Soxhlet-Randall method modification for rapid lipid extraction on example of rainbow trout

The study examines lipid extraction using a modification of the Soxhlet-Randall method. The essence of the modification is based on the improvement of such key performance indicators of the method as the extraction degree and its time, which also were boosted by avoiding fat hydrolysis stage using a binary solvent mixture - chloroform and ethanol in different ratios (1:1, 1:2, 1:4). As an example, rainbow trout (Oncorhynchus mykiss) bred on a fish farm was chosen for practical study, which reduced the likelihood of contaminants in the fish and therefore ensured the maximum purity of the experiment. With the help of an automatic extractor, a modification of the Soxhlet-Randall method was carried out for qualitative and quantitative characteristics. The optimal intervals for the three stages of the extraction of fats - immersion, extraction and washing. After the first extraction, the thimble with the sample rises up and is washed with a condensable mixture of solvents, i.e. the solvents are reused, which is an additional advantage of the method. Studies have been carried out on the subject of residual protein content by the Kjeldahl method, which did not exceed 3 %, while the amino-acid profile of the protein residue was not considered. The dry residue from the thimble of the automatic extractor was additionally tested by the Soxhlet arbitration method used in assessing the quality of fat in the food industry and showed 95 % completeness of fat extraction from trout with a rainbow modified method. The modification of the Soxhlet method has good prospects for use in the food industry to assess the quality of fish products, but it requires additional research using the example of various fish species to establish correction factors. © 2019 Latvia University of Agriculture. All rights reserved.