Acacia gum known as gum Arabic, is one of the oldest nutrient ingredient. It is used in texturing, movie forming, emulsifying or bracing belongingss. Acacia Gum has been known for many old ages by scientific community as a possible beginning of dietetic fiber. More late there has been an outgrowth of a new construct called functional nutrient which is designed for advancing wellness and nutritionary benefits. The fiber fortified nutrients have the same organoleptic qualities as conventional nutrient in add-on to a important sum of dietetic fiber. These nutrients may hold effects like flaxen texture, addition in viscousness or bad gustatory sensation or coloring material which possibly restricting factors. On the other manus, Acacia gum can be added in really big sum without impacting the original gustatory sensation and texture of the nutrient in which it is incorporated. This is because of the extremely complex polymeric construction.
Acacia Gum appears in many ‘Pharmacopoeias ‘ . The gummy exudation which flow of course or obtained by the scratch of the bole and subdivisions of Acacia Senegal and other species of African Origin is known as Acacia gum ( gum Arabic ) . these gluey exudations are purified by a simple physical procedure centrifugation and filtration without chemical or enzymatic alteration. A simple sterilization process ensures bacterial safety and eventually high H2O soluble pulverizations are obtained by spray drying and or granulation procedure.
Dissolution in H2O
Spray Drying Granulation
Fig1: Purification procedure of acacia gum
Fig2: conventional representation of Chemical Structure of Acacia Gum:
Protein Core ( 1-5 % )
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P. A. Williams and G. O. Phillips, Gum Arabic, in G. O. Phillips and P. A. Williams, Handbook of hydrocolloids, CRC Press, Cambridge, England ( 2000 ) pp. 155-168
Gum Arabic found in nature is a mixture of Ca, Mg, K salt of a polysaccharide acid ( Arabic acid ) . The chemical composing of gum Arabic is a complex and variable mixture of arabinogalactan oligosaccharides, polyoses and glycoprotein and depending on the beginning, the glycan constituents contain a greater proportion of L-arabinose comparative to D-galactose ( Acacia seyal ) or D-galactose comparative to L-arabinose ( Acacia Senegal ) . The gum from Acacia seyal besides contains significantly more 4-O-methyl-D-glucuronic acid but less L-rhamnose and un-substituted D-glucuronic acid than that of Acacia Senegal. The presence of any other carbohydrate stuff indicates that the gum is impure or contains drosss.
Physically gum Arabic is a complex, extremely branched globular molecule which is closely jammed and therefore has low viscousness. And shaped like a short stiff spiral or spiral. The length of the chief molecule concatenation ranges from 1050A to 2400A, depending on the sum of charge.
Gum Arabic consists of a combination of lower molecular weight polyose ( M.Wt. ~0.25×106 ; major constituent ) and higher molecular weight hydroxyproline-rich glycoprotein ( M.Wt. ~2.5×106 minor constituent ) with broad variableness between commercial samples. As the stuff is a combination or mixture the molecular constructions have important fluctuations and exact constructions are unsure. The glycoprotein is a high molecular weight hydroxyproline rich arabinogalactan ( ~2 % protein ) incorporating a repetitive and about symmetrical 19-residue consensus motif -ser-hypa-hypa-hypa-thr-leu-ser-hypb-ser-hypb-thr-hyp-thr-hypa-hypa-hypa-gly-pro-his with immediate hydroxyproline ( a ) attached to oligo-I±-1,3-L-arabinofurans and non-contiguous hydroxyproline ( B ) attached to galactose residues of oligo-arabinogalactans. uniting a I?-1, 3-D-galactopyran nucleus with rhamno glucurono arabino galactose pentasaccharide side ironss joined to the chief concatenation via 1, 6-linkages.
Fig 3: conventional representation of molecular construction of Acacia gum.
GAL = Galactose ARA = Arabinose
GlcA = Glucuronic acid RHA = Rhamnose
4-MeGlcA = 4-O-methylglucuronic acid
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fig 4: chemical composing representation
Gum Arabic Properties:
Gum Arabic is alone due to its high solubility in H2O. Most common gums can non be dissolved in H2O at higher concentration than approximately 5 % because of their high viscousnesss. However a solution of gum Arabic can be made of approximately 55 % concentration which acts as a high syrupy gel like mass. Due to its versatility gum Arabic can be used in lower concentration in combination with other gums as thickenings and binders. Good class gums like “ KLTA ” give solutions that are colorless, and have no gustatory sensation ( spirit ) . Poor grade gums like “ GCA ” have features coloring materials and spirits due to presence of tannic acids. Gum Arabic is indissoluble in oil and most inorganic dissolvers. It is soluble in aqueous ethyl alcohol up to l 60 % ethyl alcohol as a higher bound.
Viscosity and pH relationship
Gum Arabic is non really syrupy at low concentration. High viscousnesss are obtained with high concentration of 40 % -50 % . This ability of organizing high concentrated solution is responsible for the first-class stabilizing and emulsifying belongingss of gum Arabic when mixed with big sum of indissoluble stuffs. It has been concluded by Warner and Araujo that the first order rate for viscousness alteration may hold a definite relationship to the rate of hydrolysis of gum Arabic. Viscosity of gum Arabic rises aggressively with increasing PH to a upper limit of about 6 and falls bit by bit at approximately 12. Solution of gum Arabic is somewhat acidic with a pH of about 4-6 Because of extremely bifurcate construction ; acacia gun occupies a really low hydrodynamic volume and therefore develops a really low viscousness. decrepit acid character in H2O ( pH 4.5 ) , pH of the solution, affects the viscousness.
Fig5: Influence of concentration on viscousness of an acacia gum solution.
Fig6: Reheological features of assorted concentration of gum Arabic ( Araujo 1966 )
Rhehological gum Arabic solution exhibit typical Newtonian behavior at concentration up to 40 % and above solution become pseudo plastic as shown by lessening in viscousness with increasing shearing emphasis.
aˆ? viscousness is shear rate independent
viscousness decreases in the presence of electrolytes ( salts ) shown in fig
Fig7: realtion between viscousness ratio and concentration of salts.
Comparison with other inspissating agents shows lower viscousness of Gum Arabic solutions even at higher concentrations
Gum Arabic is an effectual emulsifying agent because of its protective colloidal functionality. Thus can be used in oil in H2O nutrient emulsion. It can bring forth stable emulsions in oil with a broad scope of pH and in the presence of an electrolyte. Mechanism of emulsification is still non clear, but gum Arabic signifiers a seeable movie at oil interface. As a movie organizing agent it prevents coalescency of the oil globules, therefore allowing a high grade of scattering by decline of the diameter of the globule. With the spread stage ( oil ) the comparative viscousness of emulsion alterations besides there is noticeable alteration in volume fraction which possibly because of the presence of a stabilising agent or its thickness… emulsifier for indispensable oils and spirits, proteins adsorb on the surface of the oil droplets formed emulsions remain stable for a long period of clip
Prolonged warming ( & gt ; 70 A°C ) of Gum Arabic solutions causes precipitation of the proteinous constituents.
Explanation of gum Arabic in drink emulsion ( gum and stabilizers for nutrient industry 15 )
Mention: Matthias Schiutz, industry demand for hydrocolloids in drink emulsion, Science and Technology, Flavour Delivery Science, Switzerland
.For drink emulsion A.senegal derived gum is by and large used. The protein anchor of that fraction is thought to represent the hydrophobic portion of the molecule with an affinity to the oil stage where as the hydrophilic polysaccharide side concatenation remain in the aqueous stage. Recently the being of glycosyl-phosphatidylinositol lips attached to AGP fraction and their importance for the emulsifying efficiency of the gum has been reported. Attention has been paid on the interfacial rehology experiments proposing at that place mechanical stableness of the surface assimilation bed formed by the gum around an emulsion droplet plays a important function reflected by significant shear snap of the interface. The droplet size in a theoretical account emulsion found non to diminish any farther when increasing gum concentration beyond 10 % . Typical gum concentration in drink emulsion with an oil stage content of up to 20wt % . Excess gum will be necessary to stabilise the emulsion i.e. to increase the viscousness of the emulsion to efficaciously forestall hits and coalescency.
Functionality of Gum Arabic.
Gum Arabic is used as an ingredient of many nutrient merchandises ; it is used to stabilise flavour oil emulsion in the soft drink industry. It has been already introduced some of the underlying mechanism involved in the surface assimilation of acacia type gums into the interface, and by far these have been most widely studied in gum Arabic. Further surveies have given consideration to the consequence of dilution on the majority uninterrupted stage on the surface rheology of gum arabic-adsorbed o/w movies and to the correlativity between surface viscousness and emulsion stableness. The surveies show that dilution in bulk stage ensures a decrease on the surface viscousness of adsorbed gum Arabic movie ( Dickinson et al 1989 ) , nevertheless this consequence proceeds easy which suggests some little but finite loss of macromolecule stuff from interfacial part. It besides presumes that structural distortion takes topographic point. In decision this hypothesis postulates that little fraction of gum Arabic supermolecule shows good movie organizing belongingss. It has been studied whether a relationship holds between N content of high molecular weight fraction which is responsible for stabilising the gum against flocculation and the strength and thickness of the movie formed at o/w interface stabilized by gum Arabic sample of changing N content. ( Dickenson and Stainsby 1988 ) . The grounds showed that effectual emulsifying behavior is found for gum holding high N content which when adsorbed gives first-class steric stabilisation.
Interaction of polyoses with adsorbed proteins
Eric Dickinson, an debut to nutrient colloids, Oxford university imperativeness, 1992
The ability of polysaccharide hydrocolloids to stabilise colloidal scattering and emulsion is normally explained in footings of a alteration of the construction and rheological belongingss of the aqueous uninterrupted stage ( Dickinsion and Stainsby ) . Due to their preponderantly hydrophilic character most polysaccharide has low surface activity at air -water and oil-water interfaces. They are non expected to organize adsorbed beds in nutrient colloids which contain proteins and low molecular weight wetting agents. Due to the low surface activity of polyoses they are seldom used ad emulsifying agents but are used as emulsion stabilizers. While sing the composing and construction of adsorbed movie in nutrient colloids, the nature and interaction between polyose & A ; adsorbed proteins and its influence on colloidal stableness are of importance. Thus it can be said that an attractive protein-polysaccharide interaction can heighten stableness by organizing a thicker and stronger steric-stabilizing bed or it can destabilise an emulsion by polyose bridging between protein-coated droplets. On the other manus a abhorrent protein-polysaccharide interaction can stabilise colloids by immobilising the spread atom in a weak or strong gel web, or it can destabilise consequence by bring oning stage separation or depletion flocculation. The ideal combination of protein polyose would bring forth optimal consequence in the preparation of nutrient colloids by conveying the emulsifying belongings of protein along with the stabilising belongings of polyose.
The strongest type of protein-polysaccharide interaction is where there is a covalent linkage of protein and saccharide medieties to organize a individual intercrossed amphiphilic supermolecule. The chief advantage of covalent bonding over noncovalent protein-polysaccharide interaction ( e.g. electrostatic ) is the care of solubility and molecular unity over a broad scope of solvent status ( pH, ionic strength, temperature. ) .
A natural protein-polysaccharide loanblend is gum Arabic ( Acacia Senegal ) . Serine and hydroxyproline residues of the proteins fractions are involved in covalent linkages to carbohydrate, ensuing in a mixture of arbinogalactan-protein complex, each incorporating from one to several branched polysaccharide units linked to a common proteins core the so called Wattle Bossoms theoretical account.
Gum Arabic is a polysaccharide heterogenous stuff. Its surface activity is low compared with nutrient proteins, it is compensated for in practise by utilizing high concentration of gums during emulsification, i.e. 1:1 gum to oil ratio, as compared with 1:10 protein-to-oil ratio for a protein-stabilized emulsion.
Shotton and Wibberley ( 1959 ) demonstrated the surface activity of Arabic acid and its salt and their ability to organize thick viscoelastic movies at oil-water interfaces.
Nakamura et Al ( 1983 ) have studied the dependance on molecular weight of the surface rheology of gums Arabic movie at the coconut oil-water interface and it is shown that there be correlativity between the surface viscousness and emulsion stableness. The survey proved that the rheological parametric quantities are increasing maps of the weight mean molecular weight, where as
interfacial tenseness under same experimental status is basically independent of molecular weight.
Anderson et Al ( 1986 ) proved that gum Arabic is similar to guar, Xanthan etc in its low degree of N. Protein content edge to the fringe of the gum molecule has major impact on its surface activity.
Testing Emulsifier efficiency
when understanding the effectivity of a nutrient emulsifying agent, it is utile to separate between emulsifying capacity ( ability to do an emulsion ) and emulsion stableness ( ability to maintain an emulsion in its freshly made province ) .
The proper manner to compare the emulsifying belongingss of nutrient proteins is to do emulsion under good controlled conditions, sooner utilizing a high force per unit area homogenizer. so to compare droplet size distribution of this emulsion as a map of clip. Taking creaming behavior of the emulsion on storage and the province of collection of the droplet. Such proving helps decrease the sever emulsifying status by utilizing lower protein concentration. There are two chief ways to find droplet size distribution for O/W emulsion, i.e. Coulter counter and light dispersing technique. In this survey light dispersing technique was used.
.In light dispersing technique atom sizing below 0.5um is used. Average particle size of droplet is determined at fixed angle. Sometime biasing towards the little atom terminal leads to overestimate of entire surface country and comparative insensitiveness to the growing of big droplets which is important in measuring emulsion stableness. In Malven Matersizer entire strength of inactive visible radiation dispersing over a broad scope of dispersing angles is used to give the complete droplet size distribution. this technique the lone uncertainness is the values of optical input parametric quantities
The Malvern Mastersizer S is a individual lens laser diffraction system. It uses a optical maser of 2 factory Wattss He Ne power to mensurate the size of atoms. Laser dispersing theory used are Mie theory, and Fraunhofer analysis. Knowledge of the dispersing theory and atom belongingss is used to transform the scattered visible radiation informations to a distribution of atom size information to the package running on Personal computer. Particle scattering size is in the scope of 0.5-3500 micrometer depending on the texture and merchandise. The samples are introduced into the optical maser by agencies of the appropriate accoutrements. The little volume sample scattering unit splashs and pumps little volumes of sample through the trial cell. It is activated by a control box, which displays and adjusts the velocity. This is connected to the Mastersizer digital I/O so that the velocity can be automatically recorded by the trial package. A
Please attach the exposure and sample consequence
A UV spectrophotometer is a device used to analyze the interaction between radiation and stuffs in the signifier of liquid concentration at a corresponding wavelength at 400-700 nanometer. It measures seeable visible radiation and seeable scope of UV and infrared spectrum. In our experiment we have used wavelength of 495 ( nanometer ) for different concentration of gum. The optical density values are plotted by taking the mention sample at 495 ( nanometer ) incorporating the mix of the dye, ethyl alcohol and deionised H2O. The optical density graph is plotted against the concentration with the available spectrophotometric reading and characteristic curve is plotted. This helped us to read the difference in behavior of KLTA and GCA at different phi
Consequence of high-hydrostatic force per unit area and Ph on gum Arabic.
A.G.Panteloglou, A.E.Bell, F.Ma, Division of nutrient scientific discipline ( Nottingham ) & amp ; Department of nutrient scientific discipline ( Reading ) , Elsevier, February 2010.
The potency of high force per unit area is been used in both nutrient processing and continuing method in nutrient industry. Gum Arabic is a natural infusion, peculiarly utile in acidic status ( Dickinson, 2003 ) . Presently as per surveies it is accepted that high force per unit area may convey about alterations in hydrophobic association, H bonding and electrostatic interaction ( Ledward, 1995 ) . High force per unit area leaves covalent bonds integral and affects merely the non covalent 1s.
It has been demonstrated by Gross et Al. ( 1994 ) that the covalent bonds and the primary construction of the proteins and polyose are non ruptured by force per unit area due to the negligible squeezability of the covalent bonds. Ability to impact the secondary bonds go forthing the covalent bonds mostly integral, high force per unit area processing denatures high molecular weight molecules and cell construction and alter their functionality and go forthing low molecular weight chemically unaffected. Till day of the month really less has been published on consequence of high force per unit area on physical belongingss of gum Arabic.
In this survey two gum of different qualities where used they were force per unit area treated at different pH ( 2, 4, 8 ) . Type1 gum was good gum called KLTA. this is a spray dried readying of Kordofan gums, described as light type due to its pale coloring material. Type 2 gum was hapless gum called GCA.which is a spray dried gum, derived from a gum corbretum and normally has inferior rheological and emulsifying belongingss.