1. Fast Antiradical Test
for Monitoring Deep
Fried Oils
Dr. Mohamed Fawzy Ramadan Hassanien
,Assistant Professor, Agricultural Biochemistry Department
,Faculty of Agriculture
Zagazig University
Egypt
5th Euro Fed Lipid Congress, 16-19 September 2007, Gothenburg, Sweden

2. The use of fat or oil for frying still remains one of the most
popular methods for the preparation of foods world wide.
The purposes of
Reduce moisture content frying
Increase oil content Efficient heat transfer
Impart desirable flavors, texture and color

3. Physical and chemical reactions during deep frying
. Frying is the most complex
of all fats and oils
applications.
. Complex reactions which
take place during frying
produce both desirable and
undesirable effects on food
and oil quality.
. Thus, quantifying the
performance of any oil, both
chemically and nutritionally
is extremely difficult if not
impossible.
Perkins and Erickson (1996) Deep frying; Chemistry, nutrition and practical applications. AOCS press
applications.

4. Analysis of deep fried oils
Disadvantages of conventional analytical methods:
1- Highly time-consuming and labor-intensive.
2- The possible use of large volume of solvents (potential environmental problem).
3- High purchasing cost.
4- Necessary calibration with reference substances.
These disadvantages are the reason to search for a new generation of
rapid methods for the analysis of deep-frying oils. As recommended
the methods for control frying oils should be:
1- Rapid tests that would correlate with internationally recognized standard methods.
2- Show ease in application provide for safe use in food processing.
3- Give quantification of oil degradation.
4- Independent of type of food and fat.

5. ?What happens in the Fryer
As deep frying is carried out at high temperatures
(between 160°C and 180°C) and in the presence of air and
moisture, the physical and chemical properties of the oil change
considerably because of hydrolysis, polymerization and
oxidation.
Hydrolysis
Polymerization )action of water(
Oxidation
Free radical chain process Can we use the
remaining
antioxidants to
The maximum
Antioxidants monitor deep-
permitted level is
limited to 200 ppm )Free radical scavengers( ? frying

6. Aim
The main goal of the work was to compare
and correlate the results of physicochemical
parameters and antiradical performance of
vegetable oils during deep frying which will be
an initial indicator for applying antiradical test
for monitoring deep-frying oils.

7. Principles of radical scavenging test
. DPPH• is widely used to test the ability of compounds to act as free radical
scavengers or hydrogen donors and to evaluate antioxidant activity of foods.
. The odd electron in the DPPH free radical gives a strong absorption
maximum at 515-517 nm and is purple in color. The color turns from purple to
yellow as the molar absorptivity of the DPPH radical reduces from 9660 to
1640 when the odd electron of DPPH radical becomes paired with hydrogen
from a free radical scavenging antioxidant to form the reduced DPPH-H.
DPPH DPPH+H
The structure of DPPH• (2,2-diphenyl-1-picrylhydrazyl) and its reduction by
an antioxidant

8. Frying protocol and oil sampling
1- Sunflower oil , cottonseed oil and palm olein
2- Oil blends (CO/PO and SO/PO )
Frying of French fries
at 180 °C for 16 h
(replenishment after 8 h)
°
Sampling after 8 and 16 h
Radical scavenging Analysis of physicochemical
parameters: PV, FFA, TPL,
activity (RSA) of oils
° colour, ° viscosity,
toward DPPH radical absorptivity at 232 and 270
nm
Ramadan et al. (2006) Eur. J. Lipid Sci. Technol . 108: 670-678

9. Antiradical test
10 mg of oil + 390 µL toluenic
solution (10-4 M ) of DPPH
radicals
and the mixture was vortexed
for 20 s at room temperature.
Against a blank of pure toluene,
the decrease in absorption at
515 nm was measured after 60
min of incubation.
% inhibition = [(absorbance of control – absorbance of
°
test sample)/ absorbance of control] x 100.
Ramadan et al. (2003) J. Agric. Food Chem . 51: 6961-6969

10. Correlation between TPL and RSA
12 50
11 Sunflower oil 45 Sunflower oil
10
Cottonseed oil 40 Cottonseed oil
9
8 35
Palm olein Palm olein
7 30
% Remaining DPPH
g/100g oil
6 25
5
20
4
15
3
2 10
1 5
0 0
0 8 16 0 8 16
Frying period (h) at 180°C Frying period (h) at 180°C
Levels of total polar compounds (g/100g Scavenging effect after 60 min incubation
oil) in different oils during frying of French of different fried oils on DPPH radical as
.fries measured by changes in absorbance
.values at 515 nm
CC = 0.98
Sulieman AM, El-Makhzangy A, Ramadan MF (2006) J. Food Lipids 13: 259-276

11. Correlation between absorptivity at 232 nm and RSA
0.5 50
0.45 45 Sunflower oil
0.4 40
0.35 35 Cottonseed oil
0.3 30
Palm olein
Absorptivity at 232 nm
25
% Remaining DPPH
0.25
0.2 Sunflower oil 20
0.15 15
Cottonseed oil
0.1 10
0.05 Palm olein 5
0 0
0 8 16 0 8 16
Frying period (h) at 180 °C Frying period (h) at 180°C
Absorptivity at 232 nm of different oils Scavenging effect after 60 min incubation
of different fried oils on DPPH radical as
.during frying
measured by changes in absorbance
.values at 515 nm
CC = 0.99
Sulieman AM, El-Makhzangy A, Ramadan MF (2006) J. Food Lipids 13: 259-276

12. Correlation between absorptivity at 270 nm and RSA
2 50
1.8 45 Sunflower oil
1.6 40
1.4 35
Cottonseed oil
1.2 30
Palm olein
Absorptivity at 270 nm
25
% Remaining DPPH
1
0.8 20
Sunflower oil
0.6 15
Cottonseed oil 10
0.4
0.2 Palm olein 5
0 0
0 8 16 0 8 16
Frying period (h) at 180 °C Frying period (h) at 180°C
Absorptivity at 270 nm of different oils Scavenging effect after 60 min incubation
of different fried oils on DPPH radical as
.during frying
measured by changes in absorbance
.values at 515 nm
CC = 0.99
Sulieman AM, El-Makhzangy A, Ramadan MF (2006) J. Food Lipids 13: 259-276

13. Correlation between TPL and RSA of oil blends
12
50
11
SO/PO 45 SO/PO
10
9 40
8 35 CO/PO
7 CO/PO
30
6
g/100g oil
% Remaining DPPH
5 25
4 20
3 15
2 10
1
5
0
0
0 8 16
0 8 16
Frying period (h) at 180 °C Frying period (h) at 180 °C
Levels of total polar compounds (g/100g Scavenging effect after 60 min incubation
.oil) in oils during frying of French fries of fried oil blends on DPPH radical as
measured by changes in absorbance
.values at 515 nm
CC = 0.98
Ramadan et al. (2006) Eur. J. Lipid Sci. Technol . 108: 670-678

14. Correlation between absorptivity at 232 nm and RSA
of oil blends
0.5
50
0.45
45 SO/PO
0.4
40
0.35
35 CO/PO
0.3
30
Absorptivity at 232 nm
0.25
% Remaining DPPH
25
0.2 SO/PO 20
0.15 15
0.1 CO/PO 10
0.05 5
0 0
0 8 16 0 8 16
Frying period (h) at 180 °C Frying period (h) at 180 °C
Absorptivity at 232 nm of oil blends during Scavenging effect after 60 min incubation
of fried oil blendss on DPPH radical as
.frying
measured by changes in absorbance
.values at 515 nm
CC = 0.99
Ramadan et al. (2006) Eur. J. Lipid Sci. Technol . 108: 670-678

15. Correlation between absorptivity at 270 nm and RSA
of oil blends
2 50
1.8 45 SO/PO
1.6 40
1.4 35 CO/PO
1.2 30
Absorptivity at 270 nm
% Remaining DPPH
1 25
0.8 20
SO/PO
0.6 15
0.4 10
CS/PO
0.2 5
0 0
0 8 16 0 8 16
Frying period (h) at 180 °C Frying period (h) at 180 °C
Absorptivity at 270 nm of oil blends during Scavenging effect after 60 min incubation
of fried oil blends on DPPH radical as
.frying measured by changes in absorbance
.values at 515 nm
CC = 0.99
Ramadan et al. (2006) Eur. J. Lipid Sci. Technol . 108: 670-678

16. Coincidently, at the same time that our research papers were published,
similar research on frying of soybean oil was carried out at Wageningen
University (The Netherlands) wherein similar findings were published by the
research group of Professor Alphons G. J. Voragen (J. Sci. Food Agric.
86:1446–1451, 2006). In this contribution, antiradical power gives insight into
early lipid oxidation events during frying of soybean oil rather than
hydroperoxides and secondary oxidation products.

17. Conclusion
. The importance of establishing fast and simple methods
for quality evaluation of deep frying oils cannot be
overemphasized.
. The results allow us to suggest that the rapid antiradical
measurement could be used to monitor deep fried oils.
. The results will be also of importance to develop a fast
method for monitoring oxidative stability of vegetable oils
during storage.
. Antiradical test is highly accurate, non-destructive, easy
to use, not expensive, and essentially independent of oil
type. However, a more accurate picture of the conclusions
need the extension of this investigation to a wider number
of samples.

18. Information
1- Ramadan MF and Moersel JT (2006) Screening of the Antiradical Action of
Vegetable Oils.
Journal of Food Composition and Analysis 19: 838-842.
2- Sulieman AM, El-Makhzangy A and Ramadan MF (2006) Antiradical
Performance and Physicochemical Characteristics of Vegetable Oils upon
Frying of French Fries: A Preliminary Comparative Study.
Journal of Food Lipids 13: 259-276.
3- Ramadan MF, Amer MMA and Sulieman AM (2006) Correlation between
Physicochemical Analysis and Radical Scavenging Activity of Vegetable Oil
Blends as Affected by Frying of French Fries.
European Journal of Lipid Science and Technology 108: 670-678.
4- Ramadan MF (2007) Monitoring Deep Frying Oils.
Inform 18: 139-141.

19. Zagazig: City and University
. One of the oldest cities
in Egypt (about 4000
years old).
. Population: 1 Million.
. Zagazig University was
established 1974 and it
include 20 colleges.
. Faculty of Agriculture was
also established 1974 and it
consist of 16 departments.
www.zu.edu.eg