Investigation of the Reaction between Ammonium Sulfide, Aldehydes, and α-Hydroxyketones or α-Dicarbonyls to Form Some Lipid-Maillard Interaction Products Found in Cooked Beef

Article abstract of DOI:10.1021/jf970065u

Aqueous reaction mixtures containing α-dicarbonyls (2,3-butanedione or 2,3-pentanedione) or α-hydroxyketones (1-hydroxypropanone, 1-hydroxy-2-butanone, or 3-hydroxy-2-butanone), alkanals (C₄-C₁₀) and ammonium sulfide were heated at 140 °C for 30 min. Among the products formed were 3-thiazolines and thiazoles with C₃-C₉ alkyl substituents in the 2-position and methyl or ethyl in positions 4 and/or 5. Similar compounds have recently been reported in cooked beef, and their presence in the reaction mixtures confirmed the proposed route of formation, in cooked beef, from the reaction of lipid-derived aldehydes with dicarbonyls, ammonia, and hydrogen sulfide produced via the Maillard reaction. Trialkylpyridines, which had been observed in cooked beef, were also formed by the reaction of three molecules of aldehyde with one of ammonia. The mass spectra of all of these compounds are reported.

Full text of DOI:10.1021/jf970065u

J. Agric. Food Chem. 1997, 45, 3595
−3602
3595
In vestiga tion of th e Rea ction betw een Am m on iu m Su lfid e,
Ald eh yd es, a n d r-Hyd r oxyk eton es or r-Dica r bon yls To F or m Som e
Lip id -Ma illa r d In ter a ction P r od u cts F ou n d in Cook ed Beef
J . Stephen Elmore* and Donald S. Mottram
Department of Food Science and Technology, The University of Reading,
Whiteknights, Reading RG6 6AP, United Kingdom
Aqueous reaction mixtures containing R-dicarbonyls (2,3-butanedione or 2,3-pentanedione) or
R-hydroxyketones (1-hydroxypropanone, 1-hydroxy-2-butanone, or 3-hydroxy-2-butanone), alkanals
(C4-C10) and ammonium sulfide were heated at 140 °C for 30 min. Among the products formed
were 3-thiazolines and thiazoles with C3-C9 alkyl substituents in the 2-position and methyl or
ethyl in positions 4 and/or 5. Similar compounds have recently been reported in cooked beef, and
their presence in the reaction mixtures confirmed the proposed route of formation, in cooked beef,
from the reaction of lipid-derived aldehydes with dicarbonyls, ammonia, and hydrogen sulfide
produced via the Maillard reaction. Trialkylpyridines, which had been observed in cooked beef,
were also formed by the reaction of three molecules of aldehyde with one of ammonia. The mass
spectra of all of these compounds are reported.
Keyw or d s: Flavor; Maillard reaction; lipids; 3-thiazolines; thiazoles; alkylpyridines
INTRODUCTION
A number of these had chain lengths of between 13 and
16 carbons, and it was suggested that aldehydes,
derived from meat plasmalogens, were involved in the
formation of these compounds. Other 2-n-alkylthiazoles
have been reported in fried chicken and fried potatoes,
although these had chain lengths of C3-C8 (Ho and
Carlin, 1989; Tang et al., 1983). We have also recently
reported a large number of alkylthiazoles and alkyl-3-
thiazolines, with C3-C9 alkyl substituents in the 2-posi-
tion, in cooked beef (Elmore et al., 1997). However, the
identifications made were tentative because no reference
compounds were available. Mass spectral interpreta-
tion and comparison of the spectra of the unknowns with
a limited number of literature spectra (Tang et al., 1983;
Werkhoff et al., 1991; J ennings and Shibamoto, 1980)
were the criteria used for the identification. It was
suggested that these thiazoles and 3-thiazolines were
derived from the interaction of aliphatic aldehydes, from
lipid oxidation, with hydrogen sulfide, ammonia, and
dicarbonyls or hydroxyketones, from the Maillard reac-
tion.
During the cooking of foods, flavor is generated from
the interaction of a number of intermediates produced
by the thermal degradation of natural flavor precursors.
The Maillard reaction, between amino acids and reduc-
ing sugars, and the thermal degradation of lipid are the
major reactions involved. Model systems have been
used to elucidate the intermediates and the pathways
involved in the formation of some of the flavor volatiles
found in cooked foods (Vernin and Pa´rka´nyi, 1982).
Alkylthiazoles and alkylthiazolines can have low odor
threshold values and may contribute to nutty, roast, and
meaty aroma characteristics in foods (Fors, 1983). They
are found in heated foods, such as coffee, meat, and
bread. Thiazoles have been found in model systems
involving cysteine and reducing sugars (Mulders, 1973;
Vernin and Pa´rka´nyi, 1982). One of the most likely
routes to the formation of alkylthiazoles and alkylthi-
azolines in foods and model systems is from the reaction
of an R-dicarbonyl or an R-hydroxyketone (from sugar
degradation), hydrogen sulfide, ammonia, and an alde-
hyde. The Strecker degradation of cysteine produces
acetaldehyde, ammonia, and hydrogen sulfide, providing
three key intermediates for thiazole and thiazoline
formation. Takken et al. (1976) found 4-ethyl-2,5-
dimethyl-3-thiazoline, 5-ethyl-2,4-dimethyl-3-thiazoline,
and the corresponding thiazoles in a reaction mixture
containing 2,3-pentanedione, acetaldehyde, hydrogen
sulfide, and ammonia. Vernin et al. (1987) identified
2-isopropyl-4,5-dimethyl-3-thiazoline and 2-isopropyl-
4,5-dimethylthiazole in a reaction mixture containing
3-hydroxy-2-butanone, 2-methylpropanal, and ammo-
nium sulfide.
In this paper we confirm this proposed route of
formation of 3-thiazolines and thiazoles in cooked beef
and report on the alkylthiazoles, alkyl-3-thiazolines, and
alkylpyridines formed in aqueous reaction mixtures
containing R-dicarbonyls (2,3-butanedione or 2,3-pen-
tanedione) or R-hydroxyketones (1-hydroxypropanone,
1-hydroxy-2-butanone, or 3-hydroxy-2-butanone), alka-
nals, and ammonium sulfide.
EXPERIMENTAL PROCEDURES
Ma ter ia ls. 3-Methylbutanal, pentanal, octanal, (E)-2-non-
enal, (E,E)-2,4-nonadienal, decanal, 1-hydroxy-2-propanone
(acetol), 1-hydroxy-2-butanone, 3-hydroxy-2-butanone (aceto-
in), 2,3-butanedione (diacetyl), 2,3-pentanedione, and am-
monium sulfide (20% in water) were obtained from Aldrich
Chemical Co., Gillingham, Dorset, U.K.; 2-methylpropanal,
hexanal, heptanal, and nonanal were from Lancaster Synthe-
sis, Morecambe, U.K.
Recently, a number of alkylthiazoles with long n-alkyl
chains in the 2-position were reported in the volatiles
of cooked beef and chicken (Farmer and Mottram, 1994).
* Author to whom correspondence should be ad-
dressed (telephone 0044-118-987-5123; fax 0044-118-
931-0080; e-mail Stephen.Elmore@afnovell.reading.ac.uk).
P r ep a r a tion of Rea ction Mixtu r es. A 0.1 M solution of
ammonium sulfide was made up in deionized water. An
aliquot (50 mL) was poured into a 100 mL autoclavable screw-
S0021-8561(97)00065-4 CCC: $14.00
© 1997 American Chemical Society

3596 J. Agric. Food Chem., Vol. 45, No. 9, 1997
Elmore and Mottram
Ta ble 1. 3-Th ia zolin es, Th ia zoles, a n d P yr id in es Isola ted fr om th e Rea ction s of r-Hyd r oxyk eton es w ith Am m on iu m
Su lfid e a n d Alip h a tic Ald eh yd es
products and relative amounts (as percentage of total chromatogram peak area)
aldehyde
3-thiazolines
%
thiazoles
%
pyridines
%
Reactions Using 3-Hydroxy-2-butanone
2-methylpropanal
3-methylbutanal
pentanal
hexanal
heptanal
octanal
nonanal
decanal
(E)-2-nonenal
4,5-dimethyl-2-isopropyla
4,5-dimethyl-2-isobutyla
2-butyl-4,5-dimethyla
4,5-dimethyl-2-pentyla
4,5-dimethyl-2-hexyla
4,5-dimethyl-2-heptyla
4,5-dimethyl-2-octyla
26.0
15.2
18.2
36.7
41.8
33.5
31.4
26.2
0.9
0.2
1.4
1.7
0.7
4,5-dimethyl-2-isopropyl
4,5-dimethyl-2-isobutyl
2-butyl-4,5-dimethyl
4,5-dimethyl-2-pentyl
4,5-dimethyl-2-hexyl
4,5-dimethyl-2-heptyl
4,5-dimethyl-2-octyl
4,5-dimethyl-2-nonyl
0.6
0.2
0.2
1.7
0.3
0.5
0.4
0.7
3,5-diisopropyl-2-isobutyl
2-butyl-3,5-dipropyl
3,5-dibutyl-2-pentyl
3,5-dipentyl-2-hexyl
3,5-dihexyl-2-heptyl
0.8
2.4
2.2
9.7
22.6
4,5-dimethyl-2-nonyla
4,5-dimethyl-2-hexyla
4,5-dimethyl-2-(1-octenyl)a
4,5-dimethyl-2-octyla
(E,E)-2,4-nonadienal
2-butyl-4,5-dimethyla
4,5-dimethyl-2-(1,3-octadienyl)a
Reactions Using 1-Hydroxy-2-propanone
3-methylbutanal
pentanal
hexanal
2-isobutyl-5-methyla
2-isobutyl-4-methyl
2-butyl-5-methyla
2-butyl-4-methyl
5-methyl-2-pentyla
4-methyl-2-pentyl
2-hexyl-5-methyla
2-hexyl-4-methyl
2-heptyl-5-methyla
2-heptyl-4-methyl
5-methyl-2-octyla
4-methyl-2-octyl
1.8
6.6
2.3
3,5-diisopropyl-2-isobutyl
2-butyl-3,5-dipropyl
3,5-dibutyl-2-pentyl
3,5-dipentyl-2-hexyl
3,5-dihexyl-2-heptyl
2.8
2.6
5.7
4.4
2-butyl-4-methyl
<0.1
4.7
18.3
3.8
14.3
1.5
4-methyl-2-pentyl
2-hexyl-5-methyl
2-hexyl-4-methyl
0.7
<0.1
0.6
heptanal
octanal
39.6
43.5
5.5
1.6
6.9
2-heptyl-4-methyl
4-methyl-2-octyl
0.5
nonanal
<0.1
Reactions Using 1-Hydroxy-2-butanone
15.2
hexanal
heptanal
octanal
5-ethyl-2-pentyla
4-ethyl-2-pentyl
5-ethyl-2-hexyla
4-ethyl-2-hexyl
5-ethyl-2-heptyla
4-ethyl-2-heptyl
5-ethyl-2-octyla
4-ethyl-2-octyl
3,5-dibutyl-2-pentyl
3,5-dipentyl-2-hexyl
3,5-dihexyl-2-heptyl
11.3
19.5
48.1
16.0
8.0
8.3
4-ethyl-2-pentyl
5-ethyl-2-hexyl
4-ethyl-2-hexyl
1.2
<0.1
1.0
4.8
7.6
10.5
21.2
4-ethyl-2-heptyl
4-ethyl-2-octyl
0.6
0.8
nonanal
a
For each 5-substituted 3-thiazoline two isomers (E and Z) were found in approximately equal quantities. Combined percentage peak
areas are given.
top jar fitted with a PTFE-lined cap. To this solution were
added 0.005 mol of aldehyde and 0.005 mol of hydroxyketone
(or dione). The components of these reaction mixtures are
shown in Tables 1 and 2. The mixtures were heated in an
autoclave for 30 min at 140 °C.
The reaction mixtures were each extracted with 30 mL of
high-purity grade dichloromethane (Fisons, Loughborough,
U.K.), and the dichloromethane layer was separated off and
stored in a brown glass bottle at 4 °C before analysis by gas
chromatography/mass spectrometry.
contained between 5 and 10 major peaks, whereas the
1-hydroxy-2-ketones were more complex. Each reacting
aldehyde and hydroxyketone/dione was present at the
end of the reaction at concentrations below 10% of the
total peak area, except for the reaction between nonanal
and 1-hydroxy-2-propanone (35% of total peak area) and
the reaction between nonanal and 2,3-butanedione
(33%). Total peak areas for all the reaction mixtures
were similar.
GC/MS. All analyses were performed on a Hewlett-Packard
5972 mass spectrometer, fitted with a HP 5890 Series II gas
chromatograph and controlled by a G1034C Chemstation.
Samples (1 µL) were injected in split mode at 250 °C (split
ratio 40:1) onto a BPX5 fused silica capillary column (50 m ×
0.32 mm i.d., 0.5 µm film thickness; Scientific Glass Engineer-
ing Ltd., Milton Keynes, U.K.). The oven was held at 60 °C
for 2 min and then heated at 10 °C/min to 280 °C, at which it
was held for 10 min. Helium at 8 psi was used as the carrier
gas, resulting in a flow of 1.75 mL/min at 40 °C. A series of
n-alkanes (C6-C22) was analyzed under the same conditions
to obtain linear retention index (LRI) values for the reaction
mixture components.
Th ia zoles a n d 3-Th ia zolin es. All of the reaction
mixtures produced 3-thiazolines and thiazoles in which
the 2-position was occupied by an alkyl group derived
from the aliphatic aldehyde, while methyl or ethyl
substituents in the 4- or 5-position were from the
dicarbonyl or hydroxyketone (Figure 1). The relative
proportions of these products varied substantially,
depending on whether a hydroxyketone or dione was
used and which aldehyde was present (Tables 1 and 2).
The highest yields of 3-thiazolines were obtained with
3-hydroxy-2-butanone, which gave 4,5-dimethyl-2-alkyl-
3-thiazolines. The 1-hydroxy-2-alkanones gave a mix-
ture of the 4-methyl- and 5-methyl-2-alkyl-3-thiazolines,
but the 4-isomers were present in greater quantities
than the 5-isomers, especially for the reactions involving
the longer chain aldehydes. For all of the 3-thiazolines
containing a substituent in the 5-position, a pair of
geometric isomers can be predicted, and for the di-
methyl-3-thiazolines (Table 1) and the methylethyl-3-
thiazolines (Table 2) these eluted as characteristic
The mass spectrometer was operated in electron impact
mode with an electron energy of 70 eV and an emission current
of 50 µA. The mass spectrometer scanned from m/ z 28 to 450
at 1.7 scans/s.
RESULTS AND DISCUSSION
The chromatograms from the reaction mixtures con-
taining 3-hydroxy-2-butanone and the alkane-R-diones

Reaction To Form Lipid−Maillard Interaction Products
J. Agric. Food Chem., Vol. 45, No. 9, 1997 3597
Ta ble 2. Th ia zolin es, Th ia zoles, a n d P yr id in es Isola ted fr om th e Rea ction s of Alk a n e-r-d ion es w ith Am m on iu m Su lfid e
a n d Alip h a tic Ald eh yd es
products and relative amounts (as percentage of total chromatogram peak area)
aldehyde
pentanal
hexanal
heptanal
octanal
3-thiazolinesa
%
thiazoles
%
pyridines
%
Reactions Using 2,3-Butanedione
2-butyl-4,5-dimethyl
4,5-dimethyl-2-pentyl
4,5-dimethyl-2-hexyl
4,5-dimethyl-2-heptyl
4,5-dimethyl-2-octyl
13.4
15.7
8.0
4.9
9.4
2-butyl-4,5-dimethyl
4,5-dimethyl-2-pentyl
4,5-dimethyl-2-hexyl
4,5-dimethyl-2-heptyl
4,5-dimethyl-2-octyl
12.8
16.8
6.9
3.3
2.6
2-butyl-3,5-dipropyl
3,5-dibutyl-2-pentyl
3,5-dipentyl-2-hexyl
3,5-dihexyl-2-heptyl
3.5
8.1
29.4
27.6
nonanal
Reactions Using 2,3-Pentanedione
3-methylbutanal
pentanal
hexanal
4-ethyl-2-isobutyl-5-methyl
5-ethyl-2-isobutyl-4-methyl
2-butyl-4-ethyl-5-methyl
2-butyl-5-ethyl-4-methyl
4-ethyl-5-methyl-2-pentyl
5-ethyl-4-methyl-2-pentyl
4-ethyl-2-hexyl-5-methyl
5-ethyl-2-hexyl-4-methyl
4-ethyl-2-heptyl-5-methyl
5-ethyl-2-heptyl-4-methyl
4-ethyl-5-methyl-2-octyl
5-ethyl-4-methyl-2-octyl
4-ethyl-5-methyl-2-nonyl
5-ethyl-4-methyl-2-nonyl
6.0
7.8
4-ethyl-2-isobutyl-5-methyl
5-ethyl-2-isobutyl-4-methyl
2-butyl-4-ethyl-5-methyl
2-butyl-5-ethyl-4-methyl
4-ethyl-5-methyl-2-pentyl
5-ethyl-4-methyl-2-pentyl
4-ethyl-2-hexyl-5-methyl
5-ethyl-2-hexyl-4-methyl
4-ethyl-2-heptyl-5-methyl
5-ethyl-2-heptyl-4-methyl
4-ethyl-5-methyl-2-octyl
5-ethyl-4-methyl-2-octyl
4-ethyl-5-methyl-2-nonyl
5-ethyl-4-methyl-2-nonyl
3.1
3.0
6.0
4.4
7.1
5.2
4.0
4.2
1.3
1.0
4.2
4.0
7.3
5.7
3,5-diisopropyl-2-isobutyl
2-butyl-3,5-dipropyl
3,5-dibutyl-2-pentyl
3,5-dipentyl-2-hexyl
3,5-dihexyl-2-heptyl
0.7
2.9
10.4
10.1
14.8
10.4
3.8
5.8
4.6
4.9
10.4
12.5
18.7
18.9
6.4
heptanal
octanal
12.2
29.1
nonanal
decanal
a
For each 3-thiazoline two isomers (E and Z) were found in approximately equal quantities. Combined percentage peak areas are
given.
All of the 3-thiazolines and thiazoles that we recently
reported in the volatiles of pressure cooked beef were
found in these reaction mixtures, and there was excel-
lent agreement in LRI values and mass spectra. This
confirms the identities of these cooked beef components
and indicates their probable precursors. In foods,
aliphatic aldehydes are products of lipid oxidation, and
we have shown the importance of the interactions
between lipid-derived components and intermediates of
the Maillard reaction. Such interactions will modify the
profile of volatiles from the Maillard reaction and hence
may be important in determining the aroma character-
istics of cooked foods (Farmer and Mottram, 1994).
The mass spectra of the 3-thiazolines and thiazoles
are shown in Tables 3 and 4, respectively. The spectra
for each type of thiazole and 3-thiazoline were very
distinctive, and their base peaks are shown in Table 5.
The fragmentation scheme for the thiazoles is straight-
forward. In each case the base peak is due to loss of an
alkene from the 2-position via cleavage alpha to the
thiazole ring. Most of the other fragments are derived
from the base peak, due to losses of alkyl groups from
the side chain in the 2-position. A mass spectral
fragmentation scheme for the 3-thiazolines identified in
the reaction mixtures is given in Figure 2. The double
bond in the thiazoline is clearly in the 3-position because
cleavage of the 2-alkyl chain occurred between the ring
and the first carbon atom of the chain, i.e., alpha to the
double bond. A 2-thiazoline would cleave alpha to the
ring, i.e., between the first and second carbons of the
alkyl chain.
The proposed scheme for the formation of these
3-thiazolines and thiazoles is shown in Figure 1. For-
mation of 3-thiazolines from an R-hydroxyketone in-
volves the substitution of the -OH group with an -SH.
This is followed by nucleophilic attack by the sulfur at
the carbon atom of an imine intermediate formed by the
reaction between ammonia and an aldehyde. Subse-
quent ring closure, with the elimination of water, gives
the 3-thiazoline. Thiazoles could result from the oxida-
tion of the thiazoline. However, ammonium sulfide
readily hydrolyzes to hydrogen sulfide, which would give
F igu r e 1. Formation of alkyl-3-thiazolines and alkylthiazoles
from the reaction of R-hydroxyketones or R-dicarbonyls with
ammonia and hydrogen sulfide in the presence of aliphatic
aldehydes
doublets in the chromatograms. In the case of the
5-methyl- and 5-ethyl-3-thiazolines (Table 1) the two
peaks were poorly resolved.
Oxidation of thiazolines leads to thiazoles, and the
reaction mixtures involving saturated aliphatic alde-
hydes all yielded thiazoles corresponding to the 3-thi-
azolines. In reaction mixtures using hydroxyketones,
the thiazoles were present at much lower concentrations
than the 3-thiazolines. When alkane-R-diones were
used, the yields of thiazoles were much higher than for
the reactions containing hydroxyketones, and the 3-thi-
azolines and thiazoles were present in approximately
equal amounts.

3598 J. Agric. Food Chem., Vol. 45, No. 9, 1997
Elmore and Mottram
Ta ble 3. Ma ss Sp ectr a l Da ta for Alk yl-3-th ia zolin es P r od u ced in th e Rea ction of Am m on iu m Su lfid e, Ald eh yd es, a n d
r-Hyd r oxyk eton es or r-Dica r bon yls
3-thiazoline
LRIa
1155
characteristic MS data, m/ z (rel intensity)
4,5-dimethyl-2-isopropylb,c
114, 87 (27), 157 (22), 82 (18), 113 (12), 39 (11), 42 (11), 41 (10), 53 (10),
55 (10), 45 (9), 59 (8), 115 (8), 116 (8), 60 (7), 100 (5)
114, 87 (27), 157 (23), 82 (18), 39 (11), 42 (10), 53 (10), 55 (10), 116 (10),
41 (9), 45 (9), 59 (8), 60 (7), 115 (7), 100 (6)
100, 124 (35), 68 (28), 101 (24), 73 (20), 110 (17), 157 (16), 41 (15), 42 (14),
39 (11), 45 (11), 69 (9), 58 (8), 57 (7), 84 (6), 102 (6)
100, 96 (62), 124 (61), 73 (32), 68 (31), 41 (26), 39 (19), 45 (18), 101 (18),
54 (17), 86 (17), 82 (16), 97 (15), 55 (12), 69 (12), 157 (11)
100, 124 (66), 96 (49), 68 (31), 73 (30), 41 (27), 54 (24), 45 (22), 39 (20),
101 (19), 86 (17), 82 (16), 57 (15), 97 (15), 55 (14), 157 (14)
114, 68 (43), 87 (34), 138 (28), 171 (26), 42 (24), 41 (22), 39 (19), 71 (19),
100 (18), 53 (15), 55 (14), 45 (13), 59 (12), 101 (12), 115 (12)
114, 68 (53), 87 (37), 171 (32), 138 (28), 42 (25), 41 (22), 71 (21), 100 (20),
39 (16), 53 (16), 115 (16), 59 (15), 101 (15), 82 (14), 55 (13)
100, 124 (41), 68 (28), 73 (23), 41 (19), 42 (19), 110 (19), 39 (16), 45 (16),
101 (16), 82 (10), 57 (6), 102 (6), 111 (6), 157 (6)
114, 68 (31), 138 (31), 87 (27), 71 (25), 42 (20), 101 (18), 171 (15), 41 (14),
55 (12), 53 (11), 110 (11), 39 (10), 59 (10), 100 (10), 115 (10)
114, 138 (36), 68 (32), 71 (28), 87 (28), 101 (20), 171 (20), 42 (18), 41 (15),
53 (12), 55 (12), 59 (11), 39 (10), 45 (10), 100 (10), 115 (10)
128, 82 (56), 41 (33), 85 (30), 101 (28), 185 (23), 59 (22), 87 (22), 69 (21),
56 (19), 114 (18), 152 (16), 124 (15), 96 (13), 39 (12), 129 (12)
128, 82 (58), 41 (38), 101 (32), 85 (30), 87 (26), 59 (25), 69 (23), 185 (23),
56 (21), 114 (18), 152 (15), 39 (14), 129 (14), 96 (12), 130 (12)
128, 68 (49), 100 (49), 101 (36), 41 (34), 185 (27), 152 (24), 42 (23), 85 (23),
59 (19), 69 (19), 110 (15), 156 (14), 39 (13), 96 (13), 129 (13)
100, 110 (74), 138 (69), 73 (28), 68 (27), 83 (27), 41 (24), 45 (20), 55 (19),
54 (18), 39 (17), 82 (17), 86 (15), 115 (15), 96 (13), 171 (7)
100, 138 (69), 110 (54), 41 (30), 83 (30), 68 (29), 73 (29), 115 (22), 82 (21),
39 (20), 86 (20), 45 (18), 54 (17), 55 (16), 111 (13), 171 (13)
128, 68 (56), 100 (54), 41 (40), 101 (39), 42 (28), 185 (27), 85 (26), 152 (23),
59 (22), 69 (22), 39 (17), 45 (15), 129 (15), 96 (14), 110 (14)
128, 82 (33), 101 (27), 152 (27), 41 (25), 85 (25), 56 (19), 59 (18), 185 (17),
69 (12), 86 (12), 110 (12), 124 (11), 39 (10), 130 (10)
100, 138 (42), 68 (22), 73 (21), 83 (19), 41 (18), 42 (16), 45 (14), 115 (14),
39 (13), 82 (13), 124 (13), 55 (11), 58 (9), 114 (9), 171 (6)
128, 82 (34), 152 (31), 101 (30), 41 (27), 85 (26), 185 (22), 56 (20), 59 (18),
110 (12), 130 (12), 69 (11), 124 (10), 39 (10)
128, 152 (33), 100 (32), 68 (27), 41 (24), 101 (21), 156 (20), 185 (19), 42 (18),
85 (18), 59 (15), 69 (12), 73 (11), 110 (11), 115 (11)
4,5-dimethyl-2-isopropylb,c
2-isobutyl-4-methylc
1175
1228
1237
1239
1253
1260
1272
1298
1308
1322
1332
1337
1343
1345
1349
1366
1377
1379
1383
1395
1401
1412
1443
1451
1457
1469
1481
1483
1485
1498
1507
1518
1551
1558
1563
1589
1573
2-butyl-5-methylb
2-butyl-5-methylb
4,5-dimethyl-2-isobutylb,c
4,5-dimethyl-2-isobutylb,c
2-butyl-4-methylc
2-butyl-4,5-dimethylb,c
2-butyl-4,5-dimethylb,c
4-ethyl-2-isobutyl-5-methylb,c
4-ethyl-2-isobutyl-5-methylb,c
5-ethyl-2-isobutyl-4-methylb,c
5-methyl-2-pentylb
5-methyl-2-pentylb
5-ethyl-2-isobutyl-4-methylb,c
2-butyl-4-ethyl-5-methylb,c
4-methyl-2-pentylc
2-butyl-4-ethyl-5-methylb,c
2-butyl-5-ethyl-4-methylb,c
2-butyl-5-ethyl-4-methylb,c
4,5-dimethyl-2-pentylb,c
4,5-dimethyl-2-pentylb,c
5-ethyl-2-pentyld
128, 152 (34), 100 (34), 68 (28), 101 (25), 41 (24), 85 (22), 185 (22), 156 (20),
42 (19), 59 (15), 69 (13), 115 (13), 45 (11), 84 (11)
114, 152 (29), 115 (28), 68 (27), 87 (26), 42 (25), 71 (24), 55 (21), 41 (19),
29 (15), 53 (15), 185 (15), 39 (13), 59 (13), 83 (13)
114, 152 (36), 115 (32), 68 (29), 87 (29), 42 (27), 71 (25), 55 (23), 41 (22),
185 (20), 39 (18), 29 (17), 53 (17), 59 (16), 45 (15), 83 (13)
114, 152 (76), 110 (56), 86 (52), 156 (28), 41 (25), 82 (25), 115 (25), 55 (23),
83 (22), 96 (19), 29 (18), 54 (18), 45 (16), 71 (15), 185 (11)
100, 124 (82), 152 (76), 68 (31), 41 (28), 55 (24), 73 (24), 97 (22), 82 (20),
86 (19), 39 (17), 96 (17), 129 (15), 43 (14), 45 (14), 54 (14), 185 (8)
114, 152 (37), 82 (23), 83 (19), 115 (19), 56 (15), 55 (14), 41 (12), 87 (12),
72 (11), 138 (10), 29 (9), 45 (9), 96 (9), 39 (7), 71 (7), 86 (7), 185 (6)
128, 82 (33), 85 (31), 115 (27), 41 (26), 56 (24), 166 (24), 59 (19), 83 (18),
199 (14), 55 (13), 29 (12), 129 (11), 67 (10), 69 (10), 114 (10),
128, 82 (33), 115 (32), 85 (30), 166 (27), 56 (22), 41 (20), 199 (19), 59 (17),
83 (15), 184 (13), 55 (11), 114 (11), 129 (11), 110 (10)
2-hexyl-5-methyld
4-ethyl-2-pentylc
4-ethyl-5-methyl-2-pentylb,c
4-ethyl-5-methyl-2-pentylb,c
2-hexyl-4-methylc
100, 152 (50), 97 (23), 68 (20), 138 (20), 41 (19), 73 (18), 42 (13), 129 (13),
45 (12), 55 (12), 82 (11), 39 (10), 128 (10), 101 (8), 185 (5)
5-ethyl-4-methyl-2-pentylb,c
5-ethyl-4-methyl-2-pentylb,c
4,5-dimethyl-2-hexylb,c
4,5-dimethyl-2-hexylb,c
5-ethyl-2-hexyld
128, 166 (30), 100 (28), 170 (23), 85 (21), 41 (20), 68 (20), 115 (20), 42 (18),
199 (17), 59 (13), 83 (13), 129 (12), 55 (11), 29 (10), 101 (10)
128, 166 (33), 100 (28), 170 (27), 115 (25), 85 (24), 199 (21), 41 (19), 68 (19),
42 (15), 129 (15), 83 (14), 59 (13), 101 (10), 29 (9), 55 (9), 69 (9)
114, 166 (36), 41 (32), 42 (31), 68 (30), 87 (28), 29 (25), 55 (25), 129 (22),
53 (21), 39 (19), 71 (19), 45 (16), 59 (16), 97 (15), 184 (14), 199 (12)
114, 166 (44), 87 (31), 129 (27), 68 (26), 41 (25), 42 (25), 71 (25), 55 (22),
184 (20), 97 (19), 199 (19), 29 (18), 53 (16), 39 (15), 45 (13), 59 (13)
114, 166 (93), 124 (74), 86 (52), 170 (35), 41 (31), 55 (28), 97 (25), 82 (24),
96 (23), 29 (20), 43 (20), 129 (20), 54 (17), 87 (17), 45 (16), 68 (16), 199 (11)
100, 138 (92), 166 (89), 41 (31), 68 (27), 73 (25), 69 (24), 86 (21), 55 (20),
57 (20), 82 (20), 54 (18), 111 (18), 143 (18), 43 (17), 45 (17), 199 (6)
114, 166 (49), 97 (27), 82 (24), 55 (18), 41 (17), 56 (16), 129 (14), 152 (14),
87 (13), 29 (12), 96 (12), 45 (11), 72 (11), 115 (9), 199 (5)
2-heptyl-5-methyld
4-ethyl-2-hexylc
2-heptyl-4-methylc
100, 166 (60), 41 (35), 152 (25), 68 (24), 42 (22), 73 (21), 39 (18), 29 (16),
69 (15), 111 (15), 82 (14), 143 (13), 101 (10), 43 (10), 199 (5)
128, 129 (35), 180 (31), 85 (26), 82 (21), 41 (19), 97 (18), 213 (18), 56 (17),
198 (15), 59 (14), 152 (13), 55 (11), 96 (10)
4-ethyl-2-hexyl-5-methylb,c

Reaction To Form Lipid−Maillard Interaction Products
J. Agric. Food Chem., Vol. 45, No. 9, 1997 3599
Ta ble 3 (Con tin u ed )
3-thiazoline
LRIa
1585
characteristic MS data, m/ z (rel intensity)
4-ethyl-2-hexyl-5-methylb,c
128, 129 (35), 180 (31), 85 (27), 97 (20), 213 (19), 82 (18), 41 (16), 56 (15),
198 (15), 59 (14), 55 (12), 96 (12), 69 (10), 130 (10)
5-ethyl-2-hexyl-4-methylb,c
5-ethyl-2-hexyl-4-methylb,c
4,5-dimethyl-2-heptylb,c
4,5-dimethyl-2-heptylb,c
5-ethyl-2-heptyld
1591
1603
1612
1623
1657
1669
1669
1678
1691
128, 180 (31), 129 (30), 100 (29), 41 (27), 85 (25), 184 (24), 68 (21), 97 (20),
42 (17), 59 (15), 213 (13), 55 (12), 101 (12), 29 (11), 69 (10)
128, 180 (34), 129 (33), 100 (31), 184 (31), 85 (27), 41 (24), 68 (19), 97 (19),
213 (17), 42 (16), 59 (14), 55 (13), 101 (13), 43 (11), 69 (11)
114, 180 (34), 41 (30), 71 (29), 87 (29), 42 (28), 68 (26), 29 (24), 55 (24),
143 (21), 53 (16), 69 (16), 39 (15), 111 (14), 43 (12), 198 (12), 213 (10)
114, 180 (39), 71 (35), 41 (33), 87 (31), 42 (29), 68 (28), 29 (25), 55 (25),
143 (27), 53 (18), 69 (17), 198 (17), 111 (16), 39 (15), 43 (13), 213 (12)
114, 138 (92), 180 (85), 41 (38), 184 (33), 82 (27), 55 (25), 69 (24), 29 (23),
96 (22), 43 (19), 139 (19), 87 (17), 45 (15), 68 (15), 213 (8)
152, 100 (94), 180 (72), 41 (42), 68 (29), 43 (28), 55 (28), 69 (26), 73 (26),
82 (21), 29 (17), 39 (17), 54 (17), 85 (17), 83 (16), 57 (15), 213 (4)
114, 180 (55), 41 (29), 29 (24), 82 (24), 56 (21), 55 (19), 45 (15), 87 (15),
166 (15), 69 (14), 143 (13), 39 (12), 96 (11), 53 (10), 72 (10), 213 (5)
128, 194 (35), 85 (25), 143 (23), 41 (22), 29 (19), 82 (19), 111 (16), 227 (16),
56 (15), 212 (15), 59 (14), 69 (14), 101 (13), 114 (13), 166 (11)
128, 41 (39), 194 (36), 143 (34), 85 (33), 82 (23), 56 (21), 29 (20), 69 (19),
59 (18), 111 (18), 101 (16), 212 (15), 227 (15), 55 (13), 67 (12)
114, 87 (14), 115 (9), 116 (7), 41 (6), 55 (4), 53 (3), 165 (3), 210 (3), 225 (2)
128, 41 (36), 194 (36), 198 (27), 85 (25), 100 (25), 143 (23), 42 (22), 68 (21),
29 (18), 69 (17), 59 (14), 111 (14), 55 (13) 101 (13), 227 (12)
100, 180 (54), 41 (28), 68 (23), 166 (23), 73 (19), 42 (15), 55 (15), 69 (14),
82 (13), 157 (13), 45 (12), 29 (11), 39 (11), 43 (11), 213 (4)
114, 87 (17), 115 (9), 116 (8), 41 (8), 210 (6), 165 (5), 225 (0)
128, 194 (34), 100 (30), 85 (29), 143 (26), 41 (25), 198 (23), 42 (14), 68 (14),
101 (14), 111 (14), 29 (13), 59 (13), 69 (12), 67 (10), 45 (9), 227 (6)
114, 194 (39), 71 (30), 87 (29), 41 (23), 68 (23), 55 (22), 157 (22), 42 (19),
212 (15), 29 (14), 53 (14), 69 (14), 43 (12), 227 (12), 82 (11)
114, 194 (50), 71 (34), 87 (32), 157 (32), 41 (24), 68 (24), 55 (23), 212 (23),
42 (19), 227 (16), 29 (14), 53 (14), 69 (14), 43 (12), 82 (12)
152, 194 (90), 114 (88), 86 (42), 41 (32), 198 (30), 55 (24), 82 (19), 157 (19),
87 (18), 153 (18), 29 (17), 43 (17), 96 (16), 69 (15), 227 (6)
114, 194 (69), 82 (24), 41 (22), 55 (19), 180 (18), 56 (16), 87 (15), 157 (14),
29 (13), 69 (13), 96 (12), 125 (12), 45 (11), 195 (10), 212 (10), 227 (6)
114, 87 (13), 53 (6), 67 (6), 115 (6), 41 (5), 116 (4), 223 (4)
128, 208 (39), 85 (29), 157 (29), 82 (21), 41 (20), 226 (16), 241 (16), 69 (14),
56 (13), 101 (13), 59 (12), 125 (12), 180 (12), 67 (10)
114, 87 (18), 53 (10), 115 (8), 41 (6), 67 (6), 116 (6), 223 (3)
128, 208 (59), 157 (40), 85 (38), 226 (31), 241 (25), 82 (21), 41 (17), 101 (16),
56 (13), 59 (13), 125 (13), 69 (12), 55 (11), 129 (11), 180 (11)
128, 208 (45), 212 (35), 157 (26), 85 (25), 100 (21), 41 (16), 241 (15), 69 (14),
101 (13), 55 (12), 59 (12), 68 (12), 42 (10), 166 (9)
128, 208 (46), 212 (41), 85 (32), 157 (31), 100 (25), 41 (23), 68 (17), 241 (17),
69 (15), 101 (15), 55 (12), 42 (11), 59 (11), 67 (10)
114, 208 (49), 71 (29), 87 (29), 41 (28), 171 (26), 55 (24), 68 (23), 226 (21), 42( 19),
29 (16), 43 (16), 241 (14), 53 (13), 180 (12)
5-methyl-2-octyld
4-ethyl-2-heptylc
4-ethyl-2-heptyl-5-methylb,c
4-ethyl-2-heptyl-5-methylb,c
4,5-dimethyl-2-(1-octenyl)b,c
5-ethyl-2-heptyl-4-methylb,c
1696
1697
4-methyl-2-octylc
1699
4,5-dimethyl-2-(1-octenyl)b,c
5-ethyl-2-heptyl-4-methylb,c
1708
1709
4,5-dimethyl-2-octylb,c
4,5-dimethyl-2-octylb,c
5-ethyl-2-octyl
1718
1729
1765
1775
4-ethyl-2-octylc
2-(1,3-octadienyl)-4,5-dimethylb,c
4-ethyl-5-methyl-2-octylb,c
1777
1782
2-(1,3-octadienyl)-4,5-dimethylb,c
4-ethyl-5-methyl-2-octylb,c
1792
1795
5-ethyl-4-methyl-2-octylb,c
5-ethyl-4-methyl-2-octylb,c
4,5-dimethyl-2-nonylb,c
1802
1814
1824
1836
1887
1900
1907
1920
4,5-dimethyl-2-nonylb,c
114, 208 (51), 41 (42), 71 (37), 87 (37), 171 (32), 55 (31), 42 (28), 68 (27), 226 (25),
29 (24), 43 (24), 53 (20), 39 (15), 82 (14), 241 (14)
128, 222 (38), 85 (34), 171 (31), 41 (24), 82 (21), 240 (18), 56 (15), 59 (14),
255 (14), 55 (13), 83 (13), 101 (13), 69 (12), 67 (11), 87 (11)
128, 85 (43), 222 (38), 171 (36), 41 (35), 82 (26), 56 (20), 240 (20), 59 (19), 55 (16),
101 (16), 69 (15), 83 (15), 43 (14), 67 (14), 255 (14)
128, 222 (42), 226 (31), 85 (29), 41 (25), 171 (25), 100 (24), 68 (17), 59 (13),
101 (13), 255 (13), 42 (12), 43 (12), 55 (12), 69 (11), 67 (10)
4-ethyl-5-methyl-2-nonylb,c
4-ethyl-5-methyl-2-nonylb,c
5-ethyl-4-methyl-2-nonylb
5-ethyl-4-methyl-2-nonylb
128, 222 (50), 226 (43), 85 (37), 171 (33), 100 (26), 41 (25), 68 (17), 255 (15),
59 (14), 101 (14), 42 (13), 43 (13), 55 (13), 67 (12), 69 (12)
a
b
Linear retention index. Two isomers (E and Z) were found for these 3-thiazolines. c Previously reported in cooked beef (Elmore et
d
al., 1997). Spectrum of two unresolved E and Z isomers.
reducing conditions in the reaction mixture, discourag-
ing thiazole formation.
from the oxidative degradation of lipids, and therefore
two reactions were carried out using an alkenal and an
alkadienal. When (E)-2-nonenal and (E,E)-2,4-nona-
dienal were reacted with 3-hydroxy-2-butanone and
ammonium sulfide, 3-thiazolines and thiazoles with C8
unsaturated 2-alkyl substituents were found only in
very small amounts. However, the (E)-2-nonenal reac-
tion also gave small amounts of 2-hexyl-4,5-dimethyl-
3-thiazoline, and (E,E)-2,4-nonadienal produced small
amounts of 2-butyl-4,5-dimethyl-3-thiazoline. This sug-
gested that, in both cases, oxidative fragmentation of
the double bonds occurred during the reaction. 2-Octyl-
4,5-dimethyl-3-thiazoline formed in the (E)-2-nonenal
A slightly different mechanism could occur with the
alkane-R-diones. The initial step requires nucleophilic
addition of -SH to one of the carbonyl groups. This
intermediate could be reduced to a mercaptoketone, or
it could react with an imine intermediate leading to a
thiazole. This route offers an explanation for the larger
quantities of thiazoles found in the dione systems.
Saturated aliphatic aldehydes all gave 3-thiazolines
and thiazoles with a saturated side chain in the 2-posi-
tion containing one fewer carbon atom than the alde-
hyde. Unsaturated aldehydes are important products

3600 J. Agric. Food Chem., Vol. 45, No. 9, 1997
Elmore and Mottram
Ta ble 4. Ma ss Sp ectr a l Da ta for Alk ylth ia zoles P r od u ced in th e Rea ction of Am m on iu m Su lfid e, Ald eh yd es, a n d
r-Hyd r oxyk eton es or r-Dica r bon yls
thiazole
LRIa
characteristic MS data, m/ z (rel intensity)
4,5-dimethyl-2-isopropyl
2-butyl-4-methyl
1139 NISTb
1222 NISTb
1225 NISTb
4,5-dimethyl-2-isobutylc
4-ethyl-2-isobutyl-5-methyl 1278 141, 140 (24), 85 (15), 168 (15), 59 (13), 142 (10), 41 (8), 126 (8), 183 (8), 39 (5), 182 (5)
2-butyl-4,5-dimethyl
1287 NISTb
5-ethyl-2-isobutyl-4-methyl 1297 141, 126 (32), 140 (18), 168 (17), 99 (14), 41 (12), 85 (12), 59 (11), 142 (10), 183 (10), 65 (9),
45 (8), 39 (7), 182 (5)
4-methyl-2-pentyl
1322 113, 126 (35), 71 (17), 112 (17), 140 (14), 72 (13), 114 (10), 41 (9), 73 (9), 127 (9), 45 (7), 169 (7) 39 (6)
2-butyl-4-ethyl-5-methyl
2-butyl-5-ethyl-4-methyl
2-hexyl-5-methyl
1334 NISTb
1356 141, 126 (31), 154 (24), 85 (11), 142 (9), 59 (8), 99 (7), 155 (7), 168 (7), 41 (6), 45 (6), 183 (6), 143 (5)
1381 113, 126 (29), 112 (20), 45 (19), 140 (18), 71 (11), 72 (11), 127 (11), 183 (9)
1384 127, 140 (34), 126 (18), 71 (15), 86 (13), 154 (11), 59 (9), 128 (9), 41 (8), 85 (8), 141 (8), 183 (8),
29 (6), 45 (6), 53 (6), 39 (5), 129 (5)
4,5-dimethyl-2-pentylc
4-ethyl-2-pentyl
2-hexyl-4-methyl
1412 127, 140 (41), 112 (20), 154 (11), 128 (10), 141 (9), 71 (8), 85 (7), 126 (7), 45 (6), 183 (6),
39 (5), 41 (5)
1426 113, 126 (37), 112 (15), 140 (13), 114 (11), 71 (10), 72 (10), 127 (10), 115 (6), 154 (6), 183 (5)
4-ethyl-5-methyl-2-pentylc 1432 141, 154 (32), 85 (15), 59 (14), 168 (12), 140 (11), 142 (11), 41 (8), 126 (8), 155 (8), 197 (6),
29 (5), 39 (5), 45 (5), 143 (5)
5-ethyl-4-methyl-2-pentyl
1454 141, 154 (40), 126 (28), 168 (14), 140 (11), 85 (10), 155 (10), 142 (9), 197 (9), 59 (8), 41 (7),
99 (7), 65 (6), 45 (5), 143 (5)
5-ethyl-2-hexyl
1457 127, 140 (38), 71 (16), 128 (11), 154 (11), 126 (9), 141 (8), 129 (6), 168 (6), 197 (5)
1485 127, 140 (33), 126 (15), 71 (13), 86 (11), 128 (9), 154 (9), 41 (7), 59 (7), 85 (7), 141 (7), 45 (6),
53 (6), 197 (6), 29 (5), 129 (5)
4,5-dimethyl-2-hexylc
4-ethyl-2-hexyl
1516 127, 140 (37), 112 (15), 154 (12), 126 (9), 141 (9), 128 (8), 71 (7), 41 (6), 168 (6), 45 (5), 85 (5),
129 (5), 197 (5)
2-heptyl-4-methyl
1532 113, 126 (39), 112 (14), 127 (10), 168 (10), 41 (7), 71 (7), 114 (7), 140 (7), 72 (6), 154 (6), 39 (5),
73 (5), 115 (5), 197 (5)
1533 141, 154 (31), 85 (11), 140 (10), 168 (10), 59 (9), 142 (9), 155 (7), 211 (7), 41 (6), 126 (6),
143 (5), 182 (5)
1556 141, 154 (39), 126 (22), 168 (11), 140 (10), 142 (9), 155 (9), 211 (9), 85 (8), 41 (7), 59 (6), 99 (6),
182 (6), 65 (5)
1588 127, 140 (30), 126 (14), 71 (11), 41 (10), 86 (10), 128 (9), 141 (8), 182 (8), 29 (7), 45 (6), 53 (6),
59 (6), 85 (6), 154 (6), 211 (6)
4-ethyl-2-hexyl-5-methylc
5-ethyl-2-hexyl-4-methyl
4,5-dimethyl-2-heptylc
4-ethyl-2-heptyl
4-methyl-2-octyl
1621 127, 140 (41), 112 (14), 182 (10), 86 (10), 126 (8), 128 (8), 141 (8), 154 (8), 211 (6), 71 (5), 85 (5)
1624 113, 126 (31), 112 (13), 71 (12), 168 (10), 73 (7), 115 (7), 127 (7), 211 (7), 72 (6), 114 (6),140 (6),
41 (5), 45 (5), 182 (5)
4-ethyl-2-heptyl-5-methylc 1634 141, 154 (29), 142 (11), 85 (9), 140 (8), 59 (7), 155 (7), 196 (7), 41 (6), 126 (5), 143 (5), 168 (5), 225 (5)
5-ethyl-2-heptyl-4-methyl
4,5-dimethyl-2-octylc
4-ethyl-2-octyl-
1657 141, 154 (36), 126 (20), 142 (9), 196 (9), 155 (8), 225 (7), 85 (6), 168 (6), 41 (5), 59 (5), 143 (5), 182 (5)
1691 127, 140 (33), 126 (11), 128 (8), 182 (8), 71 (7), 86 (7), 141 (7), 41 (6), 85 (5), 129 (5), 225 (5)
1726 127, 140 (41), 112 (13), 126 (10), 182 (10), 128 (8), 196 (8), 41 (7), 141 (7), 71 (6), 154 (6), 225 (5)
1736 141, 154 (29), 142 (9), 85 (8), 140 (8), 196 (8), 155 (7), 59 (6), 41 (5), 126 (5), 143 (5), 168 (5), 239 (5)
1760 141, 154 (37), 126 (15), 142 (9), 140 (8), 196 (8), 155 (7), 41 (6), 239 (6), 85 (5), 143 (5), 168 (5), 210 (5)
1795 127, 140 (36), 126 (12), 128 (9), 141 (7), 182 (7), 86 (6), 154 (6), 196 (6), 239 (6), 71 (5)
1839 141, 154 (28), 142 (10), 85 (7), 155 (7), 59 (6), 196 (6), 41 (5), 143 (5), 210 (5), 253 (5)
4-ethyl-5-methyl-2-octylc
5-ethyl-4-methyl-2-octylc
4,5-dimethyl-2-nonyl
4-ethyl-5-methyl-2-nonyl
5-ethyl-4-methyl-2-nonyl
1864 141, 154 (35), 126 (15), 142 (9), 155 (8), 196 (8), 210 (7), 253 (7), 41 (6), 168 (6), 85 (5), 143 (5)
a
b
Linear retention index. Spectrum reported in NIST/NIH/EPA mass spectral database. c Previously reported in cooked beef (Elmore
et al., 1997).
Ta ble 5. Ma ss Sp ectr a l Ba se P ea k s for 2-Alk ylth ia zoles
a n d 2-Alk yl-3-th ia zolin es
3-thiazolines that were expected to be present. It
appeared that two molecules of pentanal were incorpo-
rated into these compounds. The mass spectra of these
3-thiazolines suggested identities of 2-butyl-4-methyl-
5-pentyl-3-thiazoline and 2-butyl-5-methyl-4-pentyl-3-
thiazoline, each present as pairs of isomers, although
we have not yet confirmed this. The equivalent four
3-thiazolines was found in each of the reaction mixtures
containing a 1-hydroxy-2-alkanone but, as the chain
length of the aldehyde increased, the relative amounts
of these 3-thiazolines decreased.
substituent
3-thiazoline
m/ z 100
m/ z 100 (below octyl)
M•+ - 61 (octyl and above)
m/ z 114
m/ z 114 (below octyl)
M•+ - 75 (octyl and above)
m/ z 114
thiazole
2-alkyl-4-methyl
2-alkyl-5-methyl
m/ z 113
m/ z 113
2-alkyl-4-ethyl
2-alkyl-5-ethyl
m/ z 127
m/ z 127
2-alkyl-4,5-dimethyl
m/ z 127
m/ z 141
m/ z 141
2-alkyl-4-ethyl-5-methyl m/ z 128
2-alkyl-5-ethyl-4-methyl m/ z 128
Tr ia lk ylp yr id in es. A large GC peak was present
in each of the reactions, which eluted after the 3-thi-
azolines and thiazoles when the column had reached the
maximum temperature (280 °C). The mass spectra
(Table 6) were consistent with trialkylpyridines and
matched the spectra of compounds that we have recently
found in samples of pressure cooked beef (J .S.E. and
D.S.M., unpublished results). Trialkylpyridines have
been reported by Shu et al. (1985) and Hwang et al.
(1986) in reaction mixtures containing aldehydes and
ammonium sulfide, and they proposed a mode of forma-
tion involving three aldehyde molecules condensing with
ammonia. Many different trialkylpyridines were found
reaction may have arisen from traces of nonanal in the
nonenal. The main products from these reaction sys-
tems are described later in the paper.
The reactions involving 1-hydroxy-2-alkanones pro-
duced smaller amounts of the expected 3-thiazolines
than the 3-hydroxy-2-butanone systems, but significant
amounts of other 3-thiazolines were found, which have
not been fully characterized. For example, the reaction
mixture containing 1-hydroxy-2-propanone and penta-
nal gave four 3-thiazolines with a molecular weight of
227. These 3-thiazolines were present at 12% of the
total peak area, higher than the total peak area of the

Reaction To Form Lipid−Maillard Interaction Products
J. Agric. Food Chem., Vol. 45, No. 9, 1997 3601
F igu r e 2. Proposed mass spectral fragmentation pattern for alkyl-3-thiazolines (R1 ) alkyl C3-C9; R2, R3 ) H, methyl, ethyl).
Ta ble 6. Ma ss Sp ectr a of Alk ylp yr id in es P r od u ced in th e Rea ction of Am m on iu m Su lfid e, Ald eh yd es, a n d
r-Hyd r oxyk eton es or r-Dica r bon yls
pyridine
LRIa
characteristic MS data, m/ z (rel intensity)
2-isobutyl-3,5-isopropyl
2-butyl-3,5-dipropyl
1480
1643
NISTb
149, 162 (54), 177 (33), 204 (22), 176 (20), 190 (19), 150 (12), 135 (9), 160 (9), 163 (9),
120 (8), 91 (7), 29 (6), 41 (6), 132 (6), 219 (4)
3,5-dibutyl-2-pentyl
3,5-dipentyl-2-hexyl
3,5-dihexyl-2-heptyl
1918
2200
163, 190 (39), 232 (28), 205 (13), 164 (11), 176 (11), 218 (11), 177 (10), 120 (8), 146 (6),
191 (6), 174 (5), 261 (3)
177, 218 (55), 204 (27), 260 (26), 190 (20), 246 (17), 191 (15), 178 (13), 120 (11), 233 (11),
219 (9), 274 (7), 303 (3)
191, 246 (51), 204 (27), 218 (23), 288 (20), 274 (17), 192 (14), 205 (14), 261 (13), 120 (9),
247 (9), 260 (7), 216 (6), 219 (6), 302 (6), 316 (6), 345 (3)
>2200
a
b
Linear retention index. Spectrum reported in NIST/NIH/EPA mass spectral database.
in the cooked beef. They could not be individually
identified, because they were not fully resolved under
the gas chromatographic conditions used but appeared
to arise from various combinations of the many alde-
hydes present in the cooked meat. In the present work,
the largest quantities of the trialkylpyridines were
found in reaction mixtures using the longer chain
aldehydes (Tables 3 and 4), although they appeared to
be absent from the reaction mixtures containing nona-
nal and decanal, probably because the molecules were
too large to elute from the column under the conditions
used.
Oth er Com p ou n d s. A number of other compounds
were formed in the reaction mixtures at levels ranging
from trace to 30% of the total GC peak area. These
included pyrazines, pyrroles, imidazoles, oxazoles, and
alkanethiols. As expected, aldol condensation products
of the aldehydes were found in all of the reaction
mixtures and, as the alkanal chain length increased,
the relative amounts of such compounds increased. For
mixtures containing nonanal and decanal, 2-heptyl-2-
undecenal and 2-octyl-2-dodecenal were present at
approximately 20% of the total peak areas of the
respective chromatograms.
of the intermediate, 3-amino-2-butanone, produced by
the action of ammonia on the hydroxyketone. However,
reaction mixtures containing 2,3-butandione produced
much lower quantities of tetramethylpyrazine, between
0.3% and 2.0%.
In the dione reaction mixtures, 2-alkyl-4,5-dimeth-
ylimidazoles were produced, which are similar in struc-
ture to thiazoles but with a second nitrogen replacing
the sulfur. However, they were not found in the
hydroxyketone systems. This may be explained by a
modification of the proposed mechanism given in Figure
1, in which both keto groups react with ammonia.
Substitution of the hydroxy group of a hydroxyketone
with -NH2 does not occur; hence, imidazoles are not
formed. In systems containing 2,3-butanedione and
pentanal, the level of 2-butyl-4,5-dimethylimidazole was
28%; the amount of imidazole decreased as the length
of the alkanal chain increased, with only 1.4% when
nonanal was present. When 2,3-pentanedione was the
dione the level of imidazole produced was 27% for
3-methylbutanal and 10% for decanal.
The systems involving unsaturated aldehydes con-
tained only very small amounts of 3-thiazolines with no
thiazoles or trialkylpyridines. However, tetrameth-
ylpyrazine was formed in large amounts in both reaction
mixtures [16% for (E)-2-nonenal and 30% for (E,E)-2,4-
nonadienal]. 2-Pentylthiophene was a major product in
The reaction mixtures containing 3-hydroxy-2-bu-
tanone contained between 12% and 30% tetrameth-
ylpyrazine, formed by the condensation of two molecules

3602 J. Agric. Food Chem., Vol. 45, No. 9, 1997
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the reaction mixture containing (E,E)-2,4-nonadienal
(21%). Similar alkylthiophenes have been reported in
Maillard reactions between cysteine, ribose, and phos-
pholipids, in which the latter oxidized to give unsatur-
ated aldehydes (Farmer and Mottram, 1992). Two large
peaks in the reaction mixture from (E)-2-nonenal were
suggested by structure elucidation as being the two
isomers of 3,4-diheptyl-2(5H)-thiophenone (18% and
11%), formed from two molecules of (E)-2-nonenal and
one molecule of hydrogen sulfide.
Con clu sion . The 3-thiazolines and thiazoles tenta-
tively identified in pressure cooked beef were all formed
in reaction mixtures containing an R-hydroxyketone or
R-dione, an aliphatic aldehyde, and ammonium sulfide.
Other 3-thiazolines and thiazoles were also produced.
The reaction mixtures also contained other products
including trialkylpyridines, pyrazines, pyrroles, imid-
azoles, oxazoles, and alkanethiols. The results con-
firmed routes to the formation of 3-thiazolines and
thiazoles in cooked foods and demonstrated the impor-
tance of interactions between the Maillard reaction and
lipid-derived compounds in the flavor chemistry of
heated foods.
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Received for review J anuary 21, 1997. Revised manuscript
received May 19, 1997. Accepted May 28, 1997.X
We grate-
fully acknowledge funding for this project from the Ministry
of Agriculture, Fisheries and Food.
Ho, C. T.; Carlin, J . T. Formation and aroma characteristics
of heterocyclic compounds in foods. In Flavor Chemistry
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J F970065U
X Abstract published in Advance ACS Abstracts, J uly
15, 1997.