Effects of antioxidative substances from seaweed on quality of refined liver oil of leafscale gulper shark, Centrophorus squamosus during an accelerated stability study

Abstract

Crude liver oil of leafscale gulper shark, Centrophorus squamosus was clarified by sequential degumming, decolorization and vacuum deodorization. The refined oil was added with ethyl acetate extract of seaweeds and various physiochemical parameters were evaluated in a time-reliant accelerated storage study. Significantly greater induction time was observed for the oil supplemented with Sargassum wightii and Sargassum ilicifolium (> 4.5 h) than other seaweed extracts and control oil (~1 h). Among different seaweeds, the ethylacetate extracts of S. wightii maintained the oxidation indices of the refined oil below the marginal limits after the study period. No significant reduction in C20–22 long chain fatty acids (1.19%) in the refined oil added with S. wightii was apparent, and was comparable with the synthetic antioxidants (1.07–1.08%). Spectroscopic fingerprint analysis of marker compounds responsible to cause rancidity signified the efficacy of S. wightii to arrest the development of undesirable oxidation products in the refined oil during storage. The antioxidant compounds, 15-(but-19-enyl)-hexahydro-13,16-dimethyl-11-oxo-1H-isochromen-8-yl benzoate (1) and 10-(but-13-en-12-yl)- 5-((furan-3-yl)propyl)-dihydrofuran-9(3H)-one (2) isolated from S. wightii appeared to play a major role to deter the oxidative degradation of refined oil thereby enhancing the storage stability.