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The study investigated the lipid oxidation of pumpkin seed kernels (PSK) under different storage conditions (room temperature, vacuum-room temperature, refrigeration, and vacuum-refrigeration) using HPLC-MS and GC–MS. Experimental results found the vacuum-refrigeration group showed the lowest PV (0.24 g/100 g), diene (8.68), hexanal (356.64 ± 16.06 ng/g), and nonanal (132.05 ± 8.38 ng/g) after a 9-month storage. A total of 586 lipids, including 6 classes and 27 subclasses, were detected, 46 of which showed significant differences. Refrigeration samples had the highest diacylglycerol content, while room temperature samples demonstrated the highest triacylglycerol and phosphatidylcholine content. Differential lipid metabolite analyses indicated that storage conditions mainly affected glycerolipid metabolism, glycerophospholipid metabolism, and sphingolipid metabolism pathways in PSK, while glycerolipid and glycerophospholipid metabolism were still dominant. It revealed that refrigeration was more effective than vacuum in inhibiting the oxidation of PSK. These findings could offer valuable references for the storage, transportation, preservation, and the development and utilization of PSK. [Display omitted] • Aldehydes and alcohols were main differential flavor compounds in PSK. • Storage conditions significantly impacted the lipid oxidation degree of PSK. • 589 lipid metabolites, including 6 classes and 27 subclasses, were identified. • Lipid metabolism pathways in PSK under different storage conditions were revealed. [ABSTRACT FROM AUTHOR]

• Extended food use of oats calls for knowledge on compositions and storage behavior. • Lipids, volatiles and tocopherols varied between 20 pure oat cultivar batches. • Nine-month storage of flour revealed differences in oxidative stability. • Minor correlations between lipids, tocols and volatile oxidation compounds detected. Recent data showing the compositional variation and storage behavior among different oat batches for the purpose of food remains limited. Lipids of twenty oat flour samples of pure cultivars grown in Finland during 2019 were extracted and fractionated into neutral and polar-rich lipids. Flour was stored for nine months, and profiles of volatiles and tocols were analyzed to reveal oxidative stability. The lipid content was 5.9–8.9 g per 100 g of flour [DW] and consisted of 78.7 ± 2.5 % neutral and 21.3 ± 2.5 % polar lipids. Palmitic (16 %), oleic (36 %), and linoleic (39 %) acids were the most abundant fatty acids. Neutral lipids had more oleic and less linoleic and palmitic acids than polar lipids. The fresh samples correlated with tocols, pentanal, 2-pentylfuran, 2-heptanone, nonanal, 2-butanone, and heptanal, while stored samples were associated with 3-octen-2-one, 2-octenal, hexanal, and octanal. Lipid composition and oxidative stability are essential factors for selecting oat batches for food applications. [ABSTRACT FROM AUTHOR]

Models predicting lipid oxidation in oil-in-water (O/W) emulsions are a requirement for developing effective antioxidant solutions. Existing models do, however, not include explicit equations that account for composition and structural features of O/W emulsions. To bridge this gap, a mechanistic kinetic model for lipid oxidation in emulsions is presented, describing the emulsion as a one-dimensional three phase (headspace, water, and oil) system. Variation in oil droplet sizes, overall surface area of oil/water interface, oxidation of emulsifiers, and the presence of catalytic transition metals were accounted for. For adequate predictions, the overall surface area of oil/water interface needs to be determined from the droplet size distribution obtained by dynamic and static light scattering (DLS, SLS). The kinetic model predicted well the formation of oxidation products in both mono- and polydisperse emulsions, with and without presence of catalytic transition metals. • Mechanistic kinetic model describes lipid oxidation in oil-in-water (O/W) emulsions. • Compositional and structural features of O/W emulsions are included in the model. • Droplets with sizes <300 nm need to be accounted for in the model. • Kinetic rates of lipid oxidation vary with the droplet size. • Model provides good predictions for mono-and polydisperse emulsions. [ABSTRACT FROM AUTHOR]

[Display omitted] • The development of peanut oil volatile flavor requires oil to participate in thermal reaction. • Heating peanut oil to degrade the unsaturated fatty acids in the oil creates reducing aldehydes. • Linoleic acid is one of the precursors in the formation of the volatile flavor of peanut oil. • Develop a volatile flavor model capable of distinguishing different reactions. Lipid is an important precursor for volatile flavor formation, but it is not clear how to study the reactions involved in forming key volatile flavor compounds in peanut oil. In this paper, we innovatively established a flavor research model to investigate the contribution of different chemical reactions to the aroma compounds of peanut oil. The results showed that lipid participation in thermal reactions is necessary for forming major aroma compounds in hot-pressed peanut oil. Compared to the Maillard reaction, the lipid oxidation-Maillard reaction produces more compounds with 46 volatile substances identified. During the heating process, six new key substances were formed and the level of unsaturated fatty acids decreased by 7.28%. Among them, linoleic acid may be an important precursor for the formation of aroma components of hot-pressed peanut oil. Our study could provide theoretical guidance for understanding the volatile flavor mechanism of peanut oil and improving volatile flavor. [ABSTRACT FROM AUTHOR]

[Display omitted] • The evolution of volatiles in the lean and fat portions of bacon showed different patterns. • The aroma compounds were mainly provided by lean portion, and the optimal drying time was 24 h. • Eight key aroma compounds derived from different lipid fractions and fatty acids. • Linoleic acid was vital for the generation of key aroma compounds in non-smoked bacon. This study explored the evolution of key aroma compounds and their lipid precursors in the lean (LN) and fat (FT) portions of non-smoked bacon during hot air drying. The results showed that the LN portion contained most of the aroma compounds in the bacon (>88%). The volatile content of the FT portion increased as the drying time increased, whereas that of the LN portion reached a maximum within 24 h and then decreased. Based on the highest volatile contents (4889.48 ± 202.06 µg/kg) and sensory scores, 24 h was considered the optimal drying time. For key aroma compounds, hexanal and 2,3-octanedione were derived from free fatty acids and polar lipids. Notably, 1-octen-3-ol was generated only from polar lipids in the FT and LN portions. The 2-undecenal and (E, E)-2,4-decadienal were produced by the oxidation of neutral lipids in the FT portion. Dihydro-5-pentyl-2(3H)-furanone was derived from polar lipids in the LN portion. Altogether, these findings provide theoretical insights into improving the aroma of bacon by optimizing raw material selection and processing methods. [ABSTRACT FROM AUTHOR]

[Display omitted] • Toasted wheat bran protects RP in oil better from oxidation than native wheat bran. • A high bran-to-oil ratio lowers the stabilisation of vitamin A by native wheat bran. • High vitamin A and oil levels limit vitamin A stabilisation by toasted wheat bran. • Toasting reduces the capacity of wheat bran to protect lipids from oxidation. • Vitamin A acts as a pro-oxidant when mixed with oil and toasted wheat bran. Wheat bran stabilises vitamin A (retinyl palmitate, RP) in oil during storage, but the stabilisation mechanism remains unknown. We here studied the effect of the concentration of RP in oil (0.1–2%) and of RP-enriched oil in the system (5–50%) on the RP retention during accelerated storage of systems with native and toasted wheat bran. Generally, toasted bran showed better RP stabilisation than native bran. After four weeks of storage, up to 65% RP was retained in toasted bran systems, whereas the RP retention for native bran was below 10%. For native bran, a higher oil-to-bran ratio and, thus, a lower wheat lipase level resulted in better RP retention. For toasted bran, combined high oil and high RP concentrations resulted in the lowest RP retention. We, therefore, conclude that wheat bran protects RP and lipids from oxidation. This protection is reduced by the pro-oxidative effect of RP, lipid oxidation and lipase. [ABSTRACT FROM AUTHOR]

• Formulation of mechanistic kinetic model describing lipid oxidation of vegetable oils. • Oil composition (fatty acid and antioxidant) is accounted for in the kinetic model. • O 2 mass transfer accounts for different vial dimensions and O 2 permeability of cap. • Multiplication factors of kinetic constants used for second acceleration phase. • Short time data fitting is sufficient for extrapolations to long term under the same conditions. Estimating the shelf-life of vegetable oils is important to develop solutions to reduce spoilage by lipid oxidation. Typically, the shelf-life is predicted by detecting secondary oxidation markers in accelerated shelf-life tests, which are time-consuming. Existing numerical approaches using early primary oxidation products as predictive markers do not account for variations in fatty acid types, antioxidants, or storage conditions. A mechanistic kinetic model was developed incorporating these factors as a step towards shelf-life prediction for vegetable oils. Specific kinetic constants for the reactions of each unsaturated fatty acid type account for variations in fatty acid composition, and oxygen mass transfer accounts for variations in oxygen conditions. A second acceleration of lipid oxidation observed in long-term storage experiments was described by a multiplication factor for the kinetic constants related to oxidation products. Our model accurately extrapolates short-time experimental data to estimate long term formation of oxidation products under the same conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Basic amino acids inhibit the degradation of phospholipids. • Neutral lipase activity was enhanced by l -Lys and l -His. • Total oxidation degree has been reduced by basic amino acids. • 124 key lipid metabolites and 6 key volatile compounds were identified. • Alcohols and esters were positively correlated with TG containing SFA and MUFA. The effects of basic amino acids on lipid oxidation and the formation of volatile compound in low-sodium cured large yellow croaker were investigated. Basic amino acids contribute a lot in inhibiting the degradation of phospholipids, especially l -lysine. Lipid oxidation was also inhibited by basic amino acids, and the total oxidation of groups could be sorted as low-sodium (LS) > control (C) > l -Histidine participated LS group (LS-His) > l -Arginine participated LS group (LS-Arg) > l -lysine participated LS group (LS-Lys). PC 18:1/20:5, PC 16:0/18:1, triacylglycerol (TG) 16:1/20:5/22:6, etc., were found to be key differential lipid metabolites, and 1-propanol, 2-methyl, gamma-hexalactone, etc. were recognized as key differential volatile compounds. The results of correlation analysis showed that alcohols and esters were positively correlated with TG molecules composed of saturated fatty acids and monounsaturated fatty acids. These findings provided new insights into the relationship between flavor formation and the degradation and oxidation of lipids. [ABSTRACT FROM AUTHOR]

• Algorithm-assisted Raman and SERS for rapid peroxide and fatty acid analysis of oil. • Advanced chemometric approaches can identify reheating-induced chemical changes. • The developed Raman method can measure trans fats less than 2% with 94% accuracy. • The developed SERS method can measure trans fats less than 2% with 97% accuracy. Deep-fat frying of food develops lipid oxidation products that deteriorate oil and pose a health risk. This necessitates the development of a rapid and accurate oil quality and safety detection technique. Herein, surface-enhanced Raman spectroscopy (SERS) and sophisticated chemometric techniques were used for rapid and label-free determination of peroxide value (PV) and fatty acid composition of oil in-situ. In the study, plasmon-tuned and biocompatible Ag@Au core–shell nanoparticle-based SERS substrates were used to obtain optimum enhancement despite matrix interference to efficiently detect the oil components. The potent combination of SERS and the Artificial Neural Network (ANN) method could determine the fatty acid profile and PV with upto 99% accuracy. Moreover, the SERS-ANN method could quantify the low level of trans fats, i.e., < 2%, with 97% accuracy. Therefore, the developed algorithm-assisted SERS system enabled the sleek and rapid monitoring and on-site detection of oil oxidation. [ABSTRACT FROM AUTHOR]

• 13 compounds derived from lipid oxidation were quantified by HS SPME GC–MS. • A central composite rotatable design was used to optimize HS-SPME parameters. • Response surface methodology assessed the effects of extraction parameters. • Method validation included LOD, LOQ, and precision. Lipid oxidation is a major contributor to the deterioration of the sensory quality of fat-containing dairy powders. Hydroperoxides are the primary oxidation products from unsaturated fatty-acids that readily yield a complex mixture of volatile organic compounds that can adversely impact product quality and shelf life. Headspace solid-phase microextraction gas-chromatography mass-spectrometry was chosen to quantify thirteen lipid oxidation compounds in whole milk powder encompassing a range of volatilities and chemical classes. A central composite rotatable design (CCD, α = 1.1) based on a 23 factorial table was used with response surface methodology to optimize the HS-SPME parameters; determined at; 45 min extraction time and 43 °C extraction temperature. The significant model terms were found to be extraction temperature (p < 0.05) and the interaction between time and temperature (p < 0.05). Precision, accuracy, LOD and LOQ were determined and the method was validated for whole milk powder. [ABSTRACT FROM AUTHOR]

Highlights • Monitoring lipid oxidation using FFFS and MIR. • High predictive accuracy in modeling TOTOX using MIR and tryptophan spectra. • High predictive accuracy of PV and FFA using MIR spectra. Abstract The potentialities of front-face fluorescence (FFF) and mid-infrared (MIR) spectroscopies coupled with partial least square regression (PLSR) were compared to predict the lipid oxidation of pound cakes. The level of lipid oxidation in pound cakes determined using classical methods showed some changes. Similarly, the fluorescence emission (305–490 nm) and excitation (252–390 nm) spectra and MIR spectra scanned in the 4000–700 cm−1 region showed some changes in pound cakes as a function of both storage time and the type of oil used in the formulation. The application of PLSR to the MIR spectra, provided excellent predictive results for free fatty acid (R2 = 0.97) and peroxide values (R2 = 0.87). Similar results were obtained from both tryptophan and MIR spectra for the prediction of TOTOX (R2 > 0.86) demonstrating the efficiency of the MIR and FFF spectroscopies to qualify and quantify the level of lipid oxidation in pound cakes. [ABSTRACT FROM AUTHOR]

Highlights • Lignans were more efficient than phenolic acids to prevent lipid oxidation. • Both classes of compounds presented a structure/antioxidant efficiency relationship. • Membrane inserted compounds significantly inhibited lipid oxidation. • The inner membrane fraction of lignans inhibited ∼70 % of lipid oxidation. Abstract Polyunsaturated fatty acids are particularly sensitive to the damages due to reactive oxygen species and lipid oxidation has been reported to be involved in the degradation of food as well as in the early stages of several diseases. Our objective was to study the mechanisms of action of flax (Linum usitatissimum) phenolic compounds to prevent membrane lipid oxidation. To do so, several biophysical techniques (oxidative stress, surface tension, fluorescence spectroscopy and HPLC) were used to investigate the ability of the compounds to prevent lipid oxidation and to interact with membranes. We evidenced a relationship between the structure and the antioxidant efficiency as aglycone compounds were significantly more efficient (p < 0.05) than glucoside compounds. In addition, our results revealed that aglycone lignans spontaneously penetrated the membrane contrary to aglycone hydroxycinnamic acids. To conclude, the comparison of the antioxidant efficiencies revealed that membrane inserted compounds better inhibited lipid oxidation than non-inserted compounds. [ABSTRACT FROM AUTHOR]

This work aimed to investigate the effects of lipid oxidation on N ε -carboxymethyllysine (CML) and N ε -carboxyethyllysine (CEL) formation in three types of Chinese-style sausages during storage. Medium-high temperature dried sausage, naturally dehydrated sausage and smoke-dried sausage were prepared, and CML/CEL contents were measured. The result showed that CML and CEL levels increased with the increasing storage time, and an exponential correlation was found between thiobarbituric acid reactive substances (TBARs) and either CML (r 2  = 0.922) or CEL (r 2  = 0.921) in medium-high temperature dried sausages and smoke-dried sausage, which suggested that lipid oxidation could facilitate CML/CEL formation during storage. Furthermore, lipid oxidation and the Maillard reaction might have a synergistic effect on CML formation in Chinese-style sausages, as evidence by the results of model system during incubation. These findings indicated that lipid oxidation played a key role in CML/CEL formation during the storage of Chinese-style sausages. [ABSTRACT FROM AUTHOR]

[Display omitted] • Enzyme-assisted aqueous extraction of low-fat Baltic herring caused emulsion-formation. • Enzyme-assisted aqueous extraction results in poor recovery of phospholipids. • Water reduction and ethanol addition reduced emulsion, improving oil recovery. • Enzymes did not cause differences in oxidative stability or composition of the oil. Enzyme-assisted aqueous extraction (EAAE) is a green, and scalable method to produce oil and protein hydrolysates from fish. This study investigated the role of different parameters on emulsion formation, oil recovery, and the composition of crude oil during EAAE of Baltic herring (Clupea harengus membras). Fatty acid compositions, lipid classes, tocopherols, and oxidation status of the EAAE crude oils were studied. Compared to solvent-extracted oil, EAAE resulted in a lower content of phospholipids accompanied by a 57% decrease in docosahexaenoic acid. Changing fish to water ratio from 1:1 to 2:1 (w/w) with ethanol addition led to the greatest reduction (72%) of emulsion, which resulted in an increase in oil recovery by 11%. The addition of ethanol alone, or reduction of enzyme concentration from 0.4% to 0.1% also reduced emulsion-formation significantly. Overall, emulsion reduction resulted in higher content of triacylglycerols and n − 3 polyunsaturated fatty acids in the crude oil extracted. [ABSTRACT FROM AUTHOR]

• Eye and dorsal muscles have the highest lipid and protein content, respectively. • Eye muscle has the lowest water holding capacity during frozen storage. • Frozen dorsal muscle has the fastest lipid and protein oxidation rate. • Eye muscle has the loosest microstructure. The quality of fish can change due to differences in the lipid and protein oxidation rates in different muscles. This study examined vacuum-packed eye muscle (EM), dorsal muscle (DM), belly muscle (BM), and tail muscle (TM) of bighead carp frozen for 180 days. The results reveal that EM had the highest lipid content and the lowest protein content, while DM had the lowest lipid content and the highest protein content. EM also showed the highest values of centrifugal loss and cooking loss, and the correlation analysis showed that these losses were positively correlated with dityrosine content and negatively correlated with conjugated triene content. The content of carbonyl, disulfide bond, and surface hydrophobicity of myofibrillar protein (MP) also increased with time, with DM having the highest values. The microstructure of EM was looser than other muscles. Therefore, DM had the fastest oxidation rate and EM had the lowest water holding capacity. [ABSTRACT FROM AUTHOR]

Lipid oxidation of fish oil enriched cow milk and soy milk supplemented with rosemary extract stored at 2 °C was studied. Both peroxide value and volatile secondary lipid oxidation products were determined to monitor the progress of lipid oxidation. Rosemary extract inhibited lipid oxidation in fish oil enriched cow milk. In contrast, soy milk samples having much higher unsaturated fatty acid content showed higher lipid oxidation stability compared to cow milk. Reduction in the content of chlorogenic acid during storage suggested that this compound may contribute to the lipid oxidation stability of fish oil enriched soy milk product. Total carnosic acid and carnosol concentration declined much faster in soy milk than in cow milk. It is suggested from the results that food components could have significant impact on the fate of bioactive antioxidant compounds in a specific food product during storage. [ABSTRACT FROM AUTHOR]

Phenolics can trap lipid-derived reactive carbonyls as a protective function that diminishes the broadcasting of the lipid oxidative damage to food macromolecules. In an attempt to clarify the trapping of 2,4-alkadienals by phenolics, this study analyzes the reactions of 2,4-hexadienal, 2,4-heptadienal, and 2,4-decadienal with 2-methylresorcinol. These reactions produced ( E )-4-(alk-1-en-1-yl)-8-methyl-2,7-bis(prop-1-en-2-yloxy)chromanes, which were isolated and characterized by 1D and 2D NMR and MS. Carbonyl-phenol adduct formation was favored at pH > 7 and moderate temperatures (25–80 °C). Adducts were quantified and shown to be produced as a mixture of diastereomers. Diastereomers 2 R ,4 S plus 2 S ,4 R were formed to a higher extent than diastereomers 2 R ,4 R plus 2 S ,4 S under the different conditions assayed, although activation energies ( E a ) for the formation of all of them was mostly the same (∼62 kJ·mol −1 ). These results show that phenolics can trap 2,4-alkadienals and provide the basis for the later detection of the formed adducts in food pro[ducts. [ABSTRACT FROM AUTHOR]

Salts reduction/substitution have gained a lot interest from food industry since the US Food and Drug Administration (FDA) has issued a draft guidance for salt reduction. However how changes of salts in food formulation could influence lipid oxidation is still not fully understood. Using oil-in-water emulsions stabilized by a natural emulsifier – lecithin at pH 7.0 as a model system, this study evaluated how salts affect the physical parameters of the emulsion, the chelating activity of lecithin and thus the lipid oxidation of these emulsions. Results showed that salts increased the particle size, the negative charge of the oil droplets, and the amount of iron chelated by lecithin. Lipid oxidation lag phases were shortened by addition of salts, by 1 day and 2 days for lipid hydroperoxides and thiobarbituric acid reactive substances measurements respectively. These results provide some new insights on the mechanisms of how salts could affect the lipid oxidation of food emulsions. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the relative reaction rate of protein and lipid oxidation in different biphasic model systems (linoleic acid; liposome; emulsion) containing myofibrillar protein (MFP at 1, 8 and 20 mg/mL) under hydroxyl radical stress. Protein oxidation markers exhibited significant changes in 2 h: reduced tryptophan fluorescence intensity, carbonyl formation, and extensive polymerization of myosin. In contrast, no detectable changes ( P  > .05) in lipid peroxide occurred within 2 h except for samples with 1 mg/mL MFP which showed an early TBARS formation. Of the three biphasic systems, the oxidative stability of lipids followed the order of emulsion > linoleic acid > liposome, indicating the steric role of proteins. In general, MFP was more susceptible to radicals than lipids, and a higher protein:lipid ratio was associated with a slower TBARS production and more rapid protein oxidation, suggesting a sacrificing role of MFP to protect lipids. [ABSTRACT FROM AUTHOR]

The present work explored the lipid antioxidant capacity of citrus pectin addition to 5% (w/v) linseed/sunflower oil emulsions stabilized with 0.5% (w/v) Tween 80, as affected by pectin molecular characteristics. The peroxide formation in the emulsions, containing tailored pectin structures, was studied during two weeks of storage at 35 °C. Low demethylesterified pectin (≤33%) exhibited a higher antioxidant capacity than high demethylesterified pectin (≥58%), probably due to its higher chelating capacity of pro-oxidative metal ions (Fe 2+ ), whereas the distribution pattern of methylesters along the pectin chain only slightly affected the antioxidant capacity. Nevertheless, pectin addition to the emulsions caused emulsion destabilization probably due to depletion or bridging effect, independent of the pectin structural characteristics. These results evidence the potential of structurally modified citrus pectin as a natural antioxidant in emulsions. However, optimal conditions for emulsion stability should be carefully selected. [ABSTRACT FROM AUTHOR]

The reaction between 4-oxo-2-alkenals (fumaraldehyde, 4-oxo-2-hexenal, and 4-oxo-2-nonenal) and phenolic compounds (resorcinol and 2-methylresorcinol) was studied to characterize the trapping ability of phenolic compounds for these lipid oxidation products. The reaction occurred rapidly under neutral or slightly basic conditions and different carbonyl-phenol adducts were produced. However, these compounds were unstable and their stabilization had to be achieved by means of either acetylation or reduction with sodium borohydride. Three different kinds of adducts were isolated and characterized by using mass spectrometry (MS) and 1D and 2D nuclear magnetic resonance spectroscopy (NMR). They were benzofuran-6-ols, 2,3,3a,8a-tetrahydrofuro[2,3- b ]benzofuran-2,6-diols, and chromane-2,7-diols. Most of them were produced as mixtures of diasteromers and all of them had a carbonyl group in a free form or as hemiacetal. A reaction pathway that explains the formation of these compounds is proposed. These results provide the basis to understand the removal of 4-oxo-2-alkenals by phenolic compounds in foods. [ABSTRACT FROM AUTHOR]

[Display omitted] • Lipid induced scission peptides are located on the surface of the protein in random coil segments. • Scission is especially present at the N- and C-terminus of beta-lactoglobulin. • Cysteine and aliphatic amino acids were most important cleavage sites. • The α-amidation pathway was the predominant mechanism in this study. • The comparison of various oxidants of proteins are compared to their ability of protein scission and modification. Lipid oxidation induced protein scission was investigated in oleogel using beta-lactoglobulin (whey protein isolate) as gelator. Extracted cleaved peptides were measured using high resolution mass spectrometry (FT-ICR-MS), which was provided by an automatically generated annotation list approach to identify relevant masses and sum formula using the isotopic pattern. The identified oxidized peptides were then further evaluated using partial least squares regression to relevant lipid hydroperoxide formation data, which provide the significance and importance of the peptides toward lipid induced scission. Thereby, the most important peptides are located at the surface of the protein in random coil segments and especially at the ends of the protein sequence. The most important amino acids were cysteine and aliphatic amino acids, which undergo scission mostly by the α-amidation pathway. The findings compare well with studies investigating depletion of amino acids initiated by lipid oxidation in systems containing bovine albumin or gamma-globulin. [ABSTRACT FROM AUTHOR]

The degradation of phenylalanine initiated by 2-pentenal, 2,4-heptadienal, 4-oxo-2-pentenal, 4,5-epoxy-2-heptenal, or 4,5-epoxy-2-decenal in the presence of phenolic compounds was studied to determine the structure-activity relationship of phenolic compounds on the protection of amino compounds against modifications produced by lipid-derived carbonyls. The obtained results showed that flavan-3-ols were the most efficient phenolic compounds followed by single m -diphenols. The effectiveness of these compounds was found to be related to their ability to trap rapidly the carbonyl compound, avoiding in this way the reaction of the carbonyl compound with the amino acid. The ability of flavan-3-ols for this reaction is suggested to be related to the high electronic density existing in some of the aromatic carbons of their ring A. This is the first report showing that carbonyl-phenol reactions involving lipid-derived reactive carbonyls can be produced more rapidly than carbonyl-amine reactions, therefore providing a satisfactory protection of amino compounds. [ABSTRACT FROM AUTHOR]

Quillaja saponin extract comprises both, surfactants and phenolic compounds, which makes it interesting, in particular, for the formulation of sensitive functional food ingredients and its protection against oxidation. The aim of this study was to investigate the antioxidant effect of Quillaja saponin extract in oil/water emulsions. Emulsions stabilised by Quillaja saponin showed decreased oxidation stability due to naturally occurring metals but stability increased to a great extent when a chelating agent was added. Antioxidant efficiency of the saponin extract was determined photometrically by 2,2′-diphenyl-1-picrylhydrazyl (DPPH) assay and by the use of electron paramagnetic resonance spectroscopy (EPR). EPR spectroscopy applying stable hydrophilic and hydrophobic radicals is advantageous, especially for characterisation of antioxidant efficiency at the interface. The extract showed antioxidant activity towards radicals in both environments, aqueous and hydrophobic, indicating the importance of phenolic compounds for the antioxidant properties of Quillaja saponin extract and their presence at the interface facilitated by saponin molecules. [ABSTRACT FROM AUTHOR]

• We investigated potential lipid oxidation product transfer between oil droplets. • Triglyceride-bound hydroperoxides are not prone to such a transfer. • Smaller, more hydrophilic molecules (e.g. 4-hydroperoxy-2-nonenal) can be transferred. • These molecules can also promote lipid oxidation when added to emulsions. Lipid oxidation is a major factor limiting the shelf life of food and other emulsion products. In this work, we explore which lipid oxidation products may transfer between oil droplets in model food emulsions stabilized by excess amounts of surfactant, and whether this affects the overall reaction. No significant differences in concentrations of triglyceride-bound hydroperoxides were found before and after mixing 'clean' oil droplets with pre-oxidized ones. Shorter and more hydrophilic lipid oxidation products, such as 4-hydroperoxy-2-nonenal and 2,4-decadienal, were found to equilibrate between oil droplets within 30 min. Adding exogenous 4-hydroperoxy-2-nonenal to an emulsion led to overall higher lipid oxidation values, although this effect was not systematic nor instantaneous. Therefore, it may be questioned whether transfer and subsequent initiation are always relevant for oxidizing emulsion systems. In future research, this question should be addressed for complex emulsions that are closer to real-life food products. [ABSTRACT FROM AUTHOR]

The formation of 2-phenylethylamine and phenylacetaldehyde in mixtures of phenylalanine, a lipid oxidation product, and a second amino acid was studied to determine the role of the second amino acid in the degradation of phenylalanine produced by lipid-derived reactive carbonyls. The presence of the second amino acid usually increased the formation of the amine and reduced the formation of the Strecker aldehyde. The reasons for this behaviour seem to be related to the α-amino group and the other functional groups (mainly amino or similar groups) present in the side-chain of the amino acid. These groups are suggested to modify the lipid-derived reactive carbonyl but not the reaction mechanism because the E a of formation of both 2-phenylethylamine and phenylacetaldehyde remained unchanged in all studied systems. All these results suggest that the amine/aldehyde ratio obtained by amino acid degradation can be modified by adding free amino acids during food formulation. [ABSTRACT FROM AUTHOR]

The initiation of lipid autoxidation within single oil droplets in Tween-20-stabilized oil-in-water emulsion was achieved by highly focused two-photon (2P) irradiation at excitation wavelength ( λ ex ) 700 nm. The radical formation was enhanced by inclusion of the photo-cleavable radical initiator di- tert -butyl peroxide (DTBP) into the droplets, and demonstrated with confocal microscopy using radical-sensitive probe BODIPY 665/676 . The radical chain reactions progressed up to 60 μm; however, there were no indications of oxidation in neighboring droplets demonstrating that radicals and oxidized probe molecules were not able to migrate between oil droplets. In addition, the spatial propagation of lipid autoxidation increased with the degree of oil unsaturation. [ABSTRACT FROM AUTHOR]

Lipid oxidation in oil-in-water (O/W) emulsions is an important factor determining the shelf life of food products. Salts are often present in many types of emulsion based food products. However, there is limited information on influence of salts on lipid oxidation in O/W emulsions. Thus, the purpose of this study was to examine the effects of sodium and potassium chloride on lipid oxidation in O/W emulsions. Tween 20 stabilized corn O/W emulsions at pH 7.0 were prepared with different concentrations of sodium chloride with or without the metal chelators. NaCl did not cause any changes in emulsion droplet size. NaCl dose-dependently promoted lipid oxidation as measured by the lipid oxidation product, hexanal. Both deferoxamine (DFO) and ethylenediaminetetraacetic acid (EDTA) reduced lipid oxidation in emulsions with NaCl, with EDTA being more effective. Potassium chloride showed similar impact on lipid oxidation as sodium chloride. These results suggest that salts are able to promote lipid oxidation in emulsions and this effect can be controlled by metal chelators. [ABSTRACT FROM AUTHOR]

In food systems, lipid oxidation can cause oxidation of other molecules. This research for the first time investigated oxidative degradation of β-glucan induced by lipid oxidation using an oil-in-water emulsion system which simulated a multi-phased aqueous food system containing oil and β-glucan. Lipid oxidation was monitored using peroxide value and hexanal production while β-glucan degradation was evaluated by viscosity and molecular weight measurements. The study showed that while lipid oxidation proceeded, β-glucan degradation occurred. Emulsions containing β-glucan, oil and ferrous ion showed significant viscosity and molecular weight decrease after 1 week of oxidation at room temperature. Elevated temperature (40 °C) enhanced the oxidation reactions causing higher viscosity drop. In addition, the presence of β-glucan appeared to retard the hexanal production in lipid oxidation. The study revealed that lipid oxidation may induce the degradation of β-glucan in aqueous food systems where β-glucan and lipids co-exist. [ABSTRACT FROM AUTHOR]

[Display omitted] • CP treatment caused heme degradation in Mb both in solution and in fish muscle. • Heme degradation products in Mb upon CP treatment induced fish lipid oxidation. • Typical lipid oxidation products including aldehydes, ketones, alcohols etc. were produced. In this study, the degradation of myoglobin both in solution and in tuna muscle by cold plasma (CP) was investigated through ultraviolet–visible and fluorescence spectroscopy analysis, and the effect of the degradation products on lipid oxidation in washed turbot muscle (WTM) was explored. Results showed that heme in myoglobin was degraded upon CP treatment, from which a fluorescent product was formed and iron was released. The degradation products promoted lipid oxidation in WTM during cold storage, in which the released iron played an important role. Results of gas chromatography-ion mobility spectrometry analysis showed that the contents of 37 volatile compounds in WTM were increased by heme degradation products induced lipid oxidation, including 20 aldehydes, 9 alcohols, 5 ketones and 3 furans. This study provides a new insight to the mechanism of lipid oxidation in CP-treated fish during cold storage, as well as guidance for preserving myoglobin-containing foods with CP. [ABSTRACT FROM AUTHOR]

The effect of permitted antioxidants, including α-tocopherol, β-carotene, ascorbyl palmitate, ascorbic acid, citric acid, and their combinations, on the lipid oxidation of structured lipid (SL)-based infant formula (IF) was evaluated. The 3.5% oil-in-water IF emulsion was formulated with a human milk fat analogue enriched with docosahexaenoic acid and stearidonic acid, and the antioxidants were added at 0.005% and 0.02% of the oil. The peroxide value, anisidine value, and hexanal concentration of emulsion samples were measured over a 28-day period. The results showed that whether a compound exhibited antioxidant behavior depended on its mechanism of action, polarity, concentration, and environmental conditions. The most effective antioxidant was ascorbyl palmitate at 0.005%, and a synergistic antioxidant effect was found between α-tocopherol and β-carotene. A high correlation was observed between anisidine value and hexanal content. Our findings have important implications for the successful incorporation of SL into IF products for infant nutrition and health. [ABSTRACT FROM AUTHOR]

In this study, beef patties were encapsulated with 3% chitosan, pectin, onion powder, or green tea powder and the beef patties were then passed through an in vitro human digestion model. The total lipid digestibility was lowest (p<0.05) in beef patties encapsulated with chitosan and pectin after digestion in the small intestine. Thiobarbituric acid reactive substance (TBARS) values were significantly lower (p<0.05) for beef patties encapsulated with chitosan and pectin, when compared with the control, after digestion in the small intestine. In contrast, the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical-scavenging activity was highest (p<0.05) in beef patties encapsulated with onion powder and green tea powder after digestion in the small intestine. The total cholesterol oxidation product (COP) content was significantly lower (p<0.05) in beef patties encapsulated with biopolymers than in the control after digestion in the small intestine. [ABSTRACT FROM AUTHOR]

• Fish co-products were pH-shift processed with antioxidant-containing raw materials. • This cross-processing reduced lipid oxidation during protein isolation/storage. • Lingonberry press-cake greatly limited MDA/HHE formation during isolation/storage. • Apple pomace and Ulva lowered the max level of MDA/HHE in herring protein isolates. • Pigments from helpers changed the color of protein isolates. Herring and salmon filleting co-products were pH-shift processed together with seven antioxidant-containing raw materials ("helpers") including lingonberry-, apple-, oat-, barley- and shrimp-co-products, and two seaweeds (Saccharina latissima, Ulva fenestrata) to produce protein isolates stable towards lipid oxidation. Malondialdehyde (MDA) and 4-hydroxy-(E)-2-hexenal (HHE) levels revealed that all helpers, except shrimp shells, to different extents retarded lipid oxidation both during pH-shift-processing and ice storage. The three helpers performing best were: lingonberry press-cake > apple pomace ∼ Ulva. Color of protein isolates was affected by helper-derived pigments (e.g., anthocyanins, carotenoids, chlorophyll) and lipid oxidation-induced changes (e.g., metHb-formation, pigment-bleaching). In conclusion, combining fish co-products with other food side-streams or seaweeds during pH-shift processing appears a promising new tool to minimize lipid oxidation of protein isolates, both during their production and subsequent storage. Lingonberry press-cake was the most efficient helper but provided dark color which may narrow product development possibilities, something which requires further attention. [ABSTRACT FROM AUTHOR]

Highlights: [•] The increase of incubation temperature increased the lipid oxidation in krill oil. [•] The increment of lipid oxidation could increase non-enzymatic browning reactions. [•] Strecker degradation products were formed in oxidised krill oil. [•] Pyrazines and pyridines were formed when carbonyls reacted with amino acids. [•] Pyrroles may protect krill oil against lipid oxidation during incubation. [Copyright &y& Elsevier]

Highlights: [•] Lipid deterioration of two lean fish species during frozen storage was evaluated. [•] Lipid composition and degradation were evaluated on both light and dark muscles. [•] Lower storage temperature (−30°C) showed significantly more preservative effects. [•] Marked difference observed in the composition of dark muscle of the two species. [•] Tertiary lipid oxidation and hydrolysis products are strongly correlated to sensory. [ABSTRACT FROM AUTHOR]

Highlights: [•] Enriched eggs contain higher amount of n-3 fatty acids, lutein and zeaxanthin. [•] n-3 enriched egg can be spray dried without losses of fatty acids, moderate losses of antioxidants. [•] Lipid oxidation remains at a low level even after the different processing steps. [•] Whole egg powders contained higher quantities of malondialdehyde than egg yolk powders. [ABSTRACT FROM AUTHOR]

Highlights: [•] Roles of moisture on the lipid oxidation were tested in linoleic acid model system. [•] Deuterium was found in headspace volatiles formed from linoleic acid oxidation. [•] Moisture acted as a substrate for the formation of volatiles. [•] Moisture in oils plays an important role as a substrate for the lipid oxidation. [ABSTRACT FROM AUTHOR]

Highlights: [•] Lipid oxidation can be a problem during fish protein hydrolysis. [•] There was a profound contradiction between cell and chemical antioxidant assays. [•] Oxidation products can have a detrimental effect on antioxidant properties of FPH. [•] Oxidation products arised during hydrolysis may affect anti-inflammatory activity in the body. [ABSTRACT FROM AUTHOR]

Highlights: [•] Influence of authentic human gastric juice on oxidation of marine lipids is evaluated. [•] Marine lipids in emulsion and liposomes oxidised during a modelled digestion period. [•] No difference was found between oxidation in an authentic gastric juice and a hydrochloric acid solution. [•] Gastric juice inhibited pro-oxidative activity of dietary iron ions, but not met-hemoglobin. [•] Beverages may both positively and negatively affect post-prandial oxidation of marine lipids. [Copyright &y& Elsevier]

Highlights: [•] Structured lipid-based infant formula emulsion was developed. [•] Response surface methodology was successfully applied to optimise the formulation. [•] Increased lecithin concentration led to a decrease in lipid oxidation. [•] Monoacylglycerol content affected particle size and emulsion viscosity. [Copyright &y& Elsevier]

[Display omitted] • Correlations between chicken color and lipid oxidation were analyzed by kinetic model. • The change of porphyrin ring in heme was observed by fluorescence electron microscope. • Homologous model of chicken Hb was established to explore the structure at different pHs. To investigate the effect of pH on lipid oxidation of chicken muscle, chicken hemolysates were added to washed chicken muscles to analyze lipid oxidation at pH 5.7, 6.3, and 7.2. The results showed that with a blue shift of the Soret peak, oxyhemoglobin gradually transformed to methemoglobin during storage, the shape of porphyrin rings of heme in fluorescence electron microscopy changed from round to trail-like structure. These changes were more significant at low pH. Comparing hemoglobin (Hb) structure, the distance of amino acids between the E10 of lysine and metHb-7-propionate groups is longer at pH 5.7 than other pHs, which makes solvent easily enter the heme cavity, leading to the severe destruction of Hb. The linear correlation between color and lipid oxidation also further confirmed that the increased oxidation of chicken Hb causes more rapid lipid oxidation in pH 5.7 than the other 2 pHs (p < 0.05). [ABSTRACT FROM AUTHOR]

[Display omitted] • LA improved the absorption of 5-DMT by stimulating production of lipid droplets and chylomicron. • The amount of 5-DMT transported to the bacterial side also enhanced by oxidized LA. • Oxidized LA induced ROS, affected tight junction and caused damages to Caco-2 monolayer. Lipids usually contain a large ratio of polyunsaturated fatty acids (PUFAs), which are highly susceptible to oxidation. Presence of oxidized lipids in foods may affect the bioavailability of lipophilic bioactive components after ingestion. In this study, the effect of oxidized and unoxidized linoleic acid (LA) on the transport of a highly lipophilic bioactive citrus flavonoid (5-hydroxy – 6, 7, 8, 4′ tetramethoxylflavone or 5-DMT) was determined using a Caco-2 cell model. Results demonstrated that compared to free 5-DMT, unoxidized LA improved the trans-enterocyte absorption of 5-DMT by stimulating the production of lipid droplets and chylomicrons. Although the amount of 5-DMT transported across the enterocyte doubled by oxidized LA compared to free 5-DMT, it significantly induced reactive oxygen species (ROS), affected the function of tight junction and caused damages to the morphology of enterocyte monolayer. This study re-emphasized the importance of preventing lipid oxidation in foods. [ABSTRACT FROM AUTHOR]

Abstract: An antioxidant composite film was developed from defatted mustard meal (DMM) without incorporating external antioxidants and its applicability as a coating to smoked salmon has been investigated. Film-forming variables included the concentration of xanthan, heat treatment, and high pressure homogenisation. Tensile strength, elongation, water vapour permeability, and water solubility of composite films of DMM and xanthan were 5.1–8.8MPa, 2.9–5.0%, 1.5–2.4gmm/kPa/h/m2, and 1.1–1.6%, respectively. The composite film with xanthan at 5% (w/w) demonstrated antioxidant properties and the coating with the solution forming the composite film (5% xanthan) retarded lipid oxidation and significantly reduced volatile changes in smoked salmon during storage at 4, 10, and 20°C for 21days. Coated salmon was preferred to uncoated salmon in glossiness and fish smell. The composite coating improved the stability of smoked salmon against lipid oxidation without imparting a negative sensory quality to the salmon. [Copyright &y& Elsevier]

Abstract: Lipid oxidation and fishy odour development in protein hydrolysate from fresh and ice-stored Nile tilapia (Oreochromis niloticus) were investigated. During iced storage of 18days, heme iron content decreased with a concomitant increase in non-heme iron content (P <0.05). Peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) values increased. Phospholipid content decreased with a corresponding increase in free fatty acid content. The results suggested that lipid hydrolysis and oxidation took place during storage. When protein hydrolysates were produced from fresh and 18days ice-stored Nile tilapia muscle, higher lipid oxidation and fishy odour/flavour along with higher amount volatile compounds were obtained in hydrolysate for unfresh sample (P <0.05). However, the addition of mixed antioxidants during hydrolysis process markedly lowered lipid oxidation, b ∗, ΔC ∗, ΔE ∗ values, fishy odour/flavour as well as the formation of volatile compounds in the resulting hydrolysates prepared from both fresh and unfresh samples. Therefore, hydrolysate from Nile tilapia muscle with reduced fishy odour and lighter colour could be prepared by using fresh fish and incorporation of mixed antioxidants during hydrolysis. [Copyright &y& Elsevier]

Abstract: Marama bean (Tylosema esculentum) is an underutilised legume indigenous to the Kalahari Desert region of southern Africa. The bean has high lipid content and hence is a potential source for production of edible oil. The headspace volatile composition of freshly pressed marama bean oil was explored and the oil was further studied during 7months of storage under different light and temperature conditions. The oxidative stability of the oil was examined by measuring peroxide value, vitamin E content and FT-IR spectra. Additionally, the headspace volatile composition of the oil was investigated during storage by use of dynamic headspace GC–MS. The results showed that marama oil is highly stable and has good natural antioxidant properties; enzymatic lipid oxidation does not take place in marama oil. Light has a greater effect on the lipid oxidation than has temperature, and hence marama oil should preferably be stored in darkness and rather at 25°C than 35°C. Under these conditions, the marama oil has a shelf life of at least 7months. [Copyright &y& Elsevier]

Abstract: Vibrational spectroscopy (mid FTIR and FT-Raman) was used to monitor lipids extracted from hake fillets during frozen storage. Kramer shear resistance was used as a marker of texture changes and lipid damage was also investigated by following the development of conjugated dienes and free fatty acids by spectrophotometric methods. Results show that the intensity of the free fatty acid carboxylic ν(Ceasured by ATR-FTIR spectroscopy can be used for monitoring the development of lipid hydrolysis in hake lipids. Changes in the Raman ν(Ching region (1658cm−1 band), partially attributed to conjugated dienes development, were the only observed spectroscopic alterations related to lipid oxidation of hake lipids during frozen storage at −10°C. The high correlation of free fatty acids with instrumental texture and the disappearance of the ν as(PO2 −) band are consistent with membrane lipid hydrolysis being one of the factors directly related with toughening of lean fish flesh. [Copyright &y& Elsevier]

Abstract: The effects of ginger extract (GE) marination on the changes in Muscovy duck breast muscle were evaluated. Pectoralis muscles were excised from the carcasses of male Muscovy ducks and marinated for 14days in GE at 5°C. Samples were taken at the end of 0, 1, 3, 7 and 14days of the marination. The results showed that the pH was higher (p <0.05) in the GE-marinated samples than in control samples and that TBARS values were lower (p <0.05) in the GE-marinated samples. The SDS–PAGE and western blot results indicated that titin, myosin heavy chain, desmin and α-actinin degraded more rapidly in the GE-marinated samples than in the control samples and that 32- and 30-kDa troponin-T degradation components were also generated in the GE-marinated samples. Our results suggest that GE marination could not only retard lipid oxidation, but also enhance the proteolysis of Muscovy duck breast muscle. [Copyright &y& Elsevier]

Abstract: Effect of tannic acid (0.02% and 0.04%) and ethanolic kiam wood extract (EKWE) (0.04% and 0.08%) on lipid oxidation and textural properties of fish emulsion sausages during 20days of refrigerated storage was investigated. Control samples (C) had the highest peroxide value (PV) and thiobarbituric acid-reactive substances (TBARS) value up to day 16 and 8 of storage, respectively. With the addition of tannic acid and EKWE, PV and TBARS values in the sausages were retarded effectively, compared to the control (P <0.05), especially when the tannic acid and EKWE at higher level were used. At the same level, EKWE showed the lower ability in retarding the lipid oxidation, in comparison with tannic acid. Tannic acid at both levels (0.02% and 0.04%) was also effective in retarding the formation of fishy odour in the samples throughout the storage, compared to the control and EKWE treated samples (P <0.05). Both tannic acid and EKWE had no detrimental effect on the sensory attributes of sausages. However, EKWE treated sample had lower L ∗ and higher a ∗ and ΔE ∗ values, compared to the control samples (P <0.05). After 20days of storage, the sample added with 0.04% tannic acid had higher hardness, gumminess and chewiness, compared with others (P <0.05). Samples added with 0.04% tannic acid also displayed more compact structure with no visible voids. Furthermore, oil droplets with smaller size were dispersed more uniformly, compared to others. Thus, tannic acid (0.02% and 0.04%) and EKWE (0.08%) were effective in retarding lipid oxidation and fishy odour development as well as could maintain the textural properties of fish emulsion sausages during the refrigerated storage of 20days. [Copyright &y& Elsevier]

Abstract: Free fatty acids are strong prooxidants in both bulk and emulsified oils. Addition of oleic acid to an oil-in-water emulsions increased lipid hydroperoxide and hexanal formation at free fatty acid concentrations as low as 0.1% of the lipid. The prooxidant effect of free fatty acids was dependent on fatty acid type with lipid oxidation rates being in the order of linolenic

Abstract: The capacity of hydroxytyrosol (HXT) to inhibit lipid oxidation in cooked pork meat batter, oil-in-water emulsions and potential functional frankfurters formulated with a healthier oil combination (as animal fat replacer) was studied during chilling storage, and its effect compared with those produced by synthetic antioxidants (BHA/BHT). Although efficiency varied, HXT was an effective antioxidant during chilling storage in the three food matrices studied. In general the order of inhibition capacity of HXT against lipid oxidation (thiobarbituric acid-reactive substances-TBARS) was cooked meat batter>oil-in-water emulsion>frankfurters, whereas in the case of BHA/BHT (with lower inhibitory activity than HXT) it was cooked meat batter>oil-in-water emulsion, and there was no antioxidative effect in frankfurters. Whereas significant correlations were established between lipid oxidation (TBARS) and antioxidative capacity measured by photochemiluminescence (PCL) in frankfurters supplemented with HXT and BHA/BHT, no significant correlations were found between ferric reducing/antioxidant power assay (FRAP) and TBARS and PCL. [Copyright &y& Elsevier]