Detection and Quantification of Adulteration in Krill Oil with Raman and Infrared Spectroscopic Methods

Raman and infrared spectroscopy, used as individual and low-level fused datasets, were evaluated to identify and quantify the presence of adulterants (palm oil, PO; ω-3 concentrates in ethyl ester, O3C and fish oil, FO) in krill oil. These datasets were qualitatively analysed with principal component analysis (PCA) and classified as adulterated or unadulterated using support vector machines (SVM). Using partial least squares regression (PLSR), it was possible to identify and quantify the adulterant present in the KO mixture. Raman spectroscopy performed better (r² = 0.98; RMSEP = 2.3%) than IR spectroscopy (r² = 0.91; RMSEP = 4.2%) for quantification of O3C in KO. A data fusion approach further improved the analysis with model performance for quantification of PO (r² = 0.98; RMSEP = 2.7%) and FO (r² = 0.76; RMSEP = 9.1%). This study demonstrates the potential use of Raman and IR spectroscopy to quantify adulterants present in KO.

Positional Distribution of Fatty Acids in Processed Chinook Salmon Roe Lipids Determined by 13C Magnetic Resonance Spectroscopy (NMR)

Recently, there has been great interest in the lipidomic of marine lipids and their potential health benefits. Processing of seafood products can potentially modify the characteristics and composition of lipids. The present study investigated the effect of processing methods (salting and fermentation) on the positional distribution of fatty acids of Chinook salmon roe using ¹³C nuclear magnetic resonance spectroscopy (NMR). The NMR analysis provided information on the carbonyl atom, double bond/olefinic, glycerol backbone, aliphatic group, and chain ending methyl group regions. The obtained data showed that docosahexaenoic acid (DHA) is the main fatty acid esterified at the sn-2 position of the triacylglycerides (TAGs), while other fatty acids, such as eicosapentaenoic acid (EPA) and stearidonic acid (SDA), were randomly distributed or preferentially esterified at the sn-1 and sn-3 positions. Fermentation of salmon roe was found to enrich the level of DHA at the sn-2 position of the TAG. The processing of roe by both salt drying and fermentation did not appear to affect the proportion of EPA at the sn-2 position. This present study demonstrated that fish roe processing can enhance the proportion of DHA at the sn-2 position and potentially improve its bioavailability.

Multi-analytical characterization of perigonadal fat in bluefin tuna: from waste to marine lipid source

BACKGROUND

Marine lipids are widely recognized as supplements beneficial to health in the human diet. Bluefin tuna, as most migrating fish, may have high and variable marine lipid contents in their tissues. The viscera of the specimens caught in the Mediterranean Sea are generally discarded. Only ovaries are (locally) used for artisanal seafood preparations.

RESULTS

A multi-analytical approach carried out using infrared (IR), nuclear magnetic resonance (NMR) and mass spectrometry (MS) revealed that the perigonadal fats usually discarded during bluefin tuna evisceration are characterized by a high relative abundance of polyunsaturated triacylglycerols (76.2% of dry mass), with docosahexaenoic (DHA, 22:6) and eicosapentaenoic (EPA, 20:5) acids preferentially located at the sn-2 position of the glycerol backbone. By contrast, in fats from the ovarian tissues, no wax esters and phospholipids were evidenced. Cholesterol was found in very low amounts (84 mg/100 g ovarian tissue). In vitro assays showed that this fatty material is rapidly hydrolyzed by lipase and is prone to auto-oxidation, especially if compared to the stable wax esters contained in the ovary.

CONCLUSION

The results show that the perigonadal fats of bluefin tuna, traditionally wasted after evisceration, may be an interesting source for the preparation of marine lipid supplements that do not require complex fractionation processes. © 2019 Society of Chemical Industry.

mRNA abundance of genes involved in mammary lipogenesis during fish oil- or trans-10,cis-12 CLA-induced milk fat depression in dairy ewes

Milk fat depression (MFD) caused by trans-10,cis-12 18:2 is known to be mediated in cows and ewes by downregulation of mammary lipogenic genes. However, transcriptional mechanisms underlying marine lipid-induced MFD have not been well defined yet and the few available studies in ovine are not consistent. This trial was conducted to directly compare changes in animal performance, milk fatty acid composition, and particularly mammary mRNA abundance of candidate lipogenic genes and transcription factors in response to the inclusion of fish oil or trans-10,cis-12 18:2 in the dairy sheep diet. To meet this objective, 12 lactating Assaf ewes (on average, 64 days in milk, producing 1.72 kg of milk/d with 5.17% of fat) were divided into 3 groups and offered a total mixed ration without supplementation (control) or supplemented with 2.4% dry matter of fish oil (FO treatment) or 1% dry matter of a commercial product rich in trans-10,cis-12 18:2 (CLA treatment) for 39 d. Measurements and samplings were conducted before starting the treatments and at the end of the trial. Milk samples were used for RNA extraction from somatic cells. Feed intake was not affected by lipid supplements, and as designed, reductions in milk fat concentration (-31%) were similar in the 2 treatments, although the unpredicted increase in milk production with FO counteracted the anticipated reduction in milk fat yield. Nevertheless, this did not preclude the detection of FO-induced decreases in the mRNA abundance of candidate lipogenic genes [e.g., acyl-CoA synthetase short-chain family member 2 (ACSS2), fatty acid synthase (FASN), and lipin 1 (LPIN1)], thus supporting the hypothesis that transcriptional regulation would be a relevant component of this type of MFD in sheep. Expected CLA-induced downregulation of some genes, such as FASN or sterol regulatory element binding transcription factor 1 (SREBF1), could not be detected in our samples, which might be related, at least in part, to high inter-individual variation and relatively advanced lactation stage (on average 102-103 d in milk on d 38 and 39). Overall, direct comparison of the effects of dietary FO and CLA on transcript abundance of candidate lipogenic genes and transcription factors suggest that there might be relevant differences in the transcriptional control mechanisms underlying the MFD induced by each kind of supplement (i.e., fish oil or CLA).