Aroma Compounds Formed from 3-Methyl-2,4-nonanedione under Photooxidative Conditions

Abstract

The behavior of the prominent aroma compound 3-methyl-2,4-nonanedione under photooxidative conditions was investigated in a model experiment. The four well-known aroma compounds 2,3-butanedione, 2,3-octanedione, acetic acid, and caproic acid were identified. The main oxidation product was 3-hydroxy-3-methyl-2,4-nonanedione, an aroma compound with the odor description of rubbery, earthy, and plastic-like (GC-O). Its structure has been tentatively assigned based on mass (GC-MS) and vapor phase infrared spectra (GC-IR). The formal formation pathways are discussed for these compounds, and other origins described in the literature are presented.

An enzymatic approach to the synthesis of optically pure (3R)- and (3S)-enantiomers of green tea flavor compound 3-hydroxy-3-methylnonane-2,4-dione

“…On the other hand, the presence of the above compounds in green tea extracts had been already extensively reported [22,23,35]. The single ion chromatograms (m/z 88) revealed the presence of the flavor compound 3 as an enantioenriched mixture of the (R) enantiomer.…”

“…Quite recently, the chiral tertiary alcohol 3-hydroxy-3-methylnonane-2,4-dione 3 (Scheme 1) has been recognized as one of the main components of the volatile fraction responsible for the characteristic flavor of green tea brews. The structure of that compound has been initially proposed on the basis of GC-MS investigations [22] and subsequently confirmed by its racemic synthesis [23]; nevertheless, no data on the absolute configuration of the naturally occurring aroma compound are available in the literature. Herein, we describe a new chemo-enzymatic route for the synthesis of optically pure (3R)-3 and (3S)-3 that relies on the combined use of two enzymes from Bacillus licheniformis, namely the ThDP-dependent acetylacetoin synthase (AAS) and the NADH-dependent acetylacetoin reductase (AAR).…”

Dietary Compounds Influencing the Sensorial, Volatile and Phytochemical Properties of Bovine Milk

“…The thermal oxidation of vitamin A palmitate has also previously been attributed to hay-like off-flavor in non-fat milk powder [103]. Further, 2,3-pentanedione (buttery, sweet, nutty) may have been formed from 3-methyl-2,4-nonanedione through photoxidation [104] and was only detected in TMR milk samples at day nine. It is also possible that the hay-like off-flavor is being caused by a complex mixture of compounds rather than a single compound.…”

Heiße Luft oder cooler Duft? Die Trends der letzten 20 Jahre in der Riechstoffchemie

“…Um den Eindruck von Frische und Reinheit zu vermitteln, sind Charakterdüfte im grünen Bereich des Spektrums immer gefragt. Violiff (42), [39] ein grüner,v eilchenblatt-und blütenartiger Referenzduft inspirierte die Entwicklung neuer Materialien wie Tanaison (43), das eine krautige,w ürzig-grüne Note besitzt, oder Florymoss (44), das einen fürd iesen Strukturtyp einzigartigen, moosigen Geruch aufweist (Abbildung 5). [40] Diese Verbindungen werden durch Kondakov-Acylierung von Cycloocten unter Verschiebung der Doppelbindung hergestellt.…”

“…[42] Das 3-Hydroxy-Derivat 47 sowie einige hauptsächlich aus Photooxidationen resultierende Baeyer-Villiger-Produkte des Methylnonadions,k çnnen als Vorläufer von Diacetyl (2,3-Butandion), des charakteristischen Geruchsstoffs der Butter,a ngesehen werden. [43] Verbindung 47,a ls Lactadion geschützt, [44] wird auch mit der Alterung von Weinen in Zusammenhang gebracht. [45] Der cremige,b utterartige Aspekt des Methylnonadions (46)r esultiert hçchstwahrscheinlich ebenfalls aus oxidativ freigesetzten Spuren des Diacetyls.D af reies Diacetyl in der Parfümerie streng limitiert ist, [46] wurden Diacetylvorläufer,w ie das Diacetyldimer 5-Acetyldihydro-2-hydroxy-2,5-dimethyl-3(2H)furanon (48), als Präkursoren beschrieben.…”