium reagents had no positive effect upon DE. The thermal stability of products was higher than that of native starch. The esterification retained granularity of starch but the crystallinity of granules partly ceased as indicated by scanning electron microscopy (SEM) and X-ray diffractometry, respectively.

Esterification of select polyols with d-glucaric acid as model reactions for esterification of starch

Aqueous solutions of d-glucaric acid and model polyols xylitol, methyl α- d-glucopyranoside or β-cyclodextrin were freeze dried, then heated, and the product mixtures analyzed by instrumental methods that included GC–MS, electrospray ionization-mass spectrometry (ESIMS), and NMR. The thermal process and analyses were carried out with these polyols in order to determine to what extent multiple acylations of the alcohol functions occurred with d-glucaric acid lactones serving as acylating agents, the extent to which acylations occurred at the 1° alcohol sites, and the relative tendency for acylations to occur at the C1 or C6 end of the glucaryl unit. The results of these studies showed an overwhelming preference for 1° alcohol acylation and preferred acylation occurring at the C1 end of the glucaryl unit.

Selected novel materials from polysaccharides

Blending of starch with some polysaccharide gums can provide complexes improving flow behavior and textural properties of starch pastes. Either deep freezing and thawing or controlled soaking of starch granules in water improves their surface sorption and is making them effective natural microcapsules. The efficient microencapsulation can also be achieved by a rapid microwave heating of granular starch in suspension of the compounds microencapsulation of which is attempted. The microwave heating of starch blended with generated in situ Mg(HSO 4 ) 2 as well as Na 2 SeO 3 or Na 2 SeO 4 provided a wasteless, solid state esterification of starch. Magnesium salts of starch sulphate are potential plastidzers for hydraulic binders, and selenated starch can be considered as a source of bioacceptable selenium for yeast and other organisms. The oxidation of starch with periodate with electrochemical recovery of periodate provided an easy access to dialdehyde starch. It was transformed into starch dialdehyde dihydrazone, dioxime, disemicarbazone, and dithiosemicarbazone. These derivatives bind numerous metal ions forming complexes. Dialdehyde starch disemicarbazone applied to a soil contaminated with heavy metals inhibited heavy metal uptake by maize grown on that soil.

Enzymatic esterification of starch using recovered coconut oil

Modification of maize and cassava starches was done using recovered coconut oil and microbial lipase. Microwave esterification was advantageous as it gave a DS 1.55 and 1.1 for maize starch and cassava starch, respectively. Solution state esterification of cassava starch for 36 h at 60 °C gave a DS of 0.08 and semi-solid state esterification gave a DS of 0.43. TGA and DSC studies showed that the higher DS attributed to the thermostability, since onset of decomposition is at a higher temperature (492 °C) than the unmodified (330 °C) and was stable above 600 °C. α-Amylase digestibility and viscosity reduced for modified starch.

Octenyl Succinic Anhydride Modified Early Indica Rice Starches Differing in Amylose Content

Seven early indica rice starches with different amylose contents were modified by octenyl succinic anhydride (OSA) in aqueous suspension systems to evaluate the effect of amylose contents on starch esterification. The crystalline structure and pasting properties of starches were investigated using X-ray diffraction and a Rapid Visco Analyzer (RVA). The results indicated that the amylose content had a positive impact on the OSA modification. As the amylose content increased from 0 to 39.6%, the degree of substitution increased from 0.024 to 0.030 and the reaction efficiency increased from 62.8 to 77.5%. X-ray diffraction scans confirmed that the amylose was mainly present in the amorphous domain of the granule and was highly substituted after the OSA treatment. The RVA profiles demonstrated that the OSA starches had higher viscosities than their native counterparts. Moreover, negative correlations were observed between the amylose content and the major RVA parameters (e.g., peak viscosity, hot paste viscosity, cool paste viscosity, and breakdown viscosity).

Rapid preparation of starch maleate half-esters

A novel method for the rapid preparation of starch esters is described herein, by rapid heating using microwave or conventional means. A 5-min method to prepare starch maleates with degree of substitution (DS) up to 0.25 was developed when microwave or conventional source assisted fast heating of starch in dimethyl sulfoxide (DMSO) reacted with 0.5 equiv. maleic anhydride in the presence of 0.5 equiv. of pyridine with a reaction efficiency of 50%. For a given amount maleic anhydride higher amount pyridine gave higher DS. The reactivities of maleic and succinic anhydrides were compared. Succinic anhydride/starch gave DS of 0.3 as compared to only 0.1 with maleic anhydride/starch. The effects of varying reaction time, microwave power, anhydride and pyridine amount on the reaction yield and composition were studied. Proton NMR and IR were used to determine the DS. Instead of microwave when reactions were heated with a conventional heat source, starch esterification reactions gave starch maleate with lower DS.

Studies on the Film Formation of Polysaccharide Based Furan‐2‐Carboxylic Acid Esters

AbstractFuran‐2‐carboxylic acid esters of xylan, cellulose, curdlan, dextran, and starch were synthesized and studied regarding their film formation abilities. The polysaccharide esters were utilized to prepare films of different appearance. To investigate supermolecular structures of the biopolymer derivatives, atomic force‐ and scanning electron microscopy were applied. The surface roughness and the macro‐pore size and ‐distribution of the polysaccharide ester films were characterized. Starch furan‐2‐carboxylic acid ester (starch furoate) did not show film formation. In contrast, dextran furoates are very well suitable for the surface coating of inorganic compounds while the xylan‐, cellulose‐, and curdlan derivatives yield self‐supporting films with different surface characteristics.

Thermal reactions of starch with long-chain unsaturated fatty acids. Part 2. Linoleic acid

The significance and numerous applications of products resulting from reactions of starch with fatty acids induced our interest in checking thermal reaction of potato starch with linoleic acid. Behaviour of the starch–linoleic acid blends was monitored by means of thermogravimetric (TG), differential thermogravimetric (DTG), and differential scanning calorimetric (DSC) methods. The reaction carried out on conventional heating provided mixture of linoleic acid starch ester and oligomers of esterified starch. The major factors affecting the esterification reaction were optimised. The changes in the structure of starch were verified by FTIR, and 1H NMR spectroscopy, scanning electron microscopy and high pressure size exclusion chromatography. Water uptake, degree of substitution (elemental analysis and 1H nuclear magnetic resonance), reaction yield, degree of unsaturation, and susceptibility to α-amylase were also determined. As degree of esterification increased, water binding capacity of the preparations decreased. Under reaction conditions applied, starch lost, in part, its granularity, iodine value increased with degree of esterification of starch, and susceptibility of the esters to α-amylolysis slightly decreased.

Organic Solvent‐free Transesterification of Various Starches with Lauric Acid Methyl Ester and Triacyl Glycerides

AbstractThis study deals with the organic solvent‐free synthesis of fatty acid esters of high‐amylose maize (amylomaize) starch by transesterification with lauric acid methyl ester using potassium laurate as catalyst. The process involves thermal pretreatment of amylomaize in order to swell the polysaccharide and increase its accessibility and reaction with the esterification reagent. The swelling degree (Q) was monitored by UV‐Vis spectrophotometry and scanning electron microscopy (SEM), whilst the formation of a complex between amylose and potassium laurate was confirmed by X‐ray diffraction and FTIR studies. The transesterification reaction was carried out at 190°C and a central composite design was used to obtain the corresponding contour plots with a second order model (y = β0 + β1 X1 + β2 X2 + β12 X1 X2 + β11 X1 X1 + β22 X2X2) and a confidence interval of 95%. The experimental design consisted of two independent variables, reaction time (2–6 h) and catalyst (2.2 – 33.8 meq catalyst per eq. glucose), and two dependent variables, the degree of substitution (DS) and the yield of the amylomaize starch ester (Y,%). Maximum transesterification of amylomaize starch (DS = 0.61) was obtained after 4:30 h at 190°C with an intermediate concentration of catalyst (18 meq per eq. glucose). Finally, the optimized results were extended to other starch sources and vegetable oils.

Elaboration and Characterization of Starch/ Poly(caprolactone) Blends

AbstractA starch‐based biodegradable material was prepared in two steps. Firstly, starch was chemically modified by using formic acid at 20°C to obtained degrees of substitution of about 1.2. The level of destructuration was also assessed using dynamic rheological measurements. Native starch or starch ester were then mixed with poly(caprolactone) and different polyester oligomers were added as compatibilisers and plasticizing agents. PCL oligomers were found to be the most efficient ones. A significant improvement of the elongation at break of starch formate/PCL/oligo PCL blends was achieved.

Possibilities of Mass Spectrometry and Tandem‐Mass Spectrometry in the Analysis of Cellulose Ethers

AbstractThe investigation of the substituent pattern of cellulose and starch ethers and esters on various structural levels as in the glucosyl unit, along the polymer chain, and over the polymer molecules, still is a very challenging task.By means of mass spectrometric methods as ESI‐MS or MALDI‐TOF‐MS the composition of oligosaccharide mixtures which represent the substituent distribution in the original polymer can principally be determined. However, to obtain reliable quantitative data mass spectra must be recorded under appropriate instrumental conditions and after special sample preparation While O‐methyl/O‐methyl‐d3‐oligosaccharides give representative data with the mentioned MS techniques and FAB‐MS as well, hydroxyalkyl ethers require labelling with a quaternary ammonium tag and MALDI‐TOF‐MS to prevent discrimination of lower substituted oligosaccharides. In this way, information on the neighbourhood of glucosyl units in the polymer chain is available which – together with the monomer composition – is a valuable parameter to describe a random or a heterogeneous pattern with regions of local higher densities of substituents compared to the random model, a regular distribution, or a block‐like substituent pattern, i.e. a more clustered localisation of substiuents in the polymer chain. In addition, tandem‐mass spectrometry (ESI‐MSn) allows to gain further insight in the composition of isomeric oligosaccharide derivatives of the same m/z ratio and to calculate the complete monomer composition of methyl celluloses.

Enzyme-Catalyzed Regioselective Modification of Starch Nanoparticles

The selective esterification of starch nanoparticles was performed using as catalyst Candida antartica Lipase B (CAL-B) in its immobilized (Novozym 435) and free (SP-525) forms. The starch nanoparticles were made accessible for acylation reactions by formation of Aerosol-OT (AOT, bis(2-ethylhexyl)sodium sulfosuccinate) stabilized microemulsions. Starch nanoparticles in microemulsions were reacted with vinyl stearate, e-caprolactone, and maleic anhydride at 40 °C for 48 h to give starch esters with degrees of substitution (DS) of 0.8, 0.6, and 0.4, respectively. Substitution occurred regioselectively at the C-6 position of the glucose repeat units. Infrared microspectroscopy (IRMS) revealed that AOT-coated starch nanoparticles diffuse into the outer 50 μm shell of catalyst beads. Thus, even though CAL-B is immobilized within a macroporous resin, CAL-B is sufficiently accessible to the starch nanoparticles. When free CAL-B was incorporated along with starch within AOT-coated reversed micelles, CAL-B was als...

Thermal properties of starch succinates

Starch succinates are starch derivatives used as binders and thickening agents in foods, tablet disintegrants in pharmaceuticals, surface sizing agents and coating binders in paper. A series of starch esters with different degrees of substitution (DS = 0.008–0.639) prepared by reactive extrusion were studied. Potato, wheat and corn starch were investigated. Thermooxidative behaviour of starch succinates was studied by simultaneous thermal analysis–mass spectrometry (STA–MS) method. The thermal stability of starch esters depends on the degree of substitution (DS). With an increase in DS, thermal stability increases. The major differential thermogravimetric (DTG) peaks are observed below 300 °C. The most abundant ions found are H 2O + and CO 2 +.

Thermal stability of starch benzoate

Starch esterification with benzoyl chloride was performed in two steps, the first being the alkali treatment of the starch and the second, esterification. Samples of hydrophobic starch benzoate were synthesized with degrees of substitution: 0.73, 1.18 and 1.76 and their thermal stability was investigated by non-oxidative, non-isothermal thermogravimetry. It was shown that starch benzoate was thermally less stable than native starch, the thermal stability decreasing with increasing degree of substitution. The results indicated that the scission of CO 2 and/or benzoyl groups probably occurred in the temperature region 100–260 °C, depending on the degree of substitution. The overall activation energies of thermal degradation were calculated by the Flynn–Wall method.

A straight way to regioselectively functionalized polysaccharide esters

The topic of this contribution ID a novel method for regioselective esterification of starch, similar polysaccharides and cyclodextrines avoiding protecting or activating groups. A broad spectrum of polysaccharides could be acylated selectively at the C-2 position of the AGU. The reaction principle ID based on a transesterification of a carboxylic acid vinyl ester with the hydroxyl groups of the polymer ID the presence of a low molecular salt. The interaction of the reaction participants and the solution state of the polysaccharides enable this selective functionalization. The structure characterization of the new polysaccharide derivatives ID carried out by NMR spectroscopy, especially the HMBC technique, after a complete esterification of the free hydroxyl groups with a suitable carbon acid anhydride.