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

Structural arrangements of different Gums::
 Meska
 Xanthan
 Composition
 Physico-chemical properties of Meska & Xanthan
 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

Extrudate gum of the acacia tree
 Expensive – hard to source
 Low viscosity, non-gelling
 Complexed with a glycoprotein -surface
active
Gums

Meska
– 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)
Galactose & Glucuronic acid form main building blocks
Rhamnose and arabinose in minor amounts
– Very expensive compared to other gums but has
unique properties
7
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

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
9
-complex heteropolysaccharide
-low viscosity
Meska
Glucuronic acid and galactose main building blocks
Rhamnose and arabinose in minor amounts
5
1
3
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%.
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 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
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, &
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.
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.
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
Meska is dissolved in four parts distilled
water to make a liquid suitable for
adding to pigments.
A selection of gouaches
containing Meska
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

Xanthan
– 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
20
Xanthan









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
 Structure: cellulose-like backbone (b-1,4-polyglucose) 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
Xanthan
Monomer: backbone
glucose (as cellulose)
side chain
mannose/glucuronic acid
Bonding: b-1,4/b-1,2/-1,3
Xanthan
Main chain
-1,3
Trisaccharide
b-1,2
b-1,4
b-1,4/b-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-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).
Xanthan: Structure-function
Linear
molecule
-
-
-
Low pH
-
Random
coil
Xanthan and Carbogum Synergy
Carbogum
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 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
Gums- Xanthan-Characterstics

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 (10-95°C)
and pH (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
31
Questions: Xanthan

Branching augments gelation True/false

Very viscous due to uncharged branches
True/False
Questions: Xanthan

Branching augments gelation False

Very viscous due to uncharged branches
False
Questions:
General
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 viscosityTrue/False
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
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
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
Answers

Linear structure increases viscosity
True
 Branched structure increases viscosity
False
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)
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
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
?
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:

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Component
Water
Proteins
Lipids
Ions
Particle surfaces
Affects
All properties
Emulsions, foams,gels
Emulsions
Gels
Stabilization
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
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
viscosity

Guar Gum ( 2x

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.
*
some branches) requires heating to fully develop
as many branches) swells in cold water
Structure and Function

Carageenan - charge of sulfates

Xanthan - Charge on carboxyl + branches

Guar Gum- increased branches
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 -



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-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.
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.


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Gums which are complexed with other food
components may not be able to exert their
primary functions.
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.
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.
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:

Anionic seaweed polysaccharides —
– Agar, Algin, Carrageenan

Microbial gums – Xanthan, Gellan

Others – Celluloses, Pectins
Classification of Polysaccharides
Based on Structure

Neutral i.e. Not charged
–
–
–
–

Starch
Cellulose
Carobgum
Guar Gum
What are the implications of not being charged?
Classification of Polysaccharides
Based on Structure

Carboxylated i.e. Having a COOH
–
–
–
–

Algin
Carboxymethylcellulose
Pectin
Xanthan
What are the implications of having COOH groups?
Classification of Polysaccharides
Based on Structure

Sulfated i.e. SO3– Carageenan

What are the implications of having a negative
charge?
Thanks