Comparison of Two Microalgal Diets. 1. Influence on the Biochemical and Fatty Acid Compositions of Raw Oysters (Crassostrea gigas)

Abstract

Oyster farming in France is a traditional activity. Each year, 149 000 tons of oysters are fattened before being sold. More and more oyster farmers supplement the diet of oysters by microalgae to optimize the fattening process and to improve both the growth and flesh quality of oysters. In the present study, oysters were supplemented by two microalgae: Skeletonema costatum and Tahitian isochrysis clone. The ash, protein, carbohydrate (including glycogen), and lipid contents were analyzed. The growth of oysters was improved when they were fattened with microalgae, leading to an increase in the condition index. The chemical composition of oysters was influenced by the chemical composition of the microalgae, especially the level of glycogen, which was significantly increased for oysters supplemented by microalgae. The fatty acid profile of oysters fattened by microalgae was positively correlated with the fatty acid profiles of S. costatum and T. isochrysis. These results show the effectiveness of supplementation by microalgae on the growth and on the biochemical composition (glycogen and fatty acids especially) of oysters.

Effects of Dietary Oyster Extract on Lipid Metabolism, Blood Pressure, and Blood Glucose in SD Rats, Hypertensive Rats, and Diabetic Rats

“…A large portion of sugar contained in oyster meat is glycogen, 40,41) which is structurally and functionally similar to starch. Therefore, it is not thought that glycogen has different effects on lipid metabolism, blood pressure, and blood glucose than starch.…”

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

“…The texture of oysters supplemented by T. isochrysis was firmer than that of oysters supplemented by S. costatum, whose texture is melting. For the judges, this mark was due to the milky character induced by the glycogen and lipid, which was significantly higher in oysters supplemented by S. costatum than in other oysters (1).…”

“…Josephson (12) has shown the importance of some PUFAs as aroma precursors and their biosynthetic pathway. Our study aimed to enrich the fatty acid content of the diet of oysters, especially in aroma precursors, by means of two microalgae, Skeletonema costatum and Tahitian isochrysis clone (1). Knowledge of the biochemical composition of oysters could lead to the identification of the origin of some volatile compounds.…”

Extended Validation of a Simplified Extraction and Gravimetric Determination of Total Fat to Selected Foods

“…Presumably the explanation is extraction of more polar lipids not recovered by Soxhlet ether extraction or as fatty acids. Pennarun et al . (2003) have reported a total lipid content of 8 to 11 g/100 g dry weight for oysters, using chloroform/methanol extraction (Folch method, Folch et al .…”