Vol.1, No.3, 192-196 (2009)
doi:10.4236/health.2009.13032
SciRes Copyright © 2009 Openly accessible at http://www.scirp.org/journal/HEALTH/
Health
Effects of thermally modified green tea catechins on the
oxidative and hydrolytic stability of butter
Magdalena Mika*, Agnieszka Wikiera, Krzysztof Żyła
Department of Food Biotechnology, Faculty of Food Technology, University of Agriculture in Krakow, Kraków, Poland;
Received 15 September 2009; revised 9 October 2009; accepted 10 October 2009
ABSTRACT
Green tea catechins are classified as (-)-epi-
forms (2R, 3R) or (-)-forms (2S, 3R) with respect
to stereoisomerism. The (-)-forms (2S, 3R) in
catechin preparations obtained from green tea
amounts to approximately 10% of total catechins,
whereas the other 90% are (-)-epiforms (2R, 3R).
High temperature induces the conversion of
(-)-epiforms (2R, 3R) to (-)-forms (2S, 3R). This
study investigated the effect of catechin prepa-
rations containing 10, 20 and 30% (-)-forms (2S,
3R) on the oxidative and hydrolytic stability of
butter. For comparison, butter with δ-tocopherol
and BHT and butter without stabilizer were
analysed. Butter stability was examined under
conditions of refrigeration (8 oC) and freezing
(-22 oC) and at temperature of 50 oC and 100 oC.
Catechin preparations were more efficient butter
stabilizers than BHT and δ-tocopherol. Thermal
modification of catechins that led to the genera-
tion of 20% of (-) forms (2S, 3R) improved their
antioxidative efficacy, but longer treatment lead-
ing to the formation of 30% of (-) forms (2S, 3R)
decreased their antioxidative activity. The hy-
drolytic stability of butter, however, increased as
the amount of (-) forms (2S, 3R) increased.
Keywords: Oxidative; Hydrolytic Stability; Antioxi-
dants; Catechins
1. INTRODUCTION
In recent years a number of studies have been carried out
that have shown a positive effect of green tea on humans,
mainly due to polyphonies. Green tea polyphenols have
been reported to have antiatherosclerotic [1], anticar-
cinogenic [2,3] and anti-inflammatory [4,5] effects. Fla-
van-3-ols (catechins) form the most numerous group of
non-fermented green tea polyphenols. The flavan-3-ol
molecule comprises two stereogenic centres situated on
the C-ring and constituted by the C2 and C3 carbon atoms.
Tea catechins always have an R configuration at the C3
carbon atom. Based on configuration at the C2 carbon
atom, catechins can be classified into two groups: (-)
epiforms (2R, 3R) and (-) forms (2S, 3R) [6]. In catechin
preparations obtained from tea the main components are
(-) epiforms (2R, 3R): (-) epigallocatechin gallate (EG-
CG), (-) epicatechin gallate (ECG), and (-) epicatechin
(EC). At high temperatures and in anaerobic conditions
the epimerization reaction results in more (-) epiforms
(2R, 3R) being transformed to (-) forms (2S, 3R) [7,8].
Catechins that belong to the (-) forms (2S, 3R) include: (-)
gallocatechin gallate (GCG), (-) catechin gallate (CG),
and (-) catechin (C). These compounds efficiently limit
the absorption of cholesterol [9,10] and lipid hydrolysis
products in the digestive tract [11-14]. Ikeda reported that
catechin gallates, being (-) forms (2S, 3R), were most
effective in eliminating cholesterol from bile acid mi-
celles [10]. The antioxidative and antiseptic properties of
catechins suggest that these compounds could be used as
food stabilizers. Moreover, catechin preparations that are
rich in (-) forms (2S, 3R) seem to be ideal stabilizers of
high-fat foods that are also high in cholesterol. The aim of
this study was to determine the influence of catechin
preparations that differed in flavan-3-ols content on the
oxidative and hydrolytic stability of butter stored at 8 oC
and –20 oC or exposed to the temperature of 50 oC and
100 oC.
2. MATERIALS AND METHODS
2.1. Thermal Modification of Catechin
Preparations
Catechin solutions (50 mg/ml of redistilled water) were
prepared from Sigma Polyphenon 60 and subjected to
thermal modification at 140 oC for 40 minutes (prepara-
tion HMC1) or 80 minutes (preparation HMC2). Modi-
fications were carried out in Scott tubes under gaseous
nitrogen.

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2.2. Determination of Chemical Composition
of Catechin Preparations
The composition of flavan-3-ols in thermally modified
and non-modified (NMC) catechin preparations was
determined by the HPLC method as described by Lin [15].
Standards of (-) ECG, (-) EGCG, (-) GCG, (-) CG, (-) C, (-)
EC and catechin solutions (diluted 200-fold) were fil-
tered (0.45 μm) and injected (50 μl) into a LUNA 5U
C18(2) (250 x 4.6 mm) chromatographic column. The
Phase A elution solution comprised methanol, formic acid
and redistilled water (20:0.3:79.7 v/v/v) and phase B was
composed of methanol and formic acid (99.7:0.3 v/v).
Samples were eluted from the column using the following
programme: (0—10 min: 100% of phase A; 10—25 min:
100%  90% of phase A, 0%  10% of phase B, linear
gradient; 25–60 min: 90%  70% of phase A, 10% 
30% of phase B, linear gradient). Liquids were filtered
and degassed. The flow rate was 1 ml per minute and the
detection wavelength was 280 nm.
2.3. Preparation of Butter Samples
Catechin preparations (NMC, HMC1 or HMC2) were
introduced into home-made butter at concentrations of 50,
100, 200 and 400 mg per 100 g of butter. For comparison,
samples of butter stabilized with δ-tocopherol and
3,5-di-tert-4-butylhydroxytoluene (BHT) in 50 mg per
100 g of butter were used. Butter samples stabilized with
catechin preparations of various amounts of different (-)
forms (2S, 3R), BHT, δ-tocopherol and a negative control
without stabilizer (K-) were stored at 8 oC for two weeks
or at –20 oC for four weeks and then were incubated at 50
oC or 100 oC for one hour. In addition, samples prepared
from a stabilizer and fresh butter with no additions served
as positive controls (K+).
2.4. Elucidation of Oxidative and Hydrolytic
Stability of Butter
In order to determine butter stability, compounds that
reacted with thiobarbituric acid (TBARS) and total acid
number (TAN) were analysed. TBARS were detected
using the method described by Buege and Aust [16] and
were expressed as μmol of malondialdehyde (MDA)
released from 100 g of butter. TAN was determined by
titration of butter samples with 0.1 M KOH in ethanol and
was expressed as mmol of free fatty acids (FFA) per 100 g
of butter.
The concentration of FFA was determined by the
HPLC method as described by Fliszar [17] and expressed
as mmol of FFA per 100 g of butter. Standards of lauric
acid, myristic acid, oleic acid, palmitic acid, stearic acid
and butter extract were filtered (0.45 μm) and injected (20
μl) into a LUNA 5 µm C18(2) (250 x 4.6 mm) chroma-
tographic column. The column temperature was main-
tained at 40 oC, the flow rate was 1 ml per minute and
detection was performed at 220 nm. Liquids were filtered
and degassed. A gradient of acetonitrile (ACN) and
o-phosphoric acid (0.1%) was employed to achieve suit-
able separation. The linear gradient used was as follows:
30% 75% of ACN from 0 to10 min; 75%  80% of
ACN from 10 to 20 min; 88%  99% of ACN from 20 to
22 min; then held for 23 min. An equilibration time of 5
min was employed between injections.
2.5. Statistical Analysis
Data were analysed using Statgraphics Plus for Windows.
Results were compared with multifactor ANOVA and
significant differences were determined using the LSD
test at p<0.05.
3. RESULTS AND DISCUSSIONS
3.1. Thermal Modification of Catechin
Preparations
The differences in total catechin content among the
HMC1, HMC2 and NMC preparations were not signifi-
cant (Table 1). In the NMC preparation (-) form cate-
chins (2S, 3R) constituted approximately 10% of the total
catechins. As a consequence of thermal modification of
the preparation the amount of (-) forms (2S, 3R) in
HMC1 and HMC2 increased to 20 and 30% of total
catechins, respectively. It is known that high temperatures
cause γ-pyran ring opening, which enables rotation of the
group situated at position C2 of the ring and a change in
its locaion in relation to the plane of the whole molecule.
The (-) forms (2S, 3R) in which the groups at the asym-
metric carbon atoms are in trans orientation to each other
are more stable than their (-) epiforms (2R, 3R) [7]. The
rate of epimerization depends not only on the temperature
and on the time of exposure but also on the presence of
metal ions and the pH of the solution [8,18].
3.2. Oxidative Stability of Butter Enriched
with Catechins
During storage under refrigeration (8 oC) all catechin
preparations inhibited butter oxidation to an extent that
did not differ from the positive control (Table 2).
δ-Tocopherol and BHT, however, were less effective
stabilizers, although the amounts of MDA assayed in
butter samples stabilized with these agents were 39.2%
and 88% lower, respectively, in comparison to samples
without stabilizer stored at 8 oC for 14 days (negative
control, K-).
The amount of MDA assayed in butter samples stored
at –20 oC for four weeks corresponded with the amount of
MDA in the positive control for samples stabilized with
the NMC and HMC1 preparations. On the other hand, the
amount of MDA in samples stabilized with the HMC2
preparation, δ-tocopherol and BHT did not differ from the

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194
Table 1. The percentage of catechins ((-) EGCG, (-) ECG, (-) EC, (-) GCG, (-) CG, (-) C) and GA gallic acid) in a dry mass of thermally
modified (HMC1, HMC2) and non-modified (NMC) catechin preparations. Different superscripts within a column indicate significant
differences between catechin preparations (at p<0.05). All analyses were carried out in quadruplicate.
(-) epiform (2R, 3R) [% d.m] (-) form (2S, 3R) [% d.m.]
Catechin preparations
GA (-) EGCG (-) ECG (-) EC (-) GCG (-) CG (-) C
Total catechins
NMC 0.24a 49.88c 11 .30b 7.02b 4.20a 1.63a 1.64a 75.92a
HMC1 0.35b 45.10b 9.78a 5.93a 8.53b 3.03b 3.10b 75.91a
HMC2 0.47c 36.04a 9.62a 5.42a 16.04c 3.95c 4.48c 76.03a
Table 2. Concentrations of MDA assayed in 100 g of butter. All stabilizers were added at doses of 50 mg per 100 g of butter. Different
superscripts within a row indicate significant differences between samples (at p<0.05). All analyses were carried out in quadruplicate.
HMC1, HMC2 = thermally modified catechin preparations. NMC = non-modified catechin preparation. K+ denotes the amount of
MDA in fresh butter.
MDA μmol/100 g butter
Butter stabilizers Butter without stabilizer
Thermal
treatment NMC HMC1 HMC2
δ-Tocophero
l BHT K+ K-
Refrigeration
8 oC, 2 weeks 0.84a 0.85a 0.86a 3.66c 1.34b 0.77a 5.52d
Freezing
–20 oC, 4 weeks 0.82a 0.77a 1.12b 1.19b 1.21b 0.77a 1.20b
Heating
50 oC, 1 h 1.05cd 0.85a 0.96b 1.11d 1.02bc 0.77a 1.30e
Heating
100 oC, 1 h 1.08b 1.18b 1.20b 1.62c 1.25b 0.77a 1.67c
Table 3. Concentrations of FFA assayed in 100 g of butter. All stabilizers were added at doses of 50 mg per 100 g of butter. Different
superscripts within a row indicate significant differences between samples (at p<0.05). Mean values from four independently per-
formed experiments. HMC1, HMC2 = thermally modified catechin preparations. NMC = non-modified catechin preparation. K+
denotes the amount of MDA in fresh butter.
FFA mmol/100 g butter
Butter stabilizers Butter without stabilizer
Thermal
treatment NMC HMC1 HMC2 δ-TocopherolBHT K+ K-
Refrigeration
8 oC, 2 weeks 14.17cd 13.72bc 13.58b 14.85e 15.00e 4.19a 14.67de
Freezing
–20 oC, 4 weeks 4,15a 4.51a 4.42a 4.46a 4.17a 4.19a 4.15a
Heating
50 oC, 1 h 4.24a 4.30a 4.42a 4.28a 4.21a 4.19a 4.38a
Heating
100 oC, 1 h 4.33a 4.35a 4.28a 4.15a 4.24a 4.19a 4.42a
negative control.
Butter samples stabilized with the HMC1 preparation
incubated at 50 oC did not show any changes in the
amounts of TBARS compared to the fresh butter (K+). In
the conditions of the assay only the HMC1 preparation
effectively stopped the oxidation process. On the other
hand, δ-tocopherol was the least efficient butter stabilizer
(35.9% less MDA generated during incubation than in the
negative control K-). Analysis of the results obtained for
samples incubated at 100 oC did not demonstrate any
differences between the extent of oxidation of butter
stabilized with catechin preparations of various amounts
of (-) forms (2S, 3R) and BHT. These stabilizers limited
the amounts of oxidation products emerging during
heating at 100 oC by 46.7 up to 65.6% compared to the
negative control. As in the case of incubation at 50 oC,
δ-tocopherol was the least efficient stabilizer because no
differences were observed between butter stabilized with

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195
δ-tocopherol and the negative control. Neither of the
preparations used at a rate of 50 mg per 100 g of butter
stopped the oxidation of butter heated at 100 oC. In order
to establish whether any of the catechin preparations were
capable of stopping the butter oxidation process at the
level corresponding to the positive control at 100 oC,
higher doses of preparations were used (Figure 1).
At doses of up to 100 mg of catechins per 100 g of
butter, the efficacies of all preparations tested were simi-
lar. For doses higher than 100 mg of catechins per 100 g
of butter, the HMC1 preparation containing 20% of (-)
forms (2S, 3R) proved to be the most effective stabilizer.
HMC1 stopped the oxidation process at the level corre-
sponding to the positive control at a dose of 400 mg per
100 g of butter. The least effective was the HMC2
preparation with the highest proportion of (-) forms (2S,
3R). Increasing the concentration from 200 to 400 mg per
100 g of butter did not decrease the rate of oxidation
during a one-hour incubation of butter at 100 oC.
Experiments determining the efficacy of non-modified
green tea catechins as stabilizers in poultry meat [19],
beef [20,21], pork [22], fish [21] and vegetable oils [23]
have been reported. O’Sullivan and co-workers [19]
showed that catechins increase the durability of meat
under conditions of refrigeration through inhibition of the
oxidation process, but not as efficiently as BHT. However,
Chen [23] showed that catechins stopped oxidation more
efficiently than BHT in oil heated to 95 oC. These results
suggest that the (-) forms (2S, 3R) that emerge following
heating demonstrate higher antioxidative activity than the
stereoisomers classified as (-) epiforms (2S, 2R). Xu and
co-workers [24] demonstrated, however, that the highest
difference, in favour of epiforms (2S, 2R), occurs be-
tween (-) EGC and (-) GC whilst the other pairs of
stereoisomers (-) EGCG→(-) GCG; (-) EC→(-) C;
(-)ECG→(-)CG had a similar antioxidative activity. In
our study the highest antioxidative activity in the HMC1
preparation, in which the proportion of stereoisomers
classified as (-) forms (2S, 3R) amounted to 20%, was
probably due to the synergistic effect of both catechin
stereoisomers. A decrease in the antioxidative activity of
the HMC2 preparation (containing 30% of (-) forms (2S,
3R)) in samples exposed to 50 and 100 oC was most
probably due to further conversions of the (-) forms (2S,
3R) to polymeric structures typical for fermented teas.
3.3. Hydrolytic Stability of Butter Enriched
with Catechins
Incubation of butter samples for one hour at 50 oC and
100 oC and further storage at –20 oC for four weeks did
not increase the amount of FFA (Table 3).
Alterations in the amounts of FFA were observed only
for butter samples stored at 8 oC for 14 days. When sta-
bilizers were used at a level of 50 mg per 100 g of butter,
a decrease in the amounts of free fatty acids released as
0100 200 300 400
Amount catechins added to butter [mg/100g]
0.4
0.8
1.2
1.6
2.0
mol MDA / 100g
cc
cc
bb
a
d
a
a
K+
HMC1
NMC
HMC2
E-6
E-6
E-6
E-6
E-6
Figure 1. The influence of the concentration of catechin prepa-
rations (NMC, HMC1, HMC2) added to 100 g of butter on the
amount of dimalonic aldehyde released during a one-hour in-
cubation at 100 oC. Individual letters denote statistically sig-
nificant differences (at p<0.05). All analyses were carried out in
quadruplicate. K+ denotes the amount of MDA in fresh butter.
0100 200 300 400
Amount catechins added to butter [mg/100g]
10
12
14
16
mol FFA / 100g
a
b
c
c
e
e
e
ff
HMC2
HMC1
NMC
g
E-3
E-3
E-3
E-3
Figure 2. The influence of the concentration of catechin prepa-
rations (NMC, HMC1, HMC2) added to 100 g of butter on the
amount of free fatty acids (FFA) released during two weeks
storage at 8 oC. Individual letters denote statistically significant
differences (at p<0.05). All analyses were carried out in quad-
ruplicate.
compared to the negative control was observed only with
thermally modified catechins. The other compounds did
not influence the hydrolytic stability of butter. However,
the amount of fatty acids was lower by only 13.3% for
the HMC2 catechin preparation and by 10.9% for the
HMC1 preparation in comparison to the negative control.
In order to improve the hydrolytic stability of butter un-
der refrigeration conditions (8 oC) the amounts of cate-

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196
chins added were increased (Figure 2).
With increasing dose and an increased proportion of
catechins classified as (-) forms (2S, 3R), the amount of
free fatty acids decreased during storage at 8 oC. For the
HMC2 and HMC1 preparations at the highest dose the
amounts of FFA were lower by 52.1% and 40.6% re-
spectively, compared to the negative control. Inhibition
of the hydrolysis of butter lipids is most probably a sec-
ondary effect caused by suppression of microbial growth.
A number of data in the literature confirm the antiseptic
activity of polyphenols, including catechins [25,26].
Openly accessible at
In conclusion, catechin preparations were more efficient
butter stabilizers than BHT and δ-tocopherol. Thermal
modification of the catechin preparation that led to the for-
mation of 20% (-) forms (2S, 3R) improved its antioxida-
tive efficacy; however, further increases in (-) form cate-
chins (2S, 3R) to 30% of these molecules led to a decrease
in the antioxidative stability of butter. The hydrolytic stabil-
ity of butter, on the other hand, increa- sed as the concentra-
tion of catechins classified as (-) forms (2S, 3R) increased.
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