Changes in the odorants of boiled trout (Salmo fario) as affected by the storage of the raw material

Abstract

Aroma extract dilution analysis of freshly harvested and boiled trouts (A) resulted in 24 odorants, of which 19 were identified. Twelve compounds were quantified by isotope dilution assays in sample A, in boiled trouts of which the raw material had been stored for 17 weeks a t -13 "C (B), and in homogenates which were freshly prepared and boiled (C) or stored for 14 weeks a t -13 "C and then boiled (D).Calculation of odor activity values (OAVs, ratio of concentration t o odor threshold) revealed (2)-1,5-octadien-3-one, (E,Z)-2,6-nonadienal, and methional are the most potent odorants of samples A and C. After storage of the raw material, the OAVs of (Z)-3-hexenal and (Z,Z)-3,6-nonadienal were strongly enhanced. Consequently, both aldehydes contributed substantially to the fatty, fishy off-flavor of samples B and D. (Z)-3-Hexenal is proposed as an indicator substance to objectify the fatty, fishy off-flavor of boiled trouts.Fish has a characteristic flavor which is influenced by the species and the conditions used for its storage and processing (Prell and Sawyer, 1988;Lindsay, 1990). More than 280 volatile compounds have been identified in freshly harvested and processed fish (Maarse and Visscher, 19911, but little is known about the compounds that actually contribute to the flavor. Only Josephsonet al. (1983,19841, Josephson and Lindsay (1986), and Hirano e t al. (1992) have shown that carbonyl compounds and alcohols with six, eight, and nine carbon atoms are involved in the flavor of freshly harvested fish. These odorants are formed by a lipoxygenase-initiated peroxidation of the n-3 and n-6 polyunsaturated fatty acids occurring in fish tissues (German and Kinsella, 1985; Kinsella, 1986, 1989;Zhang et al., 1992).As recently reviewed (Grosch, 19931, the potent odorants of a food are localized in the capillary gas chromatogram by gas chromatography-olfactometry (GCO) of serial dilutions of the extract. This procedure is denoted aroma extract dilution analysis (AEDA), and the results are expressed as flavor dilution (FD) factors. The FD factor for a compound is the ratio of its concentration in the initial extract to its concentration in the most dilute extract in which odor was detected by GCO. After AEDA screening, the odorants with the highest FD factors are identified. Then the simplifications implicit in AEDA (Grosch, 1993) are corrected by the quantification of the levels of these compounds in the food and by the calculation of the odor activity values (OAVs, ratio of concentration to odor threshold). Odorants with high OAVs are important contributors to the characteristic flavors or offflavors and are suitable as indicator substances for the objective determination of flavor differences in foods.In the present study the AEDA procedure was applied to ascertain the odorants causing the typical odor of boiled trouts. T o reveal the influence on the odor of boiled trouts dependent on a longer storage period of the raw material a t -13 "C, the levels of the odorants showing high F D factors were determined by...

Identification and Quantification of Potent Odorants Formed by Toasting of Wheat Bread

“…1, 2 ((S) -( + ) -2-methylbutanal), 3-6, 16, 17, 23, 27, 29, 31, 36; no. 40 (3- (10), (Z) -2-nonenal (11), 6-acetyltetrahydropyridine (12), [ 2 H] -6-acetyltetrahydropyridine (13), (E,Z) -2, 4-decadienal (14) (21), [ 2 H]methylpropanal (9), [ [ 13 C 2 ]-4-Hydroxy-2, 5-dimethyl-3 (2H) -furanone was synthesized according to Sen et al (23) and then purified as follows: the reaction mixture (120 mg) containing the target compound and its acyclic precursor, in portions of 6 mg, was subjected to flash chromatography (24) on a column (36 ϫ 1.9 cm; Baker, Phillipsburg, U.S.A.) packed with Bakerbonddiol (40 µm, 10 g). After applying 2 mL of the reaction mixture, elution was performed with pentane/diethyl ether (1 + 1 by volume, 20 mL, fraction 1), pentane/ diethyl ether (3 + 7 by volume, 30 mL, fraction 2) and diethyl ether (100 mL, fraction 3).…”

Identification et comparaison des composés volatils des fruits de huit variétés de dattes marocaines

“…Par ailleurs, certains composés volatils sont connus pour avoir de faibles seuils de perception et ils pourraient être très impliqués dans l'arôme caractéristique des dattes (la 2,3-pentanedione, par exemple, qui a un seuil de 5 µg·kg -1 dans l'eau [18]). De même, d'autres composés présents à des concentrations largement supérieures à leurs seuils de perception peuvent également être importants pour l'arôme des dattes.…”

Instrumental Analysis of Seafood Flavour

“…This can be accomplished by steam distillation, high vacuum distillation, or DHS. Milo and Grosch [64] performed direct solvent extraction followed by high vacuum distillation for the isolation of volatiles from boiled trout, salmon, and cod. An alternative approach is to isolate the volatile components from the sample by distillation, followed by solvent extraction of the aqueous distillate [15,19].…”

“…The value of CI-MS in flavour analysis is to complement and supplement the data provided by EI-MS [19]. CI-MS is commonly used in stable isotope dilution analysis and has been applied to the analysis of important seafood aroma compounds [36,64,102].…”