Sterolic composition of Chétoui virgin olive oil: Influence of geographical origin

The sterol profile of Tunisian virgin olive oils produced from Chétoui cultivar, the second main variety cultivated in the north of the country, grown under different environmental conditions, was established by gas chromatography using a flame ionisation detector. More than ten compounds were identified and characterised. As expected for virgin olive oil, the main sterols found in all Chétoui olive oils were β-sitosterol, Δ5-avenasterol, campesterol and stigmasterol. Cholesterol, 24-methylenecholesterol, clerosterol, campestanol, sitostanol, Δ7-stigmastenol, Δ5,24-stigmastadienol, and Δ7-avenasterol were also found in all samples, but in lower amounts. Most of these compounds are significantly affected by the geographical origin. The majority of the Chétoui virgin olive oils analysed respected EC Regulation No. 2568, and in all cases total sterol amounts were higher than the minimum limit set by legislation, ranging from 1017 to 1522 mg/kg.     

Phytosterol content of sea buckthorn (Hippophae rhamnoides L.) seed oil: Extraction and identification

Phytosterols in sea buckthorn (Hippophae rhamnoides L.) seed oil extracted by cold pressing, hexane, and supercritical carbon dioxide were identified by GC–MS and FID. Compounds identified were campesterol, clerosterol, lanosterol, sitosterol, β-amyrin, sitostanol, Δ⁵-avenasterol, Δ²⁴⁽²⁸⁾-stigmasta-en-ol, α-amyrin, Δ^5,24(25)-stigmastadienol, lupeol, gramisterol, Δ⁷-sitosterol, cycloartenol, cycloeucalenol, Δ⁷-avenasterol, 28-methylobtusifoliol, 24-methylenecycloartanol, erythrodiol, citrostadienol, uvaol, and oleanol aldehyde. Sitosterol and Δ⁵-avenasterol were, quantitatively, the most important phytosterols. Total sterols and most individual sterols differed significantly (P ? 0.05) among all three extraction methods with supercritical carbon dioxide extracting the highest total sterol levels (1640 mg/100 g oil) and cold pressed the lowest levels (879 mg/100 g oil).     

Sterols,fatty alcohol and triterpenic alcohol changes during ripe table olive processing

The aim of the work was to study the effects of processing on the unsaponifiable matter, sterols and fatty and triterpenic alcohol in ripe olive fat (Manzanilla and Hojiblanca cultivars) and to disclose the most influential factors using GLM, PCA and DA. There were significant effects of cultivars or ps on unsaponifiable matter, β-sitosterol, Δ⁵-avenasterol, total sterols, 1-docosanol, 1-tetracosanol (ps), erythrodiol and percentage erythrodiol + uvaol. The values of most of these parameters were within the limits established by the EU Directives for olive and pomace oils but classification of the respective oils was not conclusive. Predictive discriminant analysis using these variables permitted 100% success in the classification according to cultivars and ps (68% in the case of cross validation). Results revealed that some influential steps should be re-designed, particularly the storage phase, in order to minimise changes in the studied fat components during ripe olive processing.     

Sterols of seed oils of Vernonia galamensis,Amaranthus cruentus,Amaranthus caudatus,Amaranthus hybridus and Amaranthus hypochondriacus grown in the humid tropics

Analysis of sterols of seed oils from Vernonia galamensis, Amaranthus cruentus, A caudatus, A hybridus and A hypochondriacus, the last four being exotic breeds planted in the humid tropics of Africa, is presented in this report. Identifiable sterols in all the seed oil samples include campesterol, stigmasterol, ß-sitosterol, Δ⁵-avenasterol and Δ⁷-avenasterol except for Vernonia galamensis where cholesterol was detected (63.61 mg per 100 g oil).     

Sterolic composition and triacylglycerols of Oueslati virgin olive oil: comparison among different geographic areas

The main triglycerides (TG) identified in the Oueslati virgin olive oil were 1,2,3‐trioleylglycerol (OOO), 2,3‐dioleyl‐1‐palmitoylglycerol (POO) and 2,3‐dioleyl‐1‐linoleylglycerol (LOO) representing more than 80% of the total area of peaks in the chromatogram. Other minor triacylglycerols were 2,3‐dioleyl‐1‐stearoylglycerol (SOO), 2‐oleyl‐3‐palmitoyl‐1‐stearoylglycerol (SOP), 1‐linolenoyl‐2‐oleyl‐3‐palmitoylglycerol (LnOP), 1, 2‐dilinoleyl‐3‐palmitoylglycerol (LLP), 1, 3‐dioleyl‐2‐linolenoylglycerol (OLnO), 1‐linolenoyl‐2‐linoleyl‐3‐oleylglycerol (LnLO) and 1,2,3‐trilinoleylglycerol (LLL). The sterol profile of Tunisian virgin olive oils produced from Oueslati cultivar was established by gas chromatography using a flame ionisation detector (GC‐MS). More than 10 compounds were identified and characterised. As expected for virgin olive oil, the main sterols found in all Oueslati olive oils were β‐sitosterol, Δ5‐avenasterol, campesterol and stigmasterol. Cholesterol, 24‐methylenecholesterol, clerosterol, campestanol, sitostanol, Δ7‐stigmastenol, Δ5, 24‐stigmastadienol and Δ7‐avenasterol were also found in all samples, but in lower amounts. Most of these compounds are significantly affected by the geographical origin of the oil. Besides the sterol components, two triterpene dialcohols, erythrodiol and uvaol, were also detected.     

Effect of plant sterols on the rate of deterioration of heated oils

Three different plant sterol fractions were added to refined cottonseed oil. The first fraction was isolated from olive oil, the second fraction Δ⁵-avenasterol was extracted from the green algae (Ulva lactuca) and the third fraction was a sterol mixture, made up chiefly of β-sitosterol. Cottonseed oil with the different sterols added was heated at 180±5°C and the rate of oxidation followed by changes in the composition and in physical constants. Olive oil sterol mixtures containing Δ⁵-avenasterol and Δ⁵-avenasterol alone reduced the extent of oxidation. β-sitosterol was initially ineffective and became slightly prooxidant after prolonged heating.     

Distribution and retention of phytosterols in frying oils and fried potatoes during repeated deep and pan frying

The retention and distribution of phytosterols in fried oils and French-fries during eight successive pan- and deep-frying sessions of pre-fried potatoes in sunflower oil, palm oil, cottonseed oil, virgin olive oil and a vegetable shortening were evaluated. Phytosterols (β-sitosterol, campesterol, stigmasterol, Δ⁵-avenasterol) were determined in the unsaponifiable fraction of frying oils and lipids extracted from French-fries by GC/FID after derivatization to trimethylsilyl ethers. French-fries were enriched with phytosterols due to the absorption of frying oil, with β-sitosterol predominating in both fried oils and potatoes. The amount of phytosterols decreased during frying, their overall retentions reaching 9.5–22.8% and 29.4–51.2% after eight successive pan- and deep-frying sessions, respectively, while their deterioration was found to be affected by frying time, frying technique, being more prolonged during pan-frying, and by the oils’ unsaturation, being more extended in polyunsaturated oils. Phytosterols were more or less uniformly distributed between the fried oil and the fried potatoes. The phytosterols dietary intake by consuming potatoes fried in the oils tested is discussed.     

Changes in Sterol Composition of Hazelnut During Fruit Development

Hazelnut is a valuable source of fat-soluble bioactive components. Among the fat-soluble bioactive components, phytosterols have gained much interest due to their cholesterol reducing properties. This study presents the evaluation of changes in the sterol composition of Turkish hazelnut cultivars (Tombul, Palaz, and Sivri) during fruit development. Three major sterols (β-sitosterol, campesterol, and Δ5-avenasterol), and five minor sterols (clerosterol, brassicasterol, stigmasterol, Δ7-stigmastenol, and Δ7-avenasterol) were detected in all hazelnut cultivars during all stages. The total sterol contents of Turkish hazelnut cultivars reached the maximum values at the early stage and a significant reduction in the total sterol content occurred at the harvest stage.     

Composition of total sterols (4-desmethyl-sterols) in extravirgin olive oils obtained with different extraction technologies and their influence on the oil oxidative stability

The composition and antioxidant activity of total sterols in extravirgin olive oils obtained with different extraction technologies from olives harvested at two ripening stages, were studied. The antioxidant activity was evaluated with an oxidative stability instrument (OSI), by using a model system (made of a mixture of treated/untreated commercial refined peanut oil) enriched with the total sterol fractions of the extravirgin olive oils. No correlation was found between the OSI time and the extraction technologies, the ripening stages or the actual amount of sterols added. No significant differences were observed in the percent composition of sterols of extravirgin olive oils produced with different technologies during the same harvesting period. The latter, however, had a significant effect on the percent of β-sitosterol and 5-avenasterol in extravirgin olive oils produced with the same technology.     

Phytosterol Determination and Method Validation for Selected Nuts and Seeds

A method involving alkali and/or acid hydrolysis of phytosterols followed by trimethylsilyl ether derivatization coupled with GC-FID analysis was validated and applied in the analysis of major phytosterols (campesterol, stigmasterol, β-sitosterol, and Δ⁵-avenasterol) in nuts (n = 7), seeds (n = 9), legumes (n = 2), and grain (n = 1). The acid-labile Δ⁵-avenasterol was extracted with alkaline hydrolysis only before derivatization. Quantification of all phytosterols was done using the computed relative response factor of 5α-cholestane (internal standard). Analyses of internal and external phytosterol standards showed good linearity for all phytosterols (R ² of 0.999); LOD and LOQ of phytosterols were determined to be 0.01–0.12 and 0.04–0.40 mg/100 g, respectively. Repeatability and reproducibility precision analyses showed acceptable coefficient of variation of less than 3 and 4%, respectively, and satisfactory Horwitz ratio values of <1.0. Excellent accuracy was proved by the high recovery values of 91.4–106.0% for campesterol, β-sitosterol, and stigmasterol. Δ⁵-Avenasterol, the most oxidation-susceptible sterol, showed a recovery of about 60%. The total phytosterol (sum of major phytosterols quantified) contents in the 19 samples varied from 38.8 mg/100 g (white quinoa seed) to 246.2 mg/100 g (sunflower seed). β-Sitosterol was the predominant phytosterol (54–86.0% of total) among all samples except fennel seed in which stigmasterol was predominant. Analytical quality control chart maintained during the study period showed that assays were performed under control. Method validation indicated that the analytical method can be applied for accurate determination of campesterol, β-sitosterol, and stigmasterol in selected food samples.     

The effect of sterols on the oxidation of edible oils

The effect of sterols on the oxidation of a triglyceride mixture, similar in composition to olive oil, has been studied at 180°C. Δ⁵-Avenasterol and fucosterol are effective as antioxidants, whilst other sterols, including cholesterol and stigmasterol, are ineffective. The antioxidant effect of Δ⁵-avenasterol increases with concentration in the range 0·01% to 0·1%.An hypothesis is presented to explain the effectiveness of the sterols as antioxidants. It is concluded that lipid free radicals react rapidly with sterols at unhindered allylic carbon atoms. Isomerisation leads to a relatively stable allylic tertiary free radical, which is slow to react further, and this interrupts the autoxidation chain.     

Sterol composition of butters and margarines.

Analysis of the sterol and triterpene alcohol fractions of polyunsaturated margarine, normal butter and soft butter by gas chromatography–mass spectrometry revealed that the major components in margarines were β-sitosterol, stigmasterol, Δ ⁷-stigmasterol and campesterol, while cholesterol was the major sterol in butter. The hydrogenation process used in the manufacture of margarines had no effect on the composition of the unsaponifiable components of the parent oils. Crystallisation as used in the manufacture of soft butter did not affect the quantity of cholesterol present in this product.     

Evaluation of potential and real quality of virgin olive oil from the designation of origin “Aceite Campo de Montiel” (Ciudad Real,Spain)

The potential and real qualities of virgin olive oils from the DO “Aceite Campo de Montiel” were evaluated. The regulated physicochemical and sensory parameters, the stability parameters and the fatty acid, sterol and triterpenic dialcohol compositions were analysed. The results of the regulated parameters in the potential quality study classified all the analysed oils into the “extra virgin” category. The varieties Picual and Cornicabra showed remarkably high stability, due to their high tocopherol and total polyphenol contents. Oleic and linoleic acids were the most useful fatty acids used to discriminate the predominant varieties, Picual and Cornicabra, from the others. The variety Cornicabra stood out due to its high campesterol content, Arbequina due to its low β-sitosterol content and high 24-methylenecholesterol, Δ5-avenasterol, Δ7-stigmastenol and total sterol contents, and Picual for its high sitostanol content. All the analysed samples in the real quality study were classified in the “extra virgin” category according to the regulated physicochemical parameters, but only 69% of them qualified if the sensory parameters were also taken into account. The predominance of the varieties Picual and Cornicabra in the study area was mainly responsible for the high oil stability and reflects the fatty acid and sterol compositions of the oils from the oil mills in the potential quality study.     

Dynamic accumulation of 4-desmethylsterols and phytostanols during ripening of Tunisian Meski olives (Olea europea L.)

Eleven 4-desmethylsterols and two phytostanols were identified by GC–MS during the ripening of Meski olive. The maximum levels of 4-desmethylsterols (1300 mg/100 g oil) and phytostanols (7.5 mg/100 g oil) were reached at the 26th week after the flowering date (WAFD) of fruit. β-Sitosterol (72–86% of total 4-desmethylsterols) was the major 4-desmethylsterols during the maturity of fruit, while sitostanol was the predominant phytostanols (75–85% of total phytostanols). Δ5-Avenasterol (2–18%) and campesterol (1.6–4%) were the second and the third 4-desmethylsterol levels detected, respectively, during the ripening of Meski olive. The levels of campestanol varied from 15% to 25% of phytostanols. The rate of accumulation of those compounds occurred before 30th WAFD. Some of these compounds (4-desmethylsterols and phytostanols) showed nearly the same profile during the ripening of Meski olive which could be linked to the relation between these compounds during their biosynthetic pathway.     

Characterization of several hazelnut (Corylus avellana L.) cultivars based in chemical, fatty acid and sterol composition

Nineteen cultivars of hazelnuts (Corylus avellana L.) collected during the 2001 crop, from Vila Real, Portugal, were analysed for chemical composition, including moisture, total oil content, crude protein, ash, carbohydrates and nutritional value. Fat was the predominant component, ranging from 59.3 to 69.0%. Total oil was extracted and analysed for fatty acid and sterol compositions and oxidative stability. Fatty acid and sterol compositions were determined by Gas–Liquid Chromatography coupled to a Flame Ionisation Detector (GLC/FID). Monounsaturated fatty acids, particularly oleic acid, were predominant (78.7–84.6%). Total phytosterol content ranged from 133.8 to 263.0 mg/100 g of oil. Among the nine sterols identified and quantified, β-sitosterol was the major one with a mean percentage of 83.6%, while Δ⁵-avenasterol and campesterol were the second and the third components of the group with mean values of 6.1 and 5.8%, respectively. Since hazelnut oil can be used in olive oil adulteration, the values obtained were compared with published mean values of olive oils from different geographical origins.     

Products from the autoxidation of Δ5-avenasterol

Comparison of the products from the oxidation of cholesterol and Δ⁵-avenasterol indicates that similar oxidation products are formed by oxidation in the A and B rings of the sterols during the heating of solutions of these compounds in edible oils. However, the UV spectrum of the oxidation products indicates that at least one compound is formed from Δ⁵-avenasterol which is not analogous to the oxidation products of cholesterol. The formation of 5,24(25),28-stigmastatrien-3β-ol is suggested as a possibility.     

Seed lipids of Sesamum indicum and related wild species in Sudan. The sterols

Oil extracted from seeds of different varieties of the cultivated Sesamum indicum L and three related wild species, viz S alatum Thonn, S radiatum Schum & Thonn, and S angustifolium (Oliv) Engl, were analysed for their total unsaponifiables and for the contents and composition of the three sterol fractions (desmethyl, monomethyl and dimethyl sterols). The sterols were analysed after saponification by preparative TLC, capillary GC and GC-MS of their TMS ethers. Oils from the wild species contained more unsaponifiable material (2.3-2.4%) compared with the cultivated species (1.1-1.3%). Considerable differences were observed in the total sterol contents and the relative proportions of the three sterol fractions in the oils from the four species studied. Sitosterol, campesterol, stigmasterol and Δ⁵-avenasterol were the major desmethyl sterols in all four species. The monomethyl sterol fraction consisted primarily of obtusifoliol, gramisterol, cycloeucalenol and citrostadienol. Cycloartenol and 24-methylene cycloartanol were the predominant dimethyl sterols. Variations in the composition of the three sterol fractions were observed between S indicum oils traditionally pressed by the camel-driven expellers and laboratory extracted oils from the same seeds.     

SEPARATION OF STEROLS AND TRITERPENE ALCOHOLS FROM UNSAPONIFIABLE FRACTIONS OF THREE PLANT SEED OILS

Preparative HPLC was used to separate sterols and triterpene alcohols from the unsaponifiable matters in plant oils from Camellia weiningensis L., Brassica juncea L. and Microula sikkimensis . The isolated sterols and triterpene alcohols were acetylated and further purified by AgNO₃ impregnated silica gel preparative thin layer chromatography (TLC). The isolated acetyl derivatives of sterols and triterpene alcohols were identified by melting point, specific rotation, infrared and mass spectrometry. The sterols were brassicasterol, campesterol, stigmasterol, β-sitosterol and Θ⁵-avenasterol, Θ⁷-avenasterol, Θ⁷-stigmastenol and α-spinasterol. The triterpene alcohols were cycloartanol, cycloartenol, 24-methylenecycloartanol, cyclobranol, dammaradienol, tirucalla-7,24-dienol, butyrospermol, β-amyrin, germanicol, α-4-taraxasterol and lupeol.     

Influence of fruit ripening on ‘Cornicabra’ virgin olive oil quality A study of four successive crop seasons

The aim of this work was to study the influence of the stage of fruit ripening on analytical parameters which determine oil quality during four successive crop seasons, in an attempt to establish an optimum harvesting time for ‘Cornicabra’ olives. The majority of the analytical parameters, i.e. peroxide value, UV absorption at 270 nm, pigments, sensory scores, oleic acid and total sterols, diminished during ripening, whereas free acidity, linoleic acid and Δ-5-avenasterol increased. Oil extraction yield, oxidative stability, natural antioxidants and campesterol showed more complex behaviour. On the basis of the evolution of the analytical parameters studied the best stage of maturity of ‘Cornicabra’ olive fruits for processing seems to be a ripeness index higher than 3.0 and lower than 4.0–4.5. Results indicated that probably less than 25% of commercial ‘Cornicabra’ virgin olive oils were extracted from olives harvested at an optimum ripeness index. It is therefore of crucial recommendation to the industry to bring forward harvesting to further improve the quality of the virgin olive oil produced.     

Sensory and chemical profiles of three European olive varieties (Olea europea L); an approach for the characterisation and authentication of the extracted oils

Sensory data (1–16) as described by a trained panel, several characteristics (acidity, peroxide value, extinction coefficients at 232 and 270 nm, stability and phenolic compounds) (17–30) and chemical compositional data (fatty acids, sterols and triterpene diols, aliphatic and triterpene alcohols, and triglycerides) (31–67) were obtained for virgin olive oils of three European olive varieties, Coratina (Italy), Picual (Spain) and Koroneiki (Greece), at a certain stage of maturity—when half of the olives displayed partial or total purple colour—for two consecutive years of harvest, 1995–96 and 1996–97. The most remarkable characteristics for the classification of the oils were extracted using multivariate statistical analysis (correlation, hierarchical clustering and canonical discriminant analysis). Both sensory and/or chemical and quality characteristics were found to have significant potential for the authentication of the virgin olive oil varieties under investigation. © 2000 Society of Chemical Industry