Oxidation Rates of Triacylglycerol and Ethyl Ester Fish Oils

A comprehensive two-scale model for predicting the oxidizability of fatty acid methyl ester mixtures

The intricate mechanisms of oil thermooxidation and their accurate prediction have long been hampered by the combinatory nature of propagation and termination reactions involving randomly generated radicals. To unravel this complexity, we suggest a two-scale mechanistic description that connects the chemical functions (scale 1) with the molecular carriers of these functions (scale 2). Our method underscores the importance of accounting for cross-reactions between radicals in order to fully comprehend the reactivities in blends. We rigorously tested and validated the proposed two-scale scheme on binary and ternary mixtures of fatty acid methyl esters (FAMEs), yielding three key insights: (1) The abstraction of labile protons hinges on the carrier, defying the conventional focus on hydroperoxyl radical types. (2) Termination reactions between radicals adhere to the geometric mean law, exhibiting symmetric collision ratios. (3) The decomposition of hydroperoxides emerges as a monomolecular process above 80 °C, challenging the established combinatorial paradigm. Applicable across a wide temperature range (80 °C to 200 °C), our findings unlock the production of blends with controlled thermooxidation stability, optimizing the use of vegetable oils across applications: food science, biofuels, and lubricants.

Lipid Structure Influences the Digestion and Oxidation Behavior of Docosahexaenoic and Eicosapentaenoic Acids in the Simulated Digestion System

Omega-3 fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are essential for human health but prone to oxidation. While esterification location is known to influence the stability of omega-3 in triacylglycerols (TAGs) in oxidation trials, their oxidative behavior in the gastrointestinal tract is unknown. Synthesized ABA- and AAB-type TAGs containing DHA and EPA were submitted to static in vitro digestion for the first time. Tridocosahexaenoin and DHA as ethyl esters were similarly digested. Digesta were analyzed by gas chromatography, liquid chromatography-mass spectrometry, and nuclear magnetic resonance spectroscopy. Besides the formation of di- and monoacylglycerols, degradation of hydroperoxides was detected in ABA- and AAB-type TAGs, whereas oxygenated species increased in tridocosahexaenoin. Ethyl esters were mainly unaffected. EPA was expectedly less susceptible to oxidation prior to and during the digestion process, particularly in sn-2. These results are relevant for the production of tailored omega-3 structures to be used as supplements or ingredients.

Quantitative analysis of fatty acids and vitamin E and total lipid profiling of dietary supplements from the German market

Certain polyunsaturated fatty acids with n-3 double bonds are essential nutrients for the human body and are part of the bilayer of cell membranes or precursors of tissue hormones. The most abundant dietary n-3 fatty acids in human nutrition are α-linolenic, eicosapentaenoic, and docosahexaenoic acid and can be taken up through dietary sources such as vegetable oils or fish or, alternatively, dietary supplements with high levels of n-3 fatty acids. In previous studies, considerable variation of lipid patterns and quantities of n-3 fatty acids were observed. In this study, 33 dietary supplements from the German market, based on fish-, krill-, microalgae, and plant oil, have been analyzed. Lipid profiling (LC–MS) revealed triacylglycerols as the dominant lipid species in most samples. However, krill oil was rich in phospholipids and samples containing fatty acid concentrates featured abundant fatty acid ethyl esters and diacylglycerols. Furthermore, total lipid profiles showed considerable variance depending on the lipid sources (e.g., fish or plant oil), which was also apparent in fatty acid analysis. The contents of n-3 fatty acids ranged between 150 and 570 mg/g capsule content (GC–MS) and vitamin E (α-tocopherol and tocopheryl acetate) were found in quantities ranging from 1.2 to 86.1 mg/g capsule content (HPLC–UV/Vis). While our analyses indicated a good agreement between labeled and present quantities of total n-3 fatty acids and vitamin E for the majority of samples, significant differences in agreement between individual fatty acids were observed, as well as frequent mismatches between declared and present vitamin E derivatives.

The Biorefinery of the Marine Microalga Crypthecodinium cohnii as a Strategy to Valorize Microalgal Oil Fractions

Chrypthecodinium cohnii lipids have been almost exclusively used as a source of Docosahexaenoic acid (DHA). Such an approach wastes the remaining microalgal lipid fraction. The present work presents a novel process to produce C. cohnii biomass, using low-cost industrial by-products (raw glycerol and corn steep liquor), in a 7L-bioreactor, under fed-batch regime. At the end of the fermentation, the biomass concentration reached 9.2 g/L and the lipid content and lipid average productivity attained 28.0% (w/w dry cell weight) and 13.6 mg/L h, respectively. Afterwards the microalgal biomass underwent a saponification reaction to produce fatty acid (FA) soaps, which were further converted into FA ethyl ester (FA EE). C. cohnii FA EE mixture was then fractionated, using the urea complexation method at different temperatures, in order to obtain a polyunsaturated fatty acid ethyl ester (PUFA EE) rich fraction, that could be used for food/pharmaceutical/cosmetic purposes, and a saturated fatty acid ethyl ester (SAT EE) rich fraction, which could be used as biodiesel. The temperature that promoted the best separation between PUFA and SAT EE, was −18 °C, resulting in a liquid fraction with 91.6% (w/w) DHA, and a solid phase with 88.2% of SAT and monounsaturated fatty acid ethyl ester (MONOUNSAT), which could be used for biodiesel purposes after a hydrogenation step.

New insights into the kinetic and thermodynamic evaluations of lipid peroxidation

Simultaneous evaluations over the whole practical range of peroxidation, including the initiation and propagation phases, provide more informative and reliable data than single-parameter analyses being mostly employed only over the course of the initiation phase. Besides an overview on the dominant mechanisms governing the initiation and propagation phases, this article highlights a number of unifying parameters that represent inclusively the two phases. Then, the reliable method to calculate induction period and critical reverse micelle concentration of lipid hydroperoxides as the two interstitial parameters when transitioning from the initiation to the propagation phase is reviewed. Next, a reconsidered form of the conventional methodology on the kinetics of chain-breaking antioxidants is presented. After that, the Arrhenius kinetic and thermodynamic Eyring-Polanyi parameters calculated from the initiation, composite, and decomposition rate constants are compared in order to assess oxidative stabilities. Finally, shelf-life predictions based on a number of proposed end-points of peroxidation are addressed.

Critical kinetic parameters and rate constants representing lipid peroxidation as affected by temperature

This study aimed to comparatively investigate the temperature effect on the kinetic parameters and rate constants representing lipid hydroperoxides (LOOH) formation and decomposition during initiation and propagation peroxidations. The initiation phase was characterized by induction period IP, overall initiation rate constant k_IP, initiation oxidizability O_i, and the critical reverse micelle concentration of LOOH, CMC_L. The propagation phase was characterized by its duration t_p, the maximum rate of LOOH accumulation R_max, maximum LOOH concentration [LOOH]_max, propagation oxidizability R_n, composite rate constant k_c, and LOOH decomposition rate constant k_d. O_i and R_n indicated relatively high dependencies on temperature, respectively. Among the rate constants, k_d better highlighted oxidizabilities as affected by temperature. The oxidizabilities had good correspondences with the Arrhenius kinetic (A and E_a) and Eyring thermodynamic (ΔS⁺⁺ and ΔH⁺⁺) parameters. The most endergonic reactions (ΔG⁺⁺>0) were LOOH decompositions, followed by LOOH formations during the propagation and initiation phases, respectively.

EPA/DHA Concentrate by Urea Complexation Decreases Hyperinsulinemia and Increases Plin5 in the Liver of Mice Fed a High-Fat Diet

Dietary intake of eicosapentaenoic/docosahexaenoic acid (EPA/DHA) reduces insulin resistance and hepatic manifestations through the regulation of metabolism in the liver. Obese mice present insulin resistance and lipid accumulation in intracellular lipid droplets (LDs). LD-associated proteins perilipin (Plin) have an essential role in both adipogenesis and lipolysis; Plin5 regulates lipolysis and thus contributes to fat oxidation. The purpose of this study was to compare the effects of deodorized refined salmon oil (DSO) and its polyunsaturated fatty acids concentrate (CPUFA) containing EPA and DHA, obtained by complexing with urea, on obesity-induced metabolic alteration. CPUFA maximum content was determined using the Box-Behnken experimental design based on Surface Response Methodology. The optimized CPUFA was administered to high-fat diet (HFD)-fed mice (200 mg/kg/day of EPA + DHA) for 8 weeks. No significant differences (p > 0.05) in cholesterol, glycemia, LDs or transaminase content were found. Fasting insulin and hepatic Plin5 protein level increased in the group supplemented with the EPA + DHA optimized product (38.35 g/100 g total fatty acids) compared to obese mice without fish oil supplementation. The results suggest that processing salmon oil by urea concentration can generate an EPA+DHA dose useful to prevent the increase of fasting insulin and the decrease of Plin5 in the liver of insulin-resistant mice.

Changes in markers of lipid oxidation and thermal treatment in feed-grade fats and oils

BACKGROUND

Oxidized feed lipids have been shown to have detrimental effects on food animal growth and metabolism. The present study aimed to measure classes of lipid oxidation products (LOP) in feed-grade oils at temperatures representing production and storage conditions.

RESULTS

There were significant oil type × time interactions in the accumulation of primary and secondary LOP. At 22.5 °C, peroxide value (PV), a marker for the primary phase of lipid oxidation, increased most in fish oil (FO), followed by tallow (TL), soybean oil (SO), linseed oil (LO) and modified algae oil (MAO), whereas palm oil (PO) showed no appreciable increase in PV. Secondary LOP, such as p-anisidine value, hexanal, 2,4,-decadienal, polymerized triacylglycerols and total polar compounds, increased only in FO. At 45 °C, FO and SO produced both primary and secondary LOP, whereas MAO, PO and TL had slower rates of PV increase and no secondary LOP. At 90 °C and 180 °C, all oils except for FO accumulated both primary and secondary LOP.

CONCLUSIONS

Higher polyunsaturated fatty acid:saturated fatty acid oils and higher temperatures produced greater quantities of primary and secondary LOP. However, unrefined TL was more prone to oxidation at 22.5 °C than predicted, whereas LO was more stable than predicted, indicating that pro-oxidant and antioxidant compounds can markedly influence the rate of oxidation. Measuring both primary and secondary LOP will provide better information about the oxidative status of feed oils and provide better information about which classes of LOP are responsible for detrimental health effects in animals. Published 2020. This article is a U.S. Government work and is in the public domain in the USA.

Separation of saturated fatty acids from docosahexaenoic acid-rich algal oil by enzymatic ethanolysis in tandem with molecular distillation

Algal oil, rich in docosahexaenoic acid (DHA) and an environmentally sustainable source of ω-3 fatty acids, is receiving increasing attention. In the present study, a novel approach combining ethanolysis with a 1,3-specific immobilized lipase (Lipozyme® TL IM) and molecular distillation was investigated to increase the DHA content of algal oil. Algal oil with a 45.94% DHA content was mixed with ethanol, pumped into a column filled with Lipozyme® TL IM, and then circulated for 4 hr at room temperature. The ethanol was then recycled by vacuum distillation. At an evaporator temperature of 150°C, the residue was separated by molecular distillation into a heavy component enriched with DHA glycerides (in the form of triglyceride (TG), diglyceride (DG), and monoglyceride (MG)) and a light component enriched with palmitic acid (PA) and DHA ethyl ester (EE). As a result, 76.55% of the DHA from the algal oil was present in the heavy component, whose DHA content was 70.27%. DHA-MG was collected in the heavy component mostly in the form of 1-MG. Lipozyme® TL IM appeared to specifically target PA rather than DHA at the sn-1(3) position. The Lipozyme® TL IM allowed 90.03% of the initial DHA yield to be retained after seven reaction cycles. Therefore, an eco-friendly and simple method for increasing the DHA content in algal oil has been developed.

Electric Soldering Iron Ionization Mass Spectrometry Based Lipidomics for in Situ Monitoring Fish Oil Oxidation Characteristics during Storage

An electric soldering iron ion source (ESII) coupling with rapid evaporative ionization mass spectrometry (REIMS) was developed and used for in situ monitoring the dynamic variation trend in oxidation characteristics of fish oil during storage. The lipidomics profiles of fish oil stored at various days were acquired by ESII-REIMS. The fatty acid and triacylglycerol species were structurally identified, and their abundances were analyzed according to multivariate statistical models mainly including principle component analysis as well as orthogonal partial least-squares analysis. On the shared and unique structure plot, the ions of m/z 255.23, 281.24, 877.72, and 901.72 displayed the most significant variation among the oxidized fish oil samples. Based on receiver operating characteristic curve analysis with an optimal Youden index of 0.91, these markers were further verified. The variation of viscosity and volatiles were also evaluated to further verify the oxidation characteristics of fish oil. The study demonstrated that ESII-REIMS technology used as an advanced detection method could ensure fish oil quality during storage.

Application of Plackett-Burman Design in Screening of Natural Antioxidants Suitable for Anchovy Oil

Considering the safety of synthetic antioxidants, more and more natural antioxidants have been developed and utilized in foods. This study aimed to screen out a natural antioxidant combination from many antioxidants, which could significantly affect the oxidation stability of anchovy oil, while Plackett–Burman design (PBD) methodology was employed in this screening. According to the statistical results of this design, sesamol, dihydromyricetin, teapolyphenol, and rosemary acid were four significant parameters on the oxidation stability of anchovy oil. Moreover, dihydromyricetin presented the best antioxidant effect among nine kinds of selected antioxidants when they were used alone in anchovy oil. Meanwhile, a combination including sesamol (0.02%), teapolyphenol (0.02%). and rosemary acid (0.02%) was adopted, and its antioxidant ability was similar to that of tert-butylhydroquinone (TBHQ). Additionally, phytic acid as a synergist was used and combined with sesamol, and the antioxidant ability of this combination was better than that of TBHQ. This study presented a reference for the industrial applications of natural antioxidants and synergists in anchovy oil.

The emerging role of omega-3 fatty acids as a therapeutic option in neuropsychiatric disorders

The prevalence of neurologic and psychiatric diseases has been increasing for decades and, given the moderate therapeutic efficacy and safety profile of existing pharmacological treatments, there is an urgent need for new therapeutic approaches. Nutrition has recently been recognized as an important factor for the prevention and treatment of neuropsychiatric disorders. The omega-3 polyunsaturated fatty acids (n-3 PUFAs) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) play critical roles in neuronal cell function and neurotransmission as well as inflammatory and immune reactions that are involved in neuropsychiatric disease states. A large number of experimental and epidemiological studies provide a strong basis for interventional clinical trials that assessed the clinical efficacy of n-3 PUFAs in various neurological and psychiatric disorders. Most of these trials found beneficial effects of dietary supplementation with EPA and DHA, and no serious safety concerns have emerged. This review gives an introduction to recent findings on the clinical efficacy of n-3 PUFAs in various neuropsychiatric disorders and the underlying biochemical mechanisms. In addition, the reader will be enabled to identify common methodological weaknesses of clinical studies on n-3 PUFAs, and suggestions for the design of future studies are given.

Impact of Association Colloids on Lipid Oxidation in Triacylglycerols and Fatty Acid Ethyl Esters

The impact of association colloids on lipid oxidation in triacylglycerols and fatty acid ethyl esters was investigated. Association colloids did not affect lipid oxidation of high oleic safflower and high linoleic safflower triacylglycerols, but were prooxidative in fish triacylglycerols. Association colloids retarded aldehyde formation in stripped ethyl oleate, linoleate, and fish oil ethyl esters. Interfacial tension revealed that lipid hydroperoxides were surface active in the presence of the surfactants found in association colloids. The lipid hydroperoxides from ethyl esters were less surface active than triacylglycerol hydroperoxides. Stripping decreased iron and copper concentrations in all oils, but more so in fatty acid ethyl esters. The combination of lower hydroperoxide surface activity and low metal concentrations could explain why association colloids inhibited lipid oxidation in fatty acid ethyl esters. This research suggests that association colloids could be used as an antioxidant technology in fatty acid ethyl esters.

ω-3 Fatty Acids and Cardiovascular Diseases: Effects, Mechanisms and Dietary Relevance

ω-3 fatty acids (n-3 FA) have, since the 1970s, been associated with beneficial health effects. They are, however, prone to lipid peroxidation due to their many double bonds. Lipid peroxidation is a process that may lead to increased oxidative stress, a condition associated with adverse health effects. Recently, conflicting evidence regarding the health benefits of intake of n-3 from seafood or n-3 supplements has emerged. The aim of this review was thus to examine recent literature regarding health aspects of n-3 FA intake from fish or n-3 supplements, and to discuss possible reasons for the conflicting findings. There is a broad consensus that fish and seafood are the optimal sources of n-3 FA and consumption of approximately 2-3 servings per week is recommended. The scientific evidence of benefits from n-3 supplementation has diminished over time, probably due to a general increase in seafood consumption and better pharmacological intervention and acute treatment of patients with cardiovascular diseases (CVD).