Metallic odour caused by vinyl ketones formed in the oxidation of butterfat. the identification of octa‐1,cis‐5‐dien‐3‐one

Abstract

Oct-1-en-3-one and the more potent octa-l,cis-5-dien-3-one have been identified as being responsible for the metallic odour which developed when a model system containing butterfat, a-tocopherol and cupric palmitate was allowed to oxidise at 35°C for 35 h. These vinyl ketones were synthesised, their mass and n.m.r. spectra determined, and odour descriptions and odour thresholds assessed. Octa-1 ,cis-5-dien-3-one in aqueous solution could be detected at a dilution of 1 in 10l2. Its metallic odour was also described as like geranium leaves. Oct-1-en-3-one (detectable at 1 in 1010 dilution) was described as mushroom like at low concentrations and only exhibited a metallic odour at higher concentrations. Both compounds had an odour threshold concentration about five hundred times greater in groundnut oil than in water. The significance of these compounds is discussed with reference to the published literature and their formation from (n -3) and (n -6) polyenoic fatty acids.

Volatile odorous compounds responsible for metallic, fishy taint formed in butterfat by selective oxidation

“…The vinyl ketones, oct-l-en-3-one and octa-1 ,cis-5-dien-3-one were synthesised as described in our other paper. 3 To obtain reference peaks for deca-trans-2,cis-4,cis-7-trienal and deca-trans-2,trans-4,cis-7-trienal a solution of methyl 9-hydroperoxy-trans-10,cis-l2,cis-l5-octadecatrienoate, prepared by the reaction of linolenic acid with potato lipoxygenase followed by methylation, was thermally decomposed by direct injection on to the gas chromatographic column.4 2.2. Gas-liquid chromatography (g.1.c.…”

“…Only two regions of the chromatogram gave eluates with pronounced off-odour impact, The identification of certain vinyl ketones responsible for the "metallic" taint is reported in the accompanying paper . 3 The fractions containing 2.4-dienals are indicated by their absorption at 275 nm and they had a characteristic off-odour described as "fishy". Analysis by g.1.c.…”

Volatiles from leaves of field‐grown plants and shoot cultures of Gynura bicolor DC

“…(Z)-1,5-Octadien-3-one was the most abundant aroma-impact compound (CV, 1435; OSV, 100) in the shoot cultures. This vinyl ketone was reported as a metallic odorant in the oxidation of butterfat, [13] and has been reported to be an aroma-impact compound in wheat bread crumbs, [17] Valencia Late orange juice, [35] grapefruit juice, [36] fresh tomato cultivars [37] and pink guava. [38] 1-Octen-3-one (CV, 572; OSV, 63) was identifi ed as a metallic off -fl avour compound in oxidized butter and oxidized saffl ower oil, [39] and has been reported to be an aroma-impact compound in mushroom.…”

“…Commercially unavailable (Z)-1,5-octadien-3-one was synthesized according to literature sources. [13][14][15] Purchased trans-4,5-Epoxy-(E)-2-decenal was purifi ed using silica gel column chromatography (particle size, 75-150 µm; eluent, n-hexane : ethyl acetate, 4 : 1, v/v) and the geometry of the epoxy and double bond moieties was confi rmed using 1 H-NMR coupling constants. [16][17][18] Plant Material Commercial cultivars.…”

Determination of storage stability of butter enriched with unsaturated fatty acids/conjugated linoleic acids (UFA/CLA) using instrumental and sensory methods

“…The auto-oxidation of the lipids in dairy products and the resulting off-flavours have been comprehensively studied (Badings, 1970;Swoboda & Peers, 1977;Widder, Sen, & Grosch, 1991). Badings (1970) identified hexanal (green), heptanal (oily), (E)-2-nonenal (cucumber-like), (E,E)-2,4-heptadienal (metallic), 1-octen-3-one (mushroom-like) as off-flavour compounds in cold stored butter and suggested linoleic, linolenic and arachidonic acids as precursors of these aroma compounds.…”