Salmon aroma

Additionally, key secondary oxidation products contribute distinctive aromas characteristic to certain fish species. In salmon, co-oxldatlon of polyunsaturated fatty acids of fish oils with salmon-specific carotenoid pigments leads to the formation of a characterizing cooked salmon flavor compound, and changes the ratio of carbonyl compounds formed compared to that for pure fish oil. 

Recent studies on salmon flavors revealed that a single compound appears to be responsible for the characterizing cooked salmon flavor (39). The cooked salmon flavor compound was found to have an extremely low threshold, and was Initially detected only by odor assessment of a fraction eluting at Ig of 9.6-9.7 on a Carbowax 20M packed column when headspace volatiles were analyzed from canned salmon meat. Accelerated oxidation of salmon oil did not yield salmon-llke aromas before the development of fishy oxidized aromas. However, when salmon oil was coated onto Cellte supports, and allowed to oxidize at room temperature, a distinct salmon-loaf-llke aroma developed within 24 h after Initiation of oxidation. A variety of supports were evaluated In model systems with salmon oil for their ability to produce the salmon aroma compound. Odor assessments of the oxidizing systems Table II Indicated that a range of odors developed from salmon-loaf-llke to oxidized fishy aromas, and only the Cellte system provided the aroma. 

The Interaction of the carotenoid and the fatty acid fractions on Cellte were both necessary for the odor development to occur. Studies designed to confirm an Interaction of the carotenoid and fatty acid fractions In the development of salmon flavors showed that when carotenoid fractions from salmon oils were separated from the acylglycerol fraction by column chromatography, neither yielded a salmon-llke aroma during oxidation (Table III). 

However, when the carotenoids and acylglycerols were recombined, the salmon aroma developed. Combinations of alternate sources of fish acylglycerols along with crayfish carotenoids revealed that the necessary component for salmon flavor development was the presence of carotenoids specifically derived from salmon oil (Table III). Such results strongly suggest that the compound Is derived by co-oxldatlon of fish acylglycerols with salmon carotenoids, and that the precursor Is located In the carotenoid fraction. 

Six-carbon volatile alcohols and aldehydes have been found in all freshwater fish surveyed (23-24). However, these compounds have not been found in either salmon residing in saltwater (unpublished data) or in oysters (26). Hexanal has been found in modestly fresh (5-6 days old) saltwater fish (24), but its formation may be the result of autoxldation rather than via enzyme-mediated reactions. Thus, data for the occurrence of hexanal in freshly harvested saltwater fish remains to be developed. Hexanal and (E)-2-hexenal contribute coarse, green-plant-like, aldehydic aroma notes to freshly harvested finfish where their aroma dominates the overall odors within seconds after the death of the fish. (Z)-3-Hexen-l-ol contributes a clean, green-grass-like aroma note. Hexanal always occurs in substantially greater abundance than 1-hexanol in fish. 

This phenomenon is only partially explained by the lees capacity to combine oxygen (Salmon et al., 1999), as some wines develop prematurely aged aroma although they have been maintained on total lees in used barrels or in vat. 

Regarding fresh salmon fillets, the feasibility of using an AromaScan EN to assess seafood quality and microbial safety was assessed by Du et al. [47]. AromaS-can mappings of these fillets were compared to their time related changes in microbial counts, histamine contents, and sensory panel evaluations. Promising results were... 

It is well known that on cold storage, aroma defects can appear faster in a high-fat fish than in a low-fat fish. This is clearly shown in an experiment in which salmon and cod were stored for 14 weeks at different temperatures and then boiled. While the aroma of the fish stored at —60 °C was perfect, the relatively low temperature of — 13°C had a negative effect on the aroma. The salmon had an intensive fatty/train oil odor and, in comparison, the low-fat cod had only a more intensively malty odor. The aroma defect of the fatty fish, which becomes very unpleasantly noticeable, is based on the peroxidation of polyunsaturated co-3 fatty acids, which results in a 13 fold increase in (Z)-3-hexenal (compare LII with LI in Table 13.10), an 8 fold increase in (Z)-4-heptenaI and a 9 fold increase in (Z,Z)-3,6-nonadienaI. In low-fat cod, these aldehydes increased at most by a factor of 3. 

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