High Linoleate Research Articles

Revealing adulterated olive oils by triacylglycerol screening methods: Beyond the official method

Official control methods to detect olive oil (OO) adulteration fail to provide satisfactory consumer protection. Thus, faster and more sensitive screening tools are needed to increase their effectiveness. Here, the official method for adulterant detection in OO was compared with three untargeted screening methods based on triacylglycerol analysis using high-throughput (FIA-HESI-HRMS; HT-GC–MS; HPLC-RID) and pattern recognition techniques (PLS-DA). They were assayed on a set of genuine and adulterated samples with a high natural variability (n = 143). The sensitivity of the official method was 1 for high linoleic (HL) blends at ≥2 % but only 0.39 for high oleic (HO) blends at ≥5 %, while specificity was 0.96. The sensitivity of the screening methods in external validation was 0.90–0.99 for the detection of HL and 0.82–0.88 for HO blends. Among them, HT-GC–MS offered the highest sensitivity (0.94) and specificity (0.76), proving to be the most suitable screening tool for OO authentication.

Large-scale evaluation of shotgun triacylglycerol profiling for the fast detection of olive oil adulteration

Fast and effective analytical screening tools providing new suitable authenticity markers and applicable to a large number of samples are required to efficiently control the global olive oil (OO) production, and allow the rapid detection of low levels of adulterants even with fatty acid composition similar to OO. The present study aims to develop authentication models for the comprehensive detection of illegal blends of OO with adulterants including different types of high linoleic (HL) and high oleic (HO) vegetable oils at low concentrations (2–10%) based on shotgun triacylglycerol (TAG) profile obtained by Flow Injection Analysis-Heated Electrospray Ionisation-High Resolution Mass Spectrometry (FIA-HESI-HRMS) at a large-scale experimental design. The sample set covers a large natural variability of both OO and adulterants, resulting in more than one thousand samples analysed. A combined PLS-DA binary modelling based on shotgun TAG profiling proved to be a fit for purpose screening tool in terms of efficiency and applicability. The external validation resulted in the correct classification of the 86.8% of the adulterated samples (diagnostic sensitivity = 0.87), and the 81.1% of the genuine samples (diagnostic specificity = 0.81), with an 85.1% overall correct classification (efficiency = 0.85).

Inhibition of Hydroperoxy‐, Keto‐ and Hydroxy‐FAME by Alpha‐ and Delta‐Tocopherol at Rancimat Conditions

AbstractThe effects of α‐ and δ‐tocopherol on inhibition of hydroperoxides, keto and hydroxy compounds under Rancimat conditions, i.e. 100 °C and air bubbling, were studied in samples of fatty acid methyl esters (FAME) obtained from high linoleic (HL) and high oleic (HO) sunflower oils. Primary hydroperoxides from methyl linoleate and methyl oleate and secondary keto and hydroxy compounds derived from methyl linoleate hydroperoxides were analyzed by HPLC–UV‐ELS. Different tocopherol concentrations, namely, 10, 50, 100, 500 and 1000 mg/kg, were tested. Irrespective of the lipid substrate and the initial concentration of tocopherol, results showed that the content of hydroperoxides accumulated during the induction period was remarkably higher in the samples containing δ‐tocopherol. The relative concentrations of oleate hydroperoxides in the HO samples were also higher in the presence of δ‐tocopherol. α‐Tocopherol was more effective in inhibiting hydroperoxides at low levels, with 100 mg/kg as optimal concentration, while δ‐tocopherol displayed optimal protection at 1000 mg/kg. Under the oxidation conditions applied, neither α‐ nor δ‐tocopherol showed a protective effect on hydroperoxide decomposition at any level assayed. Formation of keto‐ and hydroxy‐dienes was more related to the concentration of their hydroperoxide precursors. Furthermore, both tocopherols gave rise to increased concentrations of ketodienes at 500 and 1000 mg/kg compared to the controls. Such an effect was more pronounced for α‐tocopherol and in the HL samples.

Nonsense-mediated mRNA degradation of CtFAD2-1 and development of a perfect molecular marker for olol mutation in high oleic safflower (Carthamus tinctorius L.)

There are two types of safflower oil, high oleic (HO) with 70-75% oleic acid and high linoleic (HL) with about 70% linoleic acid. The original HO trait in safflower, found in an introduction from India, is controlled by a partially recessive allele ol at a single locus (Knowles and Bill 1964). In the lipid biosynthesis pathway of developing safflower seeds, microsomal oleoyl phosphatidylcholine desaturase (FAD2) is largely responsible for the conversion of oleic acid to linoleic acid. In vitro microsomal assays indicated drastically reduced FAD2 enzyme activity in the HO genotype compared to conventional HL safflower. A previous study indicated that a single-nucleotide deletion was found in the coding region of CtFAD2-1 that causes premature termination of translation in the HO genotypes, and the expression of the mutant CtFAD2-1Δ was attenuated in the HO genotypes compared to conventional HL safflower (Guan et al. 2012). In this study, we hypothesise that down-regulation of CtFAD2-1 expression in the HO genotype may be explained by nonsense-mediated RNA decay (NMD). NMD phenomenon, indicated by gene-specific RNA degradation of defective CtFAD2-1Δ, was subsequently confirmed in Arabidopsis thaliana seed as well as in the transient expression system in Nicotiana benthamiana leaves. We have developed a perfect molecular marker corresponding to the olol mutation that can facilitate a rapid screening and early detection of genotypes carrying the olol mutation for use in marker-assisted selection for the management of the HO trait in safflower breeding programmes.

Comparative profiling of miRNA expression in developing seeds of high linoleic and high oleic safflower (Carthamus tinctorius L.) plants.

Vegetable oils high in oleic acid are considered to be advantageous because of their better nutritional value and potential industrial applications. The oleic acid content in the classic safflower oil is normally 10–15% while a natural mutant (ol) accumulates elevated oleic acid up to 70% in seed oil. As a part of our investigation into the molecular features of the high oleic (HO) trait in safflower we have profiled the microRNA (miRNA) populations in developing safflower seeds expressing the ol allele in comparison to the wild type high linoleic (HL) safflower using deep sequencing technology. The small RNA populations of the mid-maturity developing embryos of homozygous ol HO and wild type HL safflower had a very similar size distribution pattern, however, only ~16.5% of the unique small RNAs were overlapping in these two genotypes. From these two small RNA populations we have found 55 known miRNAs and identified two candidate novel miRNA families to be likely unique to the developing safflower seeds. Target genes with conserved as well as novel functions were predicted for the conserved miRNAs. We have also identified 13 miRNAs differentially expressed between the HO and HL safflower genotypes. The results may lay a foundation for unraveling the miRNA-mediated molecular processes that regulate oleic acid accumulation in the HO safflower mutant and developmental processes in safflower embryos in general.

Formation of Hydroperoxy‐, Keto‐ and Hydroxy‐Dienes in FAME from Oils: Influence of Temperature and Addition of α‐Tocopherol

AbstractThe influence of temperature (40, 60 and 80 °C) and addition of α‐tocopherol (0, 500 mg/kg) on the formation and distribution of the main oxidation products of linoleic acid, i.e. hydroperoxy‐, keto‐ and hydroxy‐dienes, were studied in samples of fatty acid methyl esters (FAME) derived from high‐linoleic (HL) and high‐oleic (HO) sunflower oils. In the range of temperatures studied, the formation of hydroperoxydienes showed monomolecular and bimolecular rate constants that ranged from 0.01 to 1 mmol1/2kg−1/2h−1 and from 0.02 to 0.9 h−1, respectively. The overall activation energies involved were similar for both samples and for the monomolecular and bimolecular periods (63–68 kJ/mol). The relative oxidation of methyl linoleate, which depended on the fatty acid composition of the FAME sample, was unaffected by temperature. At the three temperatures assayed, hydroperoxydienes constituted approximately 90 and 50% of total hydroperoxides in the HL and HO samples, respectively. Formation of keto‐ and hydroxy‐dienes was influenced by temperature in a similar way to hydroperoxydienes and, consequently, changes in the distribution of compounds were not observed. The addition of α‐tocopherol not only decreased the overall oxidation rate, but also affected the distribution of compounds. The content of hydroperoxydienes relative to that of total hydroperoxides was not affected by the presence of the antioxidant in the HL sample, whereas a significant increase (75%) was found in the HO sample compared with the control (50%). The addition of α‐tocopherol in both samples also resulted in a slight increase of keto‐ and hydroxy‐dienes in relation to hydroperoxydienes.

Quantitation of Hydroperoxy‐, Keto‐ and Hydroxy‐Dienes During Oxidation of FAMEs from High‐Linoleic and High‐Oleic Sunflower Oils

AbstractThe objective of this work was to study the quantitative formation of hydroperoxydienes, ketodienes and hydroxydienes during autoxidation at 40 °C of fatty acid methyl esters derived from two sunflower oils with different degree of unsaturation, high‐linoleic sunflower oil and high‐oleic sunflower oil. The analysis of the oxidation compounds was carried out by NP‐HPLC–UV and results were compared to the specific extinction at 232 nm (K232) and the peroxide value (PV). Analysis of FAME polymers by HPSEC was also performed to discard samples of advanced oxidation. Results showed that the contents of hydroperoxydienes with respect to the PV were higher for the high linoleic (HL) sample. At the end of the period of slow polymerization (ΔPol ≤ 1 wt%), the content of hydroperoxydienes was found to be 86.0 and 30.7 μg/mg for the HL and high oleic (HO) samples, respectively. Throughout this period, hydroperoxydienes constituted around 90 and 50 wt% of the total hydroperoxides in the HL and HO samples, respectively, suggesting that a significant oxidation of oleic acid also occurred in both samples. The contents of ketodienes and hydroxydienes as a whole constituted 2–3 wt% of the diene compounds analyzed at the end of the period of slow polymerization. Higher contents of ketodienes than of hydroxydienes were found throughout the oxidation time, and the ratio between the contents of ketodienes and hydroxydienes increased with a factor that changed from 1 to 2 throughout the period of slow polymerization.

Emission of Volatile Aldehydes from DAG‐Rich and TAG‐Rich Oils with Different Degrees of Unsaturation During Deep‐Frying

AbstractThe purpose of the present study was to compare the emission of volatile aldehydes from diacylglycerol‐rich oils (DAG‐OILs) and triacylglycerol‐rich oils (TAG‐OILs) with different degrees of unsaturation of fatty acid moieties during the deep‐frying of sliced potatoes. To examine the effect of fatty acid composition, four kinds of oils with different fatty acid compositions were selected: rape seed (RS); sunflower oil as a high oleic (HO); safflower oil as high linoleic (HL); and, perilla oil as high linolenic (HLn) oils. The emissions of volatile aldehydes were determined during the deep‐frying of sliced potatoes by using the above fresh test oils or deteriorated RS oils. The statistical analysis showed no significant difference in volatile aldehyde emission and profile between the DAG‐OIL and TAG‐OIL with the fatty acid composition of RS, HL, and HLn. Although a statistically significant difference was noted in the volatile aldehyde emission between the DAG‐OIL and TAG‐OIL with HO, this difference was extremely small when compared to the variations found in the oils with four types of fatty acid composition. Finally, no difference was found in the volatile aldehyde emissions between the deteriorated DAG‐OIL and TAG‐OIL, although volatile aldehyde emissions increased with frying time. In addition, the acrylamide contents in potato chips prepared with RS–DAG or RS–TAG were at comparable levels.

The effects of high pressure treatment and of storage periods on the quality of vacuum-packed “salchichón” made of raw material enriched in monounsaturated and polyunsaturated fatty acids

Abstract This study investigates the effects of high-pressure processing on the microbiological, physico-chemical and sensory properties of 3 fermented Spanish dry sausages (salchichon), all high in unsaturated fatty acids. The products, manufactured from the sausage meat and back fat of pigs fed on high-oleic and high-linoleic diets and a control diet, were vacuum-packed prior to high hydrostatic pressure (HPP) treatment (500 MPa, 5 min), and storage at 6 °C for up to 210 days. High-pressure treatment slightly inhibited certain microorganisms, especially yeasts and moulds, and psychotrophic and anaerobic bacteria. Consequentially, microbial counts fell, although injured microorganisms recovered during storage except in the case of the high-linoleic salchichon, in which they remained inactive causing it to register the lowest counts. High-pressure treatment had no noticeable effect on the physico-chemical and sensory properties of the three samples suggesting that it improves the food safety of salchichon with no detrimental effects on organoleptic properties. Industrial relevance The problem of safe preservation is increasingly complex for the meat industry as today's products require longer shelf lives and greater assurance of protection from microbial spoilage. High pressure processing is finding increased use in products such as sliced cured meats, where microbial contamination can occur during the slicing process and develop over storage. This study evaluates the microbiological, physicochemical and sensory characteristics of vacuum-packed slices of dry fermented sausage – control (CO), high oleic (HO), and high linoleic (HL) salchichon samples – following high pressure treatment and subsequent chilled storage, contributing thereby to the growing body of knowledge on this new food preservation technology, which produces microbiologically safe food products with long shelf lives, whilst retaining high nutritional and sensory qualities.

Fatty Acids Cause Alterations of Human Arterial Smooth Muscle Cell Proteoglycans That Increase the Affinity for Low-Density Lipoprotein

The dyslipidemia of insulin resistance, with high levels of albumin-bound fatty acids, is a strong cardiovascular disease risk. Human arterial smooth muscle cell (hASMC) matrix proteoglycans (PGs) contribute to the retention of apoB lipoproteins in the intima, a possible key step in atherogenesis. We investigated the effects of high NEFA levels on the PGs secreted by hASMCs and whether these effects might alter the PG affinity for low-density lipoprotein. hASMC exposed for 72 hours to high concentrations (800 micromol/L) of linoleate (LO) or palmitate upregulated the core protein mRNAs of the major PGs, as measured by quantitative PCR. Insulin (1 nmol/L) and the PPARgamma agonist rosiglitazone (10 micromol/L) blocked these effects. In addition, high LO increased the mRNA levels of enzymes required for glycosaminoglycan (GAG) synthesis. Exposure to NEFA increased the chondroitin sulfate:heparan sulfate ratio and the negative charge of the PGs. Because of these changes, the GAGs secreted by LO-treated cells had a higher affinity for human low-density lipoprotein than GAGs from control cells. Insulin and rosiglitazone inhibited this increase in affinity. The response of hASMC to NEFA could induce extracellular matrix alterations favoring apoB lipoprotein deposition and atherogenesis.

Physical state of inhibitor fatty acids and linoleate solutions under lipoxygenase assay conditions

AbstractA variety of fatty acids, which are potential competitive inhibitors of soybean lipoxygenase (EC 1.13.11.12), give kinetically unstable mixtures in standard assay solutions containing linoleate (substrate). In the assay solution (pH 10, 0.1 M borate, 1.63% ethanol), each fatty acid by itself shows normal surface tension vs concentration behavior; but, despite a range of solubilization techniques in the presence of 10 μM or higher linoleate and low concentrations of these materials, irreproducible surface‐tension readings and inhibition kinetics results. This inhomogeneity (or kinetic instability) disappears as the concentration increases. Critical micelle concentration (CMC) values of mixtures are not additive, and binary mixture behavior depends on fatty acid structure. Several lines of observation, including CMC values and actual surface tension (γ) values for several systems, suggest premicellar heterodimer or higher mixed aggregate formation. Lipids with Ki significantly above the irreproducible surface‐tension range give good kinetic behavior, and Ki is reported. The results are in accord with earlier work on aspects of these systems. Complementary solution physical studies must be done for any kinetic (or specificity) determinations of enzymes using lipids.

Calcium and Fat Absorption From Infant Formulas With Different Fat Blends

Three formulas with different fat blends were fed to 29 infants from the fourth to the tenth days of life. Absorption and retention of fat, calcium, and phosphorus were measured by a metabolic balance technique. The following observations were made: 1. Absorption of oleate and linoleate was best with the formula that had a linoleate:oleate ratio similar to that of human milk. Absorption of palmitate was similar with all three formulas. Stearate absorption was low in the formula with the lowest stearate content. 2. Calcium absorption was 36 mg/kg/day or 38% of intake with the formula which had a linoleate:stearate ratio similar to that of human milk; this was significantly greater than with the other two formulas which both had much higher linoleate:oleate ratios. 3. Phosphorus absorption was approximately 90% of intake with all three formulas, equivalent to 47 to 79 mg/kg/day. Retention varied from 27 to 53 mg/kg/day.