TM 8-2e

Introduction to GRINDSTED® Pectin

KEY TOPICS • Broad formulation tolerance tional pectin (LC) and amidated pectin
• Origin of pectin page 1 • Controlled gelling (LA).
• Pectin chemistry page 2 • High and uniform gel-breaking strength
• Solubility page 3 • Excellent protein stabilisation THE ORIGIN OF PECTIN
• Gelling of high ester pectins page 4 The Danisco pectin range includes Pectin is a carbohydrate with a high
• Gelling of low ester pectins page 5 a wide variety of high ester and low molecular weight which is present in all
• Protein stabilisation page 6 ester pectins. It is categorised in families plants, primarily in the form of protopec-
designed for specific applications, as tin. Together with cellulose, protopectin
THE BENEFITS outlined later. forms part of plant cell walls and is,
GRINDSTED® Pectin is the trade name therefore, essential for plants and their
for the pectin products manufactured by INTRODUCTION structure.
Danisco. The company’s pectin produc- The word pectin comes from the Greek The term pectin relates to a number
tion facilities are situated in Mexico, the word pektos, which means firm and hard, of polymers which vary according to
Czech Republic and Denmark. reflecting the ability of pectin to form their molecular weight, chemical configu-
The pectin plants are equipped gels. ration, degree of esterification, content of
with the most up-to-date technology Pectin is the name of a natural poly- neutral sugars, etc. Different plant types
and are operated in accordance with mer used to stabilise or give texture to produce pectin with different functional
stringent ISO and HACCP procedures. food and pharmaceutical products. The properties (especially gelling properties).
By focusing on applications and build- gelling properties of pectin have been The pectin content of fruit used for
ing up an in-depth knowledge of the known for centuries, but the isolation of commercial pectin production varies
molecular chemistry of pectin, Danisco commercial pectin only started at the between 10% and 50% of the dry raw
has developed a wide pectin range for beginning of the 20th century. material used. Lime and lemon peel
adding texture to or stabilising food and The development of pectin produc- contain a particularly large amount of
pharmaceutical products. Danisco manu- tion technology has made it possible to high quality pectin (see figure 1).
factures exclusive pectin products with manufacture a number of pectin types The pectin in citrus fruit is located
the following outstanding qualities: with a variety of functional properties. primarily in the albedo and lamellae. The
• High degree of purity Commercial pectins are defined as high white layer of a citrus fruit, the albedo, is
• White pectin powder for high clarity ester (HE) and low ester (LE) pectins, the inner layer of the peel and surrounds
solutions the latter being sub-divided into conven- the juice segments. When juice and oils
• High level of process flexibility have been extracted from the fruit, the

Figure 1. 200 grams of citrus fruit produces approximately 13 grams of dry peel, resulting in 3-6 grams of pectin. This pectin is sufficient to gel 1kg of jam.
 Flavedo PECTIN TYPE DE RANGE SETTING TIME TYPICAL SETTING

(%) (SECONDS) TEMPERATURE (°C)

Albedo
Extra slow set 58 - 62 260 - 330 55
Core
Slow set 63 - 67 170 - 225 70
Medium rapid set 67 -71 120 - 160 75
Lamel
Rapid set > 70 < 110 83
Table 1. Typical setting time and temperature of HE pectins.
Note: Setting times and temperatures are highly dependent on the recipe used, especially soluble solids
level and pH.

of galacturonic acid groups in the pectin galacturonic acid backbone are key
molecule is substituted by more than factors. Through raw material selection
Figure 2. Pectin is derived from the fibrous and 50% methyl ester groups, the pectin is and process technology, Danisco is able
pulpy parts of the fruit.
known as high ester (HE). If this number to produce high ester pectins with a
is less than 50%, the pectin is called low highly controlled molecular structure to
peel is used for pectin production (see ester (LE) (see figure 5). ensure consistent performance in the
figure 2). As some LE pectins contain amide application.
Pectin today is commercially produced groups, LE pectins are subdivided into High ester pectins are standardised
mainly from apple pomace and citrus amidated pectins (LA) and non-amidated according to their application: SAG grade,
peel by an extraction process followed or conventional pectins (LC). gel strength, setting temperature, viscos-
by separation, purification, isolation and ity and protein stability are the main
then drying, milling and standardisation HE pectins parameters used for standardisation
(see figure 3). The typical degree of esterification (DE) purposes.
for commercial HE pectins ranges from
PECTIN CHEMISTRY 50% to more than 80%. LC pectins
Pectin basically consists of a chain of ga- HE pectins are characterised as being LC pectin, like HE pectin, consists of a
lacturonic acid units which are linked by able to gel in aqueous systems with linear chain of partially esterified galac-
α-1,4 glucosidic bonds. The galacturonic more than 55% soluble solids and a pH turonic acid units.
acid chain is partly esterified as methyl ranging from 2.8 to 3.5. The higher the The DE of LC pectins is below 50%
esters. Pectin molecules can have a number of ester groups, the faster the and typically ranges from 30% to 50%.
molecular weight of more than 150,000, pectin will gel. This forms the basis for With this low level of ester groups, the
corresponding to a degree of polymeri- classifying high ester pectin from rapid number of carboxyl groups is significant
sation of up to 1,000 units (figure 4). set to extra slow set. for the formation of calcium cross-links
Commercial pectins are divided in two High ester pectins are also widely used resulting in gel formation. Therefore, LC
major groups: HE and LE pectins. The for their protein stabilisation properties. pectins are characterised according to
division is related to the number of ester In this application, the details of the their degree of calcium reaction.
groups in the pectin molecule and, thus, molecular structure and especially the LC pectins are standardised according
the functional properties. If the number distribution of the ester groups on the to their application, typically in terms of

E
TER AST AR
WA LW SUG
PEE

L ON N N ION
PEE ACT
I IO ATI
O IN G NG ISAT
TRU
S R RAT IPIT DRY MIL
LI ARD
CI E X T FILT PRE
C ND
STA

L
D HO TIN
ACI ALC
O
PEC

ERY
E C OV
.R
ALC
Figure 3. Typical pectin flow process.
 dispersion in water (high shear mixing,
COOH OH COOH OH C O O C H3 dry blending with other material), the
O O O
OH OH swelling of the grains will cause them
O O O O O O
OH OH OH to agglomerate, forming lumps. These
O O
lumps are extremely difficult to dissolve
OH C O O C H3 OH C O O C H3 OH
once they are formed. For this reason,
it is of great practical importance to the
Figure 4. Chemical structure of a high ester pectin.
industrial user to obtain a good pectin
dispersion in water (see table 2).
C O O C H3 OH COOH OH COOH
O O O Rheology of pectin solutions
O OH O OH O
O O O Pectin solutions are viscous, which means
OH OH OH
O O
pectin is widely used to add viscosity,
OH COOH OH COOCH 3 OH
especially to juice and soft drinks.
Dilute pectin solutions are almost
Figure 5. Chemical structure of a low ester pectin with a DE of 40%.
Newtonian and only slightly affected
by the presence of calcium. However,
gelling, setting temperature and calcium setting temperature and calcium toler- solutions with more than 1% pectin
tolerance. ance. exhibit pseudo-plastic behaviour and are
strongly affected by calcium. The texture
LA pectins CHEMICAL AND PHYSICAL starts as water and then develops
LA pectins differ from LC pectins as a PROPERTIES through thixotropic solutions with yield
number of amide groups are situated in Solubility value to stiff gels depending on the
the pectin molecule, partially substituting Pectin is soluble in water but insoluble pectin type and concentration, level of
methyl ester groups. Legislation limits in most organic solvents. The solubility calcium and pH.
the degree of amidation to 25%. Like LC rate in water is related to the degree
pectins, LA pectins form intermolecular of polymerisation and the number and Stability
calcium cross-links, resulting in gel forma- distribution of methyl ester groups. The High ester pectins are stable at pH levels
tion. pH, temperature and ionic strength of of 2.5 to 4.5. Above a pH level of 4.5,
No direct comparison can be made the solution are of great importance β-elimination will occur, depolymerising
between calcium reactions of LA and LC to the rate of pectin dissolution. The the galacturonic acid chain. This mecha-
pectin, as the amide groups in LA pectins calcium content of the water used to nism requires an esterified carboxyl
interfere with the gelling mechanism of dissolve the pectin is particularly relevant group next to the glycosidic bond to be
the pectin (see functional properties as high water hardness will often result in cleaved (figure 6) so low ester pectins
below). incomplete pectin dissolution. are more stable at higher pH values.
LA pectins are standardised according Like any hydrocolloid, pectin grains The pectin molecular structure is quite
to their applications, typically gel strength, swell before going into solution. If pectin resistant to heat. When pH is around 3.5,
grains are not well separated upon pectin is only marginally depolymerised

METHOD PROCEDURE O O CH3

OH C
O
Solution after dry blending Dry blend pectin with 5 parts sugar.
OH O
with sugar Add to hot water (80-90°C) and mix for a few minutes. OH O
O
Direct solution Add the pectin slowly to hot water (80-90°C) during O C OH
O CH3
vigorous agitation.
Syrup dispersion Disperse the pectin into sugar syrup.
The pectin will only hydrate if the soluble solids are brought O O CH3
OH C
below 25% at a later stage of the process. O
OH
OH
Direct addition Dry blend the pectin with 5 parts sugar. OH O
Add directly to the product mix when soluble solids are below O
O C OH
25% and boil for min. 3 minutes. O CH3

Table 2. Practical ways to dissolve pectin. Figure 6. β-elimination mechanism.

 RAPID SET PECTIN SLOW SET PECTIN
the pectin molecule, and the pH, ionic
< 50°C 60°C 80°C < 60°C 80°C
strength, water activity, sugar type and
2 hours 0 3% 16% 0 14%
cooling rate of the gelling medium.
4 hours 0 6% 31% 0 36%
6 hours 0 9% 100% 0 47%
Pectin concentration
8 hours 0 13% 100% 0 57%
The concentration of high ester pectin
will increase the final gel strength of
Table 3. Loss of gel strength when storing a 4% pectin solution.
the system due to a larger number of
active junction zones. An increase in
at high temperatures. The heat stability enough for the distance between the molecular weight would have the same
of pectin is greatly improved when the pectin chains to be sufficiently reduced effect. In addition to this expected effect,
water activity of the system is lowered so hydrogen bonding can occur. In order the gelling rate is also increased with an
following the addition of sugar. to achieve sufficient hydrophobic interac- increasing pectin concentration and a
tions to stabilise the molecular network, power law can be calculated between
FUNCTIONAL PROPERTIES the water activity of the system also the two parameters.
Pectins are used in a broad variety of has to be decreased. Sugars are usually
food and pharmaceutical products. Their added for this purpose. Degree of esterification
principal properties are gel formation, Upon storage of a cooled gel, it is The degree of esterification of the
viscosity build up and protein stabilisa- typical that the texture will still develop galacturonic acids affects both the charge
tion. As methods develop for obtaining into a stronger final gel. This corresponds density of the polymer and the number
a better understanding of pectin’s to a slow reorganisation of the network of sites for hydrophobic interaction. As
molecular structure, pectin is likely to be involving the creation of new junction pectin molecules with a high degree of
attributed new functional properties in zones or an enlargement of the existing esterification are less charged, they can
the future. junctions between the pectin molecules form gels at a higher pH and will also
(see figure 7). start gelling at a higher temperature.
Gelling of high ester pectins
Gelling mechanism Parameters influencing gelling pH and ionic strength of the gelling
It is generally accepted that a high ester The gelling and final gel structure of high system
pectin gel is formed by cross-linking ester pectins are influenced by a great The lower the pH, the lower the repul-
the polymer in junction zones, in which number of parameters, the main ones sion between the pectin molecules and,
mainly hydrogen bonds but also hydro- being the pectin concentration, degree thus, the easier it will be for them to
phobic attractions between the methyl of esterification and molecular weight of interact. This means a low pH will lead
ester groups play a part. Calcium bridges
may also participate, especially if the Independent molecules in solution Gel structure
esters are distributed in blocks, leaving
large parts of the molecule as free acids.
As the pectin chains carry negative Junction zone

charges, they will tend to repel each

H+
other. This repulsion can be directly H2O
Sucrose
correlated to the pH of the medium and
the number of free galacturonic acids
of the pectin. The higher the pH and
lower the degree of esterification, the
Hydrogen bonding
higher the charge density and, hence, the
C C C C
stronger the repulsion. O O O O O
O O
This repulsion and, more importantly, H H H
CH3
the impossibility of forming hydrogen H H CH3
bonds between ionised pectin chains are O O O O
C H O O Hydrophobic
the reasons why a low pH is required C C C interaction
for high ester pectin gelling. At a low pH,
typically below 3.5, the repulsion is low Figure 7. Gelling mechanism of HE pectin.
Obtainable firmness, % Firmness range, hydrogen bonds and hydrophobic
100 interactions together can contribute to
80 the build-up of a network with maximum
elasticity. The final firmness is typically not
60
affected by the cooling rate.
40

20 Properties of high ester pectin gels

Due to the nature of the molecular
0
3.0 3.2 3.4 3.6 3.8 4.0 3.0 3.1 3.2 3.3 3.4 3.5 interactions involved in high ester pectin
Jelly pH pH
High fructose corn syrup gelling, gels made with these pectins will
DE = 63 Sucrose typically be non thermo-reversible and
DE = 73 63 DE corn syrup non shear-reversible.
DE = 81 43 DE high maltose corn syrup
When submitted to mechanical stress,
42 DE corn syrup
the broken gel will then show a high
Figure 8. The degree of esterification determines Figure 9. Effect of sugar types on HE pectin level of syneresis.
the optimal pH for gelation. gelation.

Gelling of low ester pectins

to faster gelling in high ester pectins. The most common way to reduce water Low ester pectin has traditionally been
However, below a critical level, the gel activity in a food system is through the used to gel food products when the
strength will actually be reduced as the use of sugars. The effect of sugars on conditions required to achieve a gel with
gelling process is too fast to obtain a hydrophobic interaction and, thus, on high ester pectin were not met. Recently,
well-organised polymer network and gel structure is specifically linked to their however, low ester pectins have also
precipitation can occur. The optimum pH molecular conformation and interaction found applications in high sugar and low
for gelling is controlled by the pectin’s with the neighbouring water molecules pH systems because of their specific
degree of esterification as well as the (see figure 9). texture characteristics.
soluble solids content of the medium Though the same basic mechanism
(see figure 8). Influence of cooling rate and storage applies, low ester conventional and
temperature amidated pectin differ in their gelling
Water activity and sugar types As the cooling rate is increased, the gel- properties and offer a broad range of
Water activity and sugar types both ling rate increases accordingly. However, functional properties.
affect the way hydrophobic interac- during rapid cooling and with a low
tions can develop between the pectin storage temperature, gelling can actually Gelling mechanism
molecules. As water activity is reduced, become very slow, reflecting the difficult The gelation of low ester pectin is mainly
the hydrophobic interactions are easier development of hydrophobic interac- the result of calcium bridges between
to form, causing faster gelling to occur tions in these conditions. With an inter- carboxylic groups from two pectin chains
and the final gel strength to be increased. mediate cooling rate and temperature with the participation of hydrogen bond-
ing. The most commonly accepted model
of association is the egg box model
OH OH OH
O O

COO-
O

COO-
(figure 10). Even though a number of
HO COO- HO HO O
O O O O O
O
COO- HO COO- HO COO- HO positive ions can bridge pectin molecules,
O O O

OH OH OH especially magnesium and potassium,

HO
Ca++ HO Ca++ HO Ca++
O O O
calcium is particularly effective at forming
COO- COO- COO-
OH OH
O
OH
O OH
O O OH
O O OH
O
complexes with carbohydrates.
O
HO
O
HO
O
HO The exact calcium requirements to ob-
tain a gel highly depend on the pectin’s
degrees of esterification and amidation,
-O C C C C C
Detail of the various types of possible
O H N O O O O
H
O O
H
the recipe and process parameters such
H H
Ca++
hydrogen bonding that participate in the H H H as the rate of cooling.
junction zone together with the O O- O O O O O O H
calcium chelation (far left). C C C C C An optimum calcium level can be
defined for a given pectin in specific
Figure 10. Gelling mechanism of LE pectin. conditions. Above this optimum level,
 Gel strength Gel strength then actually decreased when the pH is
GRINDSTED® lowered. In standard food systems, the
Pectin LA 410 GRINDSTED® 35% SS
availability of the natural calcium will also
Pectin LC 910 50% SS
be increased at a lower pH, reducing the
pH 3.6
need for extra calcium addition.

Influence of ionic strength

An increase in gel strength can be ob-
served at a higher ionic strength. This is
pH 3.1 pH 3.6 pH 3.1
usually explained by the neutralisation of
60 the polymers by the extra ions, allowing
0 20 40 60 80 100 0 10 20 30 40 50
Mg Ca2+/g pectin Mg Ca/g pectin the chains to be closer and leading to a
more organised and cohesive gel.
Figure 11. Gel strength of various LE pectins in Figure 12.Calcium reaction curves of a high calcium
relation to calcium. reactive LA pectin at various solid and pH levels.
Influence of water activity
pre-gelation will occur, i.e. gelling will Influence of amidation As the solids level increases, calcium
occur at temperatures too high to obtain Pectin amidation was developed in the requirements decrease. However, for
a coherent gel structure (figure 11). 1940s as a means of modifying the most pectins, a higher solids level ac-
The typical gelling mechanism of high functional properties of low ester pectins celerates gelling and increases the setting
ester pectin, with hydrogen bonds and in order to achieve better gelling control. temperature and final gel strength. It also
hydrophobic interactions, can also con- The exact involvement of amides is reduces the optimum calcium window,
tribute to the final texture of low ester not fully clear. However, gels made with thus increasing the risk of pre-gelation. In
pectin gels, especially at a low pH and amidated pectins are typically firmer and practice, this leads to a choice of pectin
with high soluble solids. require less calcium. They are also more with a higher degree of esterification
thermo-reversible than those made with (less calcium reactive) at a higher solids
Parameters influencing gelling low ester conventional pectins. level.
Although the availability of calcium is a
critical factor in the gelling of low ester Influence of molecular weight Properties of low ester pectin gels
pectins, other parameters in relation to As for any polymer gel, the length of the The properties of low ester pectin gels
the pectin molecule and media have a polymer governs the number of junction are very dependent on the type of
significant influence on gelling and the zones required to achieve a coherent pectin used (conventional or amidated)
final structure obtained. The main pa- network. Low ester pectins with a high along with the procedure and formula-
rameters are the number and distribu- molecular weight exhibit a higher gelling tion employed to make the gel. Typically,
tion of ester and amide groups, as well rate, lower calcium requirements for they are thermo-reversible and show a
as the molecular weight of the pectin gelling and an overall more cohesive high degree of thixotropy.
molecule and the pH, ionic strength and and elastic gel structure with a reduced In specific conditions it is, however,
water activity of the gelling system. tendency towards syneresis. possible to obtain heat resistant or very
brittle gels with no shear reversibility.
Influence of esterification Influence of pH
Because calcium bonds can only occur With a low sugar content, pectin mol- Protein stabilisation with high ester pectin
in esterification-free zones, gel strength ecules are neutralised with protons as In acidified conditions, casein and, more
increases with a decreasing degree pH decreases, reducing the probability generally, food proteins tend to agglom-
of esterification. For low ester pectin of junction zones forming with calcium. erate and sediment if the viscosity of the
with an average DE of above 30%, the This translates into higher calcium system is low enough. In these conditions
distribution of the esters may be highly requirements and a looser gel texture at the proteins are also very sensitive to
important as this controls the length of a low pH (see figure 12). On the other dehydration and the product can easily
possible junction zones and influences hand, when the water activity of the become sandy after heat treatment.
the gelling temperature, final gel strength system is decreased by the addition of With the rapid development of acidi-
and texture. sugar, the gelling mechanism of high ester fied dairy beverages worldwide, now
pectin starts to play a significant part in expanding with other protein sources
gelling and the calcium requirements are such as soy, the need for effective protein
 SERIES APPLICATION FUNCTION

GRINDSTED Pectin AMD series

® Acidified protein drinks Protein stabilisation
+– +– +
–+–+
––+–
+
GRINDSTED® Pectin CF series Confectionery Gelling with low setting
Bakery fillings temperature
GRINDSTED® Pectin SF series Low sugar jams and jellies Gelling with good syneresis
control
GRINDSTED® Pectin YF series Fruit preparations Texture and yield value
GRINDSTED Pectin FB series
® Bakery fillings Texture and bake stability
Table 4. The main Danisco pectin series.

an interaction leading to an increase in DANISCO PECTIN SERIES

viscosity or even gelation. This explains In addition to standard high ester and
why only high ester pectin with a fairly low ester pectins, Danisco has developed
Figure 13. Interactions between pectins and high degree of esterification is useful in pectin tailored to specific applications.
proteins. this application. In each case, the pectins are tested and
standardised in specific systems repre-
stabilisers in a low pH environment Conditions sentative of the application.
is growing fast. High ester pectin has Through its role in the ionisation of The main pectin series are outlined in
proven a very useful stabiliser in these the protein and pectin molecules, pH is table 4.
conditions. the most significant factor affecting the
electrostatic pectin-protein interactions. AVAILABLE LITERATURE
Mechanism It also plays a very significant role in Danisco offers a comprehensive range
It is generally accepted that, at sufficient the protein structure and the way the of technical literature on pectin related
pectin concentrations, the adsorption of proteins interact in a complex system topics.
the carboxyl blocks of the pectin mol- such as milk. TM 4002: GRINDSTED® Pectin for
ecule to the protein surface will stabilise The optimum pH range for interaction reduced sugar jam, jelly and fruit spread
the protein system through steric repul- between high ester pectin and casein TM 4004: GRINDSTED® Pectin for
sion (figure 13). is 3.6 to 4.5. At a lower pH, the block yogurt fruit preparations
Both the pectin’s degree of esterifica- structures of the high ester pectin will TM 2032: Determination of stability
tion and the actual distribution of the not be sufficiently ionised for proper index for GRINDSTED® Pectin AMD
esters on the polymer affect its stabilisa- protein binding as the pH is too far products
tion properties. Excessively large blocks below the pKa of the pectin. Above the PB 2001: GRINDSTED® Pectin AMD
of carboxyl groups tend to interact with isoelectrical point of the protein, the protein stabilisers for acidified beverages
the ions present in the system, such as protein-polysaccharide complex is very PB 3501: GRINDSTED® Pectin for sugar
calcium, rather than with the protein, weak or non-existent. confectionery
 Danisco A/S The information contained in this
Edwin Rahrs Vej 38 publication is based on our own
DK-8220 Brabrand, Denmark research and development work
Telephone: +45 89 43 50 00 and is to the best of our knowl-
Telefax: +45 86 25 10 77 edge reliable.
info.ingredients@danisco.com Users should, however, conduct
www.danisco.com their own test to determine the
suitability of our products for
their own specific purposes.
Statements contained herein
should not be considered as a
warranty of any kind, expressed
or implied, and no liability is
accepted for the infringement of
any patents.

10.03