Application of soya phosphatidylcholine in tuna orbital oil enrichment emulsions for Artemia

Abstract

Oil-seawater emulsions of 12%, 8%, 4% and 2% soya phosphatidylcholine (PC) in tuna orbital oil (TOO) (w:w) were tested with respect to their suitability as Artemia enrichment media. Levels of essential fatty acids (EFA) accumulated by feeding Artemia nauplii were measured after enrichment periods of 0, 14, 18 and 20 h, and the stability of polyunsaturated fatty acids levels in the emulsions were also monitored throughout the enrichment process. Artemia enrichment efficiency in terms of %DHA (docosahexaenoic acid, 22:6w-3) and DHA:EPA (eicosapentaenoic acid, 20:5w-3) ratios were similar for all four types of emulsions (10-12% and 1.7-1.8, respectively). However, 8% and 12% soya PC/TOO emulsions yielded nauplii with slightly higher mean lipid contents than the other two treatments (235-243 and 217-229 mg lipid g-1 dry body weight, respectively). Stability of polyunsaturated fatty acids (PUFA) levels within the emulsions in seawater, and of DHA and EPA levels in particular, correlated with soya PC concentration. In 12% soya PC/TOO emulsions, PUFA levels remained high after 20 h enrichment whilst those in the 2% and 4% soya PC emulsions showed a marked reduction by 18 h enrichment time. It is suggested that soya PC may protect PUFA levels in the emulsions in a dose-dependent manner, probably by acting as an antioxidant. No significant improvement in Artemia total lipid content or DHA:EPA ratio occurred when enrichment was continued for longer than 18 h. When using this enrichment system, it is preferable, therefore, to employ the 12% soya PC/TOO emulsion and to terminate the enrichment process at 18 h, thus preventing the risk of PUFA levels deteriorating in the emulsion.