Nofima reports

Bleaching and winterization of crude oil from mackerel residue

Haugen, John-Erik; Thoresen, Lars; Meisland, Ane; Oterhals, Åge

Publication details

Publisher: Nofima AS

Issue: 37/2019

Number of pages: 37

International Standard Numbers:
Printed: 978-82-8296-642-9

Open Access: none


Seven commercial bleaching soil from three suppliers have been screened for efficacy during bleaching of crude oil from mackerel residue with regard to color reduction, oxidation level (PV, AV) and volatile secondary oxidation products. 2% bleaching soil was used at 70 ° C under vacuum for 30 minutes. Largest color reduction (79%) and reduction in peroxide number (69%) were achieved with TONSIL Supreme 114F, while CelaClear 105SF produced the most reduction in anisidine number (26%), secondary oxidation products, and a color reduction of only 50%. Based on an overall assessment of the effect on bleaching and oxidation, TONSIL Supreme 114F was selected for further testing in a 3-factor optimization experiment based on the variables amount of bleaching soil (0.5-5%), activated charcoal (0.1-1.0%) and bleaching time (15-120 minutes). The amount of bleaching soil had the greatest effect on the variables studied, but the effect leveled off at doses above 3.5-4%. The addition of activated charcoal gave an independent effect on color without interaction with bleaching soil, but the effect was much lower relative to the amount of adsorbent. The marginal effect of an increase in bleaching time beyond the lowest level used in the optimization experiment was demonstrated (15 min).
The crude oil and olein fractions were analyzed by differential scanning calorimetry (DSC). DSC shows that the mackerel crude oil consists of 100% liquid fat at 20 ° C. Preliminary studies have been conducted to test alternative conditions for cold clearing (winterization) of mackerel oil based on dry fractionation. Dry fractionation at 0 ° C had a yield of 40% olein but did not pass the AOCS Cold test. But dry fractionation at 0 ° C gave an oil that remained liquid and clear at 4 ° C (refrigerator temperature). The yield of PUFA in the olein fraction was 31%. A relationship was documented between the proportion of solid fat in the crude oil at different temperatures measured with DSC and the yield of olein by dry fractionation at the respective temperatures. Optimization of conditions and yield has not been possible within the scope of this project.