Analysis of Molar Substitution of Hydroxybutyl Group by Zeisel Reaction in Starch Ethers

A new etherified starch, δ-hydroxybutyl starch (δ-HBS), was prepared by utilising 4-chlorobutan-1-ol as the etherifying reagent. The method of Zeisel gas chromatography for the determination of the molar substitution was described. This technique offers a simple and rapid method for quantitative analysis with reproducible results. Meanwhile, the mechanism of the Zeisel reaction was also investigated.

Oxidation Level and Glycidyl Ether Structure Determine Thermal Processability and Thermomechanical Properties of Arabinoxylan-Derived Thermoplastics

Herein we present arabinoxylan (AX)-based thermoplastics obtained by ring opening oxidation and subsequent reduction (dA-AX) combined with hydrophobization with three different glycidyl ethers [n-butyl (BuGE), isopropyl (iPrGE) and 2-ethylhexyl (EtHGE) glycidyl ether]. We also present the relationship of structural composition, thermal processing and thermomechanical properties. The BuGE and iPrGE etherified dA-AXs showed glass transition temperatures (T_g) far below their degradation temperatures and gave thermoplastic materials when compression-molded at 140˚C. The BuGE (3 mole) etherified dA-AX films at 19 and 31 % oxidation levels exclusively exhibit 244 % (±42) and 267 % (±72) elongation. In contrast, iPrGE-dA-AX samples with shorter and branched terminals in the side chains had maximum 60 % (±19) elongation. The dramatic difference in elongation is assumed to be due to the presence of longer alkoxide chains, higher molar substitution and dual T_g for the BuGE samples. Such superior elongation of AX thermoplastic films and its relationship with molar substitution and T_g has not been reported before.

Oxidation Level and Glycidyl Ether Structure Determine Thermal Processability and Thermomechanical Properties of Arabinoxylan-Derived Thermoplastics

Herein we present arabinoxylan (AX)-based thermoplastics obtained by ring opening oxidation and subsequent reduction (dA-AX) combined with hydrophobization with three different glycidyl ethers [n-butyl (BuGE), isopropyl (iPrGE) and 2-ethylhexyl (EtHGE) glycidyl ether]. We also present the relationship of structural composition, thermal processing and thermomechanical properties. The BuGE and iPrGE etherified dA-AXs showed glass transition temperatures (T_g) far below their degradation temperatures and gave thermoplastic materials when compression-molded at 140˚C. The BuGE (3 mole) etherified dA-AX films at 19 and 31 % oxidation levels exclusively exhibit 244 % (±42) and 267 % (±72) elongation. In contrast, iPrGE-dA-AX samples with shorter and branched terminals in the side chains had maximum 60 % (±19) elongation. The dramatic difference in elongation is assumed to be due to the presence of longer alkoxide chains, higher molar substitution and dual T_g for the BuGE samples. Such superior elongation of AX thermoplastic films and its relationship with molar substitution and T_g has not been reported before.

Evaluation of Effects of Increasing Molar Substitution of Hydroxypropylene on Physicochemical, Functional and Morphological Properties of Starch from Water Yam (Dioscorea Alata)

Amidst rising demand for modified starch, hydroxypropylated derivatives from water yam, an underutilized tropical botanical source remains unexplored. The objective of this work therefore is to extract starch from water yam, modify same by hydroxypropylation and determine their physicochemical, functional and morphological characteristics. Extraction of starch was carried out by blending peeled water yam previously soaked in 0.2%(w/v) NaHSO3 solution and filtering the resulting slurry. The filterate was next suspended in 0.2% NaOH solution, allowed to sediment and the supernatant oven-dried (400C) for 24 hrs. The dried product was subjected to hydroxypropylation (HP) (propylene oxide 4-12%/100g starch) and extent of molar substitution (MS) determined. The native and Hydroxypropylated starch (HPS) were evaluated for physicochemical, functional and morphological characteristics following standard methods. Pasting properties were analysed using Rapid Visco Analyzer (RVA) and elucidation of inherent functional groups was carried out by analyzing the FTIR Spectrum. Starch yield of 84.2% (dry wt. basis) and molar substitution (0.0024-0.05) of HPS were established. Bulk density increased (0.4988-0.6005g/cm3) with MS. There was significant (p=0.05) increase in the degree of Whiteness (W) (42.4-63.6%). Although granule size reduction was evident (33.88-33.43µm), hydroxypropylation did not affect their morphology. There was decline in concentrations of crude protein (0.18-0.01%), ash (1.35-0.34%) and amylose (44.19-37.48%) as MS rose. In contrast, there was significant (p=0.05) increase in water (1.76-2.66g/g) and oil absorption capacities (0.72-1.42g/g), swelling power (1.54-4.19g/g) and solubility (3.17-5.84g/g) at 500C. Freeze thaw cycles showed marked reduction in syneresis (10.3-1.09%) as MS increased. Peak Viscosity, pasting temperature and peak time of the HPS ranges were 297.83-583.6, 81.9-86.40C, and 4.5-7.0 mins respectively. FTIR band spectra indicated the presence of hydroxypropyl substituent groups in the modified starch. Hydroxypropylated starch (from water yam) at different molar substitution has been characterised and its properties established with strong potentials for wider applications in food systems.

DETERMINATION OF THE STRUCTURE OF CELLULOSE ETHERS BY 13C NMR SPECTROSCOPY OF PRODUCTS OF ACID-CATALYZED HYDROLYSIS

Cellulose ethers (CE) are widely used in the pharmaceutical, food and construction industries to impart the necessary rheological, thixotropic and water-retention properties to water dispersion systems. In this paper, we compare the substitution parameters of hydroxypropyl methylcellulose (HPMC), hydroxyethyl cellulose (HEC) and hydroxyethyl methylcellulose (HEMC), which are obtained from 13C NMR spectroscopy of products of acid-catalyzed hydrolysis and cellulose ethers. Accurate data on the degree of substitution at the 2, 3 and 6 positions (DSC-2, DSC-3 and DSC-6) were obtained from 13С NMR spectra of products of acid-catalyzed hydrolysis. The total degree of substitution (DStotal) and molar substitution (MS) for the hydroxyethyl and hydroxypropyl substituents were determined. The distribution of substituents at different positions of the glucopyranose link indicates that the most reactive are the C-2 and C-6 positions, as well as the hydroxyl of the hydroxyethyl fragment. Within the proposed method, the degree of substitution and molar substitution are determined: DSHPMC = 1.79 and MSHPMC = 0.38; DSHEC = 1.02 and MSHEC = 2.03; DSHEMC = 1.93 and MSHEMC = 1.82. It is shown that the results are consistent with the data obtained from 13C NMR (СРMAS) spectra of the same cellulose ethers. The proposed method of analysis is characterized by the simplicity of the experiment, the accuracy and informative of the results obtained.

DETERMINATION OF DEGREE OF SUBSTITUTION (DS) AND MOLAR SUBSTITUTION (MS) OF CELLULOSE ETHERS BY SOLID-STATE 13C NMR SPECTROSCOPY

The work is devoted to determining the substitution parameters of some commercial cellulose ethers by solid-state 13C NMR spectroscopy. The substitution parameters are the degree of substitution (DS) and molar substitution (MS). The objects of study are commercial additives based on hydroxyethyl cellulose (HEC), hydroxypropyl methyl cellulose (HPMC) and hydroxyethyl methyl cellulose (HEMC). In this paper, the degree of substitution (DS) and molar substitution (MS) were determined, and the distribution of the substituents at positions C-2, C-3 and C-6 of the glucopyranose link was established. The calculation of the degree of substitution (DS) and molar substitution (MS) is based on an analysis of relative intensity values of the spectral regions in the solid-state NMR spectra of cellulose ethers and microcrystalline cellulose. Thus the degree of substitution and molar substitution was determined: MSHEC = 1,41 иDSHEC = 1,08; MSHPMC = 0,69 и DSHPMC = 1,78; MSHEMC = 0,74иDSHEMC = 2,19. Comparison of the results with the literature data shows the effectiveness of the method. The proposed method differs from other existing methods in that it is a simple and informative.