Hydroxypropylation Of Starch Research Articles

Sheet‐extruded films from blends of hydroxypropylated and native corn starches, and their characterization

AbstractSheet‐extruded films from the blends of hydroxypropylated normal corn starch (HP) and native normal corn starch (NS) at weight ratios of 100:0, 90:10, 70:30, 50:50, 30:70, and 0:100 were prepared and characterized. Glycerol and water were added as plasticizers at 11 and 27% starch weight, respectively. The highest tensile strength (TS) and longest elongation to break (EB) for dry films were observed at 70:30 HP: NS ratio, which was 25.76 MPa, and 3.97%, respectively. However, TS and EB of this 70:30 blend extruded starch film exhibited low resistance upon wetting for 10s. The film TS and EB were reduced to 13.26 MPa and 3.35%, respectively. Addition of 0.5% (wt/wt starch) succinic acid (SA) as a cross‐linker to 70:30 HP: NS starch blend before film extrusion positively affected both TS and EB of films upon wetting; rather higher TS (16.64 MPa) and EB (4.85%) values were observed, which indicated improvement in water resistance of the films. Sheet‐extruded films from 70:30 HP: NS blends resulted in improved dry strength, and upon cross‐linking with SA, improved wet strength as well. The films had smooth and compact structure, which was explained by esterification/transesterification reactions promoted by SA, and confirmed by Fourier‐transform infrared spectroscopy analysis.Practical ApplicationsManufacturing packaging films from biological sources, as well as coating materials, would be beneficial to the environment along with wider applications. Biobased packaging materials include both edible coatings and edible films along with primary and secondary packaging materials, and could also have non‐food applications. They are derived from renewable sources and are potentially biodegradable through composting (which is a technique for waste management). Hydroxypropylation of starch results in wider functionality, and sheet‐extrusion can result in more flexible and transparent films. Blends of 70:30 HP: NS resulted in stronger sheet‐extruded films; testing of both dry and wet strengths of films indicated its suitability for both as edible coating (wet application), and other dry coatings/ films. These blend film can be an alternative to synthetic packaging films within their limitations.

Synthesis of hydroxypropylated debranched pea starch with high substitution degree in an ionic liquid, and its characterization and properties

Hydroxypropylation of debranched pea starch (DPS) has been carried out effectively in an ionic liquid, 1-butyl-3- methylimidazolium chloride, in order to shorten the long time required by starch being normally hydroxypropylated and improve the characteristics of pea starch (PS). As a result, hydroxypropylated debranched pea starch (HDPS) with molar substitution up to 1.34 has been obtained in homogeneous system within 3 h, which was much less than time (18 h) required by normal hydroxypropylation of starch. Based on the synthesis, HDPS was further characterized by infrared spectroscopy, X-ray diffraction, scanning electron microscopy and transflective polarizing microscope, respectively, and some of its properties were also compared with those of PS, DPS and hydroxypropylated pea starch (HPS). The experimental results indicated that the crystalline structure of PS belonged to a C-type; and one of DPS was between B-type and C-type, whereas HDPS structure was almost completely amorphous. The debranching and hydroxypropylation evidently influenced the pasting behavior and thermal properties of PS. The morphology and size of DPS and HDPS particles were remarkably different from those of PS owing to hydroxypropylation and debranching. The peak intensity of –OH groups in DPS and HDPS was evidently weakened by debranching compared with FTIR spectra of PS. The debranching resulted in the reduction in swelling power of DPS, but the hydroxypropylation led to the increase in the swelling power of DPS and HDPS.

Developments in Hydroxypropylation of Starch: A Review

Because hydroxypropyl starch (HPS) represents an important chemical modification of starch, extensive studies on hydroxypropylation are being carried out at various research centers worldwide. The present review summarizes development of methods for determination of the MS (molar substitution)/DS (degree of substitution) of hydroxypropyl starch, location of hydroxypropylation reaction sites in granules and on amylose and amylopectin molecules, and factors affecting reaction efficiency. Also presented is an overview of changes of physicochemical properties of starch that result from hydroxypropylation. Specifically reviewed are the effects of hydroxypropylation on granule morphology, crystallinity, thermal properties, swelling, and solubility; pasting, paste, and retrogradation properties; rheological and textural properties of HPS gels; and digestibility and uses of HPS.

The hydroxypropylation of starch in a self‐wiping twin screw extruder

AbstractPotato starch was chemically modified in an APV self‐wiping twin screw extruder to produce hydroxypropylated starch. The product obtained had a molar degree of substitution (MS) between 0.06 and 0.26. The selectivity of the hydroxypropylation reaction varied between 50 and 95%, yields varied between 15 and 95%, and conversions between 30 and 91%. Using viscosity data of native and hydroxypropylated starch, together with extruder parameters like temperatures, residence time distribution, and shear rates, a model was set up to predict the MS values, conversions, and selectivities. With this model, interactions between temperature, reaction, and viscosity can be understood and predicted. © 2003 Wiley Periodicals, Inc. Adv Polym Techn 22: 56–68, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10034

Kinetics of the hydroxypropylation of potato starch in aqueous solution

Kinetic results are presented for the hydroxypropylation of Potato starch with methyloxirane in aqueous solution. Reaction temperatures were varied from 303 to 362 K. Sodium hydroxide was used as a catalyst. The overall conversion rate of methyloxirane in alkaline starch solution is determined by the rate of four parallel reactions: the catalyzed and uncatalyzed hydroxypropylation of starch and the catalyzed and uncatalyzed hydrolysis of methyloxirane. All reactions appear to be first order in both reactants. The temperature dependency of all rate constants can be described by an Arrhenius equation, as follows: for catalyzed hydroxypropylation, k1,1 = 42.8 X 10(3)e-66390/RT; for uncatalyzed hydroxypropylation, k*1,1 = 39e-71200/RT; for catalyzed hydrolysis of methyloxirane, k1,1** = 32.8 x 10(4)e-71400/RT; for uncatalyzed hydrolysis of methyloxirane, k1,1*** = 449.4e-77150/RT; with k in m3/(mol.s), R in J/(mol.K), and the energy of activation in J/mol. The dissociation constant of starch hydroxyl groups could be calculated from the experimental results. The temperature dependency of the pK(a) of the starch hydroxyl groups could be fitted with the equation pK(a) = 2174(1/T) + 6.06 (T in K).

Identification and Quantitation of Hydroxypropylation of Starch by FTIR

AbstractFTIR spectrocopy was used to detect hydroxypropylation in modified starches. Use of derivative difference spectroscopy enabled development of a method for estimating the degree of substitution. Infra‐red spectra of a hydroxypropylated starch, and its unmodified precursor are acquired. The second derivative of the difference spectrum between the two is calculated, and the area of the peak centred at 2974cm−1 is estimated. This yields hydroxypropyl value after comparison with a calibration curve.