Improvement of Chemlali olive oil oxidative stability by blending with Chétoui and Rekhami cultivars

In order to improve the quality of Chemlali olive oil, characterised by a very low stability (2.09 h), blending with two different monovarietal oils in various proportions: Chétoui and Rekhami (known by their higher stability 7.79 and 13.99 h, respectively) was carried out. Results showed that blended oils had an improved oil composition compared to that of Chemlali. In fact, the highest percentage of Chétoui and Rekhami olive oils (90% of blending) can reduce the acidity up to 68.79% and 79.61%, respectively. At 50% blending, oleic acid increased from 53% to 59.54%, while palmitic acid decreased from 20.97% to 14.89% with Chétoui olive oil. At the lowest percentage (10–20%), chlorophylls in Chemlali olive oil underwent significant increase (from 0.18 to 0.47 and 0.65 mg kg⁻¹, respectively). The amount of carotenoids was higher when Chemlali was blended by 20–40% with Chétoui olive oil (from 2.23 to 4.13 and 4.33 mg kg⁻¹). Blending can be used in industrial applications to provide oils with improved composition related to stability, nutrition and functionality and endowed with the characteristics requested by consumers' preferences.     

Analytical evaluation of two monovarietal virgin olive oils cultivated in the south of Tunisia: Jemri‐Bouchouka and Chemlali‐Tataouin cultivars

BACKGROUND: The characterisation of virgin olive oils from two Tunisian cultivars, growing in the Tataouin zone, namely Jemri‐Bouchouka, a rare olive cultivar, and Chemlali‐Tataouin, was carried out. Several analytical parameters were evaluated; these include quality index, fatty acids, phenolic, chlorophyll, carotenoid, squalene, α‐tocopherol compositions and oxidative stability. RESULTS: Jemri‐Bouchouka olive oil had the highest value of oleic acid (74.50%) while Chemlali‐Tataouin was characterised by a high percentage of palmitic acid (14.75%), which makes this oil freeze at a low temperature. On the other hand, Jemri‐Bouchouka oil was characterised by a low phenolic and α‐tocopherol content (267.72 mg GAE kg^?1 and 278.34 mg kg^?1, respectively). Ten phenolic compounds were identified. The main phenols found in the two olive oils were oleuropein aglycon and pinoresinol. All phenolic compounds showed significant correlations with oxidative stability. CONCLUSION: The analytical parameters of virgin olive oil that were determined in this study were greatly influenced by cultivar. © 2012 Society of Chemical Industry     

Chemical and thermal characterization of Tunisian extra virgin olive oil from Chetoui and Chemlali cultivars and different geographical origin

Application of differential scanning calorimetry (DSC) to discriminate among extra virgin olive oils on the basis of cultivar–environment interaction was preliminary evaluated on Tunisian samples from two varieties (Chetoui and Chemlali) and different geographical origin relating thermal properties obtained by cooling and heating thermograms to chemical composition. Higher content of triunsaturated triacylglycerols and oleic acid and lower amount of palmitic acid were detected in Chetoui samples in comparison with Chemlali oils. Cooling thermograms exhibited two well distinguishable exothermic peaks in all samples; the major event at lowest temperature was taller and sharper in Chetoui samples whereas the other peaking at highest temperature was more evident for Chemlali oils. Crystallization enthalpy did not account for the differences observed in chemical composition between the two cultivars. On the contrary, T _on and T _off of crystallization were found to significantly differ according to the compositional differences due to cultivars and geographical provenience interaction. Heating profiles exhibited a minor exothermic peak followed by multiple endothermic events and appeared also distinctive of oil samples from two cultivars. All thermal properties obtained by the analysis of heating thermograms significantly differed among oil samples from different geographical provenience. The application of DSC appeared useful to differentiate samples of different cultivars and/or geographical proveniences.     

PHENOLIC COMPOUNDS, TOCOPHEROLS AND OTHER MINOR COMPONENTS IN VIRGIN OLIVE OILS OF SOME TUNISIAN VARIETIES

The phenols, α‐tocopherols, fatty acids and oxidative stability of six monovarietal virgin olive oils (VOOs) were determined. Fourteen phenolic compounds were detected and quantified by solid phase extraction and reversed phase‐high performance liquid chromatography. Dialdehydic form of elenolic acid linked to tyrosol and hydroxytyrosol, oleuropein and ligstroside aglycones were the main components in all samples. Pinoresinol was the most abundant component in lignan fraction. The total phenol content of these monovarietal oils varied from 66.82 mg/kg in “Neb Jmel” oil to 662.74 mg/kg in “El Hor” oil. A wide range of α‐tocopherol contents was also noticed; it varied from 141.94 mg/kg in “Semni” variety to 364.23 mg/kg in “Jdallou” variety. With regard to pigments, chlorophylls and carotenoids were found at variable concentrations: with median values of 11.33 and 3.10 mg/kg, respectively. Among the studied varieties, “Oueslati” and El Hor were characterized by the lowest levels of palmitic and linoleic acids and the highest values of oleic acid.     

Stability of virgin olive oil and behaviour of its natural antioxidants under medium temperature accelerated storage conditions

The aim of the present research is to advance the study of virgin olive oil stability, in particular the behaviour of its natural antioxidants during long term storage. The changes undergone by tocopherols and complex and simple phenolic compounds and their antioxidant activity were studied under medium temperature (50 °C) accelerated oxidation conditions over a storage period of 8 months. Different oxygen availability (open and closed bottles, OB and CB) and four different monovarietal Tunisian virgin olive oils (VOO; Chemlali, Chétoui, El Hor and Oueslati) which vary in their fatty acid profile and content of natural antioxidants were employed. Oueslati VOO showed the lowest initial oxidation rate (4.6 PV/week) and as a consequence the highest induction period (IP; 16 days) as compared to the other VOOs studied (initial rate from 7.7 to 12.1 PV/week and IP from 9 to 12 days for El Hor and Chemlali, respectively, in both cases). In all cases the complete depletion of α-tocopherol corresponded with the observed induction period. Since the oxidation rate in the varieties studied is not sufficiently different to explain the great differences in the initial degradation rate observed in the phenolic compounds (mainly between Chétoui VOO, 163 μmol/kg/week, as compared to the other VOO oils, e.g. 6.1 and 2.5 μmol/kg/week, respectively, in Chemlali and El Hor VOOs), a concentration dependent degradation rate of complex phenols is suggested.     

Study of phenolic compounds in virgin olive oils of the Picual variety

Monovarietal Picual olive oils possibly represent 25% of the world's olive oil production. HPLC was used to analyse phenolic compounds and tocopherols in Picual olive oils obtained during two successive crop seasons (1999/2000 and 2000/2001) and from different geographic areas of the Jaén province, which is located in the south of Spain. Oils obtained at the beginning of each season had a higher content of each phenolic compound than those obtained at the end, although this effect was more pronounced for orthodiphenols than for non-orthodiphenols. The main phenolic compound detected in this monovarietal oil was the aglycon of oleuropein followed by the other secoiridoid aglycons. Lignan concentration in oil showed low variability with season and harvesting time, and pinoresinol in particular was present at a concentration of about 40 ppm. Therefore, the total polyphenol content of this monovarietal oil ranged from 300 to 700 ppm. Similarly, significant differences in these compounds were not detected between geographic areas. This monovarietal oil is very stable due to its high content of oleic acid and for this reason, the storage of oils for 2 years in amber glass bottles caused only a 30% decrease in phenolic compounds. An increase was found in simple phenols such as hydroxytyrosol and tyrosol liberated from the acid hydrolysis of the secoiridoid aglycons, and minor losses in tocopherols were also observed. These data provide a basis for the evaluation of polyphenol intake from virgin olive oil consumption, particularly from the monovarietal olive oil most consumed in the world.     

Olive oil traceability by means of chemical and sensory analyses: A comparison with SSR biomolecular profiles

The relationship between genetic diversity and phenotype in olive, instrumental to improve the efficacy of olive clonal selection, is still far from being fully understood. This work reports on a comparison made between plant SSR genetic data and quality of monovarietal olive oils. Nine monovarietal oils produced by selected genotypes were characterised under chemical and sensory profiles. Fatty acid compositions were determined to evaluate quantitative differences among oils; some fatty acids are actually highly correlated with the genetic matrix, and PCA of fatty acids composition explains 85.53% variability. Moreover some oils characterised by high levels of oleic acid appeared interesting from a nutritional standpoint. Organoleptic profiles evidenced differences especially for the attributes defined as “pleasant flavours”; oils obtained by different genetic matrices were characterised by different flavour intensities of tomato or artichoke, almond or aromatic herbs, correspondence analysis among sensory pleasant attributes and olive oil samples explaining 91.68% variability.     

Influence of olive storage period on volatile compounds and oil quality of two Tunisian cultivars of Olea europea,Chemlali and Chetoui

Olives (Olea europaea cv. Chemlali and Chetoui) used for oil production were stored, in plastic containers, at 5 °C for four different periods (0–3 weeks) before oil extraction. After storage, the oils were extracted from the fruits, and the acidity, peroxide value, coefficients of specific extinction at 232 and 270 nm, stability, pigments, total phenols, fatty acids, and volatile compounds were determined. The results showed that storage of fruits produced losses in the olive oil quality. During storage, a marked decrease in total phenols content was observed. The cultivar richer in phenols (862.16 mg kg^?1 in Chétoui) had a lower loss (25%). On the contrary, in Chemlali olive oil, the starting value of 728.52 mg kg^?1 decreased to 469.25 mg kg^?1, with a loss of 35%. Chétoui and Chemlali olive oils presented the highest oxidative stability before storage (58.76 and 47.05 h, respectively), while the lowest values were recorded using olives stored for 3 weeks (54.46 and 43.43 h, respectively). The changes in the volatile bouquet were determined using headspace solid phase microextraction (HS‐SPME). Thirty compounds were characterised by GC–FID and GC–MS. Compounds belonging mainly to alcohols, esters, aldehydes, ketones and hydrocarbons chemical classes characterised the volatile profiles.     

Changes in volatile compounds and oil quality with malaxation time of Tunisian cultivars of Olea europea

While there has been considerable work examining the effect of malaxation time on different characteristics of olive oils, there have been few that deal with all the major aspects. Here, the influence of malaxation time was evaluated using major local Tunisian (cv. Chemlali and Chetoui) cultivars. Standard characteristics were measured as well as detailed analyses of volatile compounds were conducted. Headspace solid‐phase microextraction (HS‐SPME) was applied to the analysis of volatile compounds of virgin olive oils from Chemlali and Chetoui varieties with differing malaxation time. Twenty‐seven compounds were characterised by GC‐FID and GC–MS. Compounds belonging mainly to alcohols, esters, aldehydes, ketones and hydrocarbons chemical classes characterized the volatile profile. Significant differences in the proportion of volatiles from oils of different malaxation time were detected. The results suggest that besides genetic factors, malaxation time influences volatile formation. The main variables that were affected by malaxation time were the total amount of phenols and composition of the volatile compounds. At malaxation time of 30 min, Chemlali and Chetoui olive oils presented the highest total phenol content (244.19 and 877.63 mg kg^?1, respectively), while the lowest content was observed at 60 min from regardless of cultivars. In turn, this influenced the oxidative stability and peroxide value. It was also clear that the cultivars behaved differently and this prevented general conclusions being made for all of the quality characteristics.     

脂肪酸含量对植物油介电特性的影响

为了提供植物油在微波和射频等介电加热技术和通电加热技术中的应用基础数据,考察脂肪酸含量对植物油介电特性的影响,分别利用LCR阻抗测试仪和网络分析仪(同轴探针法)测量了4种植物油(橄榄油、自制橄榄油、橄榄调和油、大豆油)和5种脂肪酸(棕榈酸、硬脂酸、油酸、亚油酸、亚麻酸)在低频段(1 000 Hz~2 MHz)和高频段(300~10 000 MHz)的介电特性。结果表明:低频下,植物油的介电常数比较稳定,其均值为(1.56±0.02),介电损耗随着频率的增加而下降,其中0.7 MHz时橄榄油具有最大的介电常数(1.67±0.00)和介电损耗(7.31±0.02);高频下,植物油的介电特性随着频率的上升而缓慢下降,4种植物油之间的介电特性的差异不显著(p0.05);低频下,在植物油中加入油酸后,植物油的介电常数和介电损耗呈现先上升后下降的趋势,而添加亚油酸呈现相反的趋势。添加脂肪酸会加快油脂的氧化反应。     

Statistical analysis on Sicilian olive oils

A robust multivariate statistical procedure applied to an accurate gas chromatography (GC) analysis was used to analyze 1004 monovarietal and multivarietal Sicilian extra virgin olive oils coming from 22 cultivars of different geographical areas of Sicily and collected in nine years (1993, 1995, 1996, 1997, 1998, 1999, 2000, 2001 and 2002). The effect of the cultivar, of pedoclimatic conditions as well as of the year of harvesting on the olive oil fatty acid composition and therefore on their classification was investigated. Oleic, linoleic and palmitic fatty acids, important for the nutritional properties of an olive oil, showed a crucial rule in the characterization of olive oils.     

Classification of monovarietal Italian olive oils by unsupervised (PCA) and supervised (LDA) chemometrics

This research work was conducted to establish whether monovarietal olive oils could be differentiated by their basic classes of compounds, ie (a) fatty acids, (b) fatty alcohols, (c) polycyclic triterpenes and (d) squalene. The ratio values of biosynthetically correlated acids were also examined. The mentioned classes of compounds, formed in distinct biosynthetic compartments of the olive fruit, should represent characteristic compositional data of an olive cultivar. The widely cultivated Italian olive cultivars studied were Frantoio, Bosana, Dritta and Leccino. Principal component analysis (PCA) was applied to the analytical data to reveal the compounds (variables) with the highest weights (loadings), with the aim of using them in subsequent computations. These variables were tetracosanol, hexacosanol Δ⁵‐avenasterol, cycloartenol, 24‐methylencycloartenol, oleic, linoleic, linolenic, stearic and palmitoleic acids and the ratios palmitic/stearic, palmitic/palmitoleic and linoleic/linolenic. Linear discriminant analysis (LDA), carried out on a training set of 57 oils (13 Dritta, 25 Leccino, 12 Frantoio and seven Bosana) produced a 96% correct group classification. The prediction LDA model created with the training set was validated with a test set of 19 oil samples (six Dritta, seven Leccino, four Frantoio and two Bosana), permitting accurate classification of all the ‘unknown’ olive oils. Copyright © 2003 Society of Chemical Industry     

基于脂肪酸谱法分析山茶油掺伪

为了更好的检测市售山茶油中的掺混,本研究基于气相色谱-质谱联用技术(GC-MS)建立了一种检测山茶油中掺入其他低值植物油的方法。实验采用GC-MS检测了市售山茶油、芝麻油、花生油以及玉米油的脂肪酸组成,并对其脂肪酸成分进行比较,建立鉴别山茶油中掺混这几种植物油的方法以及掺假比例的预测与验证。结果表明,GC-MS检测出上述几种植物油的脂肪酸组成,其中主要的脂肪酸为棕榈酸、硬脂酸、油酸与亚油酸,其中山茶油的油酸含量高达78.8058%,实验检测山茶油中掺入低值油比例为10%、20%、30%、45%的掺假油,且根据特定的油酸的含量建立的回归方程的相关系数均大于0.98。因此根据该方法可以用于山茶油中掺入一种低值植物油的检测,最低检测掺入量为10%,且方法快速方便、且方法的准确率高于97%,较为灵敏。     

Application of partial least square regression to differential scanning calorimetry data for fatty acid quantitation in olive oil

A chemometric approach based on partial least (PLS) square methodology was applied to unfolded differential scanning calorimetry data obtained by 63 samples of different vegetable oils (58 extra virgin olive oils, one olive and one pomace olive oil, three seed oils) to evaluate fatty acid composition (palmitic, stearic, oleic and linoleic acids, saturated (SFA), mono (MUFA) and polysaturated (PUFA) percentages, oleic/linoleic and unsaturated/saturated ratios).     

常用食用油的营养特点和作用研究进展

常用食用油有橄榄油、花生油、大豆油、茶油、芝麻油等。不同食用油的脂肪酸组成和含量不同,特别是一些重要的脂肪酸如油酸、亚油酸、亚麻酸等不饱和脂肪酸含量不近相同。橄榄油和茶油的油酸含量高达70％以上;花生油中油酸约占40％;大豆油的多不饱和脂肪酸含量较高,主要为亚麻酸;芝麻油中亚油酸含量占到40％以上。食用油除提供能量和必需脂肪酸外,还有脂溶性维生素和一些植物化合物,一些食用油对控制脂代谢异常具有一定的作用。     

FATTY ACIDS AND TOCOPHEROL CONTENTS OF SOME PRUNUS SPP. KERNEL OILS

The oil content as well as the fatty acid and tocopherol composition of kernels from 15 Prunus spp. varieties from Turkey were determined. The oil yields from these kernels varied from 46.3 to 55.5%. The main fatty acids of Prunus spp. kernel oils were oleic acid (43.9–78.5%), linoleic acid (9.7–37%) and palmitic acid (4.9–7.3%). The total amount of vitamin-E-active compounds in the oils varied between 62.9 and 439.9 mg/kg. The predominant tocopherol in most kernel oils was γ-tocopherol. Only two varieties of P. amygdalus and one variety of P. persica showed α-tocopherol as the main vitamin-E-active compound. The composition of the oils was 9–164.5 mg/kg α-tocopherol, 21.5–41.6 mg/kg α-tocotrienol, 1.6–330.2 mg/kg γ-tocopherol and 0–39.1 mg/kg δ-tocopherol. From the results of the present study, it can be concluded that the kernels of the investigated species of Prunus fruits from Turkey may serve potential sources of valuable oil that might be used for edible and other industrial applications.

PRACTICAL APPLICATIONS

The search for new sources of vegetable oils is an ongoing challenge and the further utilization of by-products from the food processing industry is an interesting option in this field. Seed oils from Prunus species contain high amounts of recommended monounsaturated oleic acid moderate contents of linoleic acid and low amounts of saturated fatty acids that may result in more favorable oil than olive oil with regard to their fatty acid compositions. Additionally, the oils contain vitamin-E-active compounds. Both fatty acid composition and vitamin-E-active compounds may justify the further processing of seeds from Prunus species for the production of oil for food and pharmaceutical applications.     

8种枣核油脂肪酸组成及含量分析与比较

对8种枣核(贡枣、晋枣、骨头枣、北樱枣、秤砣枣、敦煌大枣、滩枣、鸡心枣)油的脂肪酸组成与含量进行分析。结果表明:8种枣核油共检出24种脂肪酸,包括13种饱和脂肪酸、11种不饱和脂肪酸;饱和脂肪酸主要为棕榈酸、硬脂酸,不饱和脂肪酸主要为亚油酸、油酸、棕榈油酸;秤砣枣核油不饱和脂肪酸含量最高,达到84.55%;北樱枣核油、秤砣枣核油、滩枣核油和鸡心枣核油中油酸和亚油酸含量较高;贡枣核油、晋枣核油、骨头枣核油和敦煌大枣核油的棕榈酸含量较高;贡枣核油中亚麻酸含量最高,达到3.57%。采用聚类分析、主成分分析及线性判别分析,通过枣核油脂肪酸组成和含量可以实现8种枣核油的有效分类与区分,为不同品种大枣的分类判别与枣种质资源研究提供了新方法。     

Chemical composition and oxidative stability of Tunisian monovarietal virgin olive oils with regard to fruit ripening

The chemical composition of virgin olive oil may be influenced by genotype and different agronomic (i.e. fruit ripeness degree, water supply) and technological factors. This article reports the evaluation of the influence of the olive ripening stage on the quality indices, the major and the minor components and the oxidative stability of the two main monovarietal Tunisian cultivars (cvv. Chétoui and Chemlali) virgin olive oils. Moreover, the olives cv. Chétoui were tested in a rain-fed control and an irrigation regime. The oils sampled at five different ripeness stages were submitted to liquid chromatographic determination (HPLC-DAD/MSD) of their quali-quantitative phenolic and tocopherolic profiles. Moreover, the triacylglycerol and fatty acid compositions, and minor components such as squalene, pigments and their relation with the oil oxidative stability were evaluated. The tested oils showed very good correlation between the oxidative stability and the concentrations of total phenols, practically secoiridoids and α-tocopherol.     

鲜榨山茶油与特级初榨橄榄油营养价值的比较

以鲜榨山茶油和特级初榨橄榄油为研究对象,对其理化指标、脂肪酸组成和营养成分进行测定并比较。结果表明:鲜榨山茶油在理化指标上与特级初榨橄榄油相当,脂肪酸组成与特级初榨橄榄油相似,但油酸含量高于特级初榨橄榄油,棕榈酸和硬脂酸含量低于特级初榨橄榄油;在维生素E、角鲨烯、植物甾醇等天然生物活性物质方面媲美特级初榨橄榄油。     

常见食用植物油中特征性脂肪酸的检测及鉴别

目的分析常见市售植物油中特征性脂肪酸构成及含量范围,并探讨在此基础上如何综合利用上述指标对常见植物油进行定性鉴别。方法从6个城市采集9个品种125份样品,每种两个批次。按照GB/T 22223—2008方法测定46种脂肪酸,分析植物油中的特征脂肪酸及其构成。结果菜籽油中的特征脂肪酸为芥酸;花生油中为C20∶0、C24∶0和C22∶0脂肪酸;茶油中的油酸含量高达75.45 g/100 g,是其特征脂肪酸;亚麻籽油的特征脂肪酸为α-亚麻酸;葵花籽油的特征脂肪酸为亚油酸;稻米油中棕榈酸含量范围为15.13～16.37 g/100 g,可以此作为其特征进行鉴别;大豆油中n6/n3比值最接近中国营养学会推荐比值;芝麻油中油酸和亚油酸的总含量及棕榈酸和硬脂酸含量的组成特征比较稳定,可以此作为芝麻油的鉴别依据;玉米油中脂肪酸特征不明显。结论结合单体特征脂肪酸、脂肪酸构成以及n6/n3比值分析可达到常见植物油定性检测的目的。