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Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel MareUniversity - Suceava
Volume XI, Issue 2 – 2012

EFFECT OF ADDITION OF CARRAGEENAN ON RHEOLOGICAL

BEHAVIOUR OF YOGURT
*Cristina DAMIAN1, Mircea-Adrian OROIAN2, Ana LEAHU3, Nicolae CARPIUC4

1-4Ştefan cel Mare University of Suceava, Faculty of Food Engineering, 13
Universităţii Street, 720229, Suceava, Romania, e-mail: 1cristinadamian@fia.usv.ro

*Corresponding author
Received 25 March 2012, accepted 12 May 2012

Abstract: The purpose of this work is to study the effect of addition of k-kappa carrageenan and i-
iota carrageenan on the rheological behaviour of different types of yogurts. The role of concentration
as well as the type of carrageenan used (k-kappa carrageenan and i-iota carrageenan) has been
analysed.The most common technique used for rheological liquids is Viscometers, measuring shear
strength, described by the coefficient of viscosity. The most common technique used for rheological
liquids is Viscometers, measuring shear strength, described by the coefficient of viscosity. For this
study, the yogurt samples were obtained in the laboratory using the cultures starter DIPROX YBA
986. The effect of addition of carrageenan in yoghurt was investigated by a rotational viscometer,
Brookfield viscometer (Brookfield Engineering Inc, Model RV – DV I Prime) with RV spindles. The
Brookfield viscometer DV I Prime with disk spindles represents an easy and cheap method for the
rheological characterization of non-Newtonian fluids, in this case of yoghurt. The cluster analysis was
performed using Unsrambler X version 10.1 (CAMO Process As, Oslo, Norway, 2005), all the
rheological and physicochemical parameters were weighed and normalized for performing the cluster
analysis. In the case of yogurt samples obtained in the laboratory, the addition of carrageenan
increases the viscosity. i-iota carrageenan has been evaluated as more effective for increasing the
viscosity of yogurt in comparison with k-kappa carrageenan (with the same concentration).

Keywords: yogurt, viscosity, viscometer

1. Introduction

Rheology is the deformation and flow
of matter [1].

Polysaccharides are widely used in
food systems as, e. g. thickeners [2].

Polysaccharides (pectin, modified
starch, xanthan gum, locust bean gum,
guar gum, alginate, etc.) are often added to
dairy products to stabilise their structure,
enhance viscosity and alter textural
characteristics [3].

Carrageenans are anionic linear
polysaccarides extracted from the red
seaweed (Rhodophyceae), consisting of
alternating α-1,4 and β-1,3 linked
anhydrogalactose residues. There are three
major fractions (k-kappa, i-iota and λ-
lambda) with varying number and position

of sulphate groups on the galactose dimer.
k-Carrageenan and i-carrageenan undergo
a temperature-dependent coil (disordered
state) to helix (ordered state) transition in
aqueous solution. Both of these
carrageenans are able to form gels (the
process of gelation is closely associated
with helix formation). k-Carrageenan
usually forms firm, britlle gels and i-
carrageenan usually generates soft, elastic
gels. The strength of the gels formed by
both polysaccarides is strongly influenced
by the presence of cations. k-Carrageenan
is especially sensitive to potassium and i-
carrageenan to calcium ions. On the other
hand, λ-lambda carrageenan is not able to
build up stable gels [4].

Yogurts are dairy products obtained by
fermentation with lactic acid bacteria

Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel MareUniversity - Suceava
Volume XI, Issue 2 – 2012

during which a weak protein gel develops
due to a decrease in the pH of the milk.
Following the fermentation of lactose
lactic acid is formed causing the
coagulation of milk proteins (casein) to
form a gel-like structure, in which fat
globules and the aqueous phase are
embedded [5]. In the liquid milk, casein
micelles are presented as individual units.
As the pH reaches pH 5.0, the casein
micelles are partially broken down and
become linked to each other under the
form of aggregated and chains forming
part of a three-dimensional protein matrix
in which the liquid phase of the milk is
immobilized. This gel structure contributes
substantially due to the overall texture and
organoleptic properties of yoghurt and
gives rise to shear and time dependent
viscosity [6].

The gel strength of yogurt is related to
the cumulative effects of the chemical
interactions [7].

The most frequent defects related to
yogurt texture that may lead to consumer
rejection are apparent viscosity variations
and the occurrence of syneresis [8].

Yogurt rheological characterization is
required for product and process
acceptability [9]. This characterization can
be made using either instrumental or
sensory measurements.

The firmness of yogurt and the
viscosity of just-stirred gel are greatly
influenced by the amount of heat treatment
the yogurt mix receives. Heating unfolds
the globular whey proteins and exposes
sulphydryl groups, which react with other
sulphydryl groups and disulfides and
induce linkages and protein-casein
aggregates [10, 11].

The gel strength of yogurt is related to
the cumulative effects of the chemical
interactions. The binding of δ-lacto
globulin to the casein micelle seems to be
responsible for the increase of gel strength
[12, 13, 14].

2. Materials and methods

1.1. Materials
UHT milk, Lactobacillus bulgaricus

and Streptococcus thermophilus pure
starter culture DIPROX YBA 986
provided by Enzymes & Derivates, Piatra
Neamț, România; k-kappa carrageenan and
i-iota carrageenan provided by Enzymes &
Derivates, Piatra Neamț, România; orbital
shaker; thermostat; Brookfield viscometer
Model RV- DV II Pro, with disk spindle,
RV3, RV4, RV5, RV6 type.

1.2. Sample preparation

The yogurt samples were made
using UHT milk, having the physical and
chemical parameters in Tabel 1.

Table 1.
Milk properties

Fat, g/100g 3
Protein, g/100 g 3
Sugar, g/100g 4.5
Ash, % 0.72
Acidity, 0T 18

Table 2.
pH of yogurt samples

Sample pH
S 1 4.0
S 2 4.5
S 3 4.2
S 4 4.0
S 5 4.5

300 mL milk was inoculated using
0.015 g starter culture. After inoculation
with starter culture, the samples were
homogenised with an orbital shaker for 15
min. at 100 rpm. After shaking the samples
were thermostated at 420C for 6 hours.
Carrageenans were added in the next
concentration to the yogurt sample: 0.9 g
k-kappa carrageenan (S1), 0.9 g i-iota
carrageenan (S2), 0.6 g k-kappa
carrageenan and 0.3 g i-iota carrageenan

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Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel MareUniversity - Suceava
Volume XI, Issue 2 – 2012

(S3), 0.45 g k-kappa carrageenan and 0.45
g i-iota carrageenan (S4) and 0.3 g k-
kappa carrageenan and 0.6 g i-iota
carrageenan (S5). The pH of the yogurt
samples is presented in table 2.

2.3. Determination of rheological
properties

Viscosity measurements were carried
out on the yogurt samples at ambient
temperature (250C), with a Brookfield
viscometer (Brookfield Engineering Inc,
Model RV- DV II Pro+) at 0.5, 1, 2, 2.5, 4,
5 and 10 rpm with RV spindle (RV3, RV4,
RV5, RV6 type). The spindle no was used
in accordance with the sample nature to get
all readings within the scale [15].

The samples in 300 mL of beaker with a
8.56 cm diameter (according to the
Brookfield requests) were kept in a
thermostatically controlled water bath for
about 10 min before measurements in
order to attain desirable temperature of
250C.

First measurements were taken 2 min.
after the spindle was immersed in each
sample, so as to allow thermal equilibrium
in the sample, and to eliminate the effect of
immediate time dependence.

All data were then taken after 40 s in
each sample. Each measurement was
duplicated on the sample.

The obtained empirical data were
converted using the Mitschka relationships
to shear rate and shear stress. The shear
rate versus shear stress data were
interpreted using the power law expression

σ = k·γn (1)
where:

σ – shear stress (N/m2),
γ is the shear rate (s-1),
n is the flow behaviour index, k is the

consistency index (Nsn/m2).
The values for the flow behaviour

index n, were obtained from plots of log
shear stress versus log rotational speed; the
slope of the line (if the dependence is

sufficiently close to a linear one) is simply
equal to the flow index of the fluid, n.

The shear stress is calculated using the
next equation:

τi = kτ·αi·C (2)
where:

τi – shear stress, (dyne/cm2)
kτ = 0.119, this constant is for the

spindle nos 2
αi – torque dial, (%)
C – 7.187 dyne/cm for RV viscometer
The shear rate is calculated using the

next equation:
γi = kγ(n)·Ni (3)

where:
γi – shear rate, (s-1)
kγ(n) – constant, depends by the value of

n
Ni – rotational speed, (rpm).

Statistical analysis The cluster analysis
was performed using Unsrambler X
version 10.1 (CAMO Process As, Oslo,
Norway, 2005), all the rheological and
physico-che mical parameters were
weighed and normalized for performing
the cluster analysis.

3. Results and discussion

The yogurt samples exhibited a non-
Newtonian behaviour. The power law
model is a suitable one for predicting the
rheological parameters.

Table 3.
Viscosity for yogurt samples

Sample Viscosity* [cP]
S1 60947
S2 107000
S3 213000
S4 106000
S5 144000

*Viscosity was measured at 0.5 1/s

In general, addition of carrageenan
increases the viscosity of yogurt, as shown
in table 3. It achieved a stabilization of

Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel MareUniversity - Suceava
Volume XI, Issue 2 – 2012

aqueous dispersions whose continuous
phase is the water and the dispersed one is
solid or liquid and tends to separate.
Through the addition of carrageenan, the
viscosity is increased and the tendency of
destabilization by separation of
components is reduced.

Upon cooling and in the presence of
appropriate cations, kappa and iota
carrageenan polymers align themselves to
form individual helices. These helices can
further associate with divalent cations that
are present, e.g. calcium, to form a gel
matrix. Figure 1 is a schematic
representation of the gelling mechanism
for carrageenan.

Figure 1. Gelation mechanism [16]

The gel texture of the basic
carrageenans can be modified by blending
carrageenans to meet specified gel texture
parameters. Figure 2 illustrates the
penetration or elasticity of carrageenan
gels before the gels are fractured. The gels
can be made more elastic or less elastic by
combining kappa and iota carrageenans
until the desired texture is achieved.

Figure 2. Gel texture [17]
Gels prepared with carrageenan are

thermally-reversible. These gels will
become fluid when heated above the

melting point of gels and will reset into a
gel when cooled, with minimal loss of the
original gel strength.

In food systems, one of the most
important properties that truly differentiate
carrageenan from other hydrocolloids is its
ability to complex or interacts with
proteins. In milk protein systems, at
peripheral locations on the casein micelle
there is a concentration of positive charges.
This positive electrostatic charge attracts
the negatively-charged sulfate groups of
the carrageenan molecule to form linkages
among the dispersed casein micelles as
illustrated in figure 3.

This reaction, in combination with the
normal water gelling capabilities of
carrageenan, can increase the gel strength
about 10-fold.

The ability of carrageenan to complex
with milk proteins, combined with its
water gelling properties enhances the
functionality of carrageenan, e.g. increased
gel potential.

Figure 3. Interaction of milk protein with
carrageenan

Figure 4 shows the evolution of
viscosity with the two hidrocolloid with its
concentration and shear rate. It can be
observed that the viscosity of the yogurt
sample with i-iota carrageenan (S2) is
higher than that of the yogurt that contains
the same amount of k-kappa carrageenan
added (S1). Carrageenan mixtures have a

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Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel MareUniversity - Suceava
Volume XI, Issue 2 – 2012

different rheological behavior on the
samples of yogurt. Thus, the sample with a
mixture of both types of echimolecular
carrageenan has the lowest viscosity,
followed by the sample with a smaller
amount of k-kappa carrageenan. Sample
S5 has the highest viscosity and also a
higher content of i-iota carrageenan.

Figure 4. Viscosity profile of yogurt sample with
0.9 g k-kappa carrageenan (S1), 0.9 g i-iota

carrageenan (S2), 0.6 g k-kappa carrageenan and
0.3 g i-iota carrageenan (S3), 0.45 g k-kappa

carrageenan and 0.45 g i-iota carrageenan (S4) and
0.3 g k-kappa carrageenan and 0.6 g i-iota

carrageenan (S5)

The results of cluster analysis shows
that the samples with k-kappa carrageenan
and i-iota carrageenan added are in the
same group, while the samples with the
mixture of the two types of carrageenans
make a different group – see figure 5.

Figure 5. Diagram of yogurt samples clustered
according to rheological and physicochemical

properties
4. Conclusion

Due to large molecular sizes, to the
specific configuration, the charge and
possible formation of intra- and
intermolecular links, gums are able to
reduce water mobility. This reduction in
water mobility increases the viscosity of
gum solutions in water.

In the case of yogurt samples obtained
in the laboratory, the addition of
carrageenan increases the viscosity. By
means of carrageenan addition, yogurt
viscosity is increased and reduces the
tendency to destabilize the separation of
components.

i-iota carrageenan has been evaluated
as more effective for increasing the
viscosity of yogurt in comparison with k-
kappa carrageenan (with the same
concentration).

5. References

1. OROIAN M. A., GUTT G., Influence of total
soluble content, starter culture and time period
on rheological behaviour of cultured buttermilk,
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2. KLEIN, C., VENEMA, P., SAGIS, L., VAN
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Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel MareUniversity - Suceava
Volume XI, Issue 2 – 2012

5. BANU, C. (coordinator), Aditivs and
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/accessories/spindles/rv_ha_hb_spindles.asp
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The following points are important in order to warrant paper publishing in the journal Food and environment safety.
The following points are important in order to warrant paper publishing in the journal Food and environment safety.
The following points are important in order to warrant paper publishing in the journal Food and environment safety.
The following points are important in order to warrant paper publishing in the journal Food and environment safety.
The following points are important in order to warrant paper publishing in the journal Food and environment safety.
The following points are important in order to warrant paper publishing in the journal Food and environment safety.
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