COMPARISON BETWEEN METHODS USING LOW-TOXICITY SOLVENTS FOR THE EXTRACTION OF LIPIDS FROM HERRING (CLUPEA-HARENGUS)

Three alkane/alcohol/water-based lipid extraction systems were evaluat ed to determine which would be the best replacement for the frequently used chloroform/methanol/water system, nowadays known to be very toxi c. All the methods were applied to samples of minced herring (Clupea h arengus) differing in quality and composition. In addition to comparis ons of total lipid yield, the extracted lipids were compared with resp ect to content of triglycerides, phospholipids, free fatty acids, alph a-tocopherol, lipid hydroperoxides and conjugated dienes. The content of phospholipids was found to differ most between the lipids extracted by the four methods. Here, the chloroform/methanol/water system was t he most efficient, followed by heptane/ethanol/water/sodium dodecyl su lphate (SDS) and then iso-propanol/hexane. However, by decreasing the level of SDS, the efficiency of the heptane/ethanol/water/SDS system i n extracting phospholipids was increased to the same level as that of the chloroform/methanol/water system. This decrease in SDS also result ed in a higher recovery of free fatty acids. The lack of correlation b etween yields of phospholipids and yields of lipid oxidation products throughout this study was surprising because of the often-described su sceptibility of phospholipids to oxidation. (C) 1998 Elsevier Science Ltd. All rights reserved.