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.     

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.     

Design and Characteristics of Novel Sensory and Nutritionally Oriented Olive,Seed, and Nut Virgin Oils’ Blendings

Virgin olive oil is considered a key component of the Mediterranean Diet, while nut and seed “cold-pressed” oils stand out as an interesting ingredient due to the growing consumer demand toward so-called gourmet and healthy oils. The main objective of this work is the development and characterization of novel virgin vegetal oils based on blendings of virgin olive oil with virgin oils obtained from seeds (sesame and flaxseed) and nuts (hazelnut and pistachio) of interest due to their peculiar nutritional and organoleptic characteristics. Oil formulations elaborated with 5% of sesame oils achieve a high content in vitamin E (842 mg kg⁻¹, 11.8 mg per standard 14 g oil dose, corresponding to an 80% of the recommended daily intake) and with 10% of flaxseed a high level in essential α-linolenic acid (6.4%, 0.90 mg per dose corresponding to a 66% of the recommended daily intake). In addition, sensory analysis shows that blends enriched with both 50% hazelnut oil and 75% pistachio oil not only maintain the typical aroma of virgin olive oil, but incorporate the characteristic nutty, roasty, seed-like, and sweet sensory attributes of nuts, providing an added value to the consumers.     

Analyses of flavor qualities of vegetable oils by gas chromatography

Soybean oil, hydrogenated soybean oil, and corn oil were exposed to fluorescent light for different periods of time to obtain a wide range of flavor qualities. The flavor qualities of these oils were evaluated by sensory and gas Chromatographic methods. Sensory evaluation was conducted using a 10-point hedonic scale to rate overall flavor quality. The sensory panel was made up of 94 members from 8 different laboratories. The correlation coefficients (r) of the flavor scores between sensory evaluation and instrumental analysis for soybean oil, hydrogenated soybean oil, and corn oil were 0.95, 0.97 and 0.97, respectively. These results were very close to the correlation coefficients (r) 0.99, 0.98 and 0.95 obtained from 10 sensory panel members from one specific laboratory.     

Pinoresinol and 1-acetoxypinoresinol, two new phenolic compounds identified in olive oil

Polyphenols of olive oil show autoprotective, sensory, and nutritional-therapeutic effects. Two new phenolic compounds have been isolated from virgin olive oils by preparative high-performance liquid chromatography and their structures established on the basis of their mass spectra and nuclear magnetic resonance spectral data. The compounds identified are the lignans pinoresinol and 1-acetoxypinoresinol. Both have been found in all the commercial virgin olive oils analyzed. Pinoresinol concentration was rather similar in all the oils. In contrast, 1-acetoxypinoresinol concentration was higher in oils of the Arbequina and Empeltre cultivars than in Picual or Picudo cultivars. Pinoresinol and 1-acetoxypinoresinol may represent the major phenolic compounds in some Arbequina and Empeltre oils. Lignans possess biological and pharmacological properties and, therefore, the two new compounds identified in olive oils may contribute to the reported beneficial effects which are attributed to polyphenols on human health of a diet rich in olive oil.     

Olive Oil Quality and Sensory Changes During House‐Use Simulation and Temporal Assessment Using an Electronic Tongue

During domestic usage, olive oil bottle manipulation may lead to a quality decrease due to agitation and oxygenation. Therefore, assessing the domestic consumption time period during which the initial quality grade is retained may allow including this information as a recommendation, ensuring olive oil consumers’ satisfaction. Temporal changes of physicochemical, chemical, and sensory parameters of extra‐virgin olive oils (EVOO) were monitored during 1‐month simulated house‐use conditions. It was observed that K₂₃₂ (R‐Pearson ≥+0.81) and ΔK increased resulting in a significant olive oil quality decrease from EVOO (during the initial 21 days of simulated usage) to lampante olive oil (after 28 days of simulated usage) as well as the appearance of rancid sensation. As lampante olive oils cannot be commercialized, it is pertinent to establish olive oil shelf life under usual home‐use conditions. Principal component analysis allowed grouping the olive oils according to home‐use time period and how bottles are stored after their first opening, showing that the overall olive oil physicochemical and sensory characteristics changed with the domestic‐use time period. Finally, a potentiometric electronic tongue coupled with linear discriminant analysis was used to discriminate olive oils according to the domestic‐use time period (leave‐one‐out cross‐validation sensitivities ≥95%). Thus, this device could be used to indirectly assess the quality of the remaining bottled olive oil by establishing for how long an olive oil bottle has been used under domestic conditions.     

Phenolic acid content and sensory properties of two Spanish monovarietal virgin olive oils

In recent years, phenolic acids have received considerable attention as they are essential to olive oil quality and nutritional properties. This study aims to validate a rapid and sensitive method based on ultra‐performance liquid chromatography/time‐of‐flight mass spectrometry (UPLC–TOF‐MS) for analyzing the phenolic acid content of olive oil and assessing its impact on virgin olive oil (VOO) sensory attributes. Once this method was validated, we used it to evaluate the phenolic acid composition of several Spanish monovarietal virgin olive oils in relation to nine different olive ripening stages. The results obtained confirm that the methodology developed in this study is valid for extracting and analyzing phenolic acids from VOO. The phenolic acid content of the virgin olive oils sampled was proven to be influenced by the type of cultivar and olive harvest date. Therefore, phenolic acids might be used as potential markers for olive oil cultivar or ripening stage. Finally, the data obtained indicate that the sensory properties of VOO may be differently affected by its phenolic acid content depending on the type of cultivar. Practical applications: The method validated in the present study – based on UPLC‐TOF‐MS – allows experts to assess the phenolic acid content of different VOO cultivars (varieties). This application will probably be very useful to the olive oil industry. The reason is that our study revealed that phenolic acids have an impact on the sensory quality of VOO, which is essential to consumer preferences and choice. In addition, there are phenolic acids that are only found in a particular variety of olive oil obtained from fruits at a specific ripening stage. Consequently, phenolic acids could be used as potential markers for olive oil variety and harvest time.     

Characterization of stored regular and low-linolenic canola oils at different levels of consumer acceptance

A ten-member trained sensory panel evaluated regular (RCO) and low-linolenic (LLCO) canola oils that had been stored at 60°C to four levels of consumer acceptance identified in a prior study. These levels were 70, 60, 50, and 40% acceptance for RCO and 80, 70, 60, and 50% acceptance LLCO. Painty odor intensity increased as consumer acceptance decreased. This same trend was found for chemical measurements of peroxide values, total volatiles, total carbonyls, unsaturated carbonyls, and dienals. These chemical indices were significantly correlated with each other, suggesting that they can be used to monitor related changes in oil quality with respect to lipid oxidation. Values for 19 individual volatiles at each consumer acceptance level were also reported. The data collected in this study provide chemical and sensory characterization of stored RCO and LLCO at distinct levels of consumer acceptance. Presented in part at the 84th Annual Meeting of the American Oil Chemists’ Society, Atlanta, Georgia, May 8–12, 1994.     

AOCS collaborative study on sensory and volatile compound analyses of vegetable oils

An AOCS collaborative study was conducted to determine the effectiveness of sensory analysis and gas chromatographic analyses of volatile compounds in measuring vegetable oils for levels of oxidation that ranged from none to high. Sixteen laboratories from industry, government, and academia in Canada and the United States participated in the study to evaluate the flavor quality and oxidative stability of aged soybean, corn, sunflower, and canola (low-erucic acid rapeseed) oils. Analytical methods included sensory analyses with both flavor intensity and flavor quality scales and gas-chromatographic volatiles by direct injection, static headspace, and dynamic headspace (purge and trap) techniques. Sensory and volatile compound data were used to rank each of the oils at four levels of oxidation—none, low, moderate, and high. For soybean, canola, and sunflower oils, 85–90% of laboratories correctly ranked the oils by either analysis. For corn oil, only 60% of the laboratories ranked the samples according to the correct levels of oxidation by either analysis. Variance component estimates for flavor scores showed that the variation between sensory panelists within laboratories was lowest for the unaged oils. As storage time increased, the variance also increased, indicating that differences among panelists were greater for more highly oxidized oils. Between-laboratory variance of sensory panel scores was significantly lower than within-laboratory variance.     

Frying quality and oxidative stability of high-oleic corn oils

To determine the frying stability of corn oils that are genetically modified to contain 65% oleic acid, high-oleic corn oil was evaluated in room odor tests and by total polar compound analysis. Flavor characteristics of french-fried potatoes, prepared in the oil, were also evaluated by trained analytical sensory panelists. In comparison to normal corn oil, hydrogenated corn oil and high-oleic (80 and 90%) sunflower oils, high-oleic corn oil had significantly (P<0.05) lower total polar compound levels after 20 h of oil heating and frying at 190°C than the other oils. Fried-food flavor intensity was significantly higher in the normal corn oil during the early portion of the frying schedule than in any of the high-oleic or hydrogenated oils; however, after 17.5 h of frying, the potatoes fried in normal corn oil had the lowest intensity of fried-food flavor. Corn oil also had the highest intensities of off-odors, including acrid and burnt, in room odor tests. High-oleic corn oil also was evaluated as a salad oil for flavor characteristics and oxidative stability. Results showed that dry-milled high-oleic corn oil had good initial flavor quality and was significantly (P<0.05) more stable than dry-milled normal corn oil after oven storage tests at 60°C, as evaluated by flavor scores and peroxide values. Although the high-oleic corn oil had significantly (P<0.05) better flavor and oxidative stability than corn oil after aging at 60°C, even more pronounced effects were found in high-temperature frying tests, suggesting the advantages of high-oleic corn oil compared to normal or hydrogenated corn oils.     

Characterization of olive paste volatiles to predict the sensory quality of virgin olive oil

One of the main challenges that virgin olive oil producers face today is an accurate prediction of the sensory quality of the final product prior to the milling of the olives. The possibility that olive paste aroma can be used as a predictive measurement of virgin olive oil quality is studied in this paper. The study was centered on distinguishing the aroma of olive pastes that produced virgin olive oils without sensory defects from the aroma of olive pastes the virgin olive oils of which showed sensory defects. Olive pastes were analyzed by solid‐phase microextraction‐gas chromatography and a sensor system based on metal oxide sensors. Forty‐four volatile compounds were identified in olive pastes, all of them being also present in virgin olive oil. Six volatile compounds – acetic acid, octane, methyl benzene, (E)‐2‐hexenal, hexyl acetate and 3‐methyl‐1‐butanol – distinguished both kinds of pastes with only five misclassified samples. Five metal oxide sensors were able to classify the olive pastes with only two erroneous classifications.     

Enhancement of Bioactive Phenols and Quality Values of Olive Oil by Recycling Olive Mill Waste Water

Mature ‘Chondrolia Chalkidikis’ olives were processed in an industrial olive oil mill equipped with a three‐phase decanter. Water was added to the decanter at a 1:2 water‐to‐paste ratio. Olive mill waste water (ΟΜWW) was used to replace the added water at a rate of 50 or 100%. Following the final separation, the obtained oil was used for chemical analysis and sensory evaluation. All oils had similar acidity, peroxide and Κ values. OMWW‐treated olive oils presented higher total phenolic content and higher antioxidant activity based on DPPH and oven tests, but lower chlorophyll and carotenoids content. However, there was no significant difference between the 50 and 100% replacement. The phenolic profile of the treated olive oils analyzed by quantitative ¹Η NMR revealed more than twofold oleocanthal and oleacein as well as oleuropein and ligstroside aglycone contents than in the control. Sensory evaluation of treated oils also showed an enhancement of fruity, bitter and pungent attributes compared to the control.     

Evolution of phenols and pigments in extra virgin olive oil from irrigated super‐intensive orchard

Phenolic compounds have a high importance in olive oil because of their effect on shelf life and sensory properties. This study reports on the HPLC profiles of the phenolic compounds of virgin olive oils obtained from Arbequina olives from the harvesting in a super‐intensive orchard under a linear irrigation system. In addition, phenolic content, carotenoid and chlorophyllic pigments, and oxidative stability were analyzed. Total phenol content and 3,4‐DHPEA‐EDA increased up to a maximum throughout the ripening process. The simple phenols tyrosol and hydroxytyrosol acetate increased throughout the ripening process, however, there was not found a clear trend in hydroxytyrosol content. Minor constituents such as vanillic acid and p‐coumaric acid increased up to a maximum and then decreased, since vanillin decreased progressively throughout the time of harvest. 3,4‐DHPEA‐EDA and lignans were present in considerable amounts in the studied samples, while oleuropein aglycone was present in a low amount. Total phenol content and oil stability followed the same trend throughout the study, so a very good correlation was established between them. Total secoiridoids and, specifically, 3,4‐DHPEA‐EDA seemed to be responsible for oil stability. The pigment content decreased during ripening, and not a positive correlation was found between pigments and oil stability. Practical applications : The results can be used to determine the best time for harvesting in order to obtain olive oils with different phenols and pigment contents. This is important for sensory characteristics of the olive oils and also for olive oil stability.     

Effect of extraction systems on the quality of virgin olive oil

Research has been carried out to ascertai the effects of different processing systems on olive oil quality. Tests were performed in industrial oil mills that were equipped with both pressure and centrifugation systems. Results show that oils extracted from good-quality olives do not differ in free fatty acids, peroxide value, ultraviolet absorption and organoleptic properties. Polyphenols ando-diphenols contents and induction times are higher in oils obtained from good-quality olives by the pressure system because it does not require addition of water to the olive paste. The centrifugation system requires the addition of warm water to the olive paste and helps to obtain oils with a lower content of natural antioxidants. Oils obtained from poorquality or from ripe olives in continuous centrifugal plants are lower in free fatty acids than those obtained by the pressure system. Dr. Mario Solinas is deceased—May 23, 1993.     

Purity,quality and stability of Argentinean virgin olive oils

In this paper we evaluate the stability, purity and regulated quality composition of fatty acids and sterols (both physico‐chemical and sensory) of commercial Argentinean virgin olive oils in order to evaluate their acceptance on the world market. For this purpose, samples of the best known and most widely distributed oils in supermarkets located in Buenos Aires (Argentina) were acquired. After thoroughly analysing these samples, only 20% were considered to have an acceptable quality. However, some were excluded because of their high campesterol content, which could be an intrinsic characteristic of these oils. The most useful analytical parameter used to confirm authenticity was ECN‐42 R – ECN‐42 T, followed by wax content and 3.5 stigmastadienes. Only 24% of the extra‐virgin olive oil samples were classified as ‘extra‐virgin’ from the regulated quality viewpoint. The low oleic and high linolenic acid contents of the Argentinean virgin olive oils stand out when compared with European virgin olive oils. The oxidative stability values may be considered very low, indeed even lower than those obtained in Spanish virgin olive oils.     

Effect of natural antioxidants in virgin olive oil on oxidative stability of refined,bleached, and deodorized olive oil

The factors influencing the oxidative stability of different commercial olive oils were evaluated. Comparisons were made of (i) the oxidative stability of commercial olive oils with that of a refined, bleached, and deodorized (RBD) olive oil, and (ii) the antioxidant activity of a mixture of phenolic compounds extracted from virgin olive oil with that of pure compounds andα-tocopherol added to RBD olive oil. The progress of oxidation at 60°C was followed by measuring both the formation (peroxide value, PV) and the decomposition (hexanal and volatiles) of hydroperoxides. The trends in antioxidant activity were different according to whether PV or hexanal were measured. Although the virgin olive oils contained higher levels of phenolic compounds than did the refined and RBD oils, their oxidative stability was significantly decreased by their high initial PV. Phenolic compounds extracted from virgin olive oils increased the oxidative stability of RBD olive oil. On the basis of PV, the phenol extract had the best antioxidant activity at 50 ppm, as gallic acid equivalents, but on the basis of hexanal formation, better antioxidant activity was observed at 100 and 200 ppm.α-Tocopherol behaved as a prooxidant at high concentrations (>250 ppm) on the basis of PV, but was more effective than the other antioxidants in inhibiting hexanal formation in RBD olive oil.o-Diphenols (caffeic acid) and, to a lesser extent, substitutedo-diphenols (ferulic and vanillic acids), showed better antioxidant activity than monophenols (p- ando-coumaric), based on both PV and hexanal formation. This study emphasizes the need to measure at least two oxidation parameters to better evaluate antioxidants and the oxidative stability of olive oils. The antioxidant effectiveness of phenolic compounds in virgin olive oils can be significantly diminished in oils if their initial PV are too high.     

Oxidative and flavor stabilities of soybean oils with low-and ultra-low-linolenic acid composition

The effects of linolenic acid (18∶3) concentration, combined with TBHQ addition, temperature, and storage time, on the oxidative and flavor stabilities of soybean oils (SBO) were evaluated. During storage under fluorescent light at both 21 and 32°C, the SBO with ultra-low-18∶3 concentration (1.0%, ULSBO) generally had greater oxidative stability than did SBO with low-18∶3 concentration (2.2%, LLSBO). The ULSBO had about half the p-anisidine value of LLSBO throughout storage. Although the ULSBO initially had significantly greater PV and poorer (lower) sensory scores for overall flavor quality than did LLSBO, significant differences disappeared with storage. The ULSBO had a lower content of polar compounds and greater oil stability indices than did LLSBO when TBHQ was present. All oils were more oxidatively stable with TBHQ addition, but the TBHQ addition did not result in improved flavor stability early in storage. In all tests, oils stored at 32°C were less stable than oils stored at 21°C. The TBHQ had a better antioxidant capacity when the 18∶3 concentration was lower. The retardation effect of TBHQ on lipid oxidation and the improved stability of ULSBO over LLSBO were more easily detected when the storage temperature was higher.     

Changes in virgin olive oil characteristics during different storage conditions

In this study we have examined the effect of olive oil storage outdoors on a comprehensive series of quality measures. The conditions used were at the extreme of those encountered during the production of bottle oil. Filtered and unfiltered oils were compared as was the influence of inert gas (nitrogen) in the headspace. Increases in K₂₃₂, K₂₇₀ and peroxides over time were very much reduced by inert headspace gas, which also reduced losses of total phenols and oxidative stability. Headspace nitrogen also reduced the rise in unconjugated phenolics as secoiridoid derivatives declined and minimised losses in polyunsaturated fatty acids. The pattern of volatile compounds detected in olive oils stored indoors or outdoors showed subtle differences. Moreover, when stored with air exposure the levels of some negative sensory components such as penten‐3‐ol and hexanal increased while other positives, like trans‐2‐hexenal were reduced. These changes would be expected to reduce quality. Finally, Panel tests were used. All oils lost perceived quality on storage and this was accelerated outdoors while headspace nitrogen slowed the deterioration significantly. Our data show that storage outdoors for 4 months in winter does not reduce olive oil quality significantly and that an inert gas in the headspace is beneficial. Practical applications : The storage of olive oil for bottling is carried out under a variety of conditions. Here we assess the effects of storage outdoors for oils from the main Greek cultivar (Koroneiki) of olive. Detailed analyses of quality (standard measures, different phenolics, lipids and volatiles) as well as Panel tests were used for evaluation. Our data show that, although storage outdoors causes deterioration quicker than indoors, changes are not serious up to 4 months. Furthermore, the use of an inert headspace gas significantly preserved quality both indoors and outdoors. Thus we would strongly recommend the latter measure to producers.