Cooking and pressing is an effective and eco‐friendly technique for obtaining high quality oil from Sardinella longiceps

Abstract

The conventional Bligh and Dyer method of extracting oil from the edible tissues of Sardinella longiceps was compared with different eco‐friendly methodologies using 40% ethanol, 95% ethanol, distilled water, and cooking followed by pressing, as well as cooking followed by the Bligh and Dyer method. Among the different methods studied, cooking followed by pressing showed a beneficial effect on the quality of the oil as evidenced by reduced saponification (209.8 mg KOH/g), peroxide (11.88 meqO­2/kg), para‐anisidine (16.2), total oxidation (39.96), and TBARS (6.18 MDAEQ/kg) values. A comparable lipid yield (8.3%) with that of the Bligh and Dyer method was attained through the cooking and pressing method. The greater induction time (0.13 h) indicated better oxidative stability of cooked and pressed oil as compared to the oil obtained using other methods. The fish oil obtained by cooking followed by pressing has been demonstrated to yield comparable amounts of eicosapentaenoic acid, docosahexaenoic acid, and total polyunsaturated fatty acid contents when compared to the Bligh and Dyer method. These results demonstrated the effectiveness of the cooking and pressing technique for obtaining the best quality oil from Sardinella longiceps. The oil obtained by the cooking and pressing mode was characterized by FTIR and NMR experiments.Practical applications: The advantages of the method involving cooking followed by pressing as compared to the traditional Bligh and Dyer method were the absence of toxic solvents along with reduced cost and labor requirements. In addition, no chemical wastes were generated in this technique. The cooking followed by pressing method has been demonstrated to improve the nutritive value and oxidative stability of the crude fish oil as compared to the new eco‐friendly methods studied and the traditional method. The utilities of FTIR and NMR analyses as new analytical tools for analyzing the chemistry of fish oil have been demonstrated in the present study. This study is significant for the extraction of greater quality marine fish oil for use in pharmaceutical industries.Oil obtained by cooking followed by pressing (E6) of Sardinella longiceps showed greater induction time (0.13 h) compared to the conventional Bligh and Dyer method (E1, 0.05 h). No significant differences in EPA, DHA, total n‐3 PUFA, or n‐3/n‐6 PUFA contents were observed between E6 and E1. The signature peaks of different fatty acids of E6 were identified from the 1H‐NMR spectral features. These results demonstrated the effectiveness of cooking and pressing technique for obtaining the best quality oil from S. longiceps.