Pecan (Carya illinoinensis) oil consumer hedonic rating,sensory characteristic,satiating and energizing effect,and drivers of overall acceptance

With increasing global health and wellness product needs, pecan oil is getting popular in recent years. Although considered a gourmet oil because of its unique sensory and nutritional values, there is no publication focusing on consumer attitude toward pecan oil. This study, for the first time, investigated consumer acceptance, sensory quality, and emotional response to five pecan oils from native and improved varieties, with a comparison to an olive oil. All five pecan oils had positive hedonic ratings (>5, with a 9-point hedonic scale) for overall acceptance and the acceptance of oil flavor, raw-nut flavor, and thickness, while the olive oil was rated slightly lower than 5 for these attributes. Pecan oils had higher intensities in raw-nut flavor, but lower in overall oil flavor, fatty flavor, astringency, and thickness compared to olive oil. Off-flavor was not perceived in pecan oils, whereas it was perceived in olive oil. The six oils did not show significant differences in satiating effects; however, olive oil was rated lower in energizing effects than pecan oils, which showed a significant variety difference (p ≤ 0.05). Consumer overall acceptance was significantly, positively driven by energizing effects, followed by the acceptability of raw-nut flavor, thickness, and oil flavor; off-flavors were negative drivers. Results obtained from this study add direct pecan oil consumer insight: an asset for pecan growers, pecan processing industry, and pecan oil marketers.     

Fatty acid composition and its relationship with physicochemical properties of pecan (Carya illinoensis) oil

The composition and physicochemical properties of pecan (Carya illinoensis) kernels and oils from different native trees of the central region of Mexico were investigated. The main compositional characteristic of the kernel was the high lipid content (70–79% w/w on dry basis) with elevated concentration of oleic acid (55–75% w/w). The results confirmed the relationship in the biosynthesis of linoleic and linolenic acids from oleic acid existing in oilseeds. Our results indicate that in pecans such relationship is a function of pecan tree age. The proportion of oleic, linoleic, and linolenic fatty acids determined the oxidative stability, viscosity, and melting/crystallization behavior of pecan oil. In general, these properties in pecan oils were similar or superior to extra-virgin olive oil and unrefined sesame oil. Although all native pecan oils studied showed a significant concentration of oleic acid, a particular group of native Mexican pecan trees produces an oil with a fatty acid composition with the nutritional appeal that consumers demand nowadays (i.e., very high oleic acid, 60–75%), with excellent natural oxidative stability (i.e., induction time for oxidation between 8.5 and 10.8 h), and substantially higher concentrations of α-, γ-, and δ-tocopherol than in pecan varieties previously reported in the literature.     

Increasing gamma‐ and delta‐tocopherols in oils improves oxidative stability

Over the past two decades, plant geneticists have revolutionized how fatty acid compositions of vegetable oils are optimized to improve oxidative stability and functionality. Now, the expertise of plant geneticists is reaching beyond altering fatty acids to changing other oil components such as tocopherols. Basic lipid research on optimizing tocopherol profiles and ratios in vegetable oils is providing information for geneticists to breed the next generation of oxidatively stable vegetable oils. This review will discuss three studies; first, a basic study to determine the oxidative stability provided by the addition of pure gamma and delta tocopherols to oils treated to remove natural tocopherols; second, a practical study to evaluate the oxidative stability of mid‐oleic sunflower oil from seeds modified by plant breeding to contain high amounts of γ‐ and δ‐tocopherols; and third, a frying test to determine the effects of gamma tocopherol addition.     

Effects of Seed Roasting on Tocopherols,Carotenoids, and Oxidation in Mustard Seed Oil During Heating

Seed roasting is practiced in the mustard oil industry in some areas of the world, and can affect the physicochemical properties of the oil for further applications. This research studied the differences in oxidative stability, tocopherols, and carotenoids during heating at 160 °C between oil extracted from roasted mustard seeds and that from unroasted seeds. The content of free fatty acids, polar compounds (PC), and lutein were not significantly different between the roasted and unroasted seed oils before heating. The fatty acid compositions of both oils were also similar, with high amounts of erucic, linoleic, and oleic acids, moderate amounts of linolenic and eicosenoic acids, and low amounts of palmitic and stearic acids. However, the levels of tocopherols and conjugated dienoic acids (CDA) were higher in the roasted seed oil. Heating increased the content of CDA and PC in both oils, but decreased tocopherols and lutein. The rates of increase in CDA and PC and the degradation rates of tocopherols and lutein during heating were lower in the roasted than in the unroasted seed oil. Overall, the increased thermo-oxidative stability of the mustard oil by roasting the seeds before oil extraction was highly correlated with improved heat stabilities for both tocopherols and lutein.     

Effect of Stripping Methods on the Oxidative Stability of Three Unconventional Oils

Stripped and non-stripped oils from Sclerocarya birrea [marula oil (SCO)], Aspongopus viduatus [melon bug oil (MBO)] and Agonoscelis pubescens [sorghum bug oil (SBO)], traditionally used for nutritional applications in Sudan, were investigated for their fatty acid and tocopherol composition, and their oxidative stability. Three stripping methods were used, phenolic compounds extraction, silicic acid column, and aluminum oxide column. The stripping methods did not affect the fatty acid composition. Non-stripped SCO, MBO and SBO contained oleic, palmitic, stearic and linoleic acids, which were not significantly (P < 0.05) different than stripped SCO, MBO and SBO. The stripping methods’ effect on the tocopherol composition of the studied oils, the total amount of tocopherol in non-stripped oils decreased by extraction of phenolic compounds, mean that part of the tocopherols was extracted with the phenolic compounds. No traces of tocopherols were found in oils stripped using silicic and aluminum columns and the tocopherols were eliminated during the stripping processes. The stability of SCO, MBO and SBO oils was 43, 38 and 5.1 h, respectively, this stability decreased by 22.0, 37.6 and 23.5%, respectively after extraction of phenolic compounds. This stability decreased by 96.9, 98.2 and 90.2% respectively, when stripped using the aluminium column and decreased by 92.6, 96.1 and 86.3% when stripped by the silicic column. It is possible to assume that the tocopherols and phenolic compounds play a more active role in the oxidative stability of the oils than the fatty acid composition and phytosterols.     

Oxidative stability of high-fatty acid rice bran oil at different stages of refining

The contents of natural antioxidants and the oxidative stability of rice bran oils at different refining steps were determined. Tocopherols and oryzanols were constant in crude and degummed oils but decreased in alkali-refined, bleached and deodorized oils. The process of degumming, alkali-refining, bleaching and deodorization removed 34% of the tocopherols and 51% of the oryzanols. During storage of deodorized oil for 7 wk, 34% of the tocopherols and 19% of the oryzanols were lost. The maximum weight gain, peroxide value and anisidine value were obtained from alkali-refined oil during storage. The order of oxidation stability was crude ≥ degummed > bleached = deodorized > alkali-refined oil.     

Possibilities of peanut,pecan and safflower seed oils as supplements for olive oil

Summary Samples of completely refined peanut oil, semirefined pecan oil, imported edible grade olive oil and crude safflower seed oil have been examined for composition, spectral transmittance and other properties. Compositions were determined by means of the modified Bertram oxidation method and application of the iodine-thiocyanogen number technique. None of the oils examined simulate olive oil in composition. Peanut and pecan oils appear capable of modification to produce a product chemically similar to olive oil and for certain purposes can replace olive oil without modification. The production of pecan oil under present market conditions with regard to prices for edible oils and seedling pecan nuts does not appear to be very attractive unless the costs of processing pecans for oil can be greatly reduced. Presented before the American Oil Chemists’ Society Meeting, Houston, Texas, April 30 to May 1, 1942.     

Predicting oxidative stability of vegetable oils using neural network system and endogenous oil components

The usefulness of Artificial Neural Network Systems (ANNW) to predict the stability of vegetable oil based on chemical composition was evaluated. The training set, comprised of a composition of major and minor components of vegetable oil as inputs and as outputs, induction period and values of slopes for initiation and propagation, was measured by oxygen consumption. The best predictability was achieved for oils stored at 35°C with light exposure, when the major fatty acids, chlorophylls, tocopherols, tocotrienols, and metals were used as predictors. For oils stored at 65°C without light, a good predictability was obtained when composition of the major fatty acids and the amounts of tocopherols and tocotrienols were used. These results suggest that vegetable oil stability can be successfully predicted by ANNW when partial oil composition is known.     

Frying Stability of Purified Mid-Oleic Sunflower Oil Triacylglycerols with Added Pure Tocopherols and Tocopherol Mixtures

To determine the effects of the addition of pure tocopherols to triacylglycerols, α, γ, and δ tocopherols were added singly and in various combinations to stripped mid-oleic sunflower oil (SMOSUN). Tortilla chips were fried in the treated oils and then aged at ambient temperature to determine storage stability of the fried food. Frying oils were evaluated for total polar compounds (TPC) as an indicator of oil deterioration, and they were also analyzed for retention of tocopherols. To determine effects of tocopherols on fried-food stability, chips were evaluated for hexanal as an indicator of oxidative stability and for odor characteristics by a trained, experienced analytical sensory panel. Oils extracted from the tortilla chips were also analyzed for residual tocopherols. TPC were highest in the SMOSUN control with no additives followed by the SMOSUN containing only α tocopherol. The SMOSUN oil containing γ tocopherol had the best fry life as indicated by the lowest TPC. Hexanal content and rancid odor intensity were highest in the chips fried in the SMOSUN control and in the SMOSUN containing only α tocopherol. The most stable tortilla chips were fried in SMOSUN containing all three (α, γ, and δ) tocopherols; however, the lowest hexanal levels were measured when γ and δ tocopherols were added at their highest concentrations.     

Antioxidant properties of myricetin and quercetin in oil and emulsions

The effect of quercetin and myricetin on the stability of sunflower oil and oil-in-water emulsions was studied by storage experiments monitored by measurement of peroxide values, conjugated dienes, and headspace volatile analysis. Myricetin showed strong antioxidant activity in oils stored at 60 or 30°C and in oil-in-water emulsions stored at 30°C, whether tocopherols or citric acid were present or not; however, quercetin showed similar antioxidant activity in stripped sunflower oil but no activity in oils that contained tocopherols and citric acid. This showed that myricetin is effective owing to strong radical scavenging and metal-chelating properties, whereas quercetin has weaker radical scavenging activity, although it is also active by metal-chelation. The effects of copper and iron salts on the antioxidant activity of myricetin and quercetin were studied in sunflower oil and oil-in-water emulsions. Quercetin and myricetin enhanced the prooxidant effect of cupric chloride in oil-in-water emulsions (pH 7.4), but this effect was not observed with cupric stearate. The addition of myricetin to emulsions that contained ferric chloride at pH 5.4 also produced a strong prooxidant effect, and small prooxidant effects of flavonols were also detected in the presence of cupric chloride under these conditions. However, myricetin and quercetin reduced the prooxidant effect of ferric palmitate in oils. Myricetin also showed a strong antioxidant effect in oil that contained cupric stearate, although quercetin had no significant effect on the oxidative stability of this system. It therefore appears that flavonols may exert a prooxidant effect in the presence of metal salts, but the nature of the metal salt is important in determining whether a prooxidant effect occurs.     

Antioxidant Activity of Phytochemicals from Distillers Dried Grain Oil

A distillate was obtained by molecular distillation of oil extracted from distillers dried grains (DDG). The distillers dried grain oil distillate (DDGD) contained phytosterols, steryl ferulates, tocopherols, tocotrienols, and carotenoids. DDGD was tested for its impact on the oxidative stability index (OSI) at 110 °C of soybean, sunflower, and high-oleic sunflower oils, as well as the same oils that were stripped of their natural tocopherols and phytosterols. In addition, the impact of added DDGD on the stability of stripped sunflower oil during an accelerated storage study conducted at 60 °C was also determined. DDGD (0.5–1% w/w) had little impact on the OSI of soybean, sunflower, and high-oleic sunflower oil, but at levels of 0.1–1% it significantly increased the OSI for stripped soybean, sunflower, and high-oleic sunflower oil in a dose-dependent manner. DDGD also delayed peroxide value, conjugated diene, and hexanal formation during accelerated storage of stripped sunflower oil. The antioxidant activity is probably due to the combination of tocopherols, tocotrienols, and steryl ferulates.     

Antioxidant activity of tocopherols and phenolic compounds of virgin olive oil

The antioxidant effects of hydrophilic phenols and tocopherols on the oxidative stability in virgin olive oils and in purified olive oil have been evaluated. Total hydrophilic phenols and the oleosidic forms of 3,4-dihydroxyphenolethanol (3,4-DHPEA) were correlated (r=0.97) with the oxidative stability of virgin olive oil. On the contrary, tocopherols showed low correlation (r=0.05). Purified olive oil with the dialdehydic form of elenolic acid linked to 3,4-DHPEA, an isomer of oleuropeine aglycon, and 3,4-DHPEA had good oxidative stability. A synergistic effect was observed in the mixture of 3,4-DHPEA and its oleosidic forms with α-tocopherol in purified olive oil by the Rancimat method at 120°C.     

Chemical Composition and Oxidative Stability of Selected Plant Oils

Scientific data on the oxidative stability of borage oil, Camelina sativa oil, linseed oil, evening primrose oil and pumpkin seed oil are scarce. Chemiluminescence (CL) methods most commonly used to determine the oxidative stability of oils include measurement of hydroperoxide, intensity of light emitted during the accelerated oxidation process performed at high (>100 °C) temperatures or assisted by forced flow of air/oxygen through the sample. The aim of this study was to investigate the chemical composition and oxidative stability of selected vegetable oils available on the Polish market. Oxidative stability was determined using a fast, novel chemiluminescence-based method, in which light emitted during oxidation process conducted at 70 °C in the presence of some catalyzing Fe²⁺ ions is measured. A reaction of the applied type has not been reported so far. High contents of tocopherols and phytosterols were found in the analyzed oil samples. Oxidative stability of the samples was in most cases higher than the stability of refined rapeseed oil, a relatively stable substance from the oxidation point of view.     

Effect of fatty acids and tocopherols on the oxidative stability of vegetable oils

The oxidative stability of vegetable oils is determined by their fatty acid composition and antioxidants, mainly tocopherols but also other non‐saponifiable constituents. The effect of fatty acids on stability depends mainly on their degree of unsaturation and, to a lesser degree, on the position of the unsaturated functions within the triacylglycerol molecule. Vegetable oils contain tocopherols and tocotrienols, especially α‐ and γ‐tocopherols, as their main antioxidants. The antioxidant behavior of tocopherols represents a complex phenomenon as they are efficient antioxidants at low concentrations but they gradually lose efficacy as their concentrations in the vegetable oils increase. The “loss of efficacy” of tocopherols, sometimes referred to as a “pro‐oxidant effect”, is witnessed by an increase in the rate of oxidation during the induction period, despite elongation of this phase. The phenomenon is much obvious for α‐tocopherol, but is also evident for other tocopherols. In agreement with nature's wisdom, the tocopherol levels in vegetable oils seem to be close to the optimal levels needed for the stabilization of these oils. The presence of other antioxidants in the oils, e.g. carotenoids, phenolic compounds, and Maillard reaction products, may synergize with tocopherols and minimize this loss of efficacy.     

Oxidative stability of flax and hemp oils

Oxidative stability of flax and hemp oils, and of flax and hemp oils stripped of their minor components, was evaluated in the dark at 60°C and under fluorescent light at 27°C. Several analytical methods were used to assess the oxidative stability of oils. Oil extracts were also investigated for their scavenging of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and for their total phenolic contents. The results indicate that bioactive constituents of these edible oils play a major role in their oxidative stability. However, the FA composition of the oils and their total content of tocopherols as well as the type of pigments present contribute to their stability. Nonstripped flax and hemp oils were more stable than their corresponding stripped counterparts. Furthermore, nonstripped hemp oil had a higher oxidative stability than nonstripped flax oil as evidenced by scavenging of DPPH radical and consideration of total phenolic contents.     

Antioxygenic properties of molecularly distilled fractions of peanut oil

Summary 1. Samples of unhydrogenated and hydrogenated peanut oils, which had been refined, bleached, and deodorized, were separated into two comparable series of fractions by molecular distillation. The various fractions were analyzed for tocopherols (and related chromogens) by the method of Furter and Meyer, and stability tests by the Swift method were made on the larger distilled fractions. 2. Molecular distillation at 140°, 160°, and 180° C. yielded antioxidant concentrates (presumably of tocopherols) from each oil; distillation at 240° yielded fractions almost devoid of antioxygenic substances. 3. In the unhydrogenated and hydrogenated oils, approximately 40 percent and 20 percent, respectively, of the chromogenic substances reacting in the Furter-Meyer tests were undistillable and remained in the residue comprising 10 percent of the original oil. 4. Evidence was found of the presence of distillable antioxidants other than tocopherols, which either do not respond to the Furter-Meyer test or else respond to it weakly, in proportion to their antioxygenic activity. 5. Hydrogenation of the oil had no appreciable effect on the activity of its distillable antioxidants. 6. The progressively increased addition of tocopherol-rich concentrates to fractions almost devoid of antioxidants resulted in first decreasing and then increasing the initial rate of peroxide formation in the stability tests. 7. In the case of the unhydrogenated oil, there was an optimum level of antioxidant concentration above which the addition of these substances had no stabilizing action. However, hydrogenated oil showed an increase in stability with the addition of antioxidants up to the highest level to which the concentration of the latter was carried (approximately 0.15 percent, calculated asa-tocopherol). Presented before the American Oil Chemists’ Society Meeting, New Orleans, Louisiana, May 12 to 14, 1943.     

A Highly Stable Soybean Oil-Rich Miscella Obtained by Ethanolic Extraction as a Promising Biodiesel Feedstock

Soybean oil is industrially obtained upon hexane extraction. In biodiesel production, soybean oil is submitted to phospholipid removal in order to improve its quality before transesterification. An extraction process was employed to produce ethanolic oil-rich miscella, which can be directly transesterified to produce biodiesel without prior refining. We assessed the oxidative stability of the miscella and three other soybean oils, namely degummed, alkali-refined, and refined–bleached–deodorized (RBD) oil. In vitro antioxidant assays as well as the identification and quantification of tocopherols and isoflavones were also performed. Although hexane-extracted oils showed higher tocopherol contents than miscella, this latter sample and its direct biodiesel demonstrated superior stability in accelerated tests. Miscella also outperformed hexane-extracted oils in all in vitro assays. This behavior can be explained by the presence of phenolic compounds with higher affinity to ethanol than hexane, which was confirmed by the identification of isoflavones glycitein, genistein, and acetyldaidzin, found only in miscella. This study showed that the ethanolic extraction of soybean oil generated a highly stable lipid feedstock for biodiesel manufacture.     

Bioactive compounds in unsaponifiable fraction of oils from unconventional sources

The aim of the research was to characterize bioactive components of unsaponifiable fraction of selected unconventional oils. Nine oils were analyzed as far as the content of tocopherols, squalene, phenolic compounds, and sterols were concerned. Tocopherols and squalene were analyzed by HPLC coupled with diode array detector and fluorescent detector (HPLC‐DAD‐FLD). The content of sterols in oils was determined by GC coupled with MS (GC‐MS). The total amount of phenolic compounds in oils was determined by the colorimetric methods using Folin–Ciocalteau phenol reagent. The examined oils were characterized by differentiated amount of particular forms of tocopherols. The oil obtained from the seeds of amaranth was the richest source of squalene (over 52 mg/g oil). The presence of 22 different compounds of sterols were identified, whereas β‐sitosterol was found in the largest amount. Total amount of sterols in the oils ranged from 90 (walnut) to 850 mg/100 g (evening primrose). Significant differentiation of total amount of phenolic compounds was observed in the examined oils. Evening primrose oil showed the highest amount of phenolic compounds (679 mg/kg). The presented results prove that plant oils obtained from nonconventional sources are a potential source of bioactive compounds.     

Oxidative Stability and Characterization of Quinoa Oil Extracted from Wholemeal and Germ Flours

Quinoa seeds are a source of lipids of great quality, and they highlight the content and composition of fatty acids and the presence of antioxidants such as tocopherols. Solvent extraction of quinoa oils was carried out from two matrices (wholemeal and germ flours), and in both cases, the extraction performance, physical–chemical characteristics, and oxidative stability were determined. Oxidative stability of the oil was assessed using an accelerated aging experiment under storage conditions at 60 °C for 12 days, in which the following parameters were measured: peroxide value, acid value, conjugated dienes and trienes, and scavenging radical capacity. Germ flour showed greater extraction yields (27.30 ± 0.15 g/100 g) compared to wholemeal (5.88 ± 0.02 g/100 g). Both oils presented similar physicochemical parameters, although the tocopherol content was higher in the oil extracted from germ flour (1354 vs. 735 mg/kg oil). At the same time, wholemeal oil showed a superior oxidative stability; hence, the wet milled process produces a minor impact on the compounds responsible for protection against lipid oxidation.     

Simultaneous detection of tocopherols,carotenoids, and chlorophylls in vegetable oils by direct injection C<Subscript>30</Subscript> RP-HPLC with coulometric electrochemical array detection

Detection and quantification of tocopherols, carotenoids, and chlorophylls in vegetable oil have been used to aid their authentication. Their importance in influencing the oxidative stability of vegetable oils and their possible health benefits have been shown in numerous studies. Therefore, the need for a rapid and reliable analysis method has become increasingly important. This study demonstrates the application of C₃₀ RP-HPLC with electrochemical detection for the simultaneous analysis of tocopherols, carotenoids, and chlorophylls in vegetable oils. Aliquots of vegetable oils were dissolved in appropriate solvents and injected directly without saponification, thus preventing sample loss or component degradation. Effective separation of tocopherols, carotenoids, and chlorophylls was achieved. Detection was performed using a coulometric electrochemical array detector set between 200 and 620 mV. For a 25-μL injection, the respective detection limits for carotenoids, tocopherols, and chlorophylls were 1 fmol, 0.15 pmol, and 0.5 pmol, representing 1000-, 25-, and 5-fold enhancement over the UV-vis methodology. The detector response was linear between 0.01 and 2.00 μg/mL for all compounds studied. Within-day variations (CV) were between 2.0 and 6.3%, whereas between-day variations were between 2.7 and 7.4%. This method can be applied for rapid and sensitive analysis in the study of oil quality and adulteration.