Food Lipids: Chemistry, Nutrition, and Biotechnology

cadienal, trans,trans-2,4-decadienal, trans,cis-2,4-heptadienal, 1-octen-3-ol, n-butanal,
and n-hexanal, in decreasing order of importance calculated from the concentration
and threshold value.
To study the importance of volatile compounds in the flavor perception of
oxidized oil, the concentration and threshold values of volatile compounds should
be considered. It has been difficult for scientists to agree on flavor perceptions of
compounds. Different people have used different terms for the same flavor compound
of edible oil. The difficulties of sensory description of a compound are partially due
to the changes in flavor perception according to concentration and evaluating conditions.
However, the flavor perceptions of some compounds have been generally
accepted by scientists in the field, as shown in Table 6.
XI. SINGLET OXYGEN OXIDATION OF SOYBEAN OIL
Containing 1.0 to 1.5 ppm of chlorophyll, soybean oil is liable to singlet oxygen
oxidation [42]. The effects of 0, 2, 4, 6, and 8 ppm added chlorophyll on the oxidation
of soybean oil under light and dark was studied by Min and Lee [43]. They
reported that head space volatile compounds of soybean oil in the serum bottle
increased as the added chlorophyll increased from 0, 2, 4, and 6 ppm to 8 ppm, as
shown in Figure 13. However, the addition of 0, 2, 4, 6, and 8 ppm chlorophyll did
not have any effect on the formation of volatile compounds under dark storage.
Soybean oil containing no chlorophyll, which was removed by silicic acid liquid
column chromatography, did not produce head space volatile compounds under light.
The formation of head space volatile compounds in the soybean oil decreased inversely
with the amount of added �-carotene, which quenches singlet oxygen [7].
The very rapid formation of volatile compounds in the soybean oil in the presence
of chlorophyll, light, and oxygen was due to the singlet oxygen oxidation.
Nearly 70% of all edible fats and oils consumed in the United States is soybean
oil [45]. Soybean oil is inexpensive and widely available compared to other edible
oils. The development of reversion flavor, described as ‘‘beany’’ or ‘‘grassy,’’ is a
defect unique to soybean oil and can be formed in soybean oils with low peroxide
values [46]. To improve the flavor stability and quality of soybean oil, reversion
flavor has been extensively studied in soybean oil since 1936 [46].
Smouse and Chang [47] identified 2-pentylfuran in reverted soybean oil and
reported that it significantly contributed to the reversion flavor of soybean oil. Or-
Table 6 Flavor Perceptions of Volatile Compounds Formed by
Lipid Oxidation
Flavor perception Responsible compounds
Cardboard
Oily
Painty
Fishy
Grassy
Deep-fried
Source: Ref. 41.
Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.
trans,trans-2,6-Nonadienal
Aldehydes
Pent-2-enal, aldehydes
trans,cis,trans-2,4,7-Decatrienol, oct-1-en-3-one
trans-2-Hexenal, nona-2,6-dienal
trans,trans-2,4-Decandienal