Journal of Cereal Science 52 (2010) 491e495
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Journal of Cereal Science
journal homepage: www.elsevier.com/locate/jcs
The effect of chitosan oligosaccharides on bread staling
Garry Kerch a, *, Janis Zicans b, Remo Merijs Meri b
a
b
Faculty of Food Technology, Latvian University of Agriculture, Jelgava, Latvia
Institute of Polymer Materials, Riga Technical University, Riga, Latvia
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 18 May 2010
Received in revised form
3 August 2010
Accepted 19 August 2010
The aim of this work was to investigate the effects of chitosan oligosaccharides and chitosan on the rate
of staling and properties of bread crumb and crust. Rates of crumb firming varied with storage time. The
possible mechanisms including prevention of amyloseelipid complexation, acceleration of dehydration
from both starch and gluten, adsorption of chitosan onto the starch surface and increase of moisture
migration rate from crumb to crust are proposed and analysed. Chitosan oligosaccharides and low
molecular weight chitosan increase bread crumb staling rate to a much lesser extent than does middle
molecular weight chitosan.
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
Chitosan oligosacharides
Bread staling
Mechanisms
1. Introduction
Consumption of dietary fibers offers health benefits including
protection against cardiovascular diseases, cancer, reduction blood
serum cholesterol and regulation of blood glucose levels (Qiang
et al., 2009).
Chitosan and chitosan oligomers are positively charged dietary
fibers (Hennen, 1996; Tungland and Meyer, 2002). Chitosan is
a copolymer of N-acetyl-glucosamine and glucosamine. This polymer is a weak base with a pKa value of the glucosamine residue of
w6.2e7.0. Therefore, it is insoluble at neutral and alkaline pH
values. In acidic media, the amino groups will be positively charged,
conferring to the polysaccharide a high charge density (Mansouri
et al., 2004; Weecharangsan et al., 2006). The charge density
depends also on the degree of deacetylation of chitosan. Biological
activities of chitosan and chitooligosaccharides include hypocholesterolemic, antimicrobial, immunostimulating, antitumor and
anticancer effects, accelerating calcium and iron absorption, antiinflammatory and antioxidant effects (Xia et al., 2010).
Chitosan oligosaccharides are more biologically active than high
molecular weight chitosan. The salts of chitosan oligosaccharides
such as lactates, ascorbates and succinates may be used for the
development of biologically active supplements for prevention and
treatment of various diseases.
Chitooligosaccharide ascorbate essentially increases the bioavailability of vitamins A, C, E, B1, B2, B3, B6, B9, B12, bioflavonoids,
* Corresponding author.
E-mail address: garrykerch@lycos.com (G. Kerch).
0733-5210/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.jcs.2010.08.007
microelements iron, zinc and copper, as well as potassium and
magnesium (Kirilenko et al., 2007). Water-soluble chitosan oligosaccharides and their salts, similarly to other dietary fibers, significantly reduce the risk for coronary, diabetic and gastroenterological
diseases, have prebiotic, antioxidant and other biologically active
properties which make them widely used for manufacture of biologically active supplements and functional nutrition (Jeon et al.,
2000; Nakakuki, 2005; Tungland and Meyer, 2002).
But flour replacement by functional health promoting ingredients changes the quality of the final product. Adverse effects of
flour replacement by dietary fibers in bread making include
weakened gluten network and disruption of the starchegluten
matrix in dough, reduction in starch availability for gelatinization,
reduction of the initial starch granule swelling, decreased loaf
volume, lowered gas retention and unsuitable taste (Collar, 2007).
Chitosan increases the rate of bread staling, increases water
migration rate from crumb to crust, prevents amyloseelipid
complexation, and increases dehydration rate of both starch and
gluten (Kerch et al., 2008).
Application of chitosan oligosaccharides in functional foods is an
area of particular interest. It must be taken into account that there
is a considerable growing demand in the world for new natural
products demonstrating functional properties concerning health
promoting or disease preventing aspects.
Addition of chitosan oligosaccharides to bakery products creates
an opportunity to combine beneficial technological properties with
beneficial biological health promoting properties.
The objective of this work was to study the effect of chitosan
oligosaccharides on the structure and properties of bread as well as
their changes during storage.
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G. Kerch et al. / Journal of Cereal Science 52 (2010) 491e495
Table 1
Formulation of rolls containing chitosan and chitosan
oligosaccharides.
Ingredient
Weight (g)
Wheat flour
Sugar
Butter
Salt
Yeast
Margarine
Water
Chitosan
Ascorbic acid
550
42.5
10
9
20
16
245
20
4
2. Materials and methods
2.1. Sample preparation
Dough was prepared based on the recipe shown in Table 1.
Wheat flour type 405 with protein content 10.3% and moisture
content 14.6% was kindly supplied by company Latgales Maiznica
(Riga,Latvia). The following chitosans and chitosan oligosaccharides
have been kindly supplied by company Oligopharm (Nizhnij Novgorod, Russian Federation):
Chitosan (low molecular weight) e viscosity 29 cP, degree of
deacetylation 97%;
Chitosan (middle molecular weight) e viscosity 70 cP, degree of
deacetylation 82%, pH 6, 7;
Chitosan succinate e viscosity 3, 1 cP, pH 3, 8 (succinic acid
content 43%);
Chitosan oligosaccharide acetate e viscosity 1, 9 cP, pH 4, 6
(acetic acid content 18, 5%);
Chitosan oligosaccharide lactate e viscosity 1, 9 cP, pH 5, 4
(lactic acid content 24, 5%);
Chitosan oligosaccharide ascorbate e viscosity 1, 8 cP, pH 5, 3
(ascorbic acid content 15, 1%);
Chitosan oligosaccharide succinate e viscosity 2, 2 cP, pH 4, 3
(succinic acid content 31%).
Viscosities and pH were determined for 1% chitosan and chitosan oligosaccharide solutions.
Dough mixer “MONO” (Model ISEN A300, Swansea, UK) was used
to make bread dough at 2 stirring rates during 10 min. The dough
was allowed to proof for 25e30 min at 38 C and relative humidity
72% and cut to pieces with weight 65 g. The rolls were baked in an
oven “MONO” (Model BX eco-touch convection oven, Swansea, UK) at
200 C for 12 min. The rolls were then cooled at room temperature
for 30 min, packed in polypropylene bags and stored at a temperature of 21 1 C.
2.2. Mechanical measurements
Zwick/Roell universal testing machine (Model Zwick/Roell
BDO-FB0.5TS, Zwick GmbH & Co. KG, Ulm, Germany) with testXpertÒ
software was used to perform travel controlled penetration tests of
bread samples. Cylinder with diameter 4 mm was used as
penetrator. Loading rate was 100 mm/min and travel distance was
30 mm. The reported mean firmness values represent measurements taken from the center of three slices (40 mm diameter) per
loaf.
2.3. Thermogravimetric analysis
The moisture content of bread was determined from
weight losses measured using a thermogravimeter Mettler Toledo
(Model TG-50, Mettler-Toledo AG, Schwerzenbach, Switzerland).
Approximately 10 mg of the samples were weighed in preweighed
aluminium pans and scanned from 25 to 150 C at 10 C/min to
volatilize the water. The sample pans were reweighed after the
analysis, and the percentage of total water content was determined.
3. Results and discussion
Bread is a complex heterogeneous unstable system and bread
making as well as staling are complex multistage dynamic
processes affected by many factors and involving multiple mechanisms operating at different space and time scales (Gray
and Bemiller, 2003). The mechanisms of staling are not yet
completely understood. Solid bread after baking contains a continuous phase composed of an elastic network of cross-linked gluten
molecules and starch polymer molecules, primarily amylose, both
uncomplexed and complexed with polar lipid molecules, and
a discontinuous phase of entrapped, gelatinized, swollen, deformed
starch granules (Gray and Bemiller, 2003).
The addition of chitosan or chitosan oligosaccharides to dough
produces marked differences in appearance of baked rolls. Only
additions of chitosan oligosaccharide lactate, chitosan oligosaccharide ascorbate and chitosan oligosaccharide acetate did not
decrease significantly the volume of rolls compared to control rolls.
The presence of chitosan succinate or middle molecular weight
chitosan contributes to especially high decrease in the volume of
rolls. Both these additives have higher molecular weights, higher
viscosities and higher pH if compared to the other oligosaccharide
salts. Reduction in the specific volume of the bread as a result of
addition of other dietary fibers was also recently reported (Filipovic
et al., 2007; Rosell and Santos, 2010).
Crust with rough surface, spots and uneven color was formed
when middle molecular weight chitosan was added to dough.
Chitosan oligosaccharides didn’t produce such negative effect on
bread crust.
The appearance of crumb and crust did not change during
storage over five days and its overall quality was still acceptable.
Effective antistaling aspects can be considered to be specific
only when they affect the increase in crumb firmness in a way
independent of loaf volume. Changes in firmness are readily
detectable, but not changes in loaf volume during storage.
The addition of chitosan and chitosan oligosaccharide succinate
to dough results in an increase in fresh roll crumb firmness (Fig. 1).
This effect was more pronounced for the crumb containing middle
molecular weight chitosan than for the crumb containing low
molecular weight chitosan. The addition of chitosan oligosaccharide lactate, chitosan oligosaccharide acetate and chitosan oligosaccharide ascorbate to dough doesn’t change significantly fresh
roll firmness. Rates of crumb firming vary with storage time at
room temperature. This confirms the idea (Gray and Bemiller,
2003) that different mechanisms of staling operate at different
time intervals of bread storage. The presence of middle molecular
weight chitosan, chitosan succinate and chitosan oligosaccharide
ascorbate leads to a major acceleration in the firming process
during the first day of storage at room temperature if compared to
control rolls and rolls containing chitosan oligosaccharide acetate.
Retardation of firming during the first day was observed for
rolls containing chitosan oligosaccharide succinate and chitosan
oligosaccharide lactate, but the rolls containing chitosan oligosaccharide succinate and chitosan oligosaccharide lactate showed
sharp increase of firmness on the second day of storage. Decrease of
firmness was indicated during the second day of storage for
rolls containing chitosan succinate and chitosan oligosaccharide
ascorbate and to some extent for rolls containing chitosan oligosaccharide acetate and control rolls. On the second stage, from day
G. Kerch et al. / Journal of Cereal Science 52 (2010) 491e495
12
10
Fo r ce , N
8
6
4
2
0
0
2
4
6
Storage time,days
Fig. 1. Mechanical penetration tests at room temperature for bread without and with
addition of chitosans and chitosan oligosaccharides: dddA e bread without chitosan; e e e D e bread þ chitosan oligosaccharide acetate; ..- e bread þ chitosan
oligosaccharide ascorbate; dd e bread þ chitosan oligosaccharide lactate; e e e* e
bread þ chitosan oligosaccharide succinate; dddB e bread þ low molecular weight
chitosan; ..> e bread þ chitosan succinate; e e e þ e bread þ middle molecular
weight chitosan.
2 to day 5, the acceleration of firming was indicated for rolls
containing chitosan succinate and low and middle molecular
weight chitosans, intermediate rates of firming were observed for
rolls containing chitosan oligosaccharide lactate and chitosan
oligosaccharide acetate, and comparatively slow firming was
indicated for control rolls and rolls containing chitosan oligosaccharide ascorbate and chitosan oligosaccharide succinate.
In fact, such behavior is in agreement with previously made
conclusion (Bechtel and Meisner, 1954; Gray and Bemiller, 2003) that
staling is a result of two independent processes: staling during the
first two days of storage is a result of changes in the organization of
starch polymer chains; thereafter, staling is caused by loss of water by
gluten. Recent calorimetry tests showed that during bread storage,
amylopectin recrystallisation can occur before crumb stiffening and
hardening of the crumb during staling (Le-Bail et al., 2009).
It may be suggested that during the first stage, chitosan increases
firming rate due to its ability to bind lipids and prevent amyloseelipid complexation, which is known (Lagendijk and Pennings,
1970) to inhibit staling and during the second stage chitosan due
to its water binding ability promotes dehydration of gluten.
It is also known that chitosanestarch interaction occurring at
the molecular level leads to the strong adhesion between starch
and chitosan. This fact was attributed to the hydrogen-bonding
interaction between chitosan and starch molecules. Cationic
properties of chitosan result in electrostatic interactions with
other anionic polysaccharides. The combination of hydrogen
bonding, opposite charge attraction between chitosan cations
493
and the negatively charged starch surface, provided a good adherence between starch and chitosan (Bangyekan et al., 2006).
Therefore, another possible mechanism is that the adsorption of
chitosan onto the starch surface prevents starch granules from
taking up the water released by gluten. As a result, this water would
be available for migration towards the crust. Chitosan oligosaccharides and low molecular weight chitosan increase staling rate to a
much lesser extent than does middle molecular weight chitosan
probably because low molecular weight substances inhibit crosslink
(hydrogen bonds) formation between starch granules and protein
fibrils (Martin and Hoseney, 1991) that are responsible for staling.
Increase of firmness of bread crumb occurs with dehydration.
But it is still unclear whether staling can be attributed to dehydration of starch or gluten. The release of water from gluten and
uptake of this water by retrograding starch was demonstrated by
a number of researchers (Bechtel and Meisner, 1954; Gray and
Bemiller, 2003; Lagendijk and Pennings, 1970). In contrast, it was
also shown (Martin and Hoseney, 1991) that water was released
from starch and taken up by gluten. It is likely that both gluten
and starch contribute to the staling process. At the same time
Ottenhof and Farhat (2004) concluded that there was no evidence
of any significant effects of the presence of gluten on the kinetics,
extent or polymorphism of amylopectin retrogradation. So it is
evident that different water binding states in bread exist with
different time dependent behavior.
The crust color of the bread depends on the presence of
chitosan. In the presence of chitosan, the color of crust is darker
and browner, possibly due to the more intensive Maillard
reactions during the process of baking. The Maillard reaction rate is
highly dependent on time, temperature, pH, and moisture. In the
presence of chitosan as well as chitosan oligosaccharides, higher
moisture content in crust contributes to the intensification of
Maillard reactions and browning of crust. We suppose that
increased color generation in bread crust is due to the increase of
total moisture content in crust in the presence of chitosan or chitosan oligosaccharides. The Maillard reaction generates different
Maillard reaction products with different biological properties
(antioxidant, antihypertensive and antibacterial activities).
Bread with chitosan could provide a combination of beneficial
health promoting properties of chitosan (no change of molecular
weight of chitosan or chitosan oligosaccharides in crumb, where
temperature during baking is not higher than 100 C) with health
promoting properties of some Maillard reaction products (higher
content of antioxidants in crust, where temperature during baking
is about 200 C).
It is well known at present that drying out of the bread does not
explain completely the process of staling (Lai and Lin, 2006). Moisture
migration from crumb to crust and moisture redistribution between
bread components have significant effects on staling processes. At
present, it can be concluded that in the crumb, interpenetrated gels
are separated by interphases which contain most of the low molecular weight solutes (Schiraldi and Fessas, 2001). The water at interphases is rather mobile and the process of the crumb-to-crust
migration of moisture can be facilitated. This local internal dehydration makes the crumb more rigid, while the concurrent moisture
increase within the crust region results in a reduction of crispness.
During the migration from crumb to crust, water can contribute to
a closer packing of the structure through which it is moving, either
within a given phase or at the interphases, by tightening the sites able
to form hydrogen bonds (Schiraldi and Fessas, 2001).
Moreover, the total moisture content after one day storage in
bread crust containing chitosan was much higher than in the crust
of control bread and bread containing chitosan oligosaccharide
lactate (Fig. 2). The water content of crust containing chitosan
didn’t decrease substantially during the first days of aging, Fig. 2.
494
G. Kerch et al. / Journal of Cereal Science 52 (2010) 491e495
water content in crust increases during the first five days of staling
and then decreases.
The results of mechanical penetration tests for crumb and crust
are shown in Fig. 3. The addition of chitosan results in an increase
of crust firmness compared to control bread. But addition of
chitosan oligosaccharide lactate results in a decrease of crust
firmness if compared with control bread. During the first five days
of staling, crust firmness decreases due to moisture migration from
crumb to crust and then it grows again in breads containing
chitosan and chitosan oligosaccharide lactate.
The crumb firmness was the same for control bread and breads
containing 2% chitosan or chitosan oligosaccharide lactate and it
was increasing during staling due to water migration from crumb to
crust.
40
35
Total moisture content, %
30
25
20
15
10
4. Conclusions
5
0
0
5
10
15
Storage time, days
Fig. 2. Changes in total moisture content in bread crust during staling at room
temperature of control bread (A), bread with chitosan (-) and bread with chitosan
oligosaccharide lactate (6).
This implies that the transfer rate of water from the crust to the
surrounding atmosphere was balanced by the water migration
from the crumb. Similar results were reported for water migration
in baguette during aging (Sereno et al., 2007). But in control bread
and in the bread containing chitosan oligosaccharide lactate, total
Acknowledgements
This work was carried out within 6th Framework Programme
CRAFT project ‘New chitosan formulations for the prevention and
treatment of diseases and dysfunctions of the digestive tract
(hypercholesterolemia, overweight, ulcerative colitis and celiac
diseases)’ and within the ESF Project “Formation of the research
group in food science” Contract Nr. 2009/0232/1DP/1.1.1.2.0/09/
APIA/VIAA/122.
9,00
8,00
7,00
Mechanical force,N
It was found that chitosan and chitosan oligosaccharides affect
redistribution and state of water in bread crust and crumb and as
a consequence affect the structure and properties of bread crust
and crumb. Chitosan facilitates dehydration of both starch and
gluten and facilitates moisture migration from crumb to crust.
Redistribution of water affects intensity of Maillard reactions in
bread crust and the rate of bread staling. Chitosan oligosaccharides
and low molecular weight chitosan increase bread crumb staling
rate to a much lesser extent than does middle molecular weight
chitosan. It is suggested that during bread staling, chitosan and
chitosan oligosaccharides can prevent amyloseelipid complexation
by adsorption of chitosan onto the starch surface.
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6,00
5,00
4,00
3,00
2,00
1,00
0,00
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6
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Storage time,days
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