Improving the Oxidative Stability of Krill Oil-in-Water Emulsions

A positively charged protein (fish gelatin) or a negatively charged protein species (heat-treated milk protein–carbohydrate mixture) was added to a primary krill oil (KO) emulsion stabilized by the phospholipids inherent in KO, with the aim of improving the oxidative stability of KO-in-water emulsions at pH 8.0 (10 % KO). The positively charged fish gelatin deposited on the primary interface of the oil droplets in the primary KO-in-water emulsion improved the oxidative stability of the KO-in-water emulsion as evidenced by the higher eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) remaining and lower propanal produced after accelerated oxidation (40 °C, 25 days). The addition of the negatively charged heat-treated milk protein–carbohydrate mixture containing Maillard reaction products (MRP) to the bulk phase of the emulsion also enhanced the oxidative stability of the KO-in-water emulsion. The addition of MRP to the aqueous phase of phospholipids stabilized emulsion droplets offered more protection to EPA and DHA of the KO emulsions compared to the formation of an additional layer at the interface of the KO emulsion droplet. This suggests that interventions based on addition of antioxidant species to the formulation were more effective for arresting oxidation than increasing the thickness of the droplet interface. The addition of proteins into KO containing emulsion formulations is a promising strategy for protecting omega-3 marine phospholipids against oxidation.     

鲫鱼肌肉脂肪测定与脂肪酸组成分析

采用国标方法提取鲫鱼肌肉中的脂肪成分,并应用GC/MS方法测定分析脂肪酸组成。结果显示:干燥鲫鱼肌肉中含有脂肪15.9%(质量分数),新鲜鲫鱼肌肉脂肪含量3.56%;共鉴定出35个脂肪酸成分。其中饱和脂肪酸13种,质量分数总和20.1%;不饱和脂肪酸22种,质量分数总和78.7%;多不饱和脂肪酸11种,质量分数总和26.2%。     

乌鳢鱼肌肉脂肪酸组成的气相色谱/质谱分析

采用国标方法提取乌鳢鱼肌肉中的脂肪成分,应用氢氧化钾/甲醇碱催化法将脂肪中的脂肪酸衍生化为脂肪酸甲酯,再应用GC/MS联用分析技术,测定分析其脂肪酸组成。结果显示:新鲜乌鳢鱼肉粗脂肪含量3.10%(质量分数,以下同),共鉴定出38个脂肪酸成分;其中,饱和脂肪酸15种,含量32.8%;不饱和脂肪酸23种,含量65.5%;以DHA、亚麻酸、EPA为代表的omega-3多不饱和脂肪酸6种,含量6.78%;以亚油酸为代表的omega-6多不饱和脂肪酸7种,含量14.6%。     

Growth Temperature and Salinity Impact Fatty Acid Composition and Degree of Unsaturation in Peanut-Nodulating Rhizobia

Growth and survival of bacteria depend on homeostasis of membrane lipids, and the capacity to adjust lipid composition to adapt to various environmental stresses. Membrane fluidity is regulated in part by the ratio of unsaturated to saturated fatty acids present in membrane lipids. Here, we studied the effects of high growth temperature and salinity (NaCl) stress, separately or in combination, on fatty acids composition and de novo synthesis in two peanut-nodulating Bradyrhizobium strains (fast-growing TAL1000 and slow-growing SEMIA6144). Both strains contained the fatty acids palmitic, stearic, and cis-vaccenic + oleic. TAL1000 also contained eicosatrienoic acid and cyclopropane fatty acid. The most striking change, in both strains, was a decreased percentage of cis-vaccenic + oleic (≥80% for TAL1000), and an associated increase in saturated fatty acids, under high growth temperature or combined conditions. Cyclopropane fatty acid was significantly increased in TAL1000 under the above conditions. De novo synthesis of fatty acids was shifted to the synthesis of a higher proportion of saturated fatty acids under all tested conditions, but to a lesser degree for SEMIA6144 compared to TAL1000. The major adaptive response of these rhizobial strains to increased temperature and salinity was an altered degree of fatty acid unsaturation, to maintain the normal physical state of membrane lipids.     

Transition-metal Catalyzed Oxidative Cleavage of Unsaturated Fatty Acids

The oxidative cleavage of the C? C-bond converts unsaturated fatty acids to carboxylic and dicarboxylic acids. The only method currently used in oleochemistry is ozonolysis. The high energy consumption of ozonolysis makes a transition-metal catalyzed alternative with a cheaper secondary oxidant attractive. Here we report new methods for ruthenium-, rhenium- and tungsten-catalyzed oxidations with peracetic acid and hydrogen peroxide. Whereas the direct oxidative cleavage of internal C? C-bonds still lacks selectivity, two-step reactions are feasible. The first possibility is to convert natural, internal unsaturated fatty acids to ω-unsaturated ones. These ω-unsaturated fatty acids can be cleaved by Ru/acac)₃/CH₃COOOH or Re₂O₇/H₂O₂ with yields up to 80 %. In the second two-step procedure the fatty acid first is hydroxylated and the diol is cleaved: the overall yield for this method is 80 %, too.     

Fatty Acid Unsaturation Degree of Plasma Exosomes in Colorectal Cancer Patients: A Promising Biomarker

Even though colorectal cancer (CRC) is one of the most preventable cancers, it is currently one of the deadliest. Worryingly, incidence in people <50 years has increased unexpectedly, and for unknown causes, despite the successful implementation of screening programs in the population aged >50 years. Thus, there is a need to improve early diagnosis detection strategies by identifying more precise biomarkers. In this scenario, the analysis of exosomes is given considerable attention. Previously, we demonstrated the exosome lipidome was able to classify CRC cell lines according to their malignancy. Herein, we investigated the use of the lipidome of plasma extracellular vesicles as a potential source of non-invasive biomarkers for CRC. A plasma exosome-enriched fraction was analyzed from patients undergoing colonoscopic procedure. Patients were divided into a healthy group and four pathological groups (patients with hyperplastic polyps; adenomatous polyps; invasive neoplasia (CRC patients); or hereditary non-polyposis CRC. The results showed a shift from 34:1- to 38:4-containing species in the pathological groups. We demonstrate that the ratio Σ34:1-containing species/Σ38:4-containing species has the potential to discriminate between healthy and pathological patients. Altogether, the results reinforce the utility of plasma exosome lipid fingerprint to provide new non-invasive biomarkers in a clinical context.     

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

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.     

Homogenization Pressure and Temperature Affect Protein Partitioning and Oxidative Stability of Emulsions

The oxidative stability of 10 % fish oil-in-water emulsions was investigated for emulsions prepared under different homogenization conditions. Homogenization was conducted at two different pressures (5 or 22.5 MPa), and at two different temperatures (22 and 72 °C). Milk proteins were used as the emulsifier. Hence, emulsions were prepared with either a combination of α-lactalbumin and β-lactoglobulin or with a combination of sodium caseinate and β-lactoglobulin. Results showed that an increase in pressure increased the oxidative stability of emulsions with caseinate and β-lactoglobulin, whereas it decreased the oxidative stability of emulsions with α-lactalbumin and β-lactoglobulin. For both types of emulsions the partitioning of proteins between the interface and the aqueous phase appeared to be important for the oxidative stability. The effect of pre-heating the aqueous phase with the milk proteins prior to homogenization did not have any clear effect on lipid oxidation in either of the two types of emulsions.     

Effect of Fatty Acid Unsaturation on Phytosteryl Ester Degradation

This study examined the thermo-oxidative degradation of stigmasterol fatty acids esters. Stigmasterol stearate, oleate, linoleate and linolenate were synthesized by chemical esterification and their purity evaluated by ¹H-NMR and GC–MS. The degradation of stigmasterol esters was examined after heating them at 60 and 180 °C for 1, 2, 4, 8 and 12 h. It was established that stigmasterol esters were prone to thermo-oxidative degradation, with time and temperature affecting the degree of degradation. The unsaturation of fatty acids affected the rate of stigmasteryl ester degradation. The kinetics of StS and StO degradation were similar and the additional double bonds in StL and StLn resulted in their faster decomposition. The esters degraded faster at 180 than at 60 °C. The sterol and fatty acid molecules degraded at different rates, such that the fatty acid moiety deteriorated faster than the sterol at both temperatures, independent of the time of heating and the level of unsaturation.     

Enantioselective Analysis of Chiral Anteiso Fatty Acids in the Polar and Neutral Lipids of Food

Anteiso fatty acids (aFA) are substituted with a methyl group on the antepenultimate carbon of the straight acyl chain. This feature leads to a stereogenic center. The 12-methyltetradecanoic acid (a15:0) and the 14-methylhexadecanoic acid (a17:0) are the most common aFA found in food, although they occur only in very small quantities. In this study we used gas chromatography in combination with a chiral stationary phase to determine the enantiomeric distribution of both a15:0 and a17:0 in the neutral and polar lipids of aquatic food samples and cheese. The best suited column was selected out of four custom-made combinations of heptakis(6-O-tert-butyldimethylsilyl-2,3-di-O-methyl)-β-cyclodextrin (β-TBDM) with different amount and polarity of an achiral polysiloxane. After separation of polar and neutral lipids of the food samples by solid phase extraction, fatty acid methyl esters were prepared and the fatty acid methyl esters were fractionated by reversed phase high performance liquid chromatography. Measurements of fractions high in aFA by enantioselective GC/MS in the selected ion monitoring mode verified the dominance of the (S)-enantiomers of a15:0 and a17:0 in both lipid fractions. However (R)-enantiomers were detectable in all samples. The relative proportion of the (R)-enantiomers was up to fivefold higher in the polar lipids than in the neutral lipids. The higher proportions in the polar lipids indicate that microorganisms might be involved in the formation of (R)-aFA.     

Chemical Form of Dietary Selenium Affects the Fatty Acids Profile and Oxidative Stability of Muscles of Broilers Supplemented with Lycopene and Oils

The aim of this study is to determine the effects of the addition of different chemical forms of selenium (Se)—selenate (SeVI) or selenized yeast (SeY) to chickens’ diet containing equal amounts of fish (FO) and sunflower oils and lycopene (Lyc) on fatty acids (FA) profile and peroxidation yield in thigh muscles of chickens. FA profile is analyzed by gas chromatography coupled with mass spectrometry while content of malondialdehyde is determined by ultra‐fast liquid chromatography (UPLC) with photodiode detection. The diets containing SeY or SeVI increase the feed conversion efficiency of chickens compared with the control diet. SeY or SeVI added to the diet containing Lyc and FO stimulates concentrations of monounsaturated and polyunsaturated (PUFA) FA in muscles. Muscles of chickens fed a diet only with Lyc and FO have the highest indices of atherogenic (A‐SFA) and thrombogenic (T‐SFA) saturated FA and the highest ratios of A‐SFA and T‐SFA to all assayed FA. Dietary Se‐compounds also decrease the PUFA peroxidation indices in muscles compared with the diet containing only FO and Lyc. Therefore Se‐compounds may be added to diets including FO and Lyc to improve the growth parameters, nutritive value, and oxidative stability of chicken meat. Practical Applications: Poultry meat, which is characterized by high protein content of high biological value, high minerals and vitamins, and low collagen and fat content, is recommended as particularly desirable in a balanced diet to replace red and highly processed meat. Also, relatively good price makes this type of meat one of the most popular among consumers. The present study aims to check if inclusion of different chemical forms of selenium into chickens’ diets improves nutritional value of broiler meat. Feeding chickens with seleno‐supplements significantly enhances poultry production efficiency and nutritional value of broilers’ meat, because it favorably modifies FA composition (enhanced monounsaturated and polyunsaturated FA and decrease atherogenic and thrombogenic saturated FA in muscles) and reduces lipid oxidation in chickens’ meat. These results are important from the both producers’ and consumers’ point of view and correspond to contemporary nutritional recommendations.     

Season and Cooking May Alter Fatty Acids Profile of Polar Lipids from Blue-Back Fish

Polar lipids (PoL) represent a new promising dietary approach in the prevention and treatment of many human diseases, due to their potential nutritional value and unique biophysical properties. This study investigates the effects of catching season and oven baking on the fatty acid profiles (FAP) of PoL in four species of blue-back fish widely present in the North Adriatic Sea: anchovy (Engraulis encrasicholus), sardine (Sardina pilchardus), sprat (Sprattus sprattus), and horse mackerel (Trachurus trachurus). PoL levels (427–652 mg/100 g flesh) varied among the four species, with no significant seasonal variations within species. FAP of raw fillets were particularly high in polyunsaturated fatty acid (PUFA), especially docosahexaenoic acid (DHA) and EPA; total PUFA was constant in all species throughout the year, while long-chain n-3 polyunsaturated fatty acid (n-3 PUFA) rose in spring (except in sprat), especially due to the contribution of DHA. The FAP response for PoL to oven baking was species-specific and, among n-3 PUFA, DHA exhibited the greatest heat resistance; the influence of oven baking on FAP was found to be correlated with the catching season, especially for anchovy and sardine, while sprat PoL were not affected by cooking processes. The four species analyzed in this study presented very low n-6/n-3 fatty acid ratios and highly favorable nutritional indices, emphasizing their PoL qualities and promoting their role in increasing human n-3 PUFA intake. The four species can be considered as superior sources of n-3 PUFA and can be employed as supplements in functional food manufacturing and in pharmaceutical and cosmetic industries.     

Fatty Acids and Flavor Components in the Oil Extracted from Golden Melon Seeds

For complete utilization of raw materials and edible oil production, the oil from golden melon seeds (GSs) is extracted via the cold-pressing, hot-pressing, and ultrasound-assisted aqueous enzymatic extraction (AEE), and the fatty acid composition, and nutritional value of the extracted GS oils (GSOs) are analyzed. The volatile compounds present in the GSOs are determined using gas chromatography–mass spectrometry. The aroma profiles of different GSO samples are further distinguished by using an electronic nose. A total of 16 fatty acids are identified in the GSO samples, with atherogenic, thrombogenic, and nutritive value indices ranging from 0.142–0.151, 0.366–0.403, and 5.019–5.299, respectively. Moreover, 43 volatile compounds, including esters, hydrocarbons, alcohols, ketones, pyrazines, and aldehydes are identified. The cold-pressed GSO presents fresh and fruity flavors, while the hot-pressed GSO presents roasted, nutty, fatty, and fruity flavors, and the GSO obtained via AEE presents fatty and fruity flavors. The acid and peroxide contents of these oil samples are 0.69–079 mg g⁻¹ and 5.17–5.79 mmol kg⁻¹, respectively. The results indicate that the extraction method affects the fatty acid composition, flavor components, and physiochemical properties of the GSO. This study may help promote the development of edible GSO. Practical applications: With high demand for edible oils, it is of great significance to find natural edible oils from different sources. The oil in golden melon seeds is extracted by different methods. Their fatty acid composition and flavor components are analyzed. The GSO extracted via AEE method is rich in fatty acids composition. This work would guide the development of an edible GSO and increase the value of golden melon.     

Multiply Methyl-Branched Fatty Acids and Diacids in the Polar Lipids of a Microaerophilic Subsurface Microbial Community

A previously unreported series of di- and tri-methylated fatty acids, as well as saturated and monounsaturated diacids were identified in polar lipids isolated from environmental subsurface sediment samples. Mechanisms are proposed for their formation, but their origin and role in cell membranes remains unknown.     

An Optical-Transmission Study of the Interaction Between Montmorillonite and Humic Acids

The interaction between montmorillonite and kaolinite clay minerals and humic acid (HA) was studied in suspensions by absorbance measurements. Changes in absorbance as a result of the interaction were interpreted as an indication of changes in the size of clay tactoids. Na-humate caused dissociation of montmorillonite tactoids in suspension. Drying-wetting cycles increased the effect of Na-humate and resulted in tactoids similar in their size to those of the Li-saturated montmorillonite. Na-humate had no effect on the absorbance of kaolinite suspensions.     

Short-Chain Fatty Acids in Chronic Kidney Disease: Focus on Inflammation and Oxidative Stress Regulation

Chronic Kidney Disease (CKD) is a debilitating disease associated with several secondary complications that increase comorbidity and mortality. In patients with CKD, there is a significant qualitative and quantitative alteration in the gut microbiota, which, consequently, also leads to reduced production of beneficial bacterial metabolites, such as short-chain fatty acids. Evidence supports the beneficial effects of short-chain fatty acids in modulating inflammation and oxidative stress, which are implicated in CKD pathogenesis and progression. Therefore, this review will provide an overview of the current knowledge, based on pre-clinical and clinical evidence, on the effect of SCFAs on CKD-associated inflammation and oxidative stress.     

Non-methylene Interrupted and Hydroxy Fatty Acids in Polar Lipids of the Alga Grateloupia turuturu Over the Four Seasons

Phospholipids (PL) and glycolipids (GL) FA in the edible Rhodophyta Grateloupia turuturu, from Brittany, France, were investigated over four seasons. The major lipid class was GL in all seasons (around 45 %). More than 80 FA occurred in polar lipids, with chains from C₁₂ to C₂₆, identified as methyl esters and N-acyl pyrrolidides by gas chromatography–mass spectrometry (GC–MS). PUFA occurred at up to 47.1 % (summer) in PL, and up to 43.6 % (summer) in GL. The major PUFA were 20:5n-3 (12.2 % in PL and 29.0 % in GL) and 20:4n-6 (25.6 % in PL and 10.4 % in GL). The unusual 18:3n-7 acid was identified in PL up to 2.2 %. Several minor unsaturated FA were identified in PL and are previously unreported in seaweeds, namely 14-tricosenoic, 15-tetracosenoic, 5,11-octadecadienoic and 5,9-nonadecadienoic. Also unprecedented in seaweeds, ten 2-hydroxy and three 3-hydroxy FA occurred mainly in PL, 13.9 % in spring with the 3-hydroxyhexadecanoic acid as the major one (8.1 % winter). Three n-9 monounsaturated 2-hydroxy FA occurred in PL. The 2-hydroxy-15-tetracosenoic acid was characterized as the dimethyl disulfide adduct of its methyl ester. The 2-hydroxy-16-pentacosenoic and 2-hydroxy-17-hexacosenoic acids were identified by comparison of mass spectra and GC mobilities with those of the 2-hydroxy-15-tetracosenoic acid, and of other homogeneous FA series. These rare n-9 monounsaturated 2-hydroxy FA are unprecedented in seaweeds.