Identification and origin of the character‐impact compounds of raw oyster Crassostrea gigas

Abstract

The French consume large amounts of raw oysters. The study of the aroma of oyster Crassostrea gigas is of economic interest because it is a good method of checking the sensory quality. Aromas were extracted by vacuum steam distillation at 20°C using whole oyster flesh. This extract presented similar sensory characteristics to raw oyster. The odour-active compounds were characterised by gas chromatography coupled with olfactometry using a panel of 10 judges trained in seafood aroma recognition. Fifty-nine volatile compounds were identified in oyster aroma extract. Among these, 25 were responsible for the overall odour of raw oyster. Four compounds identified in oysters were characterised by fresh and marine odour: 3-(E)-hexen-1-ol, decanal, 2-undecanone and 3,6-(E,Z)-nonadien-1-ol. Some compounds were identified for the first time in oysters: 4-(Z)-heptenal (white boiled fish odour), which comes from n-3 polyunsaturated fatty acid oxidation, and 3-octanol (moss and sulphury odour), 2-nonanol (cucumber odour) and octanoic acid, which arise from n-6 polyunsaturated fatty acid oxidation.

Fatty acids, volatile compounds and colour changes in high-pressure-treated oysters (Crassostrea gigas)

“…Therefore, for some m/z ratios, several possible compounds were considered. Among the 69 volatile compounds detected by PTR-MS, 27 have previously been identified in oysters or oyster by-products (Josephson et al, 1985;Pennarun et al, 2002Pennarun et al, , 2003bPiveteau et al, 2000).…”

“…A tentative identification of volatile compounds of the headspace of oyster samples is shown in Table 3 (concentrations of individual compounds are expressed in parts per billion). Unequivocal identification of these compounds was not always possible, as some isomeric compounds have been reported to be present in oysters (Josephson et al, 1985;Pennarun et al, 2002Pennarun et al, , 2003bPiveteau et al, 2000) and, although minimal, fragmentation of ions does occur (Buhr et al, 2002). Therefore, for some m/z ratios, several possible compounds were considered.…”

“…Attribution of volatiles to the masses detected by PTR-MS in the samples was based on the molecular weight of compounds with a proton transferred (i.e., molecular weight + 1), and crossreferenced to studies of flavour in raw oysters (Piveteau et al, 2000;Pennarun et al, 2002Pennarun et al, , 2003b.…”

“…No studies reporting the effects of HP on the volatile flavour components and fatty acids of oysters have been reported, although profiles of fatty acids and volatiles of fresh oysters have been extensively studied Josephson, Lindsay, & Stuiber, 1985;Linehan, O'Connor, & Burnell, 1999;Piveteau et al, 2000;Pennarun, Prost, & Demaimay, 2002;Pennarun, Prost, Haure, & Demaimay, 2003a;Pennarun, Prost, Haure, & Demaimay, 2003b). Therefore, it is necessary to investigate possible physicochemical changes which may occur during or after such processing.…”

Volatile compounds of some popular Mediterranean seafood species

“…The volatile compounds of various fresh fish (indicatively, Kawai, 1996;Prell & Sawyer, 1988;Morita et al, 2003) and other raw seafood (Chung, 1999;Piveteau et al, 2000;Pennarun et al, 2002;Zhang et al, 2010) have been studied. Sporadic data occur in the literature regarding the volatiles of Mediterranean fish species, referring mainly to sardine (Triqui & Bouchriti, 2003;Prost et al, 2004), gilthead sea bream (Grigorakis et al, 2003;Alasalvar et al, 2005) and European sea bass (Leduc et al, 2012).…”