1. The Exudate Gums
By John D. Keller

2. EXUDE per Webster’s Dictionary:
To ooze out or undergo diffusion
To cause to ooze or spread out in all directions
To display conspicuously or abundantly

3. Major Exudate Gums
Gum Acacia
Gum Tragacanth
Gum Karaya
Gum Ghatti

4. Gum Acacia (History/Facts/Commercial Importance)
Oldest known gum (5000 years) – Egypt/Middle East
AMBER-JURASSIC PARK
Widely used today-Food, Pharma, Industrial
Volume usage 3rd largest of naturals behind guar and xanthan
Availability influenced by political upheaval & drought

5. Acacia senegal Source/Botany
“it begins as a glistening teardrop on a thorny tree at the edge of the desert”1
(1) Gum Arabic-an ancient ingredient for the 21st Century

6. Gum Acacia/Gum Arabic (Source/Botany)
Acacia Tree-Large Genus
over 900 species worldwide
Africa, Australia, India, Central America, southwest US
A.senegal (80%) & A.seyal “talha” (10%)
are main species
Harvest Manual -
wild species & acacia plantations
Most of world’s supply from “gum belt” in Africa

7. Gum Acacia Source/Botany
Most of world’s production comes from southern portion of Sahara Desert between North Latitudes 11 and 14
Main producing and exporting countries include Senegal, Mali, Mauritania, Niger, Chad and Sudan
Termed “Hashab” in Sudan (local name for trees)
“THE GUM BELT”

8. Gum Acacia Source/Harvest
Tapping tree with “sunki” (a traditional native spear)
Major income for Sudan people
Product is combination of hunting wild crop and picking plantation grown trees

9. Gum Acacia Harvest/Grading/Manufacture
Three qualities:
CAS –Clean Amber Sorts
HPS-Hand Picked Selected
“Natural”
Modernization has led to
mechanical grading & sorting
in some regions

10. Gum Acacia Processing Dry Method Wet Method Harvest Dissolve Filter
Sorting
Centrifuge
Spray Dry
Pulverize
Pasteurize
Powder
Kibble

11. Gum Acacia Chemical Composition – Complex
Definition:1
A mixed (Ca++, Mg+ K+) salt of a polysaccharidic acid composed of six carbohydrate moieties: (galactose, arabinopyranose, arabinofuranose, rhamnose, glucuronic acid and 4-O-methylglucuronic acid)
Three Fractions: % of Gum % Protein
AG – arabinogalactan
AGP – arabinogalactan/protein
GP – Glycoprotein <
1- Glicksman, Food Hydrocolloids, Vol. 2, Chap.1 CRC Press, 1983

12. Acacia senegal vs. Acacia seyal
Property A. senegal A.seyal
Mol. Wt (Ave.) K K
Optical Rotation (-) (+)
Protein % %
AG Fraction % %
AGP Fraction % %
GP Fraction <1% <1%

13. Modern Hypothesis of the Structure of Gum Acacia Senegal‌
ARA
ARA
MeGLcA
GAL
GAL
ARA
ARA
GAL
GlcA
RHA
ARA
ARA
ARA
ARA
ARA
GAL
GAL
GAL
GAL
GAL
GAL
GAL
GAL
GAL
ARAf
GAL
ARA
GAL
GAL
ARA
GlcA
GlcA
GAL
ARA
RHA
RHA

14. “Wattle Blossom” Model Of Gum Arabic (Fincher 1983)
- Protein
- Arabinogalactan

15. Typical Gum Acacia Concentration Curve

16. pH Stability of Gum Acacia
Viscosity 2 4 6 8 10 pH

17. Gum Acacia-Key Functional Properties
Good acid stability (natural pH
Highly soluble & unique low viscosity
(55% solutions possible)
Good emulsion stabilizer (protein component)
- Traditional Emulsions
- Encapsulation via spray drying
cps
Concentration

18. Gum Acacia Use In An Emulsion For Spray Drying
Aqueous Phase
Organic Phase
Acacia,
Water
Flavor Oils,
Terpenes, etc
Pre-Emulsion Mix
Homogenization
Spray Drying
T C.

19. Role of Gum Acacia In Emulsion Stabilization
w/o acacia
Separated
(Coalescence)
Oil in Water Emulsion
w/ acacia
Gum Acacia Coating
Stable

20. Gum Acacia- Additional Properties
Hot and Cold Soluble
Film Former (why?)
Compatible & Synergistic (other gums/coacervates)
Soluble Fiber/Nutraceutical
Disadvantages:
- Cost in Use
- Supply Problems

21. Gum Acacia-Compatibility& Synergy
Compatible w/ most gums & ingredients
Acacia + trag (1:4) → improve emulsion
Acacia + xanthan → smoother flow
Acacia (-) + gelatin (+) = Coacervate
- Incompatibility (Cloud or ppt.)
- Encapsulated oil preparation
Acacia + CMC (instant beverages)

22. Gum Acacia Major Food Applications
Confections
Flavor emulsions/Encapsulation
Beverage and Beverage Emulsions
Baked Goods (Glazes)
Low Carb Arena (Extender for Sugar Syrups)

23. Gum Acacia Key Applications – Non Food
Pharmaceutical – Tableting (binder)
Cough drops & cough syrups
Adhesives
Cosmetics:
- Lotions & creams – smoothness
- Mascara – adhesive
- Rouge – emulsifier
Industrial - printing

24. Gum Tragacanth Astragalus gummifer

25. Gum Tragacanth History/Facts/Commercial Importance
Greek tragos ~ goat & akantha ~ horn
Ancient Mid-East Lineage
1. Genesis 37:25 & 43:11
2.“Nakaad” (Hebrew) refers to tragacanth as vegetable gum
Important item of Commerce in Biblical Times
Ink, incense, medicines and cosmetics
Once the Premier Salad Dressing Stabilizer -
Demise from Iranian conflict mid’70s & xanthan gum entry

26. Gum Tragacanth Source/Botany
Obtained from Astragalus plant (300 varieties) in mountainous regions of Syria, Turkey and Iran
Astragalus gummifer & A. bethlehemiticus are main commercial species
Plant is a low growing, highly branched shrub with long spines, inconspicuous flowers & bladderlike fruits
Gum comes from incisions into tap root

27. Gum Tragacanth “Ribbons/Flakes”

28. Gum Tragacanth Harvest/Manufacture
A plant & locality produces only ribbon or flake-not both.
Hand Collected - Ribbon (Apr-Sept) – Flake (Aug-Nov)
Manufacture:
Sorted & Graded
Ground & Sifted
Fumigated (?)
Exported
Quality:
Ribbon best quality grade/Flake best emulsifier

29. Gum Tragacanth – Molecular Structure1
A mixed, highly branched polymer consisting of two fractions:
Fraction I – Tragacanthic acid or “bassorin” (70%)
A water swellable, acidic polysaccharide composed of D-xylose, L-fucose, D-galacturonic acid, D-galactose and L-rhamnose
Fraction II – Tragacanthin (30%)
A water soluble, neutral, highly branched arabinogalactan
L-arabinose is main sugar
1 - Glicksman, M.., Food Hydrocolloids, Vol.II, Chap. 4 CRC Press 19 83

30. (- GalA – GalA– GalA–GalA- ) n
Gum Tragacanth Fraction I – Tragacanthic Acid –Suggested Structure1 (70%)
(- GalA – GalA– GalA–GalA- ) n
Xyl
Xyl
Xyl
Fucose
Gal
Where:
GalA is Galacturonic Acid
Gal is Galactose Xyl is Xylose
Fucose is fucose
1- Aspinall, G.O., Adv. Carb. Chem., 24:333, 1969 & Aspinall, G.O. and Ballie, J., J. Chem Soc., 1963:

31. Gum Tragacanth Functional Properties
Excellent pH stability (3-8)
- polymer backbone / side chains
Emulsification
- Lowers surface tension/Flake more effective
Desireable rheology
- Smooth solutions
- Pseudoplastic, but nearing Newtonian flow
1% viscosity in cps range

32. Gum Tragacanth Surface Tension Comparison With Other Materials
Material % Solution(dynes/cm2)
Xanthan
Guar
LBG
Water
Tragacanth
PGA
Methylcellulose (0.05%)
HP Cellulose

33. Gum Tragacanth Food Uses
Dressings, Sauces and Relishes
Confections and bakery fruit fillings
Icings – ready to roll type ( high sugar/fat)
Frozen desserts – sorbets and sherbets

34. Gum Tragacanth Non Food Uses
Toothpaste
Hair lotions and gels
Auto polishes

35. Gum Tragacanth “Pros & Cons”
Benefits:
Excellent pH stability
Good emulsifing properties
Liabilities:
Availability
Cost
Slow Hydration

36. Gum Karaya Source/Botany
Exudate from deciduous Sterculia urens trees & related species grown throughout India
Also known as Sterculia or Indian gum
Best quality gum collected (April, May, June) before monsoon
Maximum exudation in 1st 24 hours!
Sterculia urens

37. Gum Karaya Source/Harvest
Blazing produces large irregular tears
Yields of 1-5 kg per tapping
Max. 5 visits per tree lifetime
Cleaned, sorted, graded & ground

38. Gum Karaya - Structure
A very complex, partially acetylated, highly branched polysaccharide (M.W. 9,500,000)1
Central backbone of D-Galactose, L-Rhamnose & D-Galacturonic acid w/ side chains of D-Glucuronic acid
Very acidic polymer:
- 32.7% in acid form
- 37% uronic acid residues
- 8-13% acetyl groups
“Typical Branching”
1- Kubal and Gralen, J. Colloid Sci, 3: 457, 1948

39. Gum Karaya Functional Properties
Tremendous swelling ability
Good pH stability (▲↓)
Excellent adhesive properties
Gives viscosity, paste or gel (concentration)
Emulsification ( < 1% protein )
Solvent solubility – can gel organic solvents

40. Gum Karaya Applications
Food:
Frozen Desserts
1978 P&G “Cold Snap”
Salad Dressing
Non-Food:
Dental Adhesives
Colostomy Bag Sealing Rings
Laxatives

41. Gum Karaya “Pros and Cons”
Benefits:
Great swelling ability (40X)
Adhesive properties
pH stability
Liabilities:
Strong acetish note
Impurities

42. Gum Ghatti History/Facts/Commercial Importance
Name from transport of gum to port (Bombay) through mountain passes or “ghats”
Also called Indian gum
Of great interest as potential gum arabic replacer
Food use practically nil/world supply limited

43. Gum Ghatti Source/Botany
Translucent exudate of Anogeissus latifolia tree - India and Sri Lanka (Ceylon)
Gum is soft plastic when first exuded (Dhavda), but firms thereafter
Harvested alongside karaya/tears dried prior to shipment
Powder is gray to reddish- gray in coloration

44. Gum Ghatti (Structure)
A complex heterogeneous polysaccharide composed of L-arabinose, D-galactose, D-mannose, D-xylose and D-glucuronic acid (molar ratio 10:6:2:1:2)1
Branching can be single monomer or short chains
Two fractions:
- soluble gum portion (mixed salts)
- insoluble, but swellable, gel fraction (Ca++ salt)
Only a partial structure eludcidated!!
1 – Glicksman, M., Food Hydrocolloids, Vol. II, Chap. 2, CRC Press 1983

45. Gum Ghatti Properties/Functions
Viscosity increases with aging (all pHs)
Excellent emulsifying properties
Forms viscous dispersions (Not true solutions)
Viscosity intermediate between karaya & acacia
Natural pH ~ 4.8

46. Typical Viscosity of Various Exudate Gums Concentration (% solution)
Trag
Karaya
Viscosity
Ghatti
Acacia
Concentration (% solution)

47. Gum Ghatti Applications
Beverages and buttered syrups
Flavor fixative
Emulsifier in waxes
Suspending aid for barium sulfate in GI tract evaluations
Preparation of stable oil soluble vitamins

48. The Exudate Gums Regulatory Issues
Natural
GRAS
E Numbers:
E Tragacanth
E Acacia
E Karaya
None - Ghatti

49. -the act of expressing great joy & triumph!!!
The Exudate Gums
“Exultation”
-the act of expressing great joy & triumph!!!

50. The Exudate Gums Acknowledgements
The lecturer would like to thank the following:
The Gum Arabic Co., LTD Khartoum (Sudan) & Mr. Paul Flowerman (President) P.L. Thomas & Co., Inc., Morristown, NJ (USA) for technical information and photos on acacia gum.
Mr. William Balke (President) Hewes Research and Development, Hackettstown, NJ (USA) for technical advice on properties and applications of exudate gums.