FOOD CHEMISTRY Gums BY DR BOOMINATHAN Ph D

FOOD CHEMISTRY Gums BY DR BOOMINATHAN Ph. D. M. Sc. , (Med. Bio, JIPMER), M. Sc. , (FGSWI, Israel), Ph. D (NUS, SINGAPORE), PDF (USA) PONDICHERRY UNIVERSITY Sixth lecture 17/August/2012 Source: Collected from different sources on the internet and modified by Dr Boominathan Ph. D Ref. Food chemistry by Fennema

Goals l Structural arrangements of different Gums: : l Meska l Xanthan l Composition l Physico-chemical properties of Meska & Xanthan l Applications of Gums in food industry

Gum arabic/acacia gum/meska When the bark of some trees and shrubs is injured, the plants exude a sticky material that hardens to seal the wound and give protection from infection and desiccation. Such exudates are commonly found on plants that grow in semiarid climates.

Meska

Meska 5

Meska l Extrudate gum of the acacia tree l Expensive – hard to source l Low viscosity, non-gelling l Complexed with a glycoprotein -surface active

l Meska Gums – One of the oldest known gums, from the bark of Acacia trees – Very large complex polymer Up to 3. 500. KDalton (varies greatly with source) l Galactose & Glucuronic acid form main building blocks l Rhamnose and arabinose in minor amounts l – Very expensive compared to other gums but has unique properties 7

Meska l l l Highly branched with -Galactose backbone Molecular weight 2, 50, 000 – 7, 50, 000 Water soluble, fat insoluble but affinity for fat Low viscosity gum Viscosity affected by p. H and salts Food uses: – Stabilizer for flavor emulsions – Encapsulated flavors – Water binding – Inhibit sugar crystallization

l Gums Characteristics of Meska – Readily dissolves in water l Colorless and tasteless solutions of relatively low viscosity l Can go up to 50% w/w – Can manipulate solution viscosity of Meska by changing p. H l Low or high p. H = viscosity is reduced l p. H 6 -8 = higher viscosity is maintained 9

-complex heteropolysaccharide -low viscosity Meska Glucuronic acid and galactose main building blocks Rhamnose and arabinose in minor amounts 5 1 4 3 2 Composition: 1. D-galactose, 44%; 2. L-arabinose, 24%; 3. D-glucuronic acid, 14. 5% ; 4. L-rhamnose, 13%; 5. 4 -O-methyl-D-glucuronic acid, 1. 5%.

Meska They contain main chains of (1 3)-linked b-D-galactopyranosyl units having two- to four-unit side chains consisting of (1 3)-b-Dgalactopyranosyl units joined to it by (1 6)-linkages. Both the main chain and the numerous side chains have attached α-Larabinofuranosyl, α -L-rhamnopyranosyl, β-D-glucuronopyranosyl, and 4 -O-methyl-b-D-glucuronopyranosyl units. The two uronic acid units occur most often as ends of chains.

Plant exudate : Different Gums Gum karaya Gum ghatti Gum Tragacanth Gum arabic

Gums: Applications of Meska – Gum candy and pastilles (A medicated lozenge used to soothe throat) l Retards sugar crystallization l Functions as a Coating agent and a binder l Its functions in confections are to prevent sucrose crystallization and to emulsify and distribute fatty components. – Ice cream and sherbets (A frozen dessert made primarily of fruit juice and sugar, but also containing milk, egg-white or gelatin) l induces and maintains small ice crystals – Beverages l foam and emulsion stabilizer l used in beverage powders (e. g. citrus drink mixes) to maintain and stabilize flavor (encapsulates flavors) – Bakery and snack products l Lubricant and binder l The soft drink industry consumes about 30% of the gum supply as an emulsifier and stabilizer 14

Applications of Meska * It is an important ingredient in soft drink syrups, "hard" gummy candies such as gumdrops, marshmallows, chocolate candies and edible glitter, a very popular, modern cake-decorating staple. * For artists, it is the traditional binder used in watercolor paint, in photography for gum printing, & i is used as a binder in pyrotechnic compositions. It has been investigated for use in intestinal dialysis. * Pharmaceuticals and cosmetics also use the gum as a binder, emulsifying agent and a suspending or viscosity increasing agent.

Applications of Meska l Meska is used primarily in the food industry as a stabilizer. l Meska is a key ingredient in traditional lithography and is used in printing, paint production, glue, cosmetics and various industrial applications, including viscosity control in inks and in textile industries, although less expensive materials compete with it for many of these roles. Lithography -The process of printing from a surface on which the printing areas are not raised but are ink-receptive (as opposed to ink repellent)

Uses of Meska Powdered Meska for artists, one part A selection of gouaches Meska is dissolved in four parts distilled containing Meska water to make a liquid suitable for adding to pigments.

Questions: Meska 1. Meska increases sugar crystallization True/False 2. Meska functions as a foam and emulsion destabilizer True/false 3. Meska is highly branched with Rhamnose and arabinose backbone True/False

Branched Ionic gums: Xanthan

Gums-Xanthan Cellulose backbone Branched ionic gums l Xanthan – Produced by Xanthomonas, a l l microbe that lives on leaves of cabbage plants Cellulose backbone with charged trisaccharide branches Branching prevents gelation Very viscous due to charged branches Expensive ingredient -1, 4 -poly-glucose trisaccharide branches 20

Xanthan l l l l l Backbone same as cellulose (1 -4 Glucose) Trisaccharide side chain at 3 position of alternating glucose monomer units. Acid groups are b-D-Glucuronic acid and pyruvic acid on 1/2 of terminal mannose units. High degree of interaction between chains. Molecular weight about 15 million. Cold and hot water soluble High viscosity at low concentration Properties affected by ions Freeze stable Main chain Trisaccharide side chain

Backbone same as cellulose (1 -4) Glucose) Trisaccharide side chain About half of the side chains are normally pyruvylated.

Xanthan gum Source: Product of bacteria Xanthomonas campestris l Structure: cellulose-like backbone ( -1, 4 -polyglucose) with trisaccharide branches (stubs) on alternate monomers on the backbone carrying carboxylic acid residue l Functional Properties: Water soluble, viscous, non-gelling. Viscosity is only slightly temperature dependant l

Xanthan Monomer: backbone glucose (as cellulose) side chain mannose/glucuronic acid Bonding: -1, 4/ -1, 2/ -1, 3

Xanthan Main chain -1, 3 Trisaccharide -1, 2 -1, 4/ -1, 2/ -1, 3

Xanthan Main chain Trisaccharide Acetylated Pyruvate Main chain consists of 1, 4 linked β-glucopyranose residues On an average, every second glucose residue bears in the 3 -position a trisaccharide of the structure β-D-Manp-(1 → 4)-β-D-Glcp. A(1 → 2) -α-D-Manp as the side chain. The mannose bound to the main chain is acetylated in position 6 and 50% of the terminal mannose residues occur ketalized with pyruvate as 4, 6 -O(1 -carboxyethylidene)- D-mannopyranose (Glcp. A: glucuronic acid).

Xanthan: Structure-function Linear molecule - - Low p. H - Random coil

Xanthan and Carbogum Synergy Carbogum

Xanthan: Properties -only microbial gum permitted for use in food -has cellulose backbone -is made water soluble by the presence of short chains attached to every second glucose -exists in solution as a rigid rod stabilized by non covalent interaction between the backbone and the side chains -high viscosity -viscosity stability at elevated temp. and over a wide p. H range in the presence of salt -synergistic interaction with guar gum or Carbogum. -----Guar gum increases viscosity & produces thermoreversible gel -readily disperse in hot and cold water give high viscosity

Gums- Xanthan-Characterstics l Xanthan is widely used due to its unique function 1. Soluble in hot and cold water 2. Very high viscosity at low concentrations 3. viscosity decreases when it is poured or agitated (shear-thinning) 4. Viscosity is independent of temperature (1095°C) and p. H (2 -13) 5. High freeze-thaw stability 6. Compatible with most food grade salts 30

Gums- Xanthan-Uses Xanthan is widely used due to unique function – Ideal for emulsions excellent in fat-free dressings due to viscosity, and smooth mouth feel – Excellent food stabilizer – Good for thermally processed foods – Expensive l 31

Questions: Xanthan l Branching augments gelation True/false l Very viscous due to uncharged branches True/False

Questions: Xanthan l Branching augments gelation False l Very viscous due to uncharged branches False

Questions: General

Questions l Glucose is stored in the form of starch in humans- True/False l Glucose is stored in the form of Glycogen in Plants- True/False l Structural linearity reduces viscosity- True/False

Questions l Esterification is reduced in unripened fruits True/False l Esterification is increased in ripened fruits True/False l Decreased hydration increases viscosity True/False l Increased hydration increases viscosity True/False

Questions l Esterification is reduced in unripened fruits False l Esterification is increased in ripened fruits False l Decreased hydration increases viscosity False l Increased hydration increases viscosity True

Questions l Linear structure increases Viscosity True/False l Branched structure increases Viscosity True/False l The reason for Glucose to be stored in the form of Glycogen in humans is l Name two ionic & Non-ionic gums l Alginate is a monomer of l Carrageenan is a monomer of

Answers l Linear structure increases viscosity True l Branched structure increases viscosity False

Concepts l Linear Structure—More the linearity-- More the viscosity– lower the gel stability l Branched structure—More the branched structure—lower the viscosity– Increased gel stability l Esterification: Increased Esterification– Harder the texture (unripened fruits) l Decreased Esterification– Softer the texture (ripened fruits)

Concepts l Gelation: Linear structure– increases gelation; & Branching—decreases gelation l Hydration: Increased hydration– increases viscosity—increases stabilizing effect l Decreased hydration– decreases viscosity— decreases stabilizing effect l p. H: Decreased p. H (acidic)-- increases aggregation---increases precipitation l Increased p. H (basic)-- decreases aggregation— increases solubility

Questions l The viscosity of carrageen is quite stable over a wide range of p. H values……. . l Uses of aliginate in food industry……. l Uses of pectin in food industry…. l The most important seaweed polysaccharide used in food industry is

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Functions of Gums in Food Systems Water binding Viscosity building Gelation Suspension Emulsions stabilization Encapsulation Fat Replacement Foam stabilization Binder

Functions of gums in foods are related to interactions with other food components Gums interact with: l l l Component Water Proteins Lipids Ions Particle surfaces Affects All properties Emulsions, foams, gels Emulsions Gels Stabilization

Hydration of Gums l All functions of gums require that the gums be hydrated. l Failure to hydrate gums properly is the leading cause of problems in foods containing gums. l Competition for water with other water loving components affects properties

Hydration of Gums l Linear, uncharged polysaccharide molecules are held tightly together by hydrogen bonds. Substantial inputs of energy are required in order to make these function properly. l Amylose crystalline structure requires substantial input of heat before l Carbogum (has viscosity l Guar Gum ( 2 x l * gelatinization occurs. (No branches) some branches) requires heating to fully develop as many branches) swells in cold water Introduction of branches and/or charges into the chain limit amount of hydrogen bonding that can take place between polysaccharide molecules and thus increase the interaction with water and make gums more easy to hydrate. Increased no. of Branches increases the interaction with water. the

Structure and Function l Carageenan - charge of sulfates l Xanthan - Charge on carboxyl + branches l Guar Gum- increased branches

Interaction of Gums with Proteins Gums May affect protein stability by: l Electrostatic interaction - negatively charged hydrocolloids may interact with positively charged groups on proteins. l Interactions depend on: l p. H p. K of ionizable group Ionic strength Ratio of protein to gum Interference with calcium binding - l l -Protect calcium sensitive proteins e. g. . carageenan l Competing for water - hydrocolloids may cause proteins to precipitate by limiting the water available to hydrate the protein.

Gums and Lipids l Only a few gums show affinity for lipid. l Gum Arabic, hydroxypropyl cellulose, and propylene glycol alginate have a little affinity for lipid. Stabilization of emulsions, foams, etc. is dependent upon: l interactions with the protein on the surface and l increases in viscosity of the continuous phase. l l Gums which are complexed with other food components may not be able to exert their primary functions.

Viscosity of Gums l All are highly viscous except Gum Arabic Viscosity is dependent upon hydration of the polysaccharide. l Larger polymers generally give higher viscosity. Interactions with other polymers may dramatically affect viscosity. l

Stability of Gums l Most gums are resistant to microbial degradation l Pectin is a notable exception l Commercial stabilizers almost always are”'standardized" with sugar and thus are readily fermented. l Depolymerization upon heating is common.

Classification of gums used in food products: Non-ionic seed polysaccharides — – Guar, Carobgum Anionic (negatively charged) exudate polysaccharides — – Gum Arabic/Meska

Classification of gums used in food products: l Anionic seaweed polysaccharides — – Agar, Algin, Carrageenan l Microbial gums – Xanthan, Gellan l Others – Celluloses, Pectins

Classification of Polysaccharides Based on Structure l Neutral i. e. Not charged – – l Starch Cellulose Carobgum Guar Gum What are the implications of not being charged?

Classification of Polysaccharides Based on Structure l Carboxylated i. e. Having a COOH – – l Algin Carboxymethylcellulose Pectin Xanthan What are the implications of having COOH groups?

Classification of Polysaccharides Based on Structure l Sulfated i. e. SO 3– Carageenan l What are the implications of having a negative charge?

Thanks