1. PONDICHERRY UNIVERSITY
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 .

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

3. 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.

4. Meska

5. Meska

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

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

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

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

10. Meska -complex heteropolysaccharide -low viscosity
Glucuronic acid and galactose main building blocks
Rhamnose and arabinose in minor amounts 5 3 1 4 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%.

11. Meska
They contain main chains of (1 3)-linked b-D-galactopyranosyl units having two- to four-unit side chains consisting of ( )-b-D-galactopyranosyl units joined to it by ( )-linkages.
Both the main chain and the numerous side chains have attached α-L-arabinofuranosyl, 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.

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

14. Gums: Applications of Meska
Gum candy and pastilles (A medicated lozenge used to soothe the throat)
Retards sugar crystallization
Functions as a Coating agent and a binder
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)
induces and maintains small ice crystals
Beverages
foam and emulsion stabilizer
used in beverage powders (e.g. citrus drink mixes) to maintain and stabilize flavor (encapsulates flavors)
Bakery and snack products
Lubricant and binder
The soft drink industry consumes about 30% of the gum supply as an emulsifier and stabilizer

15. 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, & it 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.

16. Applications of Meska
Meska is used primarily in the food industry as a stabilizer.
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.
The process of printing from a surface on which the printing areas are not raised but are ink-receptive (as opposed to ink repellent)
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)

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

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

19. Branched Ionic gums:
Xanthan

20. Gums-Xanthan Xanthan Cellulose backbone Branched ionic gums
Produced by Xanthomonas, a 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
b-1,4-poly-glucose trisaccharide branches

21. Xanthan Main chain Trisaccharide side chain
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
Trisaccharide side
chain

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

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

24. Xanthan Monomer: backbone glucose (as cellulose)
side chain mannose/glucuronic acid
Bonding: -1,4/-1,2/-1,3
-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 noncovalent interaction between the backbone and the side chains
-high viscosity
-viscosity stability at elevated temp. and over a wide pH range in the presence of salt
-synergistic interaction with guar gum or locust bean gum. Guar gum increased viscosity, lbs produces thermoreversible gel
-readily disperse in hot and col water give high viscosity

25. Xanthan
Main chain
-1,3
Trisaccharide
-1,2
-1,4
-1,4/-1,2/-1,3

26. 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-GlcpA(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
(GlcpA: glucuronic acid).

27. Xanthan: Structure-function
Low pH
Linear molecule
Random coil

28. Xanthan and Carbogum Synergy

29. 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 pH 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

30. Gums- Xanthan-Characterstics
Xanthan is widely used due to its unique function
Soluble in hot and cold water
Very high viscosity at low concentrations
viscosity decreases when it is poured or agitated (shear-thinning)
Viscosity is independent of temperature (10-95°C) and pH (2-13)
High freeze-thaw stability
Compatible with most food grade salts

31. 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

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

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

40. Questions: General

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

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

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

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

45. Answers Linear structure increases viscosity True
Branched structure increases viscosity
False

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

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

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

49. ?

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

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

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

53. Hydration of Gums
Linear, uncharged polysaccharide molecules are held tightly together by hydrogen bonds. Substantial inputs of energy are required in order to make these function properly.
Amylose crystalline structure requires substantial input of heat before gelatinization occurs. (No branches)
Carbogum (has some branches) requires heating to fully develop viscosity
Guar Gum ( 2x as many branches) swells in cold water
Introduction of branches and/or charges into the chain limit the 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.

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

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

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

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

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

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

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

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

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

63. Classification of Polysaccharides Based on Structure
Sulfated i.e. SO3-
Carageenan
What are the implications of having a negative charge?

64. Thanks