Publisher : Nofima AS
International Standard Numbers
Printed : 978-82-8296-641-2
Publication type : Nofima’s reports
Series : Nofima rapportserie 40/2018
Year : 2018
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Volatile compounds in crude oil from mackerel residue have been analyzed to detect components that can contribute to odor and taste in the crude oil. Most of the detected substances, with the exception of some of the hydrocarbons, are odoriferous, have different odor thresholds, and which together will contribute to the smell and taste of the crude oil. However, due to lack of data on empirical oil phase odor threshold data of many of the compounds detected, it has not been possible to quantify odor activity values for all the compounds to arrive at the most important aroma components of the oil. Based on the measured concentrations, fat solubility of the substances, existing odor thresholds and literature data on the corresponding volatile compounds detected in marine crude oils, we can conclude that it will be the aldehydes and acids that will contribute most to the smell and taste of the crude oil. Of the aldehydes, 2-propenal and butanal had the highest odor activity values, followed by hexanal, tr, 2-pentenal, octanal, 2-butenal and tr, cis-2,4-heptadienal. Using headspace-GC/MS, it was found that most hydrocarbons (41.3%) were found, most of which were monounsaturated hydrocarbons, alcohols (17.2%), acids (15.3%), aldehydes (9.3%), sulphides/thiols (8%), ketones (2.8%), furans (1.8%), aromatics (2.1%), and 1.9% other compounds where 3 compounds were not identifiable. 18 components with the highest concentration accounted for as much as 75% of the total concentration of volatiles measured. The highest amount was found for 2,4,6,10-pentadecane, accounting for 33% of the total volatiles. Next comes dimethyl disulphide, 2,4-dimethyl-1,3-pentadiene, 1-butanol, 4-methyl-pentanoic acid and cis, cis-3,5-octadiene. Most of the hydrocarbons, aldehydes, ketones, acids (C2-C5), furans and some of the alcohols were secondary oxidation products from the peroxidation of the polyunsaturated omega-3 and omega-6 fatty acids contained in the oil. In addition, some of the volatile acids may also result from bacterial growth in the feedstock, which may also indicate the sulfides, which are formed from both bacterial degradation of sulfur-containing amino acids in the raw material or thermal chemical reactions during raw material processing. Several of the detected esters may also be bacterial secondary metabolites. Typical markers for lipid oxidation in marine oils were found, such as propanal, 1-penten-3-ol, 1-penten-3-one, tr tr-heptadienal and 2-ethylfuran.