Comparison of Two Microalgal Diets. 2. Influence on Odorant Composition and Organoleptic Qualities of Raw Oysters (Crassostrea gigas)

Abstract

Oyster farming is of real economic interest in France. Oyster farmers attach more and more importance to improving the growth and the quality of their oysters. Some fatty acids known to be aroma precursors originate from microalgae such as Skeletonema costatum and Tahitian isochrysis clone. These microalgae were used to fatten oysters in order to observe their role in the development of oysters' aroma. This study shows that the profile of fatty acids of oysters is influenced by the contribution of fatty acids from the two microalgae (as reported in the first paper in this series: Pennarun, A.-L.; Prost, C.; Haure, J.; Demaimay, M. Comparison of Two Microalgal Diets. 1. Influence on the Biochemical and Fatty Acid Compositions of Raw Oysters (Crassostrea gigas). J. Agric. Food Chem. 2003, 51, 2006-2010 (in this issue)]. As a consequence, a microalgal diet causes changes in oysters' aroma composition. Aroma concentration depends on the content of fatty acids that are aroma precursors in oysters. Some aromas are characteristic of the diet of S. costatum, such as 6-methyl-5-hepten-2-one (ether odor), and others are characteristic of T. isochrysis, such as 3-nonyne (cucumber, marine odor), 6-(E)-nonen-1-ol (green and fresh odor), and 4-ethylbenzaldehyde (aniseed odor). Moreover, the organoleptic qualities (odor, taste, and texture) of oysters are modified by the diet of microalgae.

Mise en évidence d'un espace sensoriel et caractérisation des marqueurs relatifs à l'arôme des vins issus du cépage Chardonnay.

“…D'autres critères de sélection, tout aussi déterminants, ont été évoqués dans la littérature : il s'agit de la motivation Bernet et al, 2002) et la disponibilité des sujets (Linssen et al, 1993 ;. Plusieurs auteurs ont procédé à un entraînement des sujets orienté vers la description et la reconnaissance d'odeurs à partir de solutions de standards (Linssen et al, 1993 ;Piveteau, 2000 ;Rouseff et al, 2001 ;Fu et al, 2002 ;Lablanquie et al, 2002 ;Pennarun, 2003 (Linssen et al, 1993 ;Callement et al, 2001 ;Rouseff et al, 2001) ont réalisé systématiquement des séances de familiarisation des sujets avec le dispositif olfactométrique avant de passer aux véritables séances d'analyse. La méthode utilisée est inspirée de celle proposée par Moio et al (1995).…”

“…Un compromis doit être trouvé. En moyenne, le temps d'une analyse olfactométrique se situe entre 30 et 45 minutes (Miranda-Lopez et al, 1992a ;Linssen et al, 1993 ;Rouseff et al, 2001 ;Conner et al, 2001 ;Le Fur et al, 2003 ;Pennarun et al, 2003). Benn et Peppard, 1996 ont réalisé des analyses en GC-O d'une durée de 65 minutes sans interruption.…”

“…Benn et Peppard, 1996 ont réalisé des analyses en GC-O d'une durée de 65 minutes sans interruption. Plusieurs auteurs, pour éviter l'effet de la fatigue sur la performance des sujets, divisent le temps d'analyse en deux parties (Pollien et al, 1997 ;Piveteau et al, 2000 ;Le Guen et al, 2000a ;Bernet et al, 2002 ;Engel et al, 2002 ;Pennarun et al, 2003) , voire même en trois parties (Pihlsgärd et al, 2001). …”

Identifying volatile compounds associated with sensory and fruit attributes in diploid Actinidia chinensis (kiwifruit) using multivariate analysis

“…This indicated that C4_PC2 identified 'Hort16A'-like odour volatiles'. Turin (1996) found that ethylbenzaldehyde had a typical bitter almond Rychlik et al 1998, b Fazzalari 1978Euphytica (2011 odour and Pennarun et al (2003) found that 4-ethylbenzaldehyde was characterized by a minty and aniseed odour. Propanol is an alcohol with relatively weak odour and its concentration (Table 1) was below its odour threshold (Rychlik et al 1998 Labbe et al 2007;Miyazawa et al 2008).…”

Quality perception, purchase intention, and the impact of information on the evaluation of refined Pacific cupped oysters (Crassostrea gigas) by Dutch consumers

“…In oyster refinement, market‐sized Pacific cupped oysters ( Crassostrea gigas , Thunberg) are kept in basins and fed with algae to increase the oyster tissue weight and to change the sensorial properties of the oysters . Differences in odor, taste, and appearance between refined and non‐refined oysters have been shown when trained panelists were used for the evaluation . Refined Pacific cupped oysters have been characterized by a stronger grass odor, a sweeter, less salty and less bitter flavor, in comparison to non‐refined oysters .…”