Major dietary lipids in nutrition and health.

In this chapter, an overview of the major lipids in the diet with emphasis in nutritional aspects is provided. Triacylglycerols, i.e., glycerol esterified with three fatty acids, are the predominant constituents in dietary lipids. Therefore, this chapter focuses on the nature and nutritional significance of the main fatty acids in the diet and their possible modifications during food processing and commercialization. The main fatty acids in dietary lipids are grouped into saturated, monounsaturated and polyunsaturated fatty acids. Nutritional implications, the latest intervention trials and health recommendations will be discussed. A brief description of the major sources of lipids in the diet is included, oils and fats standing out. Other food sources shortly commented are milk and dairy products, meat, poultry and eggs, fish, and structured lipids designed to improve functional and nutritional properties. Modifications of fatty acids as a result of processing and commercialization are discussed because of their great relevance for their health implications, especially oxidation compounds and trans fatty acids.

RP-UHPLC-DAD-QTOF-MS As a Powerful Tool of Oleuropein and Ligstroside Characterization in Olive-Leaf Extract and Their Contribution to the Improved Performance of Refined Olive-Pomace Oil during Heating.

Since olive leaf is a potential source of phenolic fraction that is assumed to have good antioxidative effects, we purposed to add its extract to the refined olive-pomace oil during heating to increase its oxidative stability. RP-UHPLC-DAD-QTOF-MS was employed to characterize the phenolic fraction.The oil samples were evaluated by measuring the polymers and the polar compounds and thus detecting specific oxidized compounds. Using this approach, the results showed that incorporating olive leaf extract in refined oil significantly reduced the formation of polymers from 14.39% to 10.45% and the oxidation state by the variation of extinction ΔK from 3.02 to 2.29 during 20 h of heating compared to unenriched oil. This study has proven that the use of natural substances is an opportunity to extend the life of refined oils.

Quantitative determination of major oxidation products in edible oils by direct NP-HPLC-DAD analysis.

The objective of the present study was to explore the possibilities of the direct analysis of vegetable oils by normal-phase HPLC-DAD to evaluate the amounts of the main oxidation products of triacylglycerols containing linoleate, i.e. hydroperoxy-, keto- and hydroxy-dienes. A follow-up of oxidation at 40 °C of trilinolein, used as a simplified model lipid system, high-linoleic sunflower oil and high-oleic sunflower oil was performed to evaluate samples with different fatty acid compositions and different oxidation levels. The results showed that the HPLC-DAD method proposed allows for determining the concentrations of mono-hydroperoxydienes in edible oils without applying any isolation or derivatization step. The method was found to be direct, sensitive (LOQ 0.06 mmol/kg oil), precise (CV ≤ 5%) and also accurate, with 99% of analyte recovery. It also enabled the estimation of the minor amounts of ketodienes, but not those of hydroxydienes, which presented wide chromatographic bands and coeluted with a number of different minor oxidation compounds.

Concentrates of triterpenic acids obtained from crude olive pomace oils: characterization and evaluation of their potential antioxidant activity.

BACKGROUND: Pentacyclic triterpenic acids (TA) are phytochemicals of increasing nutritional interest owing to their bioactive properties, such as anti-inflammatory, antitumoral, antihyperglycemic and hepatoprotective. Crude olive pomace oils constitute a non-exploited significant source of these compounds. In the present study, concentrates of TA were extracted and characterized from crude olive pomace oils that were obtained by centrifugation and subsequent solvent extraction, respectively. Specifically, the concentrates were obtained from the byproduct generated in the filtration of the oils. The solids were subjected to Soxhlet extractions with hexane to remove the residual oil and then with ethanol for the TA extraction. RESULTS: Concentrates containing 850-980 g kg-1 TA were isolated from the oils obtained by centrifugation, whereas those isolated from oils obtained by hexane extraction presented levels of TA that ranged from 510 to 900 g kg-1 . Oleanolic (OA) and maslinic (MA) acids were the TA found in the concentrates. The relative contents of OA and MA were, respectively, 30:70 (w/w) and 77:23 (w/w). All concentrates also presented phenolic compounds at levels of g kg-1 and displayed slight antioxidant properties. CONCLUSION: Concentrates of TA, containing MA and OA, can be readily obtained from a byproduct generated by filtration of crude olive pomace oils. Concentrates isolated from oils obtained by centrifugation were rich in MA, whereas those from oils extracted with hexane were rich in OA. The concentrates showed slight antioxidant properties that can be mainly attributed to the presence of phenolic compounds and not to TA. © 2018 Society of Chemical Industry.

Possible adverse effects of frying with vegetable oils.

The question of whether heated fats in the diet may be detrimental to health is nowadays of the upmost concern, but finding an answer is not easy and requires careful consideration of different aspects of lipid oxidation. This review is divided into two sections. The first part deals with the nature of the new compounds formed at high temperature in the frying process as well as their occurrence in the diet while the second part focuses on their possible nutritional and physiological effects. Oxidation products present in abused frying fats and oils are the compounds most suspected of impairing the nutritional properties of the oils or involving adverse physiological effects. The recent studies on their health implications include those related to their fate and those focused on their effects in metabolic pathways and the most prevalent diseases.

Influence of Picual olive ripening on virgin olive oil alteration and stability during potato frying.

Ripening modifies oil attributes and composition. However, the influence of olive ripening on virgin olive oil (VOO) thermal oxidative stability on food-frying has not been studied yet. Oils from Picual olives of low (VOO1), medium (VOO2), and high (VOO3) ripeness were obtained, and their thermal oxidative stability during 40 potato-fryings was tested. Unused VOO1 showed higher antioxidant content and oxidative stability than VOO2 and VOO3. Polar compounds (PC), oligomers, and altered fatty acid methyl esters (polar-FAME) increased, whereas linoleic acid, polyphenols, and tocopherols decreased in the three VOOs through frying. The alteration was lower in VOO1, followed by VOO2 (0.105, 0.117, and 0.042 g/100 g oil less of PC, oligomers and polar-FAME per frying, respectively, in VOO1 than in VOO3). In conclusion, VOO obtained from low-ripeness Picual olives should be preferred when frying fresh-potatoes due to its higher thermal and oxidative stability, permitting a higher number of potato-frying uses.

Effectiveness of α-, γ- and δ-Tocopherol in a CLA-Rich Oil.

Conjugated linoleic acid (CLA) is a mixture of positional and geometric isomers of octadecadienoic acid with conjugated double bounds. Positive health properties have been attributed to some isomers, such as anticarcinogenic activity, antiartherosclerotic effects and reduction of body fat gain. Hence, oils rich in CLA such as Tonalin(®) oil (TO), normally obtained through alkaline isomerization of safflower oil (SO), an oil rich in linoleic acid (LA), are currently used in functional foods. However, special care must be taken to protect them from oxidation to ensure the quality of the supplemented foods. The objective of this work was to evaluate the oxidation and effectiveness of different tocopherol homologues (α-, γ- and δ-), alone or in combination with synergists (ascorbyl palmitate and lecithin), in TO compared to SO at different conditions, ambient temperature (25 °C) and accelerated conditions in Rancimat (100 °C). The oils, the oils devoid of their antioxidants and the latter containing the antioxidants added were assayed. Results showed great differences between SO and TO in terms of formation of hydroperoxides and polymers and also in the effectiveness of tocopherols to delay oxidation. TO showed higher levels of polymerization and, in general, the effectiveness of tocopherol homologues, alone or in combination with synergists, was also lower in the TO.

Evaporative light scattering detector in normal-phase high-performance liquid chromatography determination of FAME oxidation products.

The use of an ELS detector in NP-HPLC for quantitative analysis of oxidation products in FAME obtained from oils is evaluated in this study. The results obtained have shown that the ELS detector enables the quantitative determination of the hydroperoxides of oleic and linoleic acid methyl esters as a whole, and connected in series with a UV detector makes it possible to determine both groups of compounds by difference, providing useful complementary information. The limits of detection (LOD) and quantification (LOQ) found for hydroperoxides were respectively 2.5 and 5.7 µg mL⁻¹ and precision of quantitation expressed as coefficient of variation was lower than 10%. Due to a low sensitivity the ELS detector shows limitations to determine the low contents of secondary oxidation products in the direct analysis of FAME oxidized at low or moderate temperature. Analysis of FAME samples obtained either from high linoleic sunflower oil (HLSO) or high oleic sunflower oil (HOSO) and oxidized at 80 °C showed that only ketodienes formed from methyl linoleate can be determined in samples with relatively high oxidation, being the LOD and LOQ 0.2 and 0.4 mg/g FAME, respectively, at the analytical conditions applied. The ELS detector also enabled the determination of methyl cis-9,10-epoxystearate and methyl trans-9,10-epoxystearate, which were resolved at the chromatographic conditions applied. Results showed that these compounds, which are formed from methyl oleate, were not detected in the high-linoleic sample, but occurred at non-negligible levels in the oxidized FAME obtained from HOSO.

Quantitative analysis of hydroperoxy-, keto- and hydroxy-dienes in refined vegetable oils.

Quantitative analysis of the main oxidation products of linoleic acid - hydroperoxy-, keto- and hydroxy-dienes - in refined oils is proposed in this study. The analytical approach consists of derivatization of TAGs into FAMEs and direct analysis by HPLC-UV. Two transmethylation methods run at room temperature were evaluated. The reactants were KOH in methanol in method 1 and sodium methoxide (NaOMe) in method 2. Method 1 was ruled out because resulted in losses of hydroperoxydienes as high as 90 wt%. Transmethylation with NaOMe resulted to be appropriate as derivatization procedure, although inevitably also gives rise to losses of hydroperoxydienes, which were lower than 10 wt%, and formation of keto- and hydroxy-dienes as a result. An amount of 0.6-2.1 wt% of hydroperoxydienes was transformed into keto- and hydroxy-dienes, being the formation of the former as much as three times higher. The method showed satisfactory sensitivity (quantification limits of 0.3 µg/mL for hydroperoxy- and keto-dienes and 0.6 µg/mL for hydroxydienes), precision (coefficients of variation ≤ 6% for hydroperoxydienes and ≤ 15% for keto- and hydroxy-dienes) and accuracy (recovery values of 85(± 4), 99(± 2) and 97.0(± 0.6) % for hydroperoxy-, keto- and hydroxy-dienes, respectively). The method was applied to samples of high-linoleic (HLSO), high-oleic (HOSO) and high-stearic high-oleic (HSHOSO) sunflower oils oxidized at 40 °C. Results showed that the higher the linoleic-to-oleic ratio, the higher were the levels of hydroperoxy-, keto- and hydroxy-dienes when tocopherols were completely depleted, i.e. at the end of the induction period (IP). Levels of 23.7, 2.7 and 1.1 mg/g oil were found for hydroperoxy-, keto- and hydroxy-dienes, respectively, in the HLSO when tocopherol was practically exhausted. It was estimated that hydroperoxydienes constituted approximately 100, 95 and 60% of total hydroperoxides in the HLSO, HOSO and HSHOSO, respectively, along the IP.

Heterogeneous aspects of lipid oxidation in dried microencapsulated oils.

This work was aimed at studying lipid oxidation in dried microencapsulated oils (DMOs) during long-term storage. Samples were prepared by freeze-drying of emulsions containing sodium caseinate and lactose as encapsulating components. Evaluation of lipid oxidation was approached by quantitative analysis of nonvolatile lipid oxidation products and tocopherol. Lipid oxidation products were analyzed by separation of polar compounds by adsorption chromatography followed by HPSEC with refraction index detection for quantitation of oxidized triglyceride monomers, dimers, and oligomers. The analytical method applied enabled the detection of different oxidative patterns between the free and encapsulated oil fractions. The free oil fraction of DMOs showed a typical oxidative pattern for oils in continuous phase, which consisted of a clear induction period, in which hydroperoxides (oxidized triglyceride monomers) accumulated, before oxidation accelerated. The end of the induction period was marked by the total loss of tocopherol and the initiation of polymerization. On the contrary, the encapsulated oil showed a pattern characteristic of a mixture of oils with different oxidation status. Thus, high contents of advanced oxidation compounds (polymerization compounds) were detected when the antioxidant (tocopherol) was still present in high amounts. It is concluded that the encapsulated oil was comprised of oil globules with very different oxidation status. The results obtained in this study gave evidence of heterogeneous aspects of lipid oxidation in a dispersed-lipid food system.

Quantitation of short-chain glycerol-bound compounds in thermoxidized and used frying oils. A monitoring study during thermoxidation of olive and sunflower oils.

Major short-chain glycerol-bound compounds were investigated in olive oil (OO) and conventional sunflower oil (SO) during thermoxidation at 180 degrees C for 5, 10, and 15 h. These compounds included methyl heptanoate (C7:0), methyl octanoate (C8:0), methyl 8-oxo-octanoate (8-oxo-C8:0), methyl 9-oxononanoate (9-oxo-C9:0), dimethyl octanodiate (C8:0 diester), and dimethyl nonanodiate (C9:0 diester), which were analyzed by GC after derivatization of triacylglycerols to fatty acid methyl esters. An acceptable linear correlation (r = 0.967) was found between the total content of these compounds and the total content of polar compounds, suggesting that quantitation of the major short-chain glycerol-bound compounds provides a good indication of the total alteration level of oils heated at frying temperature. Samples with levels of polar compounds around 25% on oil showed total contents within 2-3 mg/g of oil. To determine the content of these compounds in used frying oils, 10 samples from restaurants and fried-food outlets in Spain were analyzed. Results showed total levels between 2.13 and 7.56 mg/g of oil in samples with contents of polar compounds ranging from 18.8 to 55.5% on oil. Samples with levels of polar compounds of approximately 25% showed total contents of the short-chain compounds similar to those found in the thermoxidized oils, that is, within 2-3 mg/g of oil.

Formation and evolution of monoepoxy fatty acids in thermoxidized olive and sunflower oils and quantitation in used frying oils from restaurants and fried-food outlets.

The formation and evolution of monoepoxy fatty acids, arising from oleic and linoleic acids, were investigated in olive oil and conventional sunflower oil, representatives of monounsaturated and polyunsaturated oils, respectively, during thermoxidation at 180 degrees C for 5, 10, and 15 h. Six monoepoxy fatty acids, cis-9,10- and trans-9,10-epoxystearate, arising from oleic acid, and cis-9,10-, trans-9,10-, cis-12,13-, and trans-12,13-epoxyoleate, arising from linoleic acid, were analyzed by gas chromatography after oil derivatization to fatty acid methyl esters. Considerable amounts, ranging from 4.29 to 14.24 mg/g of oil in olive oil and from 5.10 to 9.44 mg/g of oil in sunflower oil, were found after the heating periods assayed. Results showed that the monoepoxides quantitated constituted a major group among the oxidized fatty acid monomers formed at high temperature. For similar levels of degradation, higher contents of the monoepoxides were found in olive oil than in sunflower oil. Ten used frying oils from restaurants and fried-food outlets in Spain were analyzed to determine the contents of the monoepoxides in real frying oil samples. Levels ranged from 3.37 to 14.42 mg/g of oil. Results show that, for similar degradation levels, the monoepoxides were more abundant in the monounsaturated oils than in the polyunsaturated oils.