Tunisian table olive phenolic compounds and their antioxidant capacity

ABSTRACT:  For the 1st time, 4 olive cultivars, the Meski, Chemlali, Besbessi, and Tounsi, from the Tunisian market were investigated to evaluate the phenolic compounds' contribution in nutritional value of table olives. From the Meski cultivar, we have chosen 4 different samples to evaluate differences within the same cultivar. Basic characteristics and total phenolic content were evaluated in flesh and kernel. The highest value of flesh phenolic content was observed in sample M4 of the Meski cultivar; however, the lowest value was observed in the Besbessi cultivar and they were 1801 and 339 mg GA/100 g dry weight, respectively. The main simple phenolic compounds identified in flesh extracts are hydroxytyrosol, tyrosol, and vanillic acid. Oleuropein was not detected in any samples. The antioxidant activity of Tunisian olive flesh varies between 212 and 462 μM TEAC/g of dry weight. Antioxidant activity of olives was related to their phenolic content but we found a low correlation between phenolic content and TEAC.     

The tocopherol content of greek olive oils

Four types of Greek olive oil were analysed for α-and γ-tocopherols by high performance liquid chromatography. Certain seed oils widely consumed in Greece were also analysed for comparison with the olive oils. Virgin, pure, residual and refined oils contained an average of 113,81,156 and 37 mg kg^?1 of α-tocopherol, respectively. The α-tocopherol level within each type of olive oil appeared to be influenced by different factors. The content of y-tocopherol averaged 17 and 33 mg kg^?1of virgin and residual oil, respectively. Refined and pure olive oil contained very low levels of y-tocopherol. The α-tocopherol equivalent per gram of polyunsaturated fatty acids was calculated to be 1·48, 0·60, 0·88, 1·07 and 0·58 for edible olive oils, corn, cottonseed, sunflower and partially hydrogenated soya bean oil, respectively.     

Sugar and polyol compositions of some European olive fruit varieties (Olea europaea L.) suitable for table olive purposes

An experimental investigation was carried out on olive fruits of Douro, Hojiblanca, Cassanese, Taggiasca and Thasos cultivars, to assess free sugar and polyol compositions and their changes during ripening and processing. TMS ethers of sugars from olive pulp were analysed by GC and GC–MS and identification of each sugar component was obtained by comparison of retention times and mass spectra with those of authentic compounds. Quantitation of sugars was performed on mixture whose tautomeric equilibria were stable. Glucose, fructose and galactose were the main sugars found in olive pulp. Appreciable quantities of mannitol were also present. Sucrose and inositol were present in very low concentrations. A significant correlation (r=0.941) between mannitol and oil contents was found. Sugar content decreased from green to cherry and black colour, according to the stage of ripeness of fruits. In processed olive-fruits, sugar contents varied among olive cultivars according to processing conditions.     

Ozonation process for the regeneration and recycling of Spanish green table olive fermentation brines

Treatment with ozone broke down the most characteristic polyphenols present in the fermentation brines of green table olives. The ozone required for their complete elimination was 15 and 7 mg/L in acidic solutions (pH 4.0) and alkaline conditions (pH 10.0), respectively. The usual microbial population of brines, lactic acid bacteria and yeasts, was simultaneously eliminated in parallel but needed higher ozone levels in acidic conditions. The ozone treated brines were then filtered through a 0.45 μm pore size and diluted (1:1) and re-used as cover brine for plain and pitted olive packing. After 3 months equilibrium, the cover brines from regenerated brines had slighter poorer colour and slightly higher pH. Fruits packed with diluted (1:1) ozonated brines in alkaline conditions had higher firmness and similar organoleptic characteristics to those using fresh brine. The partial regeneration and reuse of fermentation brines may be a cheap and technologically simple alternative for reducing the environmental problems derived from the high polluting charge of green olive fermentation brines.     

Enrichment of table olives with polyphenols extracted from olive leaves

The possibility to increase the nutritional value of table olives using polyphenols extracted from olive leaves was studied. Leaves were subjected to extraction using water with proportions of 1%, 5% and 10% of leaves and various temperatures and times (room temperature/24 h, 40 °C/10 min and 70 °C/5 min). The antioxidant activity of extracts was determined using the Rancimat method and their content in oleuropein and hydroxytyrosol was determined by HPLC. The extract with the highest antioxidant activity and polyphenol content (10% ratio of olive leaves extracted at room temperature for 24 h) was used for the treatment of debittered table olives. The treated and untreated olives were subjected to determination of their α-tocopherol, oleuropein and hydroxytyrosol content. A 457% increase was observed for oleuropein and 109% for hydroxytyrosol content after treatment. Sensory evaluation of treated table olives showed an increase in bitterness. However, treated and untreated table olives showed equal overall acceptability and overall preference.     

Effects of pasteurisation and storage on quality characteristics of table olives preserved in olive oil

Two types of products obtained from the processing of Olea europaea cv ‘Taggiasca’ were monitored: pitted olives and olive paste preserved in monovarietal extra‐virgin olive oil of the same variety. The aim of this study was to follow the trends in the main physico‐chemical and sensory parameters related to the quality of these table olives and their covering oils, for simulation of the shelf‐life conditions. From all of the analyses carried out, it can be concluded that the optimum time of storage of these two products packaged in glass jars at room temperature (between 18 and 25 °C) and under artificial light and away from heat sources is approximately 9 months. After 9 months of storage, the covering oils were greatly affected by the contact with the broken fruit, which was accompanied by reductions in their antioxidant content due to the thermal treatment. The oxidative effects seen through physico‐chemical analyses are in agreement with the organoleptic analysis.     

Exploring the yeast biodiversity of green table olive industrial fermentations for technological applications

In recent years, there has been an increasing interest in identifying and characterizing the yeast populations associated with diverse types of table olive elaborations because of the many desirable technological properties of these microorganisms. In this work, a total of 199 yeast isolates were directly obtained from industrial green table olive fermentations and genetically identified by means of a RFLP analysis of the 5.8S-ITS region and sequencing of the D1/D2 domains of the 26S rDNA gene. Candida diddensiae, Saccharomyces cerevisiae and Pichia membranifaciens were the most abundant yeast species isolated from directly brined Aloreña olives, while for Gordal and Manzanilla cultivars they were Candida tropicalis, Pichia galeiformis and Wickerhamomyces anomalus. In the case of Gordal and Manzanilla green olives processed according to the Spanish style, the predominant yeasts were Debaryomyces etchellsii, C. tropicalis, P. galeiformis and Kluyveromyces lactis. Biochemical activities of technological interest were then qualitatively determined for isolates belonging to all yeast species. This preliminary screening identified two isolates of W. anomalus with interesting properties, such as a strong β-glucosidase and esterase activity, and a moderate catalase and lipolytic activity, which were also confirmed by quantitative assays. The results obtained in this survey show the potential use that some yeast species could have as starters, alone or in combination with lactic acid bacteria, during olive processing.     

Effect of kaolin and copper based products and of starter cultures on green table olive fermentation

In the present study table olives treated in field with kaolin and copper based products against “olive-fruit fly” were fermented using two selected strains of lactic acid bacteria (LAB). The fermentation process was monitored up to 260 days from brining through physico-chemical, microbiological and sensorial analyses. Results showed a dominance of LAB and yeasts and low level of Enterobacteriaceae counts throughout the whole process both in un-treated and treated samples. When investigating the effect of the single treatments on microbial dynamics, ANOVA results highlighted that copper based products affected significantly the control sample, while the sample inoculated with LAB starters maintained high level throughout the process, guaranteeing the fermentation process. Different behavior was revealed by yeasts population, which was partially influenced by copper treatment at the beginning of the fermentation.The polyphasic approach used in the present study, which combined sensory evaluation to microbial counts and physico-chemical characteristics, let to the conclusion on the importance of starter cultures in fermentation of table olives especially those treated with “non-conventional” pesticide, which could be used to prevent olive fly damage.     

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.     

Use of selected autochthonous lactic acid bacteria for Spanish-style table olive fermentation

The present work presents a successful attempt to achieve an enhanced and more predictable fermentation process in Spanish-style green olive technology by selection and use of autochthonous starter cultures. During the first phase of this work, two Spanish-like fermentations of green table olives of cultivar (cv) "Nocellara del Belice", coming from irrigated and not irrigated fields, were monitored, in order to highlight the best agricultural conditions for drupe production and to isolate lactic acid bacteria strains with relevant technological properties. Among 88 identified isolates, one Lactobacillus pentosus strain showed remarkable biochemical features and high acidification rate in synthetic brine. In the second phase, the selected strain was used as starter culture in three different trials to establish the best conditions for its use. Microbial counting, as well as starter tracking by M13 RAPD-PCR, reflected the optimal adaptation of the strain to the environment. Spontaneous fermentation needed a 14-day long lag phase to reach the same population as the inoculated trials. Moreover, sensory traits of table olives obtained with adjunct culture showed better characteristics compared to those processed in the other trials, in particular concerning the presence of off-odours.     

Evaluating the individual effects of temperature and salt on table olive related microorganisms

Statistical modelling techniques were used in the present study to assess the individual effects of temperature and NaCl concentration on the growth of 10 lactic acid bacteria and 6 yeast strains mostly isolated from different forms of table olive processing and belonging to the species Lactobacillus pentosus, Lactobacillus plantarum, Saccharomyces cerevisiae, Wickerhamomyces anomalus and Candida boidinii. The mathematical models obtained in synthetic laboratory media show that yeasts, except for C. boidinii, were more resistant to a high salt concentration than lactic acid bacteria, with an MIC value ranging from 163.5 (S. cerevisiae) to 166.9 g/L (W. anomalus); while for L. pentosus and L. plantarum this parameter ranged from 110.6 to 117.6 g/L, respectively. With regards to temperature, lactic acid bacteria showed a slight trend towards supporting higher temperature values than yeasts, with the exception of S. cerevisiae. The maximum temperatures for growth of L. pentosus and L. plantarum were 41.9 and 43.0 °C, respectively; while for W. anomalus and C. boidinii they were 38.2 and 36.5 °C. The optimum temperatures for growth were also higher for L. pentosus and L. plantarum (35.5 and 32.9 °C), compared to W. anomalus and C. boidinii (29.3 and 26.9 °C, respectively). Additional experiments carried out in natural olive brines confirmed previous results, showing that high NaCl concentrations clearly favoured yeast growth and that at high temperatures LAB slightly overcame yeasts. Results obtained in this paper could be useful for industry for a better control of both table olive fermentation and packaging.     

Study of green Sicilian table olive fermentations through microbiological,chemical and sensory analyses

The production of five different green table olive cultivars was studied by a combined strategy consisting of chemical, microbiological and sensory analyses. Cultivable microflora of samples collected during processing was monitored by plate counts on seven synthetic culture media. In all samples Enterobacteriaceae, Pseudomonaceae, staphylococci, lactic acid bacteria and spore-forming bacteria were undetectable. Yeasts and moulds were countable from the day 42 (2 log CFU/ml) till the end of fermentation (6 log CFU/ml). The use of three different approaches for microorganism detection, including a culture-independent methodology, revealed the presence of barely three yeast species during the entire fermentation period: Candida parapsilosis, Pichia guilliermondii and Pichia kluyveri. Biochemical features of technological interest were evaluated for 94 strains in order to investigate their potential role in fermentation of green Sicilian table olives.     

Chloride salt mixtures affect Gordal cv. green Spanish-style table olive fermentation

This work studies the effects of different sodium (in the range of 4-10%), potassium (0-4%) and calcium (0-6%) chloride salt mixtures on the fermentation profile of Gordal olives processed according to the Spanish style. For this purpose, response surface methodology based on a simplex centroid mixture design with constrain (sum of salt percentages = 10%) was used. All treatments reached appropriate titratable acidity levels, but this parameter could not be related to the initial chloride salt concentration. The presence of CaCl₂ led to lower initial and after-fermentation pHs, delayed sugar diffusion into the brine, its maximum concentration and titratable acidity formation. CaCl₂ also delayed Enterobacteriaceae and yeast sprang, decreasing their overall growth. This chloride salt also showed a tendency to reduce overall lactic acid bacteria growth. KCl had a similar behaviour to NaCl but, in general, increased overall microbial growth. Thus, a partial substitution of NaCl in Spanish-style green olives with KCl and CaCl₂ does not substantially modify the fermentation profile but does produce some changes, which, when properly managed, could help to improve product processing.     

Analysis of extra virgin olive oils from stoned olives

This paper focuses on comparing the main chemical characteristics of 16 fresh commercial samples of extra virgin olive oil obtained from four harvest years (1999–2002) and derived from both stoned and whole fruits. The qualitative and quantitative contents of minor polar compounds (MPCs) together with other reference analytical parameters (acidity, peroxides, UV absorption values and Rancimat test) were evaluated. An investigation of the MPCs and oil composition obtained from only stoned olives was also carried out. The acidity values of the oils from stoned fruits were always similar to or lower than those of the corresponding oils from whole fruits. For almost all the samples from stoned olives a better resistance to oxidation was revealed in comparison with the corresponding traditional oils. Five pairs obtained from the 2000 and 2001 harvests showed higher concentrations of both MPCs and hydroxytyrosol derivatives in the oils from stoned fruits, in agreement with their higher Rancimat values. Overall, our findings with regard to acidity values, % hydrolysis, the Rancimat test and the qualitative and quantitative distribution of MPCs suggest a higher antioxidant capacity of the oils from stoned olives. Copyright © 2004 Society of Chemical Industry     

棕榈油中生育酚和生育三烯酚的HPLC测定

建立了棕榈油中生育酚和生育三烯酚的准确、快速的HPLC分析方法。选用Nucleosil硅胶柱正相分离,以正己烷-异丙醇为流动相,梯度洗脱,在紫外波长292nm下进行检测,获得较理想的分离效果。该方法线性范围为0.2275～1.3031mg/mL,平均加样回收率为100.17%,RSD=0.5905%。     

Tocopherol Quantification by HPLC in Pecans and Relationship to Kernel Quality during Storage

Changes in tocopherols were followed in Stuart, Desirable and Schley cultivars during storage at 23.9°C and 60-70% RH and 0.6°C and 75% RH for 12 mo. Quality changes in the pecans were monitored using Hunter color measurements and conjugated diene measurement. α-, β-,γ- and 8-tocopherols were found in the three cultivars and γ-tocopherol was the primary form in each. Decreases of γ- and total tocopherols and L, hue angle and saturation index values were observed for pecans stored at 23.9°C (P < 0.05). Positive correlations (P < 0.05) were found between γ- and total tocopherols and Hunter color values for samples stored at 23.9°C. Conjugated diene levels did not correlate with tocopherol levels and Hunter values (P < 0.05). Pecans could be stored at 0.6°C and 75% RH for 12 mo without changes in kernel color, oil quality, tocopherols or conjugated diene levels.     

Tocopherol Deposition in the Muscle of Atlantic Salmon (Salmo salar)

The deposition of four tocopherols (α, β, γ and δ) was studied in the muscle of Atlantic salmon (Salmo salar) smolts reared in seawater. γ-Tocopherol was deposited in proportion to the a-tocopherol content of the diet when both were added to the diet in a natural mixture. Both δ- and β-tocopherols were deposited in the muscle to a lesser extent than the a and γ forms. An equilibrium among tocopherols in muscle was reached in 15 wk.     

Cholesterol Oxidation in Egg Yolk Powder During Storage and Heating as Affected by Dietary Oils and Tocopherol

The effects of feeding flax, sunflower, palm and fish oils, with and without tocopherols, to laying hens was investigated on oxidative stability of cholesterol in egg yolk powders. Storage of spray-dried egg yolk powders at room temperature resulted in loss (p <0.05) of tocopherols. The initial levels of spray-dried yolk cholesterol oxides were 7–10 ppm and increased (p <0.05) with storage. The cholesterol oxide contents in the egg yolk powders were: fish > flax > sunflower > palm. Heating egg yolk powder increased (p <0.05) the amounts of total cholesterol oxides. Diets with tocopherol supplementation resulted in a decrease (p <0.05) of cholesterol oxides during storage and heating.     

Tocopherol Micro-Extraction Method with Application to Quantitative Analysis of Lipophilic Nutrients

A method proposed for determining vitamin E consists of extraction with n-hexane/2-propanol and separation by normal-phase HPLC. It was used to monitor tocopherol content of eggs metabolically enriched with vitamin E. It accurately evaluated nutritional uniformity of many samples in a relatively short time. Chromatographic resolution showed alpha-tocopherol as the only major peak in the enriched eggs. Quantification with HPLC or GC demonstrated that the extraction technique could also be used to determine cholesterol and fatty acids. Results from eggs containing varied ratios of fatty acids indicate that the method did not differentially extract different types of fatty acids.