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.

Incorporation of hydroxytyrosol alkyl esters of different chain length as antioxidant strategy in walnut oil spray-dried microparticles with a sodium alginate outer layer.

Omega-3 rich vegetable oils, such as walnut oil, are gaining interest because of their health benefits. Synthetized homologous series of hydroxytyrosol alkyl esters (HTEs) with different alkyl chain lengths (C4-C18) were incorporated in purified walnut oil (PWO) spray-dried microparticles, designed with Capsul® (C) as encapsulating agent and sodium alginate (SA) as outer layer (PWO-C/SA). The encapsulation efficiency (>87%) and Tg of PWO-C/SA microparticles were not affected by the HTEs. The incorporation of HTE-C10 increased the melting point (185.0 ± 1.3 °C), decreasing the formation of Dimers + Polymers (1.12 ± 0.05% at day 35 of storage) and the crystallinity of the microparticles (>170 °C). The highest stability of PWO-C(HTE-C10)/SA suggests a specific location of HTE-C10 at the oil:water interface. The SA layer delayed the release of fatty acids during in vitro digestion. The incorporation of HTEs of medium chain length can be a suitable strategy to protect unsaturated oils encapsulated by spray-drying.

Stability of Bioactive Compounds in Olive-Pomace Oil at Frying Temperature and Incorporation into Fried Foods.

The stability of minor bioactive compounds in olive-pomace oils (OPOs) was evaluated at frying temperature under the conditions of a thermoxidation test. Bioactive compounds analyzed included squalene, tocopherols, sterols, triterpenic acids and alcohols, and aliphatic alcohols. In order to determine the amount of OPO bioactive compounds incorporated into foods after frying, three different kinds of frozen products were selected, i.e., pre-fried potatoes (French fries), pre-fried battered chicken nuggets, and chicken croquettes (breaded patties), and were used in discontinuous frying experiments. Results obtained in both the thermoxidation and frying studies showed high stability of triterpenic alcohols (erythrodiol and uvaol), oleanolic acid, and aliphatic alcohols, naturally present in OPOs. In all fried foods, the content of lipids increased after frying, as expected, although the extent of absorption of OPOs into fried foods and the exchange with food lipids depended on the food characteristics. Overall, frying with OPOs improved the nutritional properties of all products tested by increasing the level of oleic acid and by the incorporation of squalene, triterpenic acids and alcohols, and aliphatic alcohols, in significant quantities.

Performance of Olive-Pomace Oils in Discontinuous and Continuous Frying. Comparative Behavior with Sunflower Oils and High-Oleic Sunflower Oils.

Frying performance of olive-pomace oils (OPOs) as compared to sunflower oils (SOs) and high-oleic sunflower oils (HOSOs) was studied in discontinuous frying (DF) and continuous frying (CF) for the first time. DF is used in household, restaurants and frying outlets, while CF is used in the food industry. Oil alteration during frying was determined by measurements of polar compounds (PC) and polymers. Fried potatoes were analyzed for oil absorption and alteration, color, and evaluated in an acceptability test. Results for DF showed that all SOs reached 25% PC at the 9th frying operation (FO), whereas HOSOs did between the 17-18th FO and variable results were found for OPOs since initial levels of diacylglycerols were different. Rates of formation of PC or polymers were the lowest for OPOs, thus showing the best performance in DF. Specifically for PC, relative rates of formation were 1.00-1.11, 2.46-2.71 and 1.37-1.41 for OPOs, SOs and HOSOs respectively. In CF, OPOs and HOSOs behaved similarly and better than SOs, although none reached 25% PC after 40 FO. The good performance of OPOs can be attributed to the high monounsaturated-to-polyunsaturated ratio, in common with HOSOs, and the additional positive effect of minor compounds, especially ß-sitosterol and squalene.

Chemical Changes of Hydroperoxy-, Epoxy-, Keto- and Hydroxy-Model Lipids under Simulated Gastric Conditions.

Chemical changes occurring in dietary lipid oxidation compounds throughout the gastrointestinal tract are practically unknown. The first site for potential chemical modifications is the stomach due to the strong acidic conditions. In this study, model lipids representative of the most abundant groups of dietary oxidation compounds were subjected to in vitro gastric conditions. Thus, methyl linoleate hydroperoxides were used as representative of the major oxidation compounds formed in food storage at low and moderate temperatures. Methyl 9,10-epoxystearate, 12-oxostearate and 12-hydroxystearate were selected as model compounds bearing the oxygenated functional groups predominantly found in oxidation compounds formed at the high temperatures of frying. Analyses were performed using gas-liquid chromatography/flame ionization detection/mass spectrometry and high performance-liquid chromatography/ultraviolet detection. Losses of methyl 9,10-epoxystearate and linoleate hydroperoxides in the ranges 17.8-58.8% and 42.3-61.7% were found, respectively, whereas methyl 12-oxostearate and methyl 12-hydroxystearate remained unaltered. Although quantitative data of the compounds formed after digestion were not obtained, methyl 9,10-dihydroxystearate was detected after digestion of methyl 9,10-epoxystearate, and some major volatiles were detected after digestion of linoleate hydroperoxides. Overall, the results showed that significant modifications of dietary oxidized lipids occurred during gastric digestion and supported that the low pH of the gastric fluid played an important role.

Influence of the Location of Ascorbic Acid in Walnut Oil Spray-Dried Microparticles with Outer Layer on the Physical Characteristics and Oxidative Stability.

Purified walnut oil (PWO) microparticles with Capsul® (C, encapsulating agent), sodium alginate (SA) as outer layer and ascorbic acid (AA) as oxygen scavenger were obtained by spray drying using a three-fluid nozzle. AA was incorporated in the inner infeed (PWO-C(AA)/SA), in the outer infeed (PWO-C/SA(AA)) and in both infeed (PWO-C(AA)/SA(AA)). PWO-C(AA)/SA (4.56 h) and POW-C(AA)/SA(AA) (2.60 h) microparticles showed higher induction period than POW-C/SA(AA) (1.17 h), and lower formation of triacylglycerol dimers and polymers during storage (40 °C). Therefore, AA located in the inner infeed improved the oxidative stability of encapsulated PWO by removing the residual oxygen. AA in the SA outer layer did not improve the oxidative stability of encapsulated PWO since oxygen diffusion through the microparticles was limited and/or AA weakened the SA layer structure. The specific-location of AA (inner infeed) is a strategy to obtain stable spray-dried polyunsaturated oil-based microparticles for the design of foods enriched with omega-3 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.

Influence of the Physical State of Spray-Dried Flavonoid-Inulin Microparticles on Oxidative Stability of Lipid Matrices.

The effect of the physical state of flavonoid-inulin microparticles (semi-crystalline/amorphous) on the oxidative stability of lipid matrices was studied. Epicatechin (E) and quercetin (Q) microparticles with inulin were formulated at two infeed temperatures (15 °C and 90 °C) by spray drying. X-ray diffraction analyses showed that flavonoid-inulin microparticles obtained at feed temperature of 15 °C were semi-crystalline (E-In-15, 61.2% and Q-In-15, 60%), whereas those at 90 °C were amorphous (Q-In-90, 1.73 and Q-In-90 2.30%). Semi-crystalline state of flavonoid-inulin microparticles enhanced the EE (68.8 and 67.8% for E and Q, respectively) compared to amorphous state (41.6 and 51.1% for E and Q, respectively). However, amorphous Q-microparticles showed the highest antioxidant activity both in methyl linoleate and sunflower oil, increasing the induction period and decreasing the polar compounds and polymer triglyceride formation during long-term oxidation study. Therefore, the physical state of spray-dried flavonoid-inulin microparticles may determine their antioxidant activity in lipid matrices.

Effect of spray-drying with organic solvents on the encapsulation, release and stability of fish oil.

Fish-oil (FO) was encapsulated with hydroxypropylcelullose (HPC) by conventional spray-drying with water (FO-water) and solvent spray-drying with ethanol (FO-EtOH), methanol (FO-MeOH) and acetone (FO-Acet) in order to study the effect of the solvent on the encapsulation efficiency (EE), microparticle properties and stability of FO during storage at 40 °C. Results showed that FO-Acet presented the highest EE of FO (92.0%), followed by FO-EtOH (80.4%), FO-MeOH (75.0%) and FO-water (71.1%). A decrease of the dielectric constant increased the EE of FO, promoting triglyceride-polymer interactions instead of oil-in-water emulsion retention. FO release profile in aqueous model was similar for all FO-microparticles, releasing only the surface FO, according to Higuchi model. Oxidative stability of FO significantly improved by spray-drying with MeOH, both in surface and encapsulated oil fractions. In conclusion, encapsulation of FO by solvent spray-drying can be proposed as an alternative technology for encapsulation of hydrophobic molecules.

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.

Release kinetics of flavonoids in methyl linoleate from microparticles designed with inulin and channelizing agent.

Quercetin (Q), naringenin (N) and epicatechin (E) were encapsulated with inulin (In) as encapsulating agent and Capsul (C) as channelizing agent by spray drying and applying a Box-Behnken design. Q-In, N-In, E-In, Q-In-C, N-In-C and E-In-C were characterised by encapsulating efficiency (EE) and their release profile in methyl linoleate (ML). The flavonoid EE was significant higher (p<0.05) for Q and E (over 60%) than for N (≈40%) in microparticles either without or with channelizing agent. An increase of the number of flavonoid hydroxyl groups enhanced EE, showing the influence of the flavonoid structural features. The release profile was fitted to Peppas and Higuchi mathematical models. The highest and lowest flavonoid release rate constants were found for N and E, respectively, for microparticles both with and without channelizing agent. The EE as indicator of flavonoid-inulin interaction was inversely related with the release rate constant in ML. Flavonoid release rate constant was significantly higher for microparticles with channelizing agent than for those without it, suggesting that Capsul induces the formation of channels inside the microparticles thus favoring the diffusion of flavonoids to ML. The mechanism of flavonoid release was only determined by channelizing agents, independently of the flavonoid nature, that is, Fickian and non-Fickian diffusion mechanisms in microparticles with and without Capsul, respectively.

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.

Changes in the lipid composition of powdered infant formulas during long-term storage.

Changes in the lipid composition of two standard infant formulas induced by 4 years of storage were determined. Lipids were thoroughly analyzed using different gas-liquid and liquid-liquid chromatographic techniques. Oleic acid and linoleic acid, which accounted for almost the total monounsaturated and polyunsaturated fatty acids, respectively, showed slight but significant decreases (P < 0.05) during the 4 years of storage (from 41.52 to 39.83% for oleic acid and from 17.35 to 15.99% for linoleic acid). Total trans fatty acid isomers showed low initial level (0.22% of total fatty acids), and such level remained unchanged during the storage period. Nonvolatile oxidation compounds including oxidized, dimeric, and polymeric triglycerides did not significantly increase during the storage period, although a significant loss of tocopherols was found in the surface oil fraction (10-15%). In general, the results obtained indicate that, although small losses of oleic and linolenic acid as well as tocopherols were found, the 4 year storage period did not lead to relevant changes in the lipid fraction of infant formulas.

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.