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.This research was funded by the Basque Government (EJ-GV) and its Departments of Universities and Research,(IT-916-16) and of Economic Development and Infrastructures, Area of Agriculture, Fisheries and Food Policy (PA19/02)

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,β-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.This work has been funded by the Spanish Ministry of Economy and Competitiveness (MINECO, AGL2015-65450-R, AEI/FEDER-EU) and by the Basque Government and its Departments of Universities and Research (EJ-GV, IT-916-16)

Effect of diet and dietary fatty acids on the transformation and incorporation of C18 fatty acids in double-muscled Belgian Blue young bulls

Three groups of double-muscled Belgian Blue young bulls were fed during different stages of production diets differing in the proportions of linolenic and linoleic acid by including linseed in the concentrate or giving grass silage as main linolenic acid suppliers. Samples of rumen and abomasal contents and of the longissimus thoracis, subcutaneous fat, and liver were taken to analyze the fatty acid pattern with emphasis on the individual trans (t) C18:1 fatty acids and cis-9,trans-11 conjugated linoleic acid (c9t11CLA). Trans C18:1 isomers represented up to 20 g/100 g of total fatty acids in rumen and abomasal contents, whereas the accumulation of c9t11CLA was limited. Total trans C18:1 content in subcutaneous fat and intramuscular fat of the longissimus thoracis comprised 8.4 and 5.2 g/100 g of total fatty acids, respectively, with t11C18:1 being the most abundant one. Compared to rumen contents, subcutaneous and intramuscular fat were enriched in c9t11CLA and contained fewer tC18:1 isomers, resulting in a higher c9t11CLA/t11C18:1 ratio (0.04, 0.22, and 0.22, respectively). This result suggests that the endogenous synthesis of c9t11CLA in adipose tissue by the Delta(9)-desaturase was more important than its ruminal production

Effect of tomato (Solanum lycopersicum L.) lycopene-rich extract on the kinetics of rancidity and shelf-life of linseed (Linum usitatissimum L.) oil

The effect of tomato lycopene-rich extract (TLE) addition on shelf-life of linseed oil was evaluated. Linseed oil was extracted by cold pressing and TLE by supercritical CO2. Linseed oils with and without TLE addition were characterized for moisture, colour, refractive index, fatty acid composition and antioxidants. Adding TLE to 80 mg lycopene/kg oil improved linseed oil stability, showing the same induction time at 110 \ub0C (by Rancimat) of control linseed oil with 200 mg/kg butylhydroxytoluene. The increase of free fatty acid, peroxide value, p-anisidine value, K232 and K268 at 40, 50, and 60 \ub0C until 90 days followed first-order kinetics. Rancidity rate augmented with temperature. TLE addition slowed oil degradation without changing the mechanism since the Arrhenius lines were parallel. Mean Ea were respectively 38.2, 24.7, 38.0, 38.2, 41.5 kJ/mol. TLE addition increased linseed oil shelf-life by 31% (Rancimat) and by 42% (stability kinetics during storage)

Assessment of the influence of soybean oil minor components, and of certain added tocopherols and dietary amino compounds on the oil oxidation process under thermoxidative conditions and/or on its evolution during in vitro digestion

419 p.In the present doctoral thesis three different topics have been addressed, these are:1- The influence of the minor compounds naturally present in commercial soybean oil on their evolution under accelerated storage conditions.It has been proved that in oils of the same botanical origin with very similar composition in acyl groups, their minor component profile has an influence on their evolution under accelerated storage conditions. This finding could contribute to establish criteria for the selection of vegetable oils with better oxidative stability among those from the same botanical source.2- The effect of adding alpha-tocopherol, gamma-tocopherol or L-lysine on the oxidative stability and the oxidation process of commercial soybean oil submitted to accelerated storage conditions.The effect of the addition of varying proportions of either alpha-tocopherol, gamma-tocopherol or L-lysine on the oxidation process of soybean oil under accelerated storage conditions has been studied in depth by means of 1H NMR. This technique provides a broad vision of the oxidation process since it allows one to monitor simultaneously the evolution of the oil acyl groups and the generation and further evolution of a wide variety of oxidation products, both primary and secondary. The differences in the mechanism of action of the studied tocopherols and of lysine have become clear, as well as their effect on soybean oil at different concentration levels. Although alpha-tocopherol exerts an overall prooxidant effect on soybean oil at most of the proportions tested, it could be said that, especially in the case of alpha-tocopherol, it is difficult to define the action of the studied tocopherols either as antioxidant or prooxidant, due to their complex effect on the rates of oil degradation and of hydroperoxide concentration increase, on the time needed to reach oil total polymerization and on the generation pace of secondary oxidation products. However, the addition of lysine clearly delays the oil oxidation process, extending its shelf-life. Furthermore, some of the modifications undergone by lysine as a consequence of the cooxidation process with soybean oil have also been identified by means of LC/MS.3- The study of the in vitro digestion process of commercial soybean oil and of the influence of the oil composition in minor components, of its initial oxidative status and of the presence of different proportions of ovalbumin on lipolysis and oxidation reactions.Within this section it has been shown that the minor components naturally present in soybean oil can slightly affect the occurrence of oxidation reactions taking place under in vitro digestion conditions. It has also been proved that the initial oxidative status of the oil not only negatively affects lipolysis but also can favour oxidation during digestion depending on the oil oxidation extent, all this reducing the bioaccessibility of lipid nutrients. Moreover, although not all the types of oxidation products initially present in the oils subjected to digestion evolve in the same way during this process, some potentially toxic ones remain in the digestates. Finally, while the presence of a low proportion of ovalbumin during the in vitro digestion of oxidized soybean oil does not significantly affect either lipolysis or oxidation or oxidation compound evolution, a high proportion of this protein can affect all these processes and contribute to both improve lipid digestion and reduce the concentration of some toxic compounds in the digestate

Oxidative stability of sunflower oils supplemented with kenaf seeds extract, roselle seeds extract and roselle extract, respectively under accelerated storage

With the concern of adverse effects of lipid oxidation on food deterioration and human health, the antioxidant activities of kenaf seed extracts (KSE), roselle seed extracts (RSE) and roselle extracts (RE) were evaluated by comparing its oxidative stability in refined, bleached & deodorised (RBD) sunflower oils with that of in synthetic antioxidant, BHA. Established methods such as peroxide values (PV), p-anisidine values (AV), TOTOX values, free fatty acids (FFA), iodine values (IV), total phenolic contents (TPC), conjugated dienes (CD) and conjugated triene (CT) were employed to assess the extent of oil deterioration. During 24 days storage, consensus was accomplished based on the results assessed by PV, TOTOX, CD, CT, IV and TPC at which the antioxidant activities of KSE, RSE and RE were better than BHA. Surprisingly, the results obtained by AV and FFA assays showed the reversed. Among the extracts, RSE exhibited the best antioxidant activities. These suggest that KSE, RSE and RE may be used as potential source of natural antioxidants in the application of food industry to prevent lipid oxidation

Synthesis of anti-inflamamtory lipid mediators using soybean flour lipoxygenase

This thesis describes the application of soybean flour as an inexpensive, natural enzyme source in the synthesis of anti-inflammatory lipid-based mediators from omega-3 fatty acids. Soybean flour has been demonstrated to be a more versatile biocatalyst than a commercial soybean enzyme in forming product efficiently and catalysing complex lipid mixtures