Pioneering Food Chemistry Research Success for Soybean Oil Flavor Quality

1
Pioneering Food Chemistry Research Success for
Soybean Oil Flavor Quality

• David B. Min
• The Ohio State University
• Columbus, Ohio, USA

2
History and Current Statistics of Soybean Oil

• Corn oil, cottonseed oil and sunflower oil were
  the major commercial oils in the world until
  1960s.
• Soybean was produced in USA and South America
  economically in 1940s.
• Soybean oil was produced commercially in a large
  industrial scale in 1960s.
• Soybean oil could not effectively compete with
  corn oil, cottonseed oil or sunflower oil due to
  the low flavor quality in 1960-1980s.
• Soybean oil is 141 billion dollars business in
  the world in 2006.
• Soybean oil represents 71 of edible oils of
  world in 2006.

3
Compositions of Vegetable Oils
4
Soybean Oil Flavor Reversion

• The return of good deodorized soybean oil flavor
  to the undesirable flavor of crude oil within a
  very short period of time is termed flavor
  reversion.
• The development of a characteristic grassy
  flavor in deodorized edible soybean oil is
  commonly called reversion flavor.

Extraction
Crude soybean oil (Grassy Flavor)
Bleaching and Deodorization
Edible soybean oil (No Grassy Flavor)
5
Soybean Oil Flavor Reversion

• Flavor reversion has been an important classical
  problem of soybean oil industry and the most
  extensively studied research subject in oils and
  foods since 1930.
• Flavor reversion makes soybean oil less
  acceptable to consumers and food manufactures.

6
Soybean Oil Processors Association

• Edward J. Dies, Chairman of the association
  invited 28 scientists to discuss the flavor
  reversion in 1946.
• Dies told them I strongly emphasize the economic
  advantages of rapid solution of soybean oil
  flavor reversion. Let us solve difficult flavor
  reversion problem in soybean oil at the earliest
  possible moment by a free exchange of ideas and
  special collaboration among scientists.

7
K. S. Markleys Review on Soybean Oil Flavor
Reversion in 1951

• Flavor reversion is a characteristic property in
  soybean oil.
• Flavor reversion occurs even at very low peroxide
  value of 2.
• Linolenic acid was reported as the precursor of
  flavor reversion in 1936.

8
K. S. Markleys Review on Soybean Oil Flavor
Reversion in 1951

• Antioxidants were not effective in flavor
  reversion.
• Phospholipid, light, and nonsaponifiable
  compounds are responsible for flavor reversion.
• None of the physical and chemical methods was
  effective to prevent soybean oil flavor reversion.

9
Rutgers University Research Activity on Soybean
Oil Flavor Reversion

• They identified 2-pentyl furan in reverted
  soybean oil and assumed it was formed from
  linoleic acid in 1966
• They assumed that 2-Pentenyl furan could be
  formed from linolenic acid in 1980.
• They synthesized 2-pentenyl furan from
  tetrahydrofuran and n-butyl lithium in 1980.

10
T. H. Smouses Review on Soybean Oil Flavor
Reversion in 1985

• Reversion flavor is observed in soybean oil in a
  few hours of storage under light
• T. H. Smouse reported Although much has been
  learned since 1930s, we do not know how to make
  soybean oil that will not revert.

11
What is the next approach to solve Soybean Oil
Reversion Flavor?
12
The Ohio State Universitys Interpretation on the
Soybean Oil Flavor Reversion Reviews by K. S.
Markleys in 1951 and T. H. Smouse in 1985

• Reversion flavor is observed in soybean oil in a
  few hours of storage Activation energy
  for flavor reversion reaction is very low.
• Antioxidants were not effective in flavor
  reversion Flavor reversion is not radical
  reaction.
• Soybean oil with flavor reversion has peroxide
  value.
• Peroxide value Flavor reversion requires
  oxygen.
• The oxygen involved in flavor reversion requires
  low activation energy to react with soybean oil
  fast.
• The ordinary triplet radical oxygen requires high
  activation energy to react with soybean oil.

13
1772 Scheele Priestley Discovered
Oxygen 1811 Avogadro Oxygen is a Diatomic
Molecule 1848 Faraday Oxygen is a
Paramagnetic Molecule 1934 Herzberg
Observation of Singlet Oxygen 1969 Foote
Wexler Rediscovered Singlet Oxygen  
Oxygen History
14
Food Oxidation

• Triplet oxygen free radical oxidation
• Singlet oxygen non-free radical oxidation

15
Electronic Configuration of Triplet Oxygen
Molecular
?
Atomic
Atomic
?
?
?
?
2Px 2Py 2Pz
2Pz 2Py 2Px
?
Energy
?
2S
2S
?
16
Mechanism of Triplet Oxygen Oxidation
14 13 12 11 10 9
C
H
C
H
C
H
C
H
C
H
C
H
C
H
R
(
C
H
)
C
H
2
2
2
2
3
3
Energy
- H
?
13 12 11 10 9
(
C
H
)
C
H
C
H
R
C
H
C
H
C
H
C
H
C
H
2
4
3
2
?
3O2
K109/sec
17
13 12 11 10 9
(
C
H
)
C
H
C
H
C
H
C
H
C
H
C
H
R
C
H
2
4
3
2
O
(K 1 M-1sec-1)
O
?
(K 107 M-1sec-1)
.
O
H
O
C
(
C
H
)
H from
3
3
?
C
(
C
H
)
3
3
O
C
H
3
O
C
H
3
18
13 12 11 10 9
C
H
C
H
C
H
C
H
C
H
C
H
R
(
C
H
)
C
H
2
2
4
3
O
Peroxide value
O
- OH
?
H
13 12 11 10 9
(
C
H
)
C
H
C
H
C
H
C
H
C
H
C
H
R
C
H
3
2
2
4
O
?
C
H
(
C
H
)
C
HO
3
2
4
C
H
(
C
H
)
C
H
3
3
2
3
19
Electronic Configuration of Singlet Oxygen
Molecular
?
Atomic
Atomic
?
?
?
?
2Px 2Py 2Pz
2Pz 2Py 2Px
?
Energy
?
2S
2S
?
?
1S
1S
?
20
Reaction of 3O2 and 1O2 with Linoleic Acid
Antioxidant effects
OOH


3O2
- H
R
R
R
1
R
R
R
1
2
1
2
2
OOH
1O2
O
R
R
2
R
1
2
R
H
O
1
OOH
No antioxidant effects
R
R
2
1O2
1
gtgtgt
in reaction with soybean oil
3O2
21
The Ohio State University Research Activity on
Soybean Oil Reversion Flavor

• Reversion flavor is observed in soybean oil in a
  few hours of storage Activation energy
  for flavor reversion reaction is very low.
• Singlet Oxygen requires very low activation
  energy to react with soybean oil
• Antioxidants were not effective in reversion
  flavor
• Singlet oxygen reacts with soybean oil by
  non-free radical reaction.
• Soybean oil with reversion flavor has peroxide
  value
• Singlet oxygen can produce peroxides in soybean
  oil

Singlet Oxygen meets all the requirements for the
reversion flavor reaction of soybean oil
22
Singlet Oxygen Formation in Foods

Light
3O2 Chlorophyll 1O2

23
Chlorophyll as Photosensitizer
H
CH
H2C
CH3
CH2CH3
H3C
N
N
H
Mg
H
N
N
CH3
H3C
O
CO2CH3
CH2
CO2
CH3
CH3
CH3
CH3
CH3
24
Excitation and Deactivation of Chlorophyll under
Light
Excited State
1Chlorophyll
K1-20?108/sec ISC
Fluorescence K 2?108/sec
3Chlorophyll
hv
K1-3?109/sec
Phosphorescence
3O2
K10-104/sec
1Chlorophyll
Singlet Oxygen
Ground State
25
ESR Spectrum of 2,2,6,6-Tetramethyl-4-Piperidone-N
-Oxyl (TAN) of Singlet Oxygen
3370 G 3390 G
3410 G
26
Soybean Oil Purification by Chromatography
Soybean oil
Silicic acid
Sugar
Charcoal-Celite
Silicic acid
Vacuum
Purified soybean oil
27
Identified Compounds in Soybean Oil

• Phospholipids
• Tocopherols
• Monoglycerides
• Diglycerides
• Oxidized polymers
• Free fatty acids
• Chlorophylls

Purified soybean oil
28
Effect of 0 and 5 ppm Chlorophyll on
2-Pentenylfuran in Soybean Oil
0 ppm
             
No grassy reversion flavor
5 ppm
2-Pentenylfuran
Trans-2-heptenal

Strong grassy reversion flavor
29
Mass Spectrum of 2-Pentenylfuran
30
2-Pentenylfuran from Linolenic Acid by 1O2
C
H
C
H
C
H
C
H
C
H
C
H
C
H
C
H
C
H
C
H
C
H
(
C
H
)
C
O
O
H
2
2
2
6
3
2
2
Non-free radical reaction No Antioxidant
effect Very low activation
1O2
C
H
C
H
C
O
O
H
(
C
H
)
C
H
C
H
C
H
C
H
C
H
C
H
C
H
C
H
C
H
2
2
6
2
3
2
2
O
O
C
H
C
H
C
O
O
H
(
C
H
)
C
H
C
H
C
H
C
H
C
H
C
H
C
H
C
H
C
H
2
2
6
2
3
2
2
O
O


C
H
C
H
C
H
C
H
C
H
C
H
C
H
C
H
C
H
3
2
2
2
O
1O2
C
H
C
H
C
H
C
H
C
H
C
H
C
H
C
H
C
H
2
3
2
2
O
O
O
31
C
H
C
H
C
H
C
H
C
H
C
H
C
H
C
H
C
H
3
2
2
2

O
O
O
Peroxide
H
- OH

C
H
C
H
C
H
C
H
C
H
C
H
C
H
C
H
C
H
2
3
2
2

O
O

C
H
C
H
C
H
C
H
C
H
C
C
H
C
H
C
H
3
2
2
2
2
O
O
C
H
C
H
H
C
H
C
H
C
C
H
C
H
C
H
C
3
2
2
O
H
O
H
- H2O
C
H
C
H
C
H
C
H
C
H
3
2
2
2-(2-pentenyl)-furan
O
32
Chlorophyll Effect on the Reversion Flavor of
Soybean Oil under Light at 10oC
Reversion Flavor Intensity
Storage in Hours
33
Singlet Oxygen Formation in Soybean Oil by
Chlorophyll under Light
Excited State
1Chlorophyll
K1-20?108/sec ISC
Fluorescence K 2?108/sec
3Chlorophyll
hv
K1-3?109/sec
Phosphorescence
3O2
K10-104/sec
Singlet Oxygen (1O2)
1Chlorophyll
Ground State
34
2-Pentenylfuran from Linolenic Acid and Singlet
Oxygen
C
H
C
H
C
H
C
H
C
H
C
H
C
H
C
H
C
H
C
H
C
H
(
C
H
)
C
O
O
H
2
2
2
6
3
2
2
1O2
K3?107/sec
C
H
C
H
C
H
C
H
C
H
3
2
2
O
35
Conclusion
36
Production of Reversion Flavor Free Soybean Oil
Excited State
1Chlorophyll
K1-20?108/sec ISC
Fluorescence K 2?108/sec
3Chlorophyll
hv
K1-3?109/sec
Phosphorescence
3O2
K10-104/sec
1Chlorophyll in Soybean Oil
Singlet Oxygen (1O2)
Ground State
2-Pentenyl furan
37
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39
Pioneering Food Chemistry Research Success in
Soybean Oil Flavor Quality

• History and Statistics of Soybean Oil
• Compositions of Vegetable Oils
• Soybean Oil Flavor Reversion
• Soybean Oil Flavor Reversion
• Soybean Oil Processors Association
• K. S. Markleys Soybean Oil Reversion Flavor
  Review in 1951
• K. S. Markleys Soybean Oil Reversion Flavor
  Review in 1951
• Rutgers University Research on Reversion Flavor
• T. H. Smouses Soybean Oil Reversion Flavor
  Review in 1985
• What is the next approach to solve Soybean Oil
  Reversion Flavor
• The Ohio State Universitys interpreation of
  Soybean Oil Reversion Flavor Reviews by K. S.
  Markley in 1951 and T. H. Smouse in 1985
• History of Oxygen
• Food Oxidation
• Electronic Configuration of Triplet Oxygen
• Mechanism of Triplet Oxygen Oxidation
• Mechanism of Triplet Oxygen Oxidation
• Mechanism of Triplet Oxygen Oxidation

40

• Electronic Configuration of Singlet Oxygen
• Reaction of Triplet Oxygen and Singlet Oxygen
  with Linoleic Acid
• The Ohio State Universitys Research on Soybean
  Oil Reversion Flavor
• Singlet Oxygen Formation in Foods
• Chlorophyll as Photosensitizer
• Excitation and Deactivation of Chlorophyll under
  Light
• ESR Spectrum of 2,2,6,6-Tetramethyl-4-Pipoeridone-
  N-Oxyl (TAN) of Singlet Oxygen
• Soybean Oil Purification by Chromatography
• Identified Compounds in Soybean Oil
• Effect of 0 and 5 ppm Chlorophyll on
  2-Pentenylfuran in Soybean Oil
• Mass Spectrum of 2-Pentenylfuran
• 2-Pentenylfuran from Linolenic Acid by 1O2
• 2-Pentenylfuran from Linolenic Acid by 1O2
• Chlorophyll Effect on the Volatile Compounds of
  Soybean Oil under Light at 10C
• Singlet Oxygen Formation in Soybean Oil by
  Chlorophyll under Light
• 2-Pentenylfuran Formation from Linolenic Acid and
  Singlet Oxygen
• Conclusion
• Production of Reversion Flavor Free Soybean Oil