The Study
Silage for upcycling oil from saithe (Pollachius virens) viscera – Effect of raw material freshness on the oil quality
This study watched what happened to fish oil when they kept the fish guts for 1, 2, or 3 days before turning them into oil. It found that the longer they waited, the more the oil changed—but it didn’t force the change to happen, so we can’t say waiting definitely caused it.
Analysis score
Maximum 44 for a cross-sectional study.
Where the score came from
Scientists tested how storing fish guts before turning them into oil affects the healthy fats. Fresh guts made the best oil — more omega-3s and less spoilage. But if you wait even one day, the good fats start breaking down, and the oil gets worse.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 544 / 100
Quality score
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Yes — this means if you want omega-3 oil from fish waste, you must process it within hours of catch; waiting even one day reduces health benefits and increases spoilage risk.
- 2Oil from fresh guts had 30–36% omega-3s; after 1–3 days storage, omega-3s dropped significantly.
- 3Oil yield jumped 100% after 24 hours but fell after 48 hours.
- 4Antioxidants cut oxidation by 30–50%.
- 5FFA rose 60x after silaging, but NMR showed FFA disappeared because it turned into cholesteryl esters.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Heliyon
Year
2023
Authors
Line Skontorp Meidell, R. Slizyte, Revilija Mozuraityte, A. Carvajal, T. Rustad, I. Standal, Monika Kopczyk, E. Falch
Related Content
Claims (6)
Adding a specific blend of antioxidants to fish silage lowers measurable signs of oil spoilage in the extracted oil compared to silage without these additives.
Storing saithe viscera with liver at 4°C for 24 hours before silaging increases oil yield, but storing for 48 to 72 hours reduces oil yield because of emulsion formation and lipid trapping.
When saithe viscera oil is stored at 4°C over time, cholesteryl esters form and free fatty acids decrease, showing that free fatty acids are being used to make esters instead of breaking down through oxidation.
Oil made from fresh saithe viscera and liver contains more free fatty acids than oil from stored viscera, but fermenting the viscera increases free fatty acids more than 60 times, showing that chemical breakdown by acid is the main cause of this increase.
When saithe viscera are stored with liver at 4°C for 1 to 3 days before processing into oil, the resulting oil contains lower levels of docosahexaenoic acid (DHA) and total omega-3 fatty acids than oil made from fresh viscera. This reduction is associated with chemical oxidation of DHA, evidenced by increased hexanal and decreased omega-3 signals in NMR analysis.
Eating oxidized omega-3 fatty acids causes more harm to health than it provides benefit.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.