Food Hydrocolloids 19 (2005) 361–369
www.elsevier.com/locate/foodhyd
Effect of limited hydrolysis of sunflower protein on the interactions
with polysaccharides in foams
K.D. Martineza, R.I. Baezaa, F. Millánb, A.M.R. Pilosofa,*
a
Facultad de Ciencias Exactas y Naturales, Departamento de Industrias, Universidad de Buenos Aires, Ciudad Universitaria,
Nunez, Buenos Aires 1428, Argentina
b
Instituto de la Grasa, CSIC, 41012 Sevilla, Spain
Abstract
The objective of the work was to study the effect of different non-surface active polysaccharides on the foaming properties of intact and
hydrolysed sunflower protein isolate (SP) (degree of hydrolysis of 1.5 and 9.8%) at neutral pH where a limited incompatibility between
macromolecules can occur. Foams were obtained by whipping and the overrun, liquid drainage and collapse of the height of foams were
evaluated.
A limited enzymatic treatment substantially enhanced foaming properties of sunflower protein. A small degree of hydrolysis (DHZ1.5%)
enhanced both foam overrun and foam stability against liquid drainage and collapse. However, an increase of DH to 9.8% did not further
improve foaming properties.
The overrun of foams was decreased in the presence of all the polysaccharides but the performance of polysaccharides as stabilizers of
foams depended on the protein hydrolysis, the structure of the polysaccharide and its concentration in the liquid used to make the foam.
Xanthan gum at 0.25 and 0.5%, due to its high viscosity performed as stabilizer of both intact and hydrolysed SP foams. The other
polysaccharides at 0.25% performed as stabilizers when added to the intact SP foams but destabilized the foams containing the hydrolysed
SP. By increasing PS concentration, the detrimental effect could be partially reverted.
The results may be interpreted in terms of the bulk and surface rheological properties of the mixed protein/polysaccharide foams and
suggest that protein–polysaccharide interactions are strongly affected by the hydrolysis of the protein.
q 2005 Elsevier Ltd. All rights reserved.
Keywords: Protein; Polysaccharide; Gums; Hydrocolloid; Foam; Drainage; Foam stability; Air–water interface
1. Introduction
Enzymatic protein hydrolysis is a common procedure for
improving the solubility as well as other functional properties of sunflower proteins, because the proteins suffer
denaturation during industrial oil extraction that reduces
their solubility (Villanueva, Vioque, Sánchez-Vioque,
Clemente, Bautista, et al., 1999; Villanueva, Vioque,
Sánchez-Vioque, Clemente, Pedroche, et al., 1999). High
quality sunflower protein hydrolysates have been obtained
in recent years, enabling its use as food ingredients, in
the fortification of liquid foods and diets of surgical
patients (Villanueva, Vioque, Sánchez-Vioque, Clemente,
* Corresponding author. Fax: C54 11 4576 3241.
E-mail address: [email protected] (A.M.R. Pilosof).
0268-005X/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.foodhyd.2004.10.002
Bautista, et al., 1999; Villanueva, Vioque, Sánchez-Vioque,
Clemente, Pedroche, et al., 1999).
Limited enzymatic treatment with proteases can substantially influence the foaming properties of proteins. It has
been reported that limited hydrolysis may improve foaming
capacity but decrease foam stability (Bernardi, Pilosof, &
Bartholomai, 1991; Bombara, Añon, & Pilosof, 1997;
Chobert, Sitohy, & Whitacker, 1988; Vioque, SánchezVioque, Clemente, Pedroche, & Millán, 2000). This could
be due to the exposure of hydrophobic areas and increased
molecular flexibility of polypeptides that increases the
affinity for the interface and the adsorption rate (Ipsen et al.,
2001). However, the decrease in molecular size resulting
from hydrolysis can be expected to decrease the ability of
the polypeptides at the interface to interact so that less
viscoelastic films will cause a decrease in foam stability.
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K.D. Martinez et al. / Food Hydrocolloids 19 (2005) 361–369
Because of the decreased foam stability of hydrolysed
proteins, their use would require the addition of polysaccharides as stabilizers. Most high-molecular-weight
polysaccharides, being hydrophilic, do not have much of a
tendency to adsorb at the air–water interface, but they can
strongly enhance the stability of protein foams by acting as
thickening or gelling agents. Alongside the use of nonsurface-active polysaccharides in food foams as thickeners,
there is recent evidence that supports an additional role with
polysaccharides at the interfacial film (Baeza, Carrera
Sanchez, Pilosof, & Rodrı́guez Patino, 2004; Carp,
Bartholomai, & Pilosof, 1999; Carp, Bartholomai, Relkin,
& Pilosof, 2001).
Protein–polysaccharide interactions in the bulk solution
or at the interface are sensitive to details of protein and
polysaccharide structures as well as to pH (Dickinson,
2003; Tolstoguzov, 1997). Aqueous solutions of proteins
and polysaccharides can exhibit one of the following
phenomena: complex coacervation (complexation), miscibility and segregation. Complex coacervation mainly occurs
below the protein isoelectric point as a result of net
electrostatic interactions between the biopolymers carrying
opposite charges and implies the separation of two phases,
one rich in the complexed biopolymers and the other phase
depleted in both.
Above the isoelectric point of the protein thermodynamic
incompatibility between the protein and polysaccharide
generally occurs because of the repulsive electrostatic
interactions and different affinities towards the solvent
(Tolstoguzov, 1997). Therefore, protein and polysaccharide
may co-exist in a single phase (miscibility) in domains in
which they mutually exclude one another or, above a critical
concentration, segregate into different phases.
Previous studies on the effect of polysaccharides on
foaming properties of intact food proteins have shown
that foam stability is strongly increased (Carp, Baeza,
Bartholomai, & Pilosof, 2004; Carp et al., 2001). This
behavior is quite different from that observed for oil-inwater emulsions where small amounts of polysaccharides
(i.e. xanthan) have been shown to reduce the stability with
respect to creaming by promoting droplet flocculation
through a depletion mechanism (Cao, Dickinson, &
Wedlock, 1990; Dickinson, 2003; McClements, 2000; Ye,
Hemar, & Singh, 2004).
In this study we investigated the effect of a limited
hydrolysis of sunflower proteins on the foaming properties
and performance of different non-surface active polysaccharides as foam stabilizers.
2. Materials and methods
2.1. Materials
A sunflower protein isolate (SP) 83.8% protein,
prepared as previously described, was used as substrate
for the hydrolysis (Villanueva, Vioque, Sánchez-Vioque,
Clemente, Bautista, et al., 1999). The isoelectric point of
protein was 4.5. The enzyme preparation used was
Alcalase 2.4 L (Novo Nordisk, Denmark), a microbial
protease from Bacillus licheniformis with endopeptidade
activity. The activity of the enzyme preparation was 2.4
Anson Units/g. The protein isolate (50 g) resuspended in
1000 mL water, was hydrolyzed batchwise by treatment
with the enzyme (0.3 Anson Units/g) at pH 8 and 50 8C,
in a pH-stat for different times. Hydrolysis was stopped by
dropping the pH to 5. Hydrolysates were clarified by
centrifugation at 4000!g for 30 min, and the supernatants
were freeze-dried. The degree of hydrolysis (DH), defined
as the percentage of peptide bonds cleaved, was calculated
from the determination of free amino groups by reaction
with trinitrobenzenesulphonic acid according to AddlerNissen (1979). Protein hydrolysates with degree of
hydrolysis of 1.5% (HSP1) and 9.8% (HSP2) were
obtained.
The following polysaccharides (PS), from Sanofi Bioindustries, Argentina were used without further purification:
xanthan (X), l and k-carrageenan (lC and kC), guar (G) and
locust bean gum (LB).
2.2. Electrophoresis
Intact SP as well as the hydrolysed proteins (HSP) were
analysed by PAGE-electrophoresis using a Mini-Protean II
dual slab cell system (Bio-Rad Laboratories) in dissociating
conditions (SDS) according to the procedure of Laemmli
(1970). Samples were diluted in distilled water to 0.2% and
then mixed (1:4) with the sample buffer (pH 6.8, 0.5 M
Tris–HCl and glycerol with SDS). The weight of deposed
protein was 40 mg. The resolving and stacking gels
contained 15 and 4.5% acrylamide, respectively. Mixed
Tris–HCl (0.4 M) glycine with SDS in distilled water
solution to pH 8.3 or 8.8, respectively, was the running
buffer. Proteins were stained with Coomassie brilliant blue
solution (0.1%) and destained with a mixture 1:1 of
methanol–glacial acetic acid (20%).
2.3. Preparation of solutions
Solutions of polysaccharides were made in distilled
water at 1 wt% kC solution was prepared by dissolving the
polysaccharide in 0.005 mol/l KH2PO4/NaHPO4 buffer, pH
7, at 70 8C. To avoid bacterial growth, 0.2 g/l sodium azide
was added to the solutions.
The sunflower protein isolate and the hydrolysates were
prepared in distilled water and pH was adjusted to 7 with
0.1 N NaOH. Protein hydrolysates were 100% soluble at
this pH. The insoluble fraction from SP (50%) was removed
by centrifugation 4000!g for 30 min. The soluble fractions
were used to prepare the protein/polysaccharide mixed
systems at 3 wt% protein and 0.25% or 0.5 wt%
polysaccharides.
K.D. Martinez et al. / Food Hydrocolloids 19 (2005) 361–369
363
2.4. Foam formation
Mixed solutions (30 mL) were foamed at 25 8C in a
graduated tube (3 cm diameter) for 3 min with Griffin and
George stirrer at 2500 rpm. Overrun was calculated as:
FO ð%Þ Z ½ðfoam volume K 30Þ=30 !100
(1)
The data reported are means of at least two replicates.
The error was less than 10%.
2.5. Foam drainage and collapse
The volume of liquid drained to the bottom of the
graduated tubes and foam height (collapse) were recorded
over time. The following mathematical model was applied
to fit drainage over time (Carp et al., 1997a,b,c)
vðtÞ Z Vtn =C C tn
(2)
where v(t) is the drained volume at time t; V is the maximun
drained volume; n is a constant related to the sigmoid shape
of the curves; and c is a constant related to drainage half
time by c1/n. The rate constant for drainage (kdr) was
calculated as:
kdr Z n=Vc1=n
(3)
The data reported are means of at least two replicates.
The relative error in kdr was less than 15%.
The decrease of foam volume (V) over time (foam
collapse) was described by two parameters: tc, the time
when the collapse started and the rate of volume decay after
that lag time, that was fitted with the following linear model
V Z Kc t C b
Fig. 1. SDS-PAGE electrophoresis of intact (SP) and hydrolysed sunflower
protein. HSP1 DHZ1.5%; HSP2 DHZ9.8%.
(4)
where Kc is the collapse rate.
The data reported are means of at least two replicates.
The relative error in tc was less than 15% and in kc less than
20%.
the starting sunflower meal. The protein bands between 45
and 20 kDa were almost degraded in the HSP1 (DHZ1.5%)
sample, but the band of 60 kDa and that corresponding to
protein aggregates were more resistant to enzymatic breakdown. Nevertheless at DHZ9.8% (HSP2), the intensity of
those bands were also strongly decreased. Both hydrolysed
samples were composed by peptides of molecular mass less
than 6.5 kDa.
In the absence of polysaccharides, overrun was increased
by protein hydrolysis (Fig. 2), which is in accordance with
results reported for limited hydrolysis of other proteins such
3. Results
3.1. Foam overrun
SDS-PAGE in Fig. 1 shows that the intact sunflower
protein isolate (SP) was mainly composed by polypeptides
of molecular mass 60 kDa (band B), 40–45 kDa (band C),
28 kDa (band D) and 20 kDa (band E). Proteins with this
molecular mass has been reported by Jasso de Rodriguez,
Romero-Garcı́a, Rodrı́guez-Garcı́a, and Angulo Sánchez
(2002). The major seed storage globulin helianthinin has
been studied by Anisimova (1992), who found three main
groups of polypeptides: one basic of 20 kDa and two acid
with 30 and 40 kDa. The noticeable band with high
molecular mass (band A) could be attributed to protein
aggregates formed during the industrial processing of
Fig. 2. Foam overrun in the presence of 0.25 wt% polysaccharides as a
function of the degree of hydrolysis. SP: sunflower protein; X: xanthan;
G: guar; kC: kappa carrageenan; lC: lambda carrageenan; LB: locust bean
gum.
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K.D. Martinez et al. / Food Hydrocolloids 19 (2005) 361–369
0.25, being xanthan, guar and kC the polysaccharides that
promoted the strongest decrease. A similar behavior was
observed by increasing PS concentration to 0.5% as can be
seen in Fig. 3, where the overrun of foams made with a
sunflower protein with DHZ9.8% are shown.
The decrease in foamability in the presence of PS can be
attributed to the increased viscosity of the solutions that
precludes air incorporation. A similar behavior has been
reported for soy protein foams in the presence of xanthan
gum (Carp et al., 2001) or kC (Carp et al., 2004).
3.2. Rate of liquid drainage
Fig. 3. Foam overrun of hydrolysed sunflower protein isolate (DH 9.8%)
HSP2 in the presence of 0.5 wt% polysaccharides.
as soybean (Bernardi et al., 1991), wheat (Bombara et al.,
1997) and rapeseed (Vioque et al., 2000). The decreased
molecular size, increased solubility, flexibility and the
exposure of hydrophobic areas resulting from hydrolysis
(Addler-Nissen, 1986) increases the affinity and faster
adsorption to the interface and hence leads to the observed
higher overrun.
Polysaccharides alone were tested and they did not form
foams; therefore, they can be regarded as non-surface
active. The effect of addition of 0.25% polysaccharides to
sunflower protein solutions on the overrun is shown in
Fig. 2, as a function of the degree of protein hydrolysis.
Except for LB gum, that increased the overrun of the foam
obtained from HSP1 (DHZ1.5%), the overrun was
decreased in the presence of all the polysaccharides at
Depending on the protein and enzyme used, limited
protein hydrolysis may improve foam stability of proteins.
However, above a certain DH these properties decrease as a
consequence of the smaller peptide size that enables the
peptides to interact at the interface giving rise to the
viscoelastic film structure necessary for foam stabilization
(Bernardi et al., 1991). As can be seen in Fig. 4, drainage
rates of foams were strongly decreased by hydrolyzing only
1.5% of peptide bonds, but an increase of DH to 9.8% did
not further improve drainage stability.
As shown in Fig. 4, the performance of polysaccharides
regarding the rate of liquid drainage from foams was
strongly affected by the hydrolysis of protein and also
depended on the structure of the polysaccharide. Xanthan at
0.25% strongly decreased the rate of liquid drainage of
foams made with intact SP (Fig. 4a); kC, lC and guar also
decreased the drainage rate of foams made with intact SP
but at a lower extent (Fig. 4b–d); LB did not show a
significant effect (Fig. 4e).
Fig. 4. Effect of polysaccharides at 0.25 wt% on the drainage rates of foams made from intact (SP) and hydrolysed (HSP) sunflower protein isolate.
K.D. Martinez et al. / Food Hydrocolloids 19 (2005) 361–369
365
a dramatic increase of the rate of drainage of HSP2
(KdrZ0.385 (ml min)K1).
3.3. Foam collapse
Fig. 5. Effect of polysaccharides at 0.5 wt% on the drainage rates of foams
made from hydrolysed (HSP2) sunflower protein isolate (DH 9.8%).
In Fig. 4a it can be seen that xanthan addition at 0.25%
did not modify the drainage rate of the foam made with the
hydrolysed protein HSP1 (DHZ1.5%) but decreased the
drainage rate of the foam containing HSP2 (DHZ9.8%). On
the contrary, the other polysaccharides at 0.25% strongly
increased the rates of liquid drainage of foams containing
the hydrolysed proteins (Fig. 4b–e).
When the polysaccharides were added at 0.5% to a foam
containing the protein hydrolysate HSP2 (DHZ9.8%), it
was observed that xanthan continued to perform as stabilizer
and guar slightly decreased the rate of liquid drainage
(Fig. 5). However, the addition of 0.5% lC or LB continued
to be detrimental for the drainage stability of foams (Fig. 5),
but at a lower extent than in the presence of kC. A special
behavior was shown by kC that at 0.5% promoted
Fig. 6 shows that in the absence of PS, the time when the
collapse of foams started (lag time) was decreased up to
100% by SP hydrolysis. The lag time for foam collapse is
influenced by the time before drainage leads to very thin
films that rupture at the top of the foam. Therefore, the lower
the rates of drainage are, the higher the lag times for
collapse are expected to be. Nevertheless, the film structure
and mechanical properties play a determinant role on the
rupture of films. The decrease in molecular size resulting
from hydrolysis (Fig. 1) can be expected to decrease the
ability of the polypeptides at the interface to interact.
Increased aggregation of the interfacial film has been related
to enhanced resistance to foam collapse (Carp et al., 2001).
The addition of polysaccharides at 0.25% to foams
containing the intact SP increased the stability of the foams
against collapse, being xanthan the best stabilizer and kC
and LB the least effective (Fig. 6a–e). Xanthan also
stabilised the foam containing HSP2 (DHZ9.8%) but did
not affect that containing HSP1 (DHZ1.5%). Nevertheless,
the other polysaccharides strongly decreased the lag
times for collapse of foams containing the hydrolysed SP
(Fig. 6b–e).
When the polysaccharides were added at 0.5% to a foam
containing the protein hydrolysate HSP2 (DHZ9.8%), it
was observed that xanthan dramatically increased the
stability of the foam against collapse as the foam height
Fig. 6. Effect of polysaccharides at 0.25 wt% on the lag time for collapse of foams made from intact (SP) and hydrolysed (HSP) sunflower protein isolate.
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K.D. Martinez et al. / Food Hydrocolloids 19 (2005) 361–369
Fig. 7. Effect of polysaccharides at 0.5 wt% on the lag time for collapse
of foams made from hydrolysed (SPH2) sunflower protein isolate
(DHZ9.8%).
started to decrease after 2880 min. The addition of 0.5% kC
gave rise to a high increase of the lag time (Fig. 7) besides
having dramatically increased the rate of drainage as shown
above. This unexpected behavior would be related to the
time-dependent gelling of the continuous phase containing
kC (Carp et al., 2004). As a consequence, the foam drained a
considerable amount of liquid whilst the foam was not
gelled, but as far as the kC in the non-drained foam gelled, it
retarded the rupture of the foam. LB and guar promoted a
lower increase in the stability against collapse. However, the
addition of 0.5% lC continued to be detrimental for the lag
time for collapse (Fig. 7).
The rates at which foams collapsed (R2R0.90) after the
lag time were decreased by SP hydrolysis (Fig. 8). The
addition of polysaccharides, at 0.25 or 0.5%, always
decreased the rates of collapse for the intact or hydrolysed
protein (Figs. 8 and 9).
Fig. 8. Effect of polysaccharides at 0.25 wt% on the collapse rates of foams
made from intact (SP) and hydrolysed (HSP) sunflower protein as a
function of the degree of hydrolysis.
Fig. 9. Effect of polysaccharides at 0.5 wt% on the collapse rates of foams
made from hydrolysed (HSP2) sunflower protein isolate (DH 9.8%).
4. Discussion
When foams are initially formed, the air bubbles are
spherical and lamella are thick containing large amounts of
water. With time the liquid drains from the foam, the
lamella thins, and air bubbles pack closer and assume
polyhedral shapes. Drainage of liquid from lamellae is the
main destabilizing force as it allows the bubbles to become
closer where, if the film is permeable, disproportionation
occurs and large bubbles grow at the expense of small
ones (Prins, 1988). Finally, rupture of the film at the air–
foam interface leads to a decrease of the foam column
(collapse).
Both bulk and surface rheological properties have been
shown to impact foam destabilization (Carp et al., 2001;
Kloek, van Vliet, & Meinders, 2001). Increased bulk
viscosity is known to retard foam drainage and bubble
disproportionation can be retarded by the presence of a
viscous interface or viscous bulk if the relevant viscosity is
larger than a critical value. The presence of either a
completely elastic interface or completely elastic bulk can
stop bubble shrinkage (Kloek et al., 2001).
In protein/polysaccharide systems, the possible phase
separation could further influence foam stability. In bulk
solution, the mixtures of proteins and PS at pH 7
appeared to be governed by segregative or limited
thermodynamic incompatibility phenomena (Tolstoguzov,
1997). However, at the interface local net attractive
interactions between proteins and polysaccharides may
also occur. Under the adsorption of the protein, the
character of protein–polysaccharide interactions may be
different than in bulk solution because of the altered
conformation of protein at the interface. Evidence for the
synergistic interaction of xanthan and soy proteins at the
air–water interface was previously provided by measurements of surface shear viscosity (Carp, Elizalde,
Bartholomai, & Pilosof, 1997) and electrophoresis
analysis of protein aggregation at the air–water interface
(Carp et al., 1999).
K.D. Martinez et al. / Food Hydrocolloids 19 (2005) 361–369
Table 1
Yield stress and viscosity of hydrolysed sunflower protein (DHZ9.8%) and
polysaccharide mixed solutions
Polysaccharide
Yield stress
(dyn/cm2)
Apparent viscosity
(60 sK1) (cps)
Xanthan (0.25%)
Xanthan (0.5%)
Guar (0.25%)
l-Carrageenan (0.25%)
k-Carrageenan (0.25%)
Locust bean (0.25%)
10
20
–
–
–
–
83
149
4.7
8.8
3.4
5.0
The stability of both intact and hydrolysed sunflower
protein foams in the presence of xanthan was controlled
by the high viscosity of the bulk phase containing 0.25 or
0.5% of the gum and to the existence of a yield stress
(Table 1). Xanthan is an anionic polysaccharide that
produces high viscosities at low concentrations (Imeson,
1992) and, being highly hydrophilic and without any
significant hydrophobic bonds, is not adsorbed at the air–
water interface (Yilmazer, Carrillo, & Kokini, 1991).
Enhanced hydration is attributed to side chains of anionic
character consisting in units of a-D mannnose, b-D
glucuronic and pyruvate, occurring on the cellulose
structure backbone. The presence of xanthan (0.5 wt%)
halted liquid drainage and collapse of the hydrolysed SP
(DHZ9.8%) for 6 h that can be attributed to the existence
of a yield stress for this system , that imparts a gel-like
character to the continuous phase of the foam (Sánchez,
Bartholomai, & Pilosof, 1995). Similarly, kC at 0.5%
halted foam collapse because of the gelling of the
polysaccharide in the presence of proteins (Baeza, Carp,
Perez, & Pilosof, 2002).
For more low-viscosity foams such as those containing
the carrageenans and galactomannans, the surface rheological properties should become important and stability
would be determined by both bulk and interfacial
properties. Polysaccharides alongside increasing the viscosity of the aqueous phase may influence the viscoelastic
character and thickness of the adsorbed macromolecular
layer reducing the thinning rate of lamella and hence
increasing the stability of the foam (Dickinson & Izgi,
1996). Recently, Baeza et al. (2004) supported this view
by showing that the low-term dilatational elasticity of
the air–water interface of b-lactoglobulin/xanthan and
b-lactoglobulin/lC mixed systems was higher than that of
the b-lactoglobulin film, indicating an increase of the solid
character of the films. Moreover, they evaluated the
impact of surface properties and bulk rheological properties (apparent viscosity) on the different mechanisms of
foam destabilization by linear regression analysis and
found that the dilatational elasticity of interfacial films
explained on its own 82.2% of the variations in the rates
of drainage of b-lactoglobulin/polysaccharide stabilised
foams. The higher the surface dilatational elasticity,
367
the lower the rate of drainage may be attributed to the
ability of strong elastic films to enhance local viscosity in
the foam lamellae which tends to inhibit liquid drainage.
For the same foams, the lag time for foam collapse
showed a high correlation (R2Z81.6%) with the surface
dilatational elasticity and the bulk viscosity (R2Z97.2%).
It may be concluded that both parameters are relevant for
this mechanism of foam destabilization.
Therefore, the increased stability of intact SP foams in
the presence of PS would be related to the increased bulk
viscosity as a consequence of the presence of PS and to a
possible increase in dilatational elasticity of intact SP films
due to protein/PS interactions at the interface.
The antagonistic effect that carrageenans and galactomannans (0.25%) had on the stability of foams containing
the hydrolysed sunflower protein should be attributed to a
possible change in the protein/polysaccharide interactions at
the interfacial film, as the bulk viscosity of both intact or
hydrolysed SP/PS systems was mainly dominated by the PS
that were present at the same concentration. The results
suggest that, as a result of protein hydrolysis, an
antagonistic interaction between the polysaccharides and
the hydrolysed protein should take place at the interface, so
that the increasing of the bulk phase viscosity could not
balance the loss of mechanical properties of the interface.
Above a critical PS concentration, that is dependent on
the PS structure/viscosity (i.e. 0.5%), this effect would
be overcome, being the foam stability controlled by the
viscous bulk.
The depletion mechanism could also occur in protein/
polysaccharide foams, promoting the liquid flow out
(drainage) of the lamella, a faster thinning, hence a faster
foam collapse. Nevertheless, it cannot explain why the PS
performed as detrimental only in the presence of the
hydrolysed SP. In fact, it is expected that the driving force
for the solvent to flow out of the lamella would be lower as
thermodynamic incompatibility between the adsorbed
protein and the PS decreases. The decreasing of the
molecular weight of the protein as a consequence of
hydrolysis is expected to reduce the biopolymer incompatibility (Grinberg & Tolstoguzov, 1997). However, other
factors as the increase of the charge density with the
hydrolysis could further influence the degree of
incompatibility.
Additional studies of SP films in the presence of
polysaccharides are needed to elucidate how the hydrolysis
of the protein affects the viscoelastic properties and
interactions at the air–water interface.
5. Conclusions
A limited enzymatic treatment with Alcalase could
substantially enhance foaming properties of sunflower
protein. A small degree of SP hydrolysis (DHZ1.5%)
enhanced both foam overrun and foam stability against
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K.D. Martinez et al. / Food Hydrocolloids 19 (2005) 361–369
liquid drainage and collapse. However, an increase of DH to
9.8% did not further improve foaming properties.
The overrun of foams was decreased in the presence
of all the polysaccharides but the performance of
polysaccharides as stabilizers of foams depended on the
protein hydrolysis, the structure of the polysaccharide
and its concentration in the liquid used to make the
foam.
Xanthan gum at 0.25 and 0.5%, due to its high
viscosity performed as stabilizer of both intact and
hydrolysed SP foams. The other PS at 0.25% performed
as stabilizers when added to the intact SP foams but
destabilized the foams containing the hydrolysed SP. By
increasing PS concentration the detrimental effect could
be partially reverted.
Acknowledgements
This research was supported by CYTED through project
XI.17. The authors also acknowledge the support from
Universidad de Buenos Aires and Consejo Nacional de
Investigaciones Cientı́ficas y Técnicas de la República
Argentina.
References
Addler-Nissen, J. (1979). Determination of degree of hydrolysis of food
protein hydrolysates by trinitrobenzenesulfonic acid. Journal of
Agricultural and Food Chemistry, 27, 1256–1262.
Addler-Nissen, J. (1986). Enzymic hydrolysis of food proteins. London:
Elsevier.
Anisimova, I. N. (1992). Sunflower seed 11S globulin (helianthinin)
as genetic marker. In Proceedings of the 13th international
sunflower conference, Pisa, Italy, 7–11 September 1992 (Vol. 1)
(pp. 501–512).
Baeza, R. I., Carp, D. J., Perez, O., & Pilosof, A. M. R. (2002). kcarrageenan-protein interactions: effect of proteins on polysaccharide
gelling and textural properties. Lebensmittel Wissenschaft und Technologie, 35, 741–747.
Baeza, R. I., Carrera Sanchez, C., Pilosof, A. M. R., & Rodriguez
Patino, J. M. (2004). Interactions of polysaccharides with blactoglobulin at the air–water interface and the influence on foam
properties. In E. Dickinson (Ed.), Food colloids: Interactions
microstructure and processing. Cambridge: The Royal Society of
Chemistry, in press.
Bernardi, L. S., Pilosof, A. M. R., & Bartholomai, G. B. (1991).
Enzymatic modification of soy protein concentrates by fungal and
bacterial proteases. Journal of the American Oil Chemists’ Society,
68, 102–105.
Bombara, N., Añon, M. C., & Pilosof, A. M. R. (1997). Functional
properties of protease modified wheat flours. Lebensmittel Wissenschaft
und Technologie, 30, 441–447.
Cao, Y., Dickinson, E., & Wedlock, D. J. (1990). Creaming and
flocculation in emulsions containing polysaccharide. Food Hydrocolloids, 4, 185–195.
Carp, D. J., Baeza, R. I., Bartholomai, G. B., & Pilosof, A. M. R. (2004).
Impact of proteins- k-carrageenan interactions on foam properties.
Lebensmittel Wissenschaft und Technologie, 37, 573–580.
Carp, D. L., Bartholomai, G. B., & Pilosof, A. M. R. (1997). A kinetic
model to describe liquid drainage from soy protein foams over an
extensive concentration range. Lebensmittel Wissenschaft und Technologie, 30, 253–258.
Carp, D. J., Bartholomai, G. B., & Pilosof, A. M. R. (1999). Electrophoretic
studies for determining soy proteins-xanthan gum interactions in foams.
Colloids and Surfaces B: Biointerfaces, 12, 309–316.
Carp, D. J., Bartholomai, G. B., Relkin, P., & Pilosof, A. M. R. (2001).
Effects of denaturation on soy protein–xanthan interactions: comparison of a whipping-rheological and bubbling method. Colloids and
Surfaces B: Biointerfaces, 21, 163–171.
Carp, D. J., Elizalde, B. E., Bartholomai, G. B., & Pilosof, A. M. R. (1997).
Foaming properties of soy proteins as affected by xanthan gum. In R.
Jowitt (Ed.), Engineering and food (pp. 69–72). New York: Academic
Press.
Carp, D. J., Wagner, J., Bartholomai, G. B., & Pilosof, A. M. R.
(1997). Rheological method for kinetics of drainage and disproportionation of soy proteins foams. Journal of Food Science, 62,
1105–1109.
Chobert, J. M., Sitohy, M. Z., & Whitaker, J. R. (1988). Solubility and
emulsifying properties of caseins modified enzymatically by Staphylococcus aureus. Protease, 36, 220–224.
Dickinson, E. (2003). Hydrocolloids at interfaces and the influence
on the properties of dispersed systems. Food Hydrocolloids, 17,
25–40.
Dickinson, E., & Izgi, E. (1996). Foam stabilization by protein–
polysaccharide complexes. Colloids and Surfaces A: Physicochemical
and Engineering Aspects, 113, 191–201.
Grinberg, V., Y, ., & Tolstoguzov, V. B. (1997). Thermodynamic
incompatibility of proteins and polysaccharides in solutions. Food
Hydrocolloids, 11, 145–158.
Imeson, A. (1992). hickening and gelling agents for foods. New York:
Blackie.
Ipsen, R., Otte, J., Sharma, R., Nielsen, A., Gram Hansen, L., & Qvist, K.
(2001). Effect of limited hydrolysis on the interfacial rheology and
foaming properties of (-lactoglobulin A. Colloids and Surfaces B:
Biointerfaces, 21, 173–178.
Jasso de Rodriguez, D., Romero-Garcı́a, J., Rodrı́guez-Garcı́a, R., &
Angulo Sánchez, J. L. (2002). Characterization of proteins from
sunflower leaves and seeds: Relationship of biomass and seed yield. In
J. Janick, & A. Whipkey (Eds.), Trends in new crops and new uses (pp.
143–149). Alexandria, VA: ASHS Press.
Kloek, W., van Vliet, T., & Meinders, M. (2001). Effect of bulk and
interfacial rheological properties on bubble dissolution. Journal of
Colloids and Interface Science, 237, 158–166.
Laemmli, U. K. (1970). Cleavage of structural proteins during the assembly
of head of bacteriophague T4. Nature, 227, 680–687.
Mc Clements, D. J. (2000). Comments on viscosity enhancement and
depletion flocculation by polysaccharides. Food Hydrocolloids, 14,
173–177.
Prins, A. (1988). Principles of foam stability. In E. Dickinson, & G.
Stainsby (Eds.), Advances in food emulsions and foams (pp. 91–122).
London: Elsevier, 91–122.
Sánchez, V. E., Bartholomai, G. B., & Pilosof, A. M. R. (1995).
Rheological properties of food gums as related to their water binding
capacity and to soy protein interaction. Lebensmittel Wissenschaft und
Technologie, 28, 380–385.
Tolstoguzov, V. B. (1997). Protein–polysaccharide interactions. In S.
Damodaran, & A. Paraf (Eds.), Food proteins and their application (pp.
171–198). New York: Marcel Decker.
Villanueva, A., Vioque, J., Sanchez-Vioque, R., Clemente, A., Bautista, J.,
& Millán, F. (1999). Production of an extensive sunflower protein
hydrolysate by secuential hydrolysis with endo-and exo-proteases.
Grasas y Aceites, 50, 472–476.
Villanueva, A., Vioque, J., Sanchez-Vioque, R., Clemente Pedroche, J. A.,
Bautista, J., & Millán, F. (1999). Peptide characteristics of sunflower
K.D. Martinez et al. / Food Hydrocolloids 19 (2005) 361–369
protein hydrolysates. Journal of the American Oil’s Chemist Society,
76, 1455–1460.
Vioque, J., Sanchez-Vioque, R., Clemente, A., Pedroche, J., & Millán, F.
(2000). Partially hydrolyzed rapessed protein isolates with improved
functional properties. Journal of the American Oil’s Chemist Society,
77, 1–4.
369
Ye, A., Hemar, Y., & Singh, H. (2004). Enhancement of coalescence by
xanthan addition to oil-in -water emulsions formed with extensively
hydrolysed whey proteins. Food Hydrocolloids, 18, 737–746.
Yilmazer, A. R., Carrillo, A. R., & Kokini, J. (1991). Effect of propylene
glycol alginate and xanthan gum on stability of o/w emulsions. Journal
of Food Science, 46, 513–517.