Rheological Properties of Carboxymethylcellulose
and Whey Model Solutions before and after Freezing
Vesna Hegeduši}*, Zoran Herceg and Suzana Rimac
Department of Food Engineering, Faculty of Food Technology and Biotechnology,
University of Zagreb, Pierottijeva 6, HR – 10000 Zagreb, Croatia
Received: June 11, 1999
Accepted: November 17, 1999
Summary
Hydrocolloids, macromolecular carbohydrates are added to many foodstuffs with the
aim to achieve the appropriate rheological properties, to prevent syneresis or to increase
the viscosity and stability of foodstuffs.
In this work, the influence of the type and concentration of commercial hydrocolloids (carboxymethylcelluloses)
on the rheological properties of model solutions of whey, whey proteins,
sucrose, sorbitol and lactose was examined. The influence of freezing on rheological
properties of model solutions was also checked. Measurements were done using a Brookfield
DV-III rotational viscometer at temperature of 20 °C.
The results have shown that all examined systems are non-Newtonian. Depending on the
chemical composition and on the mass fraction of hydrocolloids, they exhibited pseudoplastic
or dilatant properties. All CMC effected a significant increase of the model solutions
viscosity.
The freezing process had no significant effect on the viscosity of the model solution prepared
with water. However, whey based solutions had a greater viscosity after freezing.
The results of variance analysis showed that all examined sources of variation (composition
of model solution, type of CMC and freezing process) had a significant influence on
the rheological parameters.
Key words: rheological properties, carboxymethylcelluloses, whey proteins, freezing
Introduction
Hydrocolloids are mostly complex carbohydrates
which are used to improve consistency and textural characteristics
(rheological properties) of liquid and semiliquid
foodstuffs. Their activity depends on the kind and
concentration of hydrocolloids, temperature and process
condition, as well as on solid matter content and chemical
composition of foodstuffs. They can be added in various
combinations and phases of production and may
have various final effects (1).
The type of hydrocolloids largely determines overall
appearance, texture and rheological properties of food,
whereby nutritional values and sensory qualities of food
products are not changed (2–5). Their activity could depend
on the interactions among hydrocolloids and other
components of food (6–8).
Carboxymethylcellulose (CMC), as a typical hydrocolloid,
has no direct influence on the taste and flavour
of foodstuffs, but at the same time has a significant effect
on gel formation, water retention, emulsifying and
aroma retention (9,10). In the food industry CMC is
used as a stabilizer, binder, thickener, suspending and
water-retaining agent, in ice-cream and other frozen des-
V. HEGEDUŠI] et al.: Rheological Properties of CMC and Whey Model Solutions, Food technol. biotechnol. 38 (1) 19–26 (2000) 19
* Corresponding author; Fax: ++385 (0)1 4836 083; E-mail: [email protected]
serts, fluid and powdered fruit drinks, sauces and
creams, cake mixes and slimming and dietary foods.
Ultrafiltrated whey and whey proteins are commonly
used in the food industry for dairy desserts production.
They are also gelling agents or enhance functional
properties of food (11–15).
The functional role of proteins as a food ingredient
depends on a complex interaction of various factors,
such as heating or cooling rates, protein concentration,
pH, ionic strength and interactions with other food components,
sugars, minerals etc. (16–20).
The aim of this paper was to find out the influence
of the type of carboxymethylcelulloses on the rheological
properties of whey model solutions, as well as of
whey protein, sucrose, sorbitol and lactose model solutions
and to examine the influence of freezing process
on the viscosity of the model solutions.
Materials and Methods
The studies were carried out with eight model solutions
(marked as samples 1 to 8 in Table 1) prepared by
mixing of following ingredients:
¿ Sucrose, sugar – Še}erana @upanja
¿ Sorbitol p.a. – »Merck«
¿ Ultrafiltrated whey (10 % solid matter) – »Dukat«
d.d.
¿ Whey proteins concentrate (WPC) (60 % proteins
in solid matter) – »Dukat« d.d.
¿ Proteins free whey (10 % solid matter)
¿ Carboxymethylcelluloses (commercial names –
YO-EH, DIKO, HVEP) – Guliver-Chemie, Wiener
Neudorf
Preparation of proteins free whey
Ultrafiltrated whey was cooked in water bath at the
temperature of 90 °C for 20 minutes. After that, it was
cooled to 20 °C and filtrated through a gauze. The residuum
on the gauze contained coagulated whey proteins.
The filtrate, protein free whey with 6 % solid matter was
evaporated on the water bath to the 10 % solid matter.
The rheological properties of three different types of
commercial CMC (YO-EH, DIKO, HVEP) were examined.
CMC dispersions with 0.1, 0.2, and 0.4 % mass fractions
were prepared in distilled water by vigorous hand
mixing at 20 °C.
The model solutions of sucrose, sorbitol and lactose
(samples No. 5–7, Table 1) were prepared with the aim
to find out the influence of carbohydrates and CMC interactions
on the rheological properties of these model
systems.
The samples No. 1, 2, 8, as well as No. 3 and No. 4
(Table 1), were prepared with the purpose to determine
the possible interactions among proteins, inorganic compounds,
CMC and carbohydrates.
Measurements
The measurements were performed using a rotational
viscometer, Brookfield DV-III, with coaxial cylin-
serts, fluid and powdered fruit drinks, sauces and
creams, cake mixes and slimming and dietary foods.
Ultrafiltrated whey and whey proteins are commonly
used in the food industry for dairy desserts production.
They are also gelling agents or enhance functional
properties of food (11–15).
The functional role of proteins as a food ingredient
depends on a complex interaction of various factors,
such as heating or cooling rates, protein concentration,
pH, ionic strength and interactions with other food components,
sugars, minerals etc. (16–20).
The aim of this paper was to find out the influence
of the type of carboxymethylcelulloses on the rheological
properties of whey model solutions, as well as of
whey protein, sucrose, sorbitol and lactose model solutions
and to examine the influence of freezing process
on the viscosity of the model solutions.
Materials and Methods
The studies were carried out with eight model solutions
(marked as samples 1 to 8 in Table 1) prepared by
mixing of following ingredients:
¿ Sucrose, sugar – Še}erana @upanja
¿ Sorbitol p.a. – »Merck«
¿ Ultrafiltrated whey (10 % solid matter) – »Dukat«
d.d.
¿ Whey proteins concentrate (WPC) (60 % proteins
in solid matter) – »Dukat« d.d.
¿ Proteins free whey (10 % solid matter)
¿ Carboxymethylcelluloses (commercial names –
YO-EH, DIKO, HVEP) – Guliver-Chemie, Wiener
Neudorf
Preparation of proteins free whey
Ultrafiltrated whey was cooked in water bath at the
temperature of 90 °C for 20 minutes. After that, it was
cooled to 20 °C and filtrated through a gauze. The residuum
on the gauze contained coagulated whey proteins.
The filtrate, protein free whey with 6 % solid matter was
evaporated on the water bath to the 10 % solid matter.
The rheological properties of three different types of
commercial CMC (YO-EH, DIKO, HVEP) were examined.
CMC dispersions with 0.1, 0.2, and 0.4 % mass fractions
were prepared in distilled water by vigorous hand
mixing at 20 °C.
The model solutions of sucrose, sorbitol and lactose
(samples No. 5–7, Table 1) were prepared with the aim
to find out the influence of carbohydrates and CMC interactions
on the rheological properties of these model
systems.
The samples No. 1, 2, 8, as well as No. 3 and No. 4
(Table 1), were prepared with the purpose to determine
the possible interactions among proteins, inorganic compounds,
CMC and carbohydrates.
Measurements
The measurements were performed using a rotational
viscometer, Brookfield DV-III, with coaxial cylin-
ders, carrying out shear stress () and shear rate () with
shear rate increasing from the lowest value (3.9 s–1) for
every system to 317 s–1 (upwards), as well as from 317
s–1 (downwards) to the lowest shear rate. At the highest
shear rate, shear stress lasted two minutes, and after
that the rotational rate successively decreased to the initial
value.
After preparations and after freezing (–20 °C) in a
laboratory freezer, all measurements were made at temperature
of 20 °C. All solutions were kept frozen for 24
h. After thawing at ambient temperature for 14 hours,
the measurements of rheological properties were performed
again at the same conditions as before freezing.
The rheological parameters (consistency coefficient
and flow behavior index) were calculated by a computer
program according to Ostwald de Waele power-law
model (7).
= k ·
n /1/
where: – shear stress (Pa), – shear rate (L/s), n – flow
index, k – consistency coefficient (Pa sn)
Apparent viscosity at 60 s–1 was calculated using
Newtonian law:
= a · / 2 /
where: – shear stress (Pa), – shear rate (L/s), a – apparent
viscosity (Pa s)
The analysis of variance was used to examine the
influence of sources of variation (model solution composition
composition,
type of hydrocolloid, freezing process) on the rheological
parameters.
Results and Discussion
The rheological properties of food are influenced by
temperature, chemical composition, solid matter content,
processing, the interactions of food components
and others (1). The aim of this work was to find out the
influence of the interactions among carboxymethylcelluloses
and other components in solutions (sucrose, sorbitol,
whey proteins, lactose and inorganic compounds)
on their rheological properties. Through the experiments
an attempt to eliminate the effect of solid matter fraction
was made. Therefore all model solutions had the same
fraction (10 %) of solid matter (Table 1). Throughout the
study it was apparent that the composition of solid matter
had a significant influence on the efficiency of CMC.
Model solutions prepared with water addition (samples
No. 5, 6 and 7) had a higher viscosity than solutions
prepared with ultrafiltrated whey (samples No. 1, 3 and
4) or concentrated whey proteins (sample No. 8) even
though the solid matter content was the same in all solutions
(Table 2). Solutions containing concentrated
whey proteins (WPC – sample No. 8) and 0.1 % hydrocolloids
(YO-EH, DIKO, HVEP) have significantly lower
viscosity than those prepared with water. When the addition
of hydrocolloids increased to 0.2 and 0.4 %, the
viscosity, expressed as apparent viscosity as well as the
consistency coefficient value of the WPC solutions significantly
increased, compared to the viscosity of the so
lution containing ultrafiltrated whey. The viscosity
matched the quality of the solution prepared with water
(Tables 2–4). Such behavior of hydrocolloids could be
explained by interactions between proteins and hydrocolloids
(6,7). When the hydrocolloid content is lower
(0.1 %) an interaction occurs between the positive (active)
groups of proteins and negative groups of hydrocolloids.
When the hydrocolloid content was higher (0.2
and 0.4 %), its effectiveness increased, because the number
of free, active groups of proteins decreased. This allows
the hydrocolloids to bind greater amount of water
and this can partially explain the differences in the viscosity
between solutions prepared with ultrafiltrated
whey and solutions prepared with water.
It is important to take into consideration the presence
of significant amount of inorganic compounds in
ultrafiltrated whey and protein free whey, as well as the
presence of polyanion polysacharides (CMC) for binding
greater amounts of cations. This type of interaction
can improve homogenity of the systems. The contact of
ion pairs (inorganic compounds – CMC) has a negative
effect on the rheological properties of the model solutions
which can be seen from the viscosity values of solutions
containing protein free whey (containing a major
quantity of inorganic compounds). The viscosity obtained
was by far the lowest regardless on the quantity
of hydrocolloids (Tables 2–4).
The above observation confirms the fact that all
model solutions prepared with sucrose, sorbitol or lactose
(samples No. 5, 6 and 7) have a distinctly higher
viscosity than the other solutions. This can be explained
by non-existence of the interaction between proteins and
hydrocolloids or inorganic compounds and hydrocolloids.
Rheological properties of examined model solutions
are adequately described according to Ostwald de Waele
power-law model and expressed as consistency coefficient
(k) and flow behaviour index (n).
From the shape of shear stress and shear rate curves
(Fig. 1) and flow behaviour index values it is obvious
that all examined model solutions exhibit a non-Newtonian
character. Almost all solutions were pseudoplastic
(structural – viscous behavior) except the solutions prepared
with ultrafiltrated whey or WPC and with 0.1 %
HVEP or DIKO addition (Tables 2 and 3) that exhibited
dilatant properties.
It was mentioned that hydrocolloids have a significant
influence on the flow behaviour since all the model
solutions prepared with 0.2 or 0.4 % of CMC exhibited
pseudoplastic properties. The increase of the hydrocolloid
content in the solution made the pseudoplastic
characteristics more apparent and it also increased significantly
the viscosity of the model solutions.
Hydrocolloids, such as carboxymethycellulose, are
important ingredients in frozen dairy product preparations
because of their ability to control crystallization
and inhibit recrystallization. Therefore, the influence of
the freezing process on the rheological properties of
model solutions containing 0.4 % CMC was studied (Table
5). It was pointed out that after freezing all solutions
had the same non-Newtonian character (structural-viscous)
as before freezing (Fig. 2). The coefficient consistency
values (k) of the model solutions prepared with
water (samples No. 5–7) did not change significantly.
The coefficient consistency values of the model solution
prepared with whey (samples No. 1–4 and 8) increased
dramatically, probably as a consequence of changes in
binding capacity of whey proteins effected by water
crystallization during freezing.
To verify the statistical significance of some variance
sources (the composition of model solution, hydrocolloid
content and freezing process) on the viscosity, the
showed that all variance sources do indeed have an effect
on rheological parameters.
In order to demonstrate the influence of model solution
compositions, type of hydrocolloids and freezing
process on the rheological properties of examined model
systems, the analysis of variance and probability was executed
(Table 6 and 7).
Fisher quotient values for composition of model solutions
and type of hydrocolloids after freezing (F-values)
were higher than the limiting values (P 0.05) (Table 6),
which means that the influence on rheological proper
ties of examined model systems is statistically significant.
Conclusion
Coefficient consistency and flow behavior index values
of CMC solutions are determined by Ostwald de
Waele power-law.
When the amount of hydrocolloids was low (0.1 %
wt), model solutions prepared with ultrafiltrated whey
and WPC, exhibited dilatant characteristics. By increasing
the amount of hydrocolloid (0.2 and 0.4 % wt) all the
model solutions had a pseudoplastic flow (structural –
viscous behavior).
As a result of interactions between whey proteins
and hydrocolloids, or inorganic compounds and hydrocolloids,
the viscosity of solutions prepared with ultrafiltrated
whey was significantly lower then those of
model solutions prepared with water.
Freezing process increased the viscosity of whey solution,
while the viscosity of solutions prepared with
water did not change significantly.
The results of variance analysis showed that all the
examined model solutions had a significant influence on
the rheological parameters
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