1H NMR Study of the In Vitro Digestion of Highly Oxidized Soybean Oil and the Effect of the Presence of Ovalbumin.

Oxidized lipids containing a wide variety of potentially toxic compounds can be ingested through diet. However, their transformations during digestion are little known, despite this knowledge being essential in understanding their impact on human health. Considering this, the in vitro digestion process of highly oxidized soybean oil, containing compounds bearing hydroperoxy, aldehyde, epoxy, keto- and hydroxy groups, among others, is studied by 1H nuclear magnetic resonance. Lipolysis extent, oxidation occurrence and the fate of oxidation products both present in the undigested oil and formed during digestion are analyzed. Furthermore, the effect during digestion of two different ovalbumin proportions on all the aforementioned issues is also addressed. It is proved that polyunsaturated group bioaccessibility is affected by both a decrease in lipolysis and oxidation occurrence during digestion. While hydroperoxide level declines throughout this process, epoxy-compounds, keto-dienes, hydroxy-compounds, furan-derivatives and n-alkanals persist to a great extent or even increase. Conversely, α,ß-unsaturated aldehydes, especially the very reactive and toxic oxygenated ones, diminish, although part of them remains in the digestates. While a low ovalbumin proportion hardly affects oil evolution during digestion, at a high level it diminishes oxidation and reduces the concentration of potentially bioaccessible toxic oxidation compounds.

Different Effects of Vitamin C-Based Supplements on the Advance of Linseed Oil Component Oxidation and Lipolysis during In Vitro Gastrointestinal Digestion.

Although widely consumed, dietary supplements based on Vitamin C contain high doses of this compound, whose impact on lipid oxidation during digestion needs to be addressed. Therefore, the effect of seven commercial supplements and of pure l-ascorbic acid and ascorbyl palmitate on linseed oil during in vitro gastrointestinal digestion was tackled. The advance of lipid oxidation was studied through the generation of oxidation compounds, the degradation of polyunsaturated fatty acyl chains and of gamma-tocopherol, by employing Proton Nuclear Magnetic Resonance. Supplements containing exclusively l-ascorbic acid enhanced the advance of linseed oil oxidation during digestion. This was evidenced by increased formation of linolenic-derived conjugated hydroxy-dienes and alkanals and by the generation of conjugated keto-dienes and reactive alpha,beta-unsaturated aldehydes, such as 4,5-epoxy-2-alkenals; moreover, gamma-tocopherol was completely degraded. Conversely, supplements composed of mixtures of ascorbic acid/salt with citric acid and carotenes, and of ascorbyl palmitate, protected linseed oil against oxidation and reduced gamma-tocopherol degradation. The study through Solid Phase Microextraction-Gas Chromatography/Mass Spectrometry of the volatile compounds of the digests corroborated these findings. Furthermore, a decreased lipid bioaccessibility was noticed in the presence of the highest dose of l-ascorbic acid. Both the chemical form of Vitamin C and the presence of other ingredients in dietary supplements have shown to be of great relevance regarding oxidation and hydrolysis reactions occurring during lipid digestion.

Assessment of Soybean Oil Oxidative Stability from Rapid Analysis of its Minor Component Profile.

The minor components of vegetable oils are important for their oxidative stability. In order to know to what extent they can influence oil behaviour under oxidative conditions, two commercial soybean oils, one virgin and the other refined, both with very similar compositions in acyl groups but differing in their minor component profiles, were subjected to accelerated storage conditions. They were characterized by 1H nuclear magnetic resonance (NMR) and direct immersion solid-phase microextraction coupled to gas chromatography/mass spectrometry (DI-SPME-GC/MS), while oil oxidation was monitored by 1H-NMR. The lower levels of tocols and sterols in the virgin oil, together with its higher free fatty acid content when compared to the refined one, result in a lower oxidative stability. This is deduced from faster degradation of acyl groups and earlier generation of hydroperoxides, epoxides, and aldehydes in the virgin oil. These findings reveal that commercial virgin soybean oil quality is not necessarily higher than that of the refined type, and that a simple and rapid analysis of oil minor components by DI-SPME-GC/MS would enable one to establish quality levels within oils originating from the same plant species and similar unsaturation level regarding composition in potentially bioactive compounds and oxidative stability.

A Dual Perspective of the Action of Lysine on Soybean Oil Oxidation Process Obtained by Combining 1H NMR and LC-MS: Antioxidant Effect and Generation of Lysine-Aldehyde Adducts.

Little is still known about both the effect of amino acids on the oxidation course of edible oils and the modifications that the former may undergo during this process. Bearing this in mind, the objective of this work was to study the evolution of a system consisting of soybean oil with 2% of l-lysine under heating at 70 °C and stirring conditions, analyzing how the co-oxidation of the oil and of the amino acid affects their respective evolutions, and trying to obtain information about the action mechanism of lysine on soybean oil oxidation. The study of the oil progress by 1H Nuclear Magnetic Resonance (1H NMR) showed that the presence of lysine noticeably delays oil degradation and oxidation products generation in comparison with a reference oil without lysine. Regarding lysine evolution, the analysis by 1H NMR and Liquid Chromatography-Mass Spectrometry of a series of aqueous extracts obtained from the oil containing lysine over time revealed the formation of lysine adducts, most of them at the position, with n-alkanals, malondialdehyde, (E)-2-alkenals, and toxic oxygenated α ß-unsaturated aldehydes. However, this latter finding does not seem enough to explain the antioxidant action of lysine.

Influence of minor components on lipid bioaccessibility and oxidation during in vitro digestion of soybean oil.

BACKGROUND: Minor components of edible oils could influence their evolution during in vitro digestion. This might affect the bioaccessibility of lipid nutrients and the safety of the ingested food. Bearing this in mind, the evolution of virgin and refined soybean oils, which are very similar in acyl group composition, has been studied throughout in vitro digestion using 1 H nuclear magnetic resonance (NMR) and solid-phase microextraction-gas chromatography /mass spectrometry, focusing on lipolysis and oxidation reactions. The fate of γ-tocopherol, the main antioxidant present in soybean oil, has also been analyzed with 1 H NMR. RESULTS: There were no noticeable differences in lipolysis between the two oils that were studied. The extent of oxidation during digestion, which was very low in both cases, was slightly higher in the virgin type, which showed lower tocopherols and squalene concentrations than the refined one, together with a considerable abundance of free fatty acids. This can be deduced both from the appearance after digestion of conjugated hydroperoxy- and hydroxy-dienes only in the virgin oil, and from its higher levels of volatile aldehydes and 2-pentyl-furan. Under in vitro digestion conditions, the formation of epoxides seemed to be favored over other oxidation products. Finally, although some soybean oil essential nutrients like polyunsaturated fatty acids exhibited no significant degradation after digestion, γ-tocopherol concentration diminished during this process, especially in the virgin oil. CONCLUSION: Although the minor component composition of the soybean oils did not affect lipolysis during in vitro digestion, it influenced the extent of their oxidation and γ-tocopherol bioaccessibility. © 2019 Society of Chemical Industry.

A new methodology capable of characterizing most volatile and less volatile minor edible oils components in a single chromatographic run without solvents or reagents. Detection of new components.

The possibilities offered by a new methodology to determine minor components in edible oils are described. This is based on immersion of a solid-phase microextraction fiber of PDMS/DVB into the oil matrix, followed by Gas Chromatography/Mass Spectrometry. It enables characterization and differentiation of edible oils in a simple way, without either solvents or sample modification. This methodology allows simultaneous identification and quantification of sterols, tocols, hydrocarbons of different natures, fatty acids, esters, monoglycerides, fatty amides, aldehydes, ketones, alcohols, epoxides, furans, pyrans and terpenic oxygenated derivatives. The broad information provided by this methodology is useful for different areas of interest such as nutritional value, oxidative stability, technological performance, quality, processing, safety and even the prevention of fraudulent practices. Furthermore, for the first time, certain fatty amides, gamma- and delta-lactones of high molecular weight, and other aromatic compounds such as some esters derived from cinnamic acid have been detected in edible oils.

Complexity and uniqueness of the aromatic profile of smoked and unsmoked Herreño cheese.

In this work, the volatile fraction of unsmoked and smoked Herreño cheese, a type of soft cheese from the Canary Islands, has been characterized for the first time. In order to evaluate if the position in the smokehouse could influence the volatile profile of the smoked variety, cheeses smoked at two different heights were studied. The volatile components were extracted by Solid Phase Microextraction using a divinylbenzene/carboxen/ polydimethylsiloxane fiber, followed by Gas Chromatography/Mass Spectrometry. In total, 228 components were detected. The most numerous groups of components in the unsmoked Herreño cheese were hydrocarbons, followed by terpenes and sesquiterpenes, whereas acids and ketones were the most abundant. It is worth noticing the high number of aldehydes and ketones, and the low number of alcohols and esters in this cheese in relation to others, as well as the presence of some specific unsaturated hydrocarbons, terpenes, sesquiterpenes and nitrogenated derivatives. The smoking process enriches the volatile profile of Herreño cheese with ketones and diketones, methyl esters, aliphatic and aromatic aldehydes, hydrocarbons, terpenes, nitrogenated compounds, and especially with ethers and phenolic derivatives. Among these, methylindanones or certain terpenes like α-terpinolene, have not been detected previously in other types of smoked cheese. Lastly, the results obtained suggest a slightly higher smoking degree in the cheeses smoked at a greater height.

Application of multivariate analysis to the effects of additives on chemical and sensory quality of stored coffee brew.

The aim of this work was to obtain a black coffee brew to be consumed hot by extension of its shelf life, by addition of additives. Four pH-regulator agents (sodium and potassium carbonates and bicarbonates), one pH regulator and antioxidant (sodium citrate), three antioxidants [sodium ascorbate, ethylenediaminetetracetic acid (EDTA), and sodium sulfite], and lactoserum were tested by sensory analysis. Sodium carbonate and bicarbonate were selected for a study of the physicochemical (soluble and volatile compounds related to the sensory properties) and sensorial quality of coffee brew stored for 90 days at 4 degrees C. Although both additives extended the shelf life of the coffee brew up to 60 days, sodium carbonate was the chosen additive because it was the most useful in limiting the pH decrease and perception of sourness, which are some of the main factors involved in the rejection of stored coffee brews, and it better maintained the aroma and taste/flavor. Moreover, the application of multivariate analysis facilitated first the description of the global changes of the coffee brews with or without additives throughout the storage using principal component analysis and second the obtainment of a simple equation only with pH and caffeic acid parameters to discriminate the three types of coffee brews and simplify the analytical process, by means of the stepwise discriminant analysis.

Changes in volatile compounds and overall aroma profile during storage of coffee brews at 4 and 25 degrees C.

In this work, the chemical changes occurring in the volatile fraction of Arabica coffee brews during storage at 4 and 25 degrees C for 30 days have been characterized for the first time by means of HS-GC-MS. A total of 47 compounds were identified and quantified: 2 sulfur compounds, 7 aldehydes, 3 esters, 15 furans, 5 ketones, 1 alcohol, 2 thiophenes, 4 pyrroles, 1 pyridine, 5 pyrazines, 1 alkene, and 1 acid. No new volatile compounds were detected at the end of the storage time. The changes observed are, in general, slower and less pronounced at refrigeration temperature. Storage also affects the sensory characteristics of the stored coffee brews, which lose part of their aroma intensity and freshness, acquiring some nondesirable notes such as rancid aroma, mainly during storage at 25 degrees C. Furthermore, seven aroma indices have been proposed as indicators of coffee brew staling, which show a good correlation with some sensory attributes, not only for aroma but also overall sensory quality. Consequently, they could be considered useful to monitor both the "age" and the sensory quality of stored coffee brews.

Load of polycyclic aromatic hydrocarbons in edible vegetable oils: importance of alkylated derivatives.

The presence of polycyclic aromatic hydrocarbons (PAHs) has been studied in different samples of olive oil, extra virgin olive oil, and refined seed oils. A high number of PAHs have been found, with a wide range of molecular weights and in concentrations that are high or even very high compared with the data obtained by other authors, especially in the seed oils. Among the PAHs identified, more than half are alkylated compounds, which account for the major part of the total PAH concentration in some of the samples. The total PAH concentrations in olive oils and extra virgin olive oils are similar, but the former present a higher proportion of heavy PAHs than the latter. The seed oils, in general, have much higher concentrations than the different types of olive oil and their PAH profiles are different. One of the olive oil samples exhibited a PAH distribution similar to that observed in olive pomace oil, suggesting possible adulteration. These data reveal that, in some cases, PAH profile provides useful information in relation to the possible origin of the contamination. We also observed large differences in PAH distribution between oils with the same label but from different batches. PAHs with varying degrees of carcinogenicity have been identified in all the samples, including benzo[a]pyrene, although this PAH was identified neither in the extra virgin olive oils nor in two of the seed oil samples.

Occurrence of polycyclic aromatic hydrocarbons in smoked cheese.

The presence of polycyclic aromatic hydrocarbons (PAH) in smoked cheeses of different origin was studied. The samples were subjected to an initial extraction of fat and an alkaline treatment, extracted with cyclohexane, cleaned up by means of solid-phase extraction tubes, and analyzed by gas chromatography/mass spectrometry (GC/MS) operating in selective ion-monitoring mode (SIM). The results revealed the presence of numerous polycyclic aromatic hydrocarbons in the exterior zone of the samples, some of them with methyl groups. In all cases, the concentrations of compounds of low molecular weight were much higher than those of high molecular weight. Polycyclic aromatic hydrocarbons with varying degrees of carcinogenicity were identified, including benzo(a)pyrene in concentrations, which, although they did not exceed the limit established for this compound in the rind of ripened cheeses, do exceed the limit of 0.03 microg/kg fixed for other foods smoked with smoke flavorings. Significant differences in the number and concentration of PAH in smoked cheese also were observed from rind to interior, the rind being the most contaminated zone.

Polycyclic aromatic hydrocarbons and olive pomace oil.

The occurrence of polycyclic aromatic hydrocarbons (PAHs) in five samples of olive pomace oil has been studied to determine the contamination degree of this type of oil and to evaluate if specific purification steps must be introduced during its manufacture. The PAHs present have been determined by gas chromatography-mass spectrometry. A high number of PAHs, with a wide range of molecular weights and in very high concentrations, have been found in four of the samples studied. A very high number of alkyl derivatives and, in many cases, in higher concentrations than their respective parent PAHs, have also been identified. One of the samples, however, presents a more reduced number of PAHs and in significantly lower concentrations than the others. These findings reveal that it is necessary to introduce adequate cleanup steps in the manufacturing process of olive pomace oil, which can give rise to oils with a relatively low content of PAHs. Some carcinogenic PAHs have also been identified, both unalkylated and alkylated.