Glyn O. Phillips

Food Polysaccharides and Their Applications

Introduction, Alistair M. Stephen and Shirley C. Churms Starch: Structure, Analysis, and Application, Henry F. Zobel and Alistair M. Stephen Modified Starches, Otto B. Wurzburg Starch Hydrolysates, Paul H. Blanchard and Frances R. Katz Cellulose and Cellulose Derivatives, Donald G. Coffey, David A. Bell, and Alan Henderson Galactomannans and Other Cell Wall Storage Polysaccharides in Seeds, Michael J. Gidley and J.S. Grant Reid Agars, Norman F. Stanley Gelling Carrageenans, Lennart Piculell Alginates, Kurt Ingar Draget, Storker T. Moe, Gudmund Skjak-Braek, and Olav Smidsrod Inulin, Anne Franck Pectins: Structure, Functionality, and Uses, J.A. Lopes da Silva, and M.A. Rao Bacterial Polysaccharides, V.J. Morris Gums and Mucilages, Peter A. Williams, Glyn O. Phillips, Alistair M. Stephen, and Shirley C. Churms Chitosans, Kjell M. Varum and Olav Smidsrod Polysaccharides in Food Emulsions, George A. van Aken Polysaccharide Rheology and In-Mouth Perception, K. Nishinari Phase Behavior in Mixed Polysaccharide Systems, Vladimir Tolstoguzov Dietary Fiber, Andrew Chesson Genetic Engineering and Food Crops, Jennifer A. Thomson Detection and Determination of Polysaccharides in Foods, Yolanda Brummer and Steve W. Cui Index

Handbook of hydrocolloids

Introduction. Agar. Starch. Gelatin. Carrageenan. Xanthum Gum. Gellan Gum. Gallactomannans. Gum Arabic. Pectins. Milk Proteins. Cellulosis. Tragacanth and Karaya. Xyloglucan. Curdlan. Glucans. Soluble Soybean Polysaccharide. Bacterial Cellulose. Microcrystalline Cellulose. Gums for Coating and Adhesives.Chitosan Hydrogels. Alginates. Frutafit-Inulin. The CRC Emulsifying Biopolymer.

Introduction to food hydrocolloids

Abstract: This introductory chapter provides an overview of the source, market, functional characteristics and regulatory aspects of hydrocolloids used in foods. Examples of a number of different food products are given and the role of the hydrocolloids in controlling their texture and properties is discussed. A brief introduction to the rheological properties of the various types of hydrocolloids is provided and comparisons of the viscosity and viscoelastic behaviour are given. Many hydrocolloids are able to form gels in response to changes in temperature and/or in the presence of ions. The various mechanisms by which gelation occurs are summarised. The interactions that occur in systems containing mixtures of hydrocolloids are considered and combinations demonstrating synergistic behaviour are highlighted. The role of hydrocolloids as dietary fibre is an area of increasing importance because of the associated benefits for health and this area is briefly reviewed.

New Insights into the Structural Characteristics of the Arabinogalactan−Protein (AGP) Fraction of Gum Arabic

The structural characteristics of the gum exudate of Acacia senegal (gum arabic) have been investigated by monitoring the composition and physicochemical properties before and after treatment with proteolytic enzyme and various alkaline systems. Molecular mass ( M w) and radius of gyration ( R g) measurements were performed using gel permeation chromatography (GPC) coupled to refractive index, UV absorbance, and multiangle light scattering detectors and indicated that the macromolecules present have a compact structure. It was found that treatment with proteolytic enzyme caused the arabinogalactan-protein component (AGP) with average molecular mass approximately 2 x 10 (6) Da to degrade, yielding material of molecular mass approximately 4 x 10 (5) Da, whereas the bulk of the material corresponding to the protein-deficient arabinogalactan component (AG) with molecular mass 4 x 10 (5) remained unaffected. Barium hydroxide was found to hydrolyze the polysaccharide component (AG) itself in addition to the proteinaceous component as demonstrated in control experiments using dextran. However, sodium borohydride/sodium hydroxide treatments were unable to hydrolyze dextran and were assumed to hydrolyze only the proteinaceous component of gum arabic. The AGP component was completely degraded, yielding material of molecular mass approximately 4.5 x 10 (4) Da. It has been concluded, therefore, that the enzyme did not fully hydrolyze all of the protein present and that the AGP component of gum arabic consists of carbohydrate blocks of approximately 4.5 x 10 (4) Da linked to a polypeptide chain consistent with the wattle blossom structure. Because the AGP was degraded to differing extents using a mild and more severe sodium borohydride/sodium hydroxide treatment, it was concluded that the polysaccharide moieties were linked through both O-serine and O-hydroxyproline residues. The gum arabic sample was deglycosylated by treatment with anhydrous hydrogen fluoride and revealed the presence of two putative core proteins of approximately 3 x 10 (4) and approximately 5 x 10 (3) Da, respectively, which correspond to proteins of approximately 250 and 45 amino acids in length. A new model for the structure of the AGP component has been proposed.

The molecular characterisation of the polysaccharide gum from Acacia senegal

Abstract Gum arabic (Acacia senegal gum) was fractionated by hydrophobic interaction chromatography on Phenyl-Sepharose CL-4B and yielded four fractions of similar carbohydrate composition, whilst differing in protein content, amino acid composition, and molecular mass distribution. All four fractions interacted with an array of anti-arabinogalactan-protein (AGP) monoclonal antibodies via anti-carbohydrate epitopes and were precipitated by Yarivs reagent, suggesting that they were all AGPs. Further characterisation using SDS-PAGE and Western blotting showed that all fractions contained proteins of molecular mass 30 000–45 000 with at least one protein unique to each fraction. The fractions were subjected to enzymatic (with pronase) and alkaline hydrolysis, and the molecular mass distribution of the products was monitored by gel permeation chromatography. The fractions showed various degrees of resistance to hydrolysis, thus illustrating differences in their macromolecular structure.

Viscometric and spectroscopic studies on the solution behaviour of hydrophobically modified cellulosic polymers

Abstract The solution properties of hydroxyethyl cellulose (HEC) and hydrophobically modified hydroxyethyl cellulose (HM-HEC) have been investigated by means of viscometric and spectroscopic techniques involving free radical and fluorescent probes. The greater viscosity of HM-HEC solutions above a critical polymer concentration (Cp) of approximately 0·2% has been interpreted in terms of the formation of a three-dimensional network structure in which the polymer chains are effectively crosslinked by the intermolecular association of neighbouring hydrophobic side chains. Cp is considerably less than the predicted polymer coil overlap concentration (C∗) of approximately 1%. The interaction of the polymers with an anionic surfactant, sodium dodecyl sulphate (SDS) has also been investigated. A mechanism involving the interaction of free surfactant with the regions of intermolecular hydrophobic association is suggested to account for the considerable differences in the rheological behaviour of the polymers in the presence of SDS.

The reactivity of various free radicals with hyaluronic acid: steady-state and pulse radiolysis studies

The reactions of the primary water radicals with the biopolymer hyaluronic acid have been studied by pulse radiolysis. Bimolecular rate constants, expressed in terms of the disaccharide repeating sub-unit of hyaluronic acid, for OH., H. and eaq- were found to be 7 X 10(8) M-1 X s-1, 5 X 10(7) M-1 X s-1 and less than 5 X 10(6) M-1 X s-1, respectively. By comparing the viscosities of samples, gamma-irradiated in the steady state under a variety of conditions, with unirradiated controls, the efficiencies with which selected radicals cause chain breakage have been determined. Efficiencies of 30%, 15%, 0%, 0.2% and 5% were estimated for OH., H., eaq-, methanol radicals and tert-butanol radicals, respectively. The presence of oxygen during irradiation increased the extent of chain breakage by a factor of 1.75.

A LASER FLASH PHOTOLYSIS STUDY OF THE NATURE OF FLAVIN MONONUCLEOTIDE TRIPLET STATES AND THE REACTIONS OF THE NEUTRAL FORM WITH AMINO ACIDS

Abstract— Primary photochemical processes in aqueous solution have been characterised for FMN. The influence of pH on these processes is attributed to protonation of the neutral triplet and not to the presence of a dimeric species as postulated earlier. Second order rate constants for reaction between the neutral triplet and some naturally occurring amino acids are reported.

Comparative rheological behavior of hyaluronan from bacterial and animal sources with cross-linked hyaluronan (hylan) in aqueous solution

Using a variety of rheological techniques, the behavior of hyaluronan (M(w) 0.8-2.2 x 10(6)), cross-linked hyaluronan (hylan) (M(w) 1.8-12.5 x 10(6)), and Healon (M(w) approximately 5 x 10(6)) (a proprietary hyaluronan) was studied over a large range of molecular weights. The object was to study the effect of the cross-links in hylan on the various rheological parameters, in comparison with linear hyaluronan. There are significant differences. The Huggins constant and the critical overlap parameter C*[eta] are considerably lower for hylan and an increase in moduli at low frequencies was observed for hylan compared with the hyaluronan samples at all molecular weights studied. The results point to a difference in structure in dilute solution for hylan due to the ability to form networks, which can be removed by pressure filtration. In contrast, we do not find an increase of the steady shear viscosity and elastic modulus at higher concentrations when a homogeneous entangled network is reached. We attribute this behavior to the semirigid character of the hyaluronan chain and to the predominance of entanglements over the cross-link points present in hylan in the semidilute domain. Due to the higher apparent molecular weights that are possible with hylan structures but not with the hyaluronans currently available, a wider range of applications can be achieved with hylans when viscoelasticity is required, particularly for the viscosupplementation of synovial fluid damaged by osteoarthritis.

Complexation of Bovine Serum Albumin and Sugar Beet Pectin: Structural Transitions and Phase Diagram

The complexation between bovine serum albumin (BSA) and sugar beet pectin (SBP) was studied in situ by coupling glucono-δ-lactone (GDL) induced acidification with dynamic light scattering and turbidity measurements. Individual measurements at specific pHs and mixing ratios were also carried out using zeta potentiometry, gel permeation chromatography-multiangle laser light scattering (GPC-MALLS), and isothermal titration calorimetry (ITC). These investigations together enabled the establishment of a phase diagram of BSA/SBP and the identification of the molecular events during protein/polysaccharide complexation in relation to the phase diagram, which showed five regions: (I) a stable region of mixed individual soluble polymers, (II) a stable region of intramolecular soluble complexes, (III) a quasi-stable region of intermolecular soluble complexes, (IV) an unstable region of intermolecular insoluble complexes, and (V) a second stable region of mixed individual soluble polymers, on lowering pH. We found for the first time that the complexation could take place well above the critical pH(c), the value that most previous studies had regarded as the onset occurrence of complexation. A model of structural transitions between the regions was proposed. The borderline between region II and region III represents the BSA/SBP stoichiometry for intramolecular soluble complex at a specific pH, while that between region III and region IV identifies the composition of the intermolecular insoluble complex. Also studied was the effect of NaCl and CaCl(2) on the phase diagram and structural transitions.