Free Fatty Acids in Commercial Krill Oils: Concentrations, Compositions, and Implications for Oxidative Stability

Abstract

The concentrations and pro‐oxidative effects of free fatty acids in commercial krill oil are not well defined. We now report that krill oil free fatty acids account for 2–13% of total lipids in commercial krill oil (n = 8) that these compounds are enriched in eicosapentaenoic acid (+7.1%) and docosahexaenoic acid (+6.3%) relative to whole oils; and that this composition make them highly pro‐oxidizing in marine triacylglycerol oils, but not in krill oil, which derives oxidative stability from both its phospholipids, and neutral lipids (the latter because of astaxanthin). Specific fatty acid esterification patterns showed that krill oil free fatty acids predominantly (88–93%) originated from phospholipids, mainly from the sn‐2 position, which was eight‐fold more hydrolyzed than the sn‐1 position. Lipolysis was not ongoing in stored oils. Adding small amounts of krill oil (1–5%) to marine triacylglycerol oils significantly increased their oxidative stability and also their resistance to free fatty acid‐mediated pro‐oxidative effects.

Shrimp Oil Extracted from Shrimp Processing By-Product Is a Rich Source of Omega-3 Fatty Acids and Astaxanthin-Esters, and Reveals Potential Anti-Adipogenic Effects in 3T3-L1 Adipocytes

“…Generally, high free fatty acids cause hydrolytic rancidity and affect the quality of oils, thus, the amount of free fatty acids is considered as a quality parameter for oils [41]. The acceptable range of free fatty acids in commercially available krill oils is suggested to be up to 2 wt% [42], while the extracted SO contained much lower amounts of free fatty acids confirming superior quality.…”

Raman and Infrared Spectroscopic Data Fusion Strategies for Rapid, Multicomponent Quantitation of Krill Oil Compositions

“…FAME profiles were measured as described previously. 5 Briefly, samples (10 mg) were weighed into screw-top reaction tubes (10 mL), adding acetyl chloride (2 mL, 2% v/v in dry methanol/toluene 10:1), and heating (90 °C for 60 min). After cooling, FAME were recovered from the reaction mixture by adding hexane (3.8 mL), mixing well, and collecting the upper hexane/toluene layer for analysis by gas chromatography mass spectrometry (GC-MS).…”

“…2,6,7 Unlike fish oil, krill oil also contains astaxanthin, a naturally occurring ketocarotenoid with potent antioxidant activity, which gives these oils a distinctive red color and protects their PUFA-containing molecules from oxidation. 5 For decades fatty acid concentrations (including EPA and DHA) have been routinely measured by gas chromatography− mass spectrometry (GC-MS). 8−9 This method can simultaneously quantitate dozens of individual fatty acids accurately and precisely, but oils must first be derivitised to more volatile formats (e.g., methyl esters) and separated chromatographically over time.…”

“…Raman spectral models for predicting EPA+DHA and astaxanthin were also produced from spectra acquired directly through krill oil capsules, an approach previously applied to encapsulated fish oils. 5 Reference data for EPA+DHA PLSR models were determined by GC-MS. Reference data for astaxanthin PLSR models were determined by UV spectrophotometry.…”

Lipid yield from the diatom Porosira glacialis is determined by solvent choice and number of extractions, independent of cell disruption

“…Studies have found that high levels of FFA reduces the oxidative stability of vegetable and marine oils by acting as a prooxidant 40,41 . The high levels of FFA may have resulted in a reduction in the observed amount of PUFA in our samples, as the rate of oxidation is positively correlated with the degree of unsaturation.…”