Biosci. Biotechnol. Biochem., 69 (12), 2416–2420, 2005
Identification of Novel Decenoic Acids in Heated Butter
y
Nobuhiko ITO, Shigeru WADA, Yousuke YAMANAKA, Hitoshi TAKAGAKI, and Hironori NAKAMURA
Research and Development Section, Soda Aromatic Co., Ltd., 1573-4 Funakata, Noda, Chiba 270-0233, Japan
Received July 26, 2005; Accepted September 25, 2005
Novel decenoic acids such as (E)-4-decenoic acid and
E)- and (Z)-5-,6-decenoic acid were detected as minor
chloride, active clay, and trimethylsilyldiazomethane in
hexane were obtained from reliable commercial sources
and used without further purification. (Z)-4-Decenoic
acid and methyl ester were purchased from Orils (Paris,
France). (E)-4-Decenoic acid was purchased from Inoue
Perfumery Co., Ltd. (Tokyo). [(E)- and (Z)]-5- and -6-
Decenoic acids were prepared using a known pathway.
9-Decenoic acid was purchased from Tokyo Kasei
Kogyo Co., Ltd. (Tokyo). The methyl esters of (E)-4-
decenoic acid, [(E)- and (Z)]-5- and -6-decenoic acid,
and 9-decenoic acid were obtained from the reaction of
the corresponding acids and trimethylsilyldiazomethane
(
components in heated butter using GC and GC/MS.
The formation mechanism of these novel decenoic acids
is discussed on the basis of the result of the reaction of
ꢀ-decalactone with active clay in a model experiment.
Key words: (E)-4-decenoic acid; (E)- and (Z)-5-,6-dec-
enoic acid; flavor; identification; heated
butter
Butter is widely used as a seasoning in cooking,
suggesting that it plays an important role in the formation
ꢀ
in hexane, benzene, and methanol at 25 C for 30 min. ꢀ-
and ꢁ-Decalactone were production of Soda Aromatic
Co., Ltd. (Tokyo).
1
–4)
of flavors during heating.
A number of papers have
reported the flavor constituents of butter.5–8) The fatty
acid components of butter, in particular, have been
studied for a considerable period of time, and the
constituent compounds have been reported to be of
Analysis of acidic fraction of heated butter. Butter
(98.0 g) was placed in a three neck round bottom flask
equipped with a thermometer, a mechanical stirring
system, and a Liebig condenser for removal of water.
9
,10)
importance in giving butter its flavor.
However,
concurrent studies on the amounts of these compounds in
butter have revealed that the flavor was almost entirely
due to n-alkanoic acids such as acetic acid, butyric
ꢀ
The flask was heated to 170 C with stirring for 5 h and
ꢀ
then cooled to 25 C. Ethyl acetate (200 g) and 200 g of
acid, octanoic acid, decanoic acid, dodecanoic acid, and
–3,5,6)
2.5 wt % sodium hydroxide solution were added and
extracted. The water layer was extracted with 100 g of
ethyl acetate. The water layer was then washed with
10 wt % sulfuric acid solution, and 100 g of ethyl acetate
was added to the mixture. The upper organic layer was
washed with 100 g of 5 wt % sodium acetate solution and
100 g of 20 wt % sodium chloride solution. It was
subsequently evaporated to give 82.3 mg of a brown-
colored syrup. This syrup was analyzed by GC and GC/
MS. An Agilent 6890 GC system (Agilent Technologies,
Palo Alto CA) equipped with a TC-WAX (30 m ꢁ
0:25 mm i.d.; film thickness of 0.25 mm; GL Sciences,
Tokyo) and flame ionization detector (FID) or an
Agilent 5973 mass selective detector (MSD) was used
for the analysis. The operating conditions were as
tetradacanoic acid.1
Butter was also observed to
contain unsaturated alkanoic acids such as (Z)-9-octa-
decenoic acid (oleic acid) and (Z),(Z)-9,12-octadeca-
dienoic acid (linoleic acid), but these do not contribute to
1
0,11)
butter flavor owing to their non-volatility.
the series of decenoic acids that were synthesized, it was
Among
demonstrated that (E)-6-decenoic acid, in particular, had
a highly significant intense milky flavor as compared to
others.1
presence of these decenoic acids, including (E)-6-
2,13)
Our area of interest was in ascertaining the
decenoic acid, in heated butter. 9-Decenoic acid has
1
4–16)
been isolated from butter,
but limited information is
available on the position, number, and geometry of the
double bonds of other decenoic acids. In this paper, we
describe the identification and formation mechanism of
novel decenoic acids in heated butter.
ꢀ
follows: injector temperature, 250 C; detector temper-
ꢀ
ature, 250 C; ionization voltage, 70 eV; ionsource
ꢀ
temperature, 150 C; helium carrier gas flow, constant
pressure mode of 14.99 psi (FID) or 2.56 psi (MSD);
Materials and Methods
ꢀ
ꢀ
oven temperature program, from 65 C to 120 C at a
ꢀ
ꢀ
ꢀ
A commercial unsalted sweet butter was purchased
from Yukijirushi Co. (Tokyo). Ethyl acetate, hexane,
sodium hydroxide, sulfuric acid, sodium acetate, sodium
rate of 3 C/min and then from 120 C to 250 C at a rate
ꢀ
of 5 C/min. The sample (0.2 ml) was injected in a split
ratio of 1:150.
y
To whom correspondence should be addressed. Fax: +81-471-29-8581; E-mail: nobuhiko ito@soda.toray.co.jp