Volatile Lipid Oxidation Products Research Articles

Analysis of Early Lipid Oxidation in Salmon Pâté with Cod Liver Oil and Antioxidants

Analytical methods that can detect early stages of lipid oxidation in complex food matrixes are highly needed, and the interest in rapid methods is great. In the present study, sensory analysis, dynamic headspace/gas chromatography-mass spectrometry (GC-MS), front-face fluorescence spectroscopy, and an electronic nose were used to detect early lipid oxidation in salmon pâte. The pâte was enriched with cod liver oil to increase the n-3 content, and citric acid (CA) or calcium disodium ethylenediamine tetraacetate (EDTA) were used as metal chelators. The sensory panel, GC-MS, and fluorescence methods detected oxidative changes in the pâte after 4 wk of storage. The fluorescence intensity increased with time. More volatile lipid oxidation products were formed in pâte with cod liver oil than in pâte without oil, but no differences were found between the batches with regard to rancid odor and flavor. CA and EDTA slightly promoted formation of volatile oxidation products. EDTA had a small positive impact on the sensory perception of the samples, whereas CA did not work favorably. With better packaging and antioxidant protection, n-3 enriched salmon pâte could be viable. Front-face fluorescence and dynamic headspace/GC-MS could be well suited to monitor lipid oxidation in such products.

Evaluation of oxidative stability of canola oils by headspace analysis

AbstractLipid oxidation is a major factor affecting flavor quality and shelf life of vegetable oils. Oxidative stability is therefore an important criterion by which oils are judged for usefulness in various food applications. In this study a method based on headspace analysis was developed to evaluate relative oxidative stability of canola oils. The method does not require the use of chemicals, involves minimal sample preparation, and can be performed on a relatively small sample size in comparison with traditional wet chemical methods. Canola oils freshly extracted in the laboratory from different seed samples were subjected to accelerated oxidation and analyzed for PV by standard methods and headspace volatiles by solid phase microextraction/GC‐MS. Forward stepwise regression analysis of the data revealed a relationship between PV and headspace concentration of the volatile lipid oxidation products hexanal and trans,trans‐2,4‐heptadienal. The PV calculated using this formula correlated (R2=0.73) with those measured by conventional methods.

Modeling the sensory impact of defined combinations of volatile lipid oxidation products on fishy and metallic off-flavors.

The volatiles (E,Z)-2,6-nonadienal, 1-penten-3-one, (Z)-4-heptenal, and (E,E)-2,4-heptadienal were added to milk containing 1.5% fat according to a central composite design, to evaluate the individual and combinatory effects of these volatiles on sensory properties. The milk samples with added volatiles were subjected to sensory descriptive analysis for fishy and metallic off-flavors. The data were analyzed using partial least-squares regression and multiple linear regression to develop mathematical models. The models revealed significant main effects of (E,Z)-2,6-nonadienal and 1-penten-3-one and highlighted the importance of two-factor interactions for contribution toward off-flavors. The results suggest that (E,Z)-2,6-nonadienal and 1-penten-3-one could be useful markers for fishy and metallic off-flavors in fish oil and fish oil enriched foods. Within the addition levels of the volatiles there was a curvature effect of (E,Z)-2,6-nonadienal, a compensatory effect of (Z)-4-heptenal and (E,E)-2,4-heptadienal, and a synergistic effect of (E,Z)-2,6-nonadienal and (Z)-4-heptenal in the development of fishy off-flavors.

The effect of Lactococcus lactis starter cultures on the oxidative stability of liquid whey.

The oxidative stability of liquid Cheddar cheese whey was evaluated using 2 Lactococcus lactis starter cultures in combination and alone along with a control, utilizing glucono-delta-lactone for acid development. Fresh and stored whey were evaluated for volatile composition, free fatty acids, and flavor by descriptive sensory analysis. A significant increase in volatile lipid oxidation products, most notably, hexanal, occurred during storage, and a corresponding decline in the free fatty acid linoleic acid was found. The flavor and aroma characteristic, cardboardy, was correlated to the increase in volatile lipid oxidation products and the decline in linoleic acid. Evidence strongly suggested that lipid oxidation was initiated during whey production and escalated during storage and that the starter cultures significantly influenced the level of volatile lipid oxidation products. Further understanding of the impact of starter cultures on whey may allow for the production of higher quality whey ingredients with wider food application.

Volatile Compound analysis of ageing Pinus sylvestris L. (Scots pine) seeds

AbstractThe volatile compound profiles of 11 Scots pine (Pinus sylvestris L.) seed lots were determined by solid phase microextraction combined with GC–MS analysis. Typical monoterpene constituents of pine volatile oils were identified, and total monoterpene content of these seeds was measured semi‐quantitatively as peak area. Considerable variation in monoterpene composition was found between seeds of different origin, especially in two major constituents, 3‐carene and α‐pinene. The relative concentrations of these compounds varied between 0–67 and 16–52%, respectively. Comparison of total monoterpene amounts showed that reduced monoterpene content was typical for aged, poorly germinating seeds. However, high germinability was not always associated with a high monoterpene content. Therefore, no clear dependency between monoterpene content and seed ageing could be established based on this data. The possible protective role of monoterpenes in pine seed ageing during long‐term storage is discussed. In addition, a drastic increase in volatile lipid oxidation products was found in the oldest seed lots. In 20 year‐old seeds, the percentage of hexanal, an oxidation product of fatty acids, was 3% of the total volatiles, whereas in 31 year‐old seeds it was 17%. No hexanal or other lipid oxidation products were detected in younger seeds. Copyright © 2003 John Wiley & Sons, Ltd.

Differences Between Sensory Profiles and Development of Rancidity During Long‐Term Storage of Native and Processed Oat

ABSTRACTChanges in the sensory attributes, lipid composition, and amounts of volatile and phenolic compounds of native and processed (germinated and dried) crushed oat were followed during a 12‐month storage period. The influence of the chemical attributes on the sensory profiles of oats was analyzed by statistical multivariate techniques (PLS regression). During the storage period, significant changes in the sensory profiles of the native and processed oat groats were observed. The stability of oat groats was significantly increased through germination and subsequent drying because the chemical changes causing rancidity and bitterness developed more slowly in the processed oat when compared with the native oat. In native oat, the most intensive changes due to deteriorat ion had already occurred after one month of storage, whereas in processed oat, these changes were perceived considerably later. Stored oat that had deteriorated was evaluated as being musty and earthy in odor and bitter and rancid in flavor. The accumulation of free fatty acids and volatile compounds related to lipid oxidation were closely correlated with the development of the undesired sensory attributes described above. The total amount of phenolic compounds, as well as the volatile aromatic and branched chain compounds derived mainly from protein degradation, showed a significant relationship with favorable sensory attributes such as roasted odor and flavor. Lipid oxidation occurred during the storage and was observed both in the polar and in the nonpolar lipid classes of native oat, whereas in the processed oat, these changes were nonsignificant. Photo‐oxidation of acylated fatty acids may significantly contribute to the development of volatile lipid oxidation products during storage.

Aroma compounds of oxidised sunflower oil and its oil-in-water emulsion: volatility and release under mouth conditions

The influence of medium composition on the release and volatility (vapour/liquid partitioning) of volatile lipid oxidation products was studied in order to explain the differences in composition of volatiles released from oxidised sunflower oil and its 40% oil-in-water emulsion in a model mouth system. Volatile compounds were analysed by gas chromatography combined with flame ionisation detection and mass spectrometry. Larger amounts of volatiles, formed during oxidation, were released from the emulsion than from the bulk oil. Differences in release influenced the results as well as the partitioning, but showed contrary effects. Added reference compounds were released in larger quantities from the oil than from the emulsion in the model mouth, and higher vapour/liquid partitioning values were obtained for the emulsion in comparison with the oil. In addition, water and saliva components influenced the release of reference compounds in the model mouth and the partitioning, giving different results for the oil and the emulsion. In conclusion, differences in the release of volatile compounds due to medium composition influenced the composition of the volatile lipid oxidation products of sunflower oil and its emulsion, as well as the lipid oxidation rate.

Oxidation mechanisms in real food emulsions: oil-water partition coefficients of selected volatile off-flavor compounds in mayonnaise

A method for the determination of oil/water partition coefficients, P o/w, for volatile lipid oxidation products in mayonnaise enriched with fish oil has been developed. Selected volatile off-flavor compounds (2-pentenal, 3-heptanone, octanal, 1-octen-3-ol, 2,4-heptadienal, and 2-nonanone) were added in levels ranging from 80 to 480 ng/g mayonnaise. The mayonnaises were separated by a procedure involving freezing, centrifugation, and ultracentrifugation. The P o/w values were then determined from the concentrations of volatiles quantified by dynamic headspace gas chromatography on the separated lipid and aqueous phases. The P o/w values for the selected volatiles ranged from 4.9 to infinity. Increased addition levels of the six volatile compounds resulted in an increase of the apparent P o/w values and higher recoveries of the volatiles. Also, the effect on P o/w values of an additional emulsifier (Panodan TR) and three different antioxidant systems (Grindox 1032, Toco 70, and ascorbic acid) added to mayonnaise was studied. Addition of ascorbic acid seemed to increase recoveries, which resulted in higher P o/w values. In contrast, addition of extra emulsifier and a water dispersible tocopherol preparation (Grindox 1032) resulted in lower P o/w values and lower recoveries for analysis. We propose that the effect of Grindox 1032 addition may be due to the ability of this antioxidant preparation, via its emulsifier content, to promote increased binding or entrapment of volatile compounds at the oil/water interface of mayonnaise. The data may be useful for selecting antioxidant and emulsifier systems to mask off-flavor development in food emulsion systems.

Reduced oxidative susceptibility of LDL from patients participating in an intensive atherosclerosis treatment program

The goal of this investigation was to determine whether participation in an atherosclerosis treatment program would reduce the oxidative susceptibility of LDL from patients with coronary artery disease. The treatment program included intensive exercise therapy, stress management, and consumption of a diet containing 10% fat. The size and antioxidant and lipid contents of LDL particles from 25 patients were analyzed at baseline and after 3 mo of therapy. The susceptibility of LDL to copper-mediated oxidation was measured by a conjugated diene assay and headspace gas chromatography (HSGC). Atherosclerosis treatment significantly reduced plasma total cholesterol and apolipoprotein B concentrations and the molar ratio of LDL cholesterol ester to apolipoprotein B (P < 0.01). The LDL content of a-tocopherol and β-carotene was increased (27% and 17%, respectively, P < 0.04) and the molar ratio of LDL cholesterol ester the sum of LDL a-tocopherol and LDL b-carotene decreased from 159 at baseline to 122 at 3 mo (P < 0.01). The lag phase of LDL conjugated diene formation increased 24%, whereas the maximum rate of oxidation slowed 29% (P < 0.01). As assessed by HSGC, copper-catalyzed formation of volatile lipid oxidation products was reduced 15% (P < 0.007); the reduction in volatiles was correlated with an increase in the α-tocopherol content of LDL (r = 20.48, P < 0.01). The principal determinants of reduced LDL oxidative susceptibility were the particle contents of α-tocopherol and β-carotene. To our knowledge, this is the first report to document a reduction in LDL oxidation in coronary artery disease patients undergoing atherosclerosis-reversal therapy.

Volatile Lipid Oxidation Products of Wagyu and Domestic Breeds of Beef

The influence of beef source, cooking method, and refrigerated storage time on the contents of volatile lipid oxidation products of Wagyu and domestic sources of beef was determined. Longissimus dorsi muscle from Japanese Wagyu, American Wagyu, Longhorn, Angus, and U.S. Choice carcasses was boiled or roasted and stored for 0 or 3 days at refrigerator temperatures. With storage time, the contents of lipid oxidation products increased significantly (P < 0.05). Interactions between beef source and storage time were significant (P < 0.05) for hexanal, 2-pentylfuran, octanal, nonanal, and other major lipid oxidation products. Beef source was shown to have a significant effect on the content of these compounds following 3 days of storage but not immediately following cooking (0 day). The contents of lipid oxidation products were higher in the Japanese and American Wagyu breeds than in other domestic beef sources. In general, cooking method had only minor influences on the content of lipid oxidation products. Ke...

Formation of headspace volatiles by thermal decomposition of oxidized fish oilsvs. oxidized vegetable oils

To understand the reasons for differences in oxidative stability among edible oils, the temperature dependence was investigated for the development of volatile lipid oxidation products in fish oils and in vegetable oils. A rapid headspace capillary gas chromatographic method was developed to determine volatile oxidation products of omega‐6 (n‐6) polyunsaturated fats (pentane and hexanal) and omega‐3 (n‐3) polyunsaturated fats (propanal) at different decomposition temperatures. Headspace gas chromatographic analyses of partially oxidized menhaden, bonita and sardine oils could be performed at 40°C, whereas soybean, canola, safflower, high‐oleic sunflower and high‐oleic safflower oils required temperatures greater than 100°C. Volatile formation by thermal decomposition of oxidized oils had lower apparent activation energies in fish oils than in vegetable oils, and significantly higher apparent activation energies in high‐oleic oils than in polyunsaturated oils. The activation energy data on headspace volatiles provided another dimension toward a better understanding of the thermal stability of flavor precursors in unsaturated fish and vegetable oils.

Lipase Activity and Development of Rancidity in Oats and Oat Products Related to Heat Treatment during Processing

A pilot plant process simulation of dry and wet hydrothermic treatment of oats was performed in order to study the effect of the different process steps on lipase activity and the storage stability of the fat phase. A comparison was made between oats that had passed through a dry kiln treatment prior to steam preparation and oats that had only been steam-treated. Samples were taken after step in the process as well as during storage at +30°C for up to 44 weeks. The lipase activity disappeared after steam preparation, but not after the dry-heat treatment used in this process experiment. The fat phase was analysed with regard to the amount of free fatty acids (FFA) and the content of individual fatty acids. The initial content of FFA was about 8-9%. The hydrolysis of fat, giving an increase in the amount of FFA, took place in all the stored samples, but was much more pronounced in the samples that had not undergone dry- heat treatment. In the dry-heat-treated samples, the FFA concentration reached a maximum at 13-15% after 16 weeks of storage. In the samples that had not been dry- heat-treated, the FFA reached over 30% in whole oat grains after 16 weeks of storage and continued to increased to over 40% after 30 weeks of storage. In the flour the FFA concentration was lower than in whole grains. Unexpectedly, lipolysis in this case was more pronounced in the whole kernels than in the flour samples. Lipolysis was not related to the measured remaining lipase activity. Head-space analyses of hexanal indicated that the formation of volatile lipid oxidation products was dependent on the process design, but the hexanal concentration was not related to the amount of FFA.

Loss of Volatile Lipid Oxidation Products during Thermal Desorption in Dynamic Headspace‐Capillary Gas Chromatography

ABSTRACTUnsaturated aldehydes from lipid oxidation, t‐2‐hexenal, t‐2‐heptenal, t, t‐2,4‐heptadienal and t,t‐2,4‐decadienal were investigated for structural alteration during dynamic headspace (DHS)‐gas chromatographic (GC) analysis. After thermal desorption during which the GC carrier gas, hydrogen, flowed through Tenax TA adsorbent trap, both 2‐alkenals and 2,4‐alkadienals produced partially and fully hydrogenated compounds as artifacts. The loss due to hydrogenation was most severe with 2,4‐decadienal, its recovery being 31.2%. Hydrogenated artifacts were not observed after thermal desorption with helium as the GC carrier gas. It is recommended that helium instead of hydrogen be used as the carrier gas in conducting DHS‐GC analysis of unsaturated lipid oxidation compounds.

Determination of volatile lipid oxidation products by dynamic headspace-capillary gas chromatographic analysis with application to milk-based nutritional products

A dynamic headspace-capillary gas chromatographic analysis technique with cryofocusing was investigated for the quantitation of volatile lipid oxidation products. Alkanals, t-2-alkenals, t,t-2,4-alkadienals, and 1-pentanol were purged, trapped onto Tenax TA, and then back-flushed into a gas chromatograph by thermal desorption. Back-flushed compounds were reconcentrated at -150 o C and then injected into a capillary column by rapid heating, resulting in a satisfactory separation with no band broadening. Volatile compounds were transferred quantitatively during thermal desorption

Development of a fluorescence sensor to monitor lipid oxidation. 1. Fluorescence spectra of chitosan powder and polyamide powder after exposure to volatile lipid oxidation products

The fluorescence spectra of chitosan and polyamide powder after exposure to lipid oxidation volatiles were obtained by solid-sample fluorescence spectrophotometry. Chitosan powder fluoresced after exposure to the volatile oxidation products from oxidizing methyl arachidonate and methyl linolenate. Chitosan powder also fluoresced after exposure to pure malonaldehyde vapor. Chitosan fluorescence after exposure to volatile malonaldehyde had an excitation maximum at 395 nm and an emission maximum at 460 nm

Thermal decomposition of methyl linoleate and methyl linolenate hydroperoxides analyzed by capillary gas chromatography.

Much work has been reported on the volatile oxidation products of unsaturated fats because they cause rancidity in foods and cellular damage in the body. Decomposition of fatty ester hydroperoxides creates a wide range of carbonyl compounds, hydrocarbons, furans, and other materials that contribute to flavor deterioration of foods and that are implicated in biological oxidation. Interaction of some of these degradation products with DNA, proteins, and enzymes may be involved in cell-damaging reactions.2–4 Although fatty acid hydroperoxides are the recognized precursors of volatile secondary products, relatively little information is available on the mechanism of their decorposition. New information on the volatile lipid oxidation products is needed to better evaluate precursors of oxidative deterioration in lipid-containing foods and to understand the biological significance of lipid peroxidation.

Chemical lonization‐mass spectrometry of secondary oxidation products from methyl linoleate and linolenate

AbstractChemical ionization‐mass spectrometry (CI‐MS) with a direct exposure probe was used to analyze a series of hydroperoxy cyclic peroxides and dihydroperoxides obtained from methyl linoleate and linolenate by either autoxidation or photosensitized oxidation. The mass spectra obtained with isobutane and ammonia as reacting gases showed fragmentation patterns similar to those ditions of gas chromatography (GC)‐electron impact (EI)‐MS. Because the fragmentation patterns obtained under either CI‐MS with a direct exposure probe or GC‐(EI)‐MS conditions are sufficiently predictable, these techniques are powerful analytical tools for the structural characterization of lipid oxidation products. These techniques are also useful to elucidate the cleavage pathways to volatile lipid oxidation products of flavor and biological significance.

Analysis of autoxidized fats by gas chromatography‐mass spectrometry. IX. Homolytic vs. Heterolytic cleavage of primary and secondary oxidation products

AbstractTo elucidate the genesis of volatile lipid oxidation products, thermal homolytic and acid heterolytic decomposition processes were compared. Secondary oxidation products were decomposed thermally (200 C), and the volatiles formed were identified by capillary gas chromatography‐mass spectrometry (GC‐MS). Oxidation products also were decomposed in the presence of HCl‐methanol, and the resulting dimethyl acetals were identified by GC‐MS. The volatile thermal decomposition products were those expected by homolytic β‐scission on both sides of the hydroperoxide group. No dialdehydes were identified under our thermal decomposition conditions. In contrast, the acetals formed by acid decomposition were those expected by selective heterolytic scission between the hydroperoxide group and the allylic double bond. Dialdehydes identified from acid decomposition of cyclic peroxides and dihydroperoxides included malonaldehyde and 2,4‐hexadienedial.

Lipid oxidation catalysts and inhibitors in raw materials and processed foods

This paper is limited to those catalysts and lipid oxidation inhibitors which have been found to be present either in the raw food materials or in processed food as a result of its processing. Lipoxygenase and haemoproteins are very powerful lipid oxidation catalysts in many foods. Heat treatment usually inactivates lipoxygenase but can, under certain conditions, activate haemoproteins as non-enzymatic metal catalysts. Tocopherol, normally referred to as an antioxidant, can, under certain concentration conditions, shift to pro-oxidative properties. Even volatile lipid oxidation products have been shown to accelerate lipid oxidation. Inhibitors present in raw materials are found among proteins, amino acids and plant constituents such as flavonoids. Most spices and herbs have antioxidative properties, particularly in darkness. Some microorganisms in their normal metabolism inhibit lipid oxidation or the consequences thereof. Some enzymes, especially superoxide dismutase, are claimed to inhibit lipid oxidation. Among process-induced lipid oxidation inhibitors, Maillard reaction products are those most investigated, together with protein hydrolysates. Smoking generates antioxidative compounds. In most cases the mechanism of lipid oxidation inhibition is still unknown for these materials.

1640. Second thoughts on rubratoxin B: Moss, M. O., Robinson, F. V. & Wood, A. B. (1968). Rubratoxin B, a toxic metabolite of Penicillium rubrum. Chemy Ind. p. 587

The physical stability, interfacial composition and protein-lipid co-oxidation of O/W emulsions stabilised by whey protein isolate under different pH conditions (3.0, 5.0, 7.0 and 9.0) with fixed storage times were assessed in the present study. The results revealed that different pH conditions had distinct effects on the physical stability of the emulsions, as verified by the droplet size, ζ-potential and interfacial composition. Acidic conditions had an unnoticeable impact on protein-lipid co-oxidation. Remarkable physical barrier-like protection of the lipid core provided by adsorbed proteins (AP) was observed in the O/W emulsions under neutral conditions. However, alkaline conditions (pH 9.0) could induce the most severe protein-lipid co-oxidation when the storage time was extended, as indicated by the highest levels of protein and lipid oxidation products (carbonyl, N′-formyl-l-kynurenine, lipid hydroperoxides, thiobarbituric acid-reactive substances and volatile lipid oxidation products), in addition to the obvious molecular changes in unadsorbed proteins (UAP) or AP. Free radicals and metal ions could more easily react with highly unfolded and negatively charged AP under strong alkaline conditions. Our findings clearly revealed that the co-oxidation phenomenon of O/W emulsion systems were closely related to the synergistic effects between the transformation of interfacial composition and aggregation of oil droplets that occurred under different pH conditions.