Volatile and Sensory Profiles of Algerian Extra‐Virgin Olive Oil from Souidi and Zeletni Cultivars

In this study, the volatile and sensory profiles of monovarietal extra‐virgin olive oil (EVOO) from two less widespread Algerian autochthonous cultivars (Souidi and Zeletni) were obtained using headspace solid‐phase microextraction coupled to gas chromatography‐mass spectrometry and a panel test, respectively. A total of 14 and 10 volatile compounds belonging to different chemical classes were identified and quantified in the Souidi and Zeletni EVOOs, respectively. Zeletni EVOO contains 2.07 times more (E)‐2‐hexenal than Souidi EVOO. In addition, the amounts of C6 compounds from LA and LnA, as well as the total amount of the compounds of the LOX pathway were higher in Zeletni than in the Souidi EVOO. Another important finding was the predominance of sesquiterpene β‐ocimene in the composition of the volatile fraction of Souidi EVOO. The sensory profiles of the EVOOs analyzed were characterized by fruity, bitter and pungent sensory positive attributes, perceived at medium intensity in both oils studied.     

Effect of fungal species involved in the olive fruit rot on the qualitative properties of olive oil

Olive oil is the most important product of olive fruits with worldwide consumption, particularly in Mediterranean countries. Olive oil is generally extracted mechanically from the olive fruits. Some biotic and abiotic factors may affect the quality of oil extracted from olive fruit. Contamination with fungi during growth period in the garden or during the conservation of the harvested crop under storage condition may leave negative effects on the quality of olive oil. However, there is no data available on the effects of fungal infections on qualitative properties of olive oil in Iran. In the present study effects of several fungal groups previously isolated from rotten olive fruit in olive orchards including Alternaria alternata, Fusarium nygamai, Aspergillus ochraceus, Arthrinium phaeospermum, Cladosporium cladosporioides, Aureobasidium pullulans, Epicoccum nigrum, Penicillium expansum, Truncatella angustata, Trichothecium roseum and Trichoderma harzianum were evaluated on some qualitative properties of olive oil, under laboratory condition on two olive cultivars (Zard & Roghani). For this purpose fresh and healthy fruits of olive, were surface sterilisation with 96% ethanol and rinsed with sterile water and then inoculated with each of the fungal groups separately using spore suspension (10^6?ml^?1). The experiment was carried out in two replicates for each treatment (fungal isolates). The results of this study revealed that fungal infection caused significant increase in the extracted oil acidity and peroxide values. However, there was no significant difference in the acidity and peroxide values among different treatments (fungal isolates).     

Enumeration and rapid identification of yeasts during extraction processes of extra virgin olive oil in Tuscany

The aim of this study was to evaluate the occurrence of yeast populations during different olive oil extraction processes, carried out in three consecutive years in Tuscany (Italy), by analysing crushed pastes, kneaded pastes, oil from decanter and pomaces. The results showed yeast concentrations ranging between 10³ and 10⁵ CFU/g or per mL. Seventeen dominant yeast species were identified by random amplified polymorphic DNA with primer M13 and their identification was confirmed by restriction fragments length polymorphism of ribosomal internal transcribed spacer and sequencing rRNA genes. The isolation frequencies of each species in the collected samples pointed out that the occurrence of the various yeast species in olive oil extraction process was dependent not only on the yeasts contaminating the olives but also on the yeasts colonizing the plant for oil extraction. In fact, eleven dominant yeast species were detected from the washed olives, but only three of them were also found in oil samples at significant isolation frequency. On the contrary, the most abundant species in oil samples, Yamadazyma terventina, did not occur in washed olive samples. These findings suggest a phenomenon of contamination of the plant for oil extraction that selects some yeast species that could affect the quality of olive oil.     

Extra virgin olive oil improves synaptic activity,short‐term plasticity,memory, and neuropathology in a tauopathy model

In recent years, increasing evidence has accumulated supporting the health benefits of extra virgin olive oil (EVOO). Previous studies showed that EVOO supplementation improves Alzheimer's disease (AD)‐like amyloidotic phenotype of transgenic mice. However, while much attention has been focused on EVOO‐mediated modulation of Aβ processing, its direct influence on tau metabolism in vivo and synaptic function is still poorly characterized. In this study, we investigated the effect of chronic supplementation of EVOO on the phenotype of a relevant mouse model of tauopathy, human transgenic tau mice (hTau). Starting at 6 months of age, hTau mice were fed chow diet supplemented with EVOO or vehicle for additional 6 months, and then the effect on their phenotype was assessed. At the end of the treatment, compared with control mice receiving EVOO displayed improved memory and cognition which was associated with increased basal synaptic activity and short‐term plasticity. This effect was accompanied by an upregulation of complexin 1, a key presynaptic protein. Moreover, EVOO treatment resulted in a significant reduction of tau oligomers and phosphorylated tau at specific epitopes. Our findings demonstrate that EVOO directly improves synaptic activity, short‐term plasticity, and memory while decreasing tau neuropathology in the hTau mice. These results strengthen the healthy benefits of EVOO and further support the therapeutic potential of this natural product not only for AD but also for primary tauopathies.     

Identification of yeast strains isolated from a two-phase decanter system olive oil waste and investigation of their ability for its fermentation

A dynamic fed-batch microcosm system is described which permits assessment of the progressive growth of yeasts through olive oil waste. We report on its application to measure the effects of the growth of yeast strains upon the chemical composition of "alpeorujo", the waste of a two-phase decanter system used for the extraction of olive oil. Six phenotypically distinct groups of yeasts were isolated. Three selected isolates were identified as being most closely related to Saccharomyces sp., Candida boidinii and Geotrichum candidum using biochemical tests and partial 18S rDNA gene sequence analysis. This is the first report of yeast growth on "alpeorujo" by the use of a fed-batch microcosm system, resulting in the change of the initial chemical composition of "alpeorujo" and in the decrease of the toxic substances such as phenols.     

Quantitative study of lipase secretion, extracellular lipolysis, and lipid storage in the yeast Yarrowia lipolytica grown in the presence of olive oil: analogies with lipolysis in humans

Lipase secretion, extracellular lipolysis, and fatty acid uptake were quantified in the yeast Yarrowia lipolytica grown in the presence of olive oil and/or glucose. Specific lipase assays, Western blot analysis, and ELISA indicated that most of the lipase activity measured in Y. lipolytica cultures resulted from the YLLIP2 lipase. Lipase production was triggered by olive oil and, during the first hours of culture, most of the lipase activity and YLLIP2 immunodetection remained associated with the yeast cells. YLLIP2 was then released in the culture medium before it was totally degraded by proteases. Olive oil triglycerides were largely degraded when the lipase was still attached to the cell wall. The fate of lipolysis products in the culture medium and inside the yeast cell, as well as lipid storage, was investigated simultaneously by quantitative TLC–FID and GC analysis. The intracellular levels of free fatty acids (FFA) and triglycerides increased transiently and were dependent on the carbon sources. A maximum fat storage of 37.8% w/w of yeast dry mass was observed with olive oil alone. A transient accumulation of saturated FFA was observed whereas intracellular triglycerides became enriched in unsaturated fatty acids. So far, yeasts have been mainly used for studying the intracellular synthesis, storage, and mobilization of neutral lipids. The present study shows that yeasts are also interesting models for studying extracellular lipolysis and fat uptake by the cell. The quantitative data obtained here allow for the first time to establish interesting analogies with gastrointestinal and vascular lipolysis in humans.     

Comparison of the chemical composition and the organoleptic profile of virgin olive oil from two wild and two cultivated Tunisian Olea europaea

With the aim to select new olive cultivars with superior physical and chemical properties than the cultivar Chemlali Sfax, the present study focused on the comparison of the chemical composition and the sensory profile of the virgin olive oils (VOOs) of two wild olive trees (Oleasters K and M) with those of VOOs obtained from Chemlali Sfax and Neb Jmel olive cultivars, all growing in the coastal region of Tunisia. Despite the variability in the chemical composition (fatty acids, pigments, and phenolic and volatile compounds) and the organoleptic profile of the VOOs of the oleasters and the cultivars, the quality indices (free fatty acids, peroxide value, and spectrophotometric indices K232 and K270) as well as the fatty acid composition of all VOOs studied met the commercial standards. Both the α-tocopherol and phenol contents varied between the genotypes. The Neb Jmel and Oleaster K VOOs had more than two times higher total phenol levels than the Chemlali Sfax and Oleaster M VOOs. Also the contents of volatile compounds differed between the olive oils studied. Chemlali Sfax and Oleaster K oils were more abundant in aldehydes, whereas Oleaster M VOO had higher contents of alcohols. These results were confirmed by a sensorial analysis showing that the later oil was deprived for consumption despite its abundance in α-tocopherol. In conclusion, the oleasters studied revealed to be interesting, since they produced oils with good quality characteristics in terms of minor compounds (phenols and volatiles) compared to the Chemlali Sfax cultivar.     

Mannose-containing polysaccharides of yeasts

The known species of yeasts produce at lest 180 different polysaccharides having mannose as a major constituent. The type of mannan formed is characteristic of the yeast species, and can be used as an aid in identification and classification. The immunological characteristics of yeasts depend largely upon the nature of the mannans. Some of the yeast mannans can be produced in relatively high yields, and have been suggested as replacements for plant and bacterial gums as thickeners, dispersing agents, and similar applications. However, more significant uses, based on the finer differences in their chemical structures and the specific reactions they undergo, may result from a closer study of these polymers.     

Marine yeasts as biocontrol agents and producers of bio-products

As some species of marine yeasts can colonize intestine of marine animals, they can be used as probiotics. It has been reported that β-glucans from marine yeast cells can be utilized as immuno-stimulants in marine animals. Some siderophores or killer toxins produced by marine yeasts have ability to inhibit growth of pathogenic bacteria or kill pathogenic yeasts in marine animals. The virulent factors from marine pathogens can be genetically displayed on marine yeast cells, and the yeast cells displaying the virulent factors can stimulate marine animals to produce specific antibody against the pathogens. Some marine yeast cells are rich in proteins and essential amino acids and can be used in nutrition for marine animals. The marine yeast cells rich in lipid can be used for biodiesel production. Recently, it has been reported that some strains of Yarrowia lipolytica isolated from marine environments can produce nanoparticles. Because many marine yeasts can remove organic pollutants and heavy metals, they can be applied to remediation of marine environments. It has been shown that the enzymes produced by some marine yeasts have many unique properties and many potential applications.     

Survival of yeasts inoculated in flavoured extra virgin olive oil

The survival of four strains of yeast belonging to the speciesSaccharomyces cerevisiae, Candida wickerhamii, Candida boidinii andWilliopsis californica was studied in extra virgin olive oil flavoured with garlic, lemon, oregano and red chilli pepper. The ingredients used in the doses of 1%, 5% and 10% profoundly modified the habitat of the extra virgin olive oil, reducing drastically, in 90 days of storage, the survival of the yeasts by 20–50%, in the following decreasing order: lemon, garlic, oregano and red chilli pepper. Among the yeasts studied,W. californica strain 1639 was found to be one of the most sensitive, whileS. cerevisiae strain 1525 was one of the most tolerant regarding the ingredients present in the flavoured olive oil. The observations carried out with a scanning electron microscope (SEM) highlighted the presence of frequent lesions on the cellular wall ofC. wickerhamii 1532,C. boidinii 1638 andS. cerevisiae 1525 and only in a few rare cases inW. californica 1639. Nevertheless, since the survival ofW. californica 1639 in the flavoured olive oil was compromised to a greater extent in respect to the other species, it is plausible to deduct that the damage to the cellular wall represents only one of the causes responsible for the death of the yeasts in the flavoured olive oil.     

Detoxification of olive mill wastewaters by Moroccan yeast isolates

A total of 105 yeast strains were isolated from Moroccan olive oil production plants and evaluated for their ability to grow in olive oil mill wastewaters (OMW). The 9 isolates that grew best on OMW were selected for further study to evaluate their effect on removal of organic pollutants and OMW phytotoxicity (barley seed germination test). The results showed that at least four yeast isolates effectively lowered the toxicity of this effluent in addition to providing very useful materials in terms of both yeast biomass (6 g/l DW) and an irrigation fluid. This group of yeast isolates significantly reduced the concentration of total phenols (44% removal) and Chemical Oxygen Demand, COD (63% removal). The best germination rate of 80% for undiluted OMW was obtained for strain Candida holstii that also increased the pH from 4.76 to 6.75. Principal component analysis of the results obtained for the best yeast strains confirmed the importance of COD and total phenol reduction along with increase of organic nitrogen and final pH for the improvement of germination rates and phytotoxic reduction. This study has highlighted the potential of indigenous yeasts in detoxification of olive mill wastewaters.     

Oleaginous yeasts: Biodiversity and cultivation

Microbial lipids produced by oleaginous microorganisms, also called microbial oils and single cell oils (SCOs), are very promising sources for several oil industries. The exploration of efficient oleaginous yeast strains, meant to produce both high-quantity and high-quality lipids for the production of biodiesel, oleochemicals, and the other high value lipid products, have gained much attention. At present, the number of oleaginous yeast species that have been discovered is 8.2% of the total number of known yeast species, most of which have been isolated from their natural habitats. To explore high lipid producing yeasts, different methods, including high-throughput screening methods using colorimetric or fluorometric measures, have been developed. Understanding of the fatty acid composition profiles of lipids produced by oleaginous yeasts would help to define target lipid-related products. For lipid production, the employment of low-cost substrates suitable for yeast growth and lipid accumulation, and efficient cultivation processes are key factors for successfully increasing the amount of the accumulated lipid yield while decreasing the cost of production.     

Multivariate analysis to discriminate yeast strains with technological applications in table olive processing

This survey uses a multivariate classification analysis to discriminate yeast strains with interesting biochemical activities for the processing of table olives among a collection of 32 isolates belonging to 16 different yeast species. Lipase, esterase and β-glucosidase activities (desirable characteristics) were quantitatively evaluated in both extracellular and cellular fractions for all isolates in different types of culture media. The study of the quantitative data by cluster and principal component analyses led to the identification of several Wickerhamomyces anomalus, Candida boidinii and Candida diddensiae isolates with promising characteristics (the best global activity levels), clearly differentiated from the rest of the yeasts. The results obtained in this work open up new alternatives to this methodology for the study, classification and selection of the most suitable yeasts to be used as starters, alone or in combination with lactic acid bacteria, during table olive processing.     

Oleaginous yeasts for biodiesel: Current and future trends in biology and production

Production of biodiesel from edible plant oils is quickly expanding worldwide to fill a need for renewable, environmentally-friendly liquid transportation fuels. Due to concerns over use of edible commodities for fuels, production of biodiesel from non-edible oils including microbial oils is being developed. Microalgae biodiesel is approaching commercial viability, but has some inherent limitations such as requirements for sunlight. While yeast oils have been studied for decades, recent years have seen significant developments including discovery of new oleaginous yeast species and strains, greater understanding of the metabolic pathways that determine oleaginicity, optimization of cultivation processes for conversion of various types of waste plant biomass to oil using oleaginous yeasts, and development of strains with enhanced oil production. This review examines aspects of oleaginous yeasts not covered in depth in other recent reviews. Topics include the history of oleaginous yeast research, especially advances in the early 20th century; the phylogenetic diversity of oleaginous species, beyond the few species commonly studied; and physiological characteristics that should be considered when choosing yeast species and strains to be utilized for conversion of a given type of plant biomass to oleochemicals. Standardized terms are proposed for units that describe yeast cell mass and lipid production.     

Survival of Candida parapsilosis yeast in olive oil

Candida parapsilosis is a human opportunistic pathogen yeast isolated from different habitats like animals, man, pickled cucumber, fruit juices, and water. Recent studies have demonstrated that C. parapsilosis can survive in olive oil for very long periods even exceeding 24 months. The survival of two strains of C. parapsilosis named DAPES 1890 and 1892, previously isolated from extra virgin olive oil, was influenced by the state of hydration of the cells and the polyphenols concentration of olive oil. When the cells of the two strains of C. parapsilosis were inoculated under a liophilized form into olive oil containing 45–312 mg/kg of total polyphenols, their survival in some olive oil samples reached approximately 18 months. However, if the above-mentioned inoculum was rehydrated with 1 % of distilled water, then the survival of both yeast strains in some samples of oil exceeded 24 months. The two yeast strains, recovered from the olive oil samples after 24 months of storage, showed, under SEM, spherical shapes with and without buds according to whether the inoculum was made up of rehydrated or lyophilized cells. The survival of all the C. parapsilosis strains was also negatively influenced by the polyphenols concentration of the olive oil samples inoculated both with lyophilized and rehydrated yeast cells. In the oily habitat, the polyphenols sorption to the C. parapsilosis yeast surface was observed, and during storage the polyphenols reacted with the yeast cell walls according to their concentration in the inoculated olive oil.     

Antimicrobial, antioxidant and anti-inflammatory phenolic activities in extra virgin olive oil

The Mediterranean diet is associated with a lower incidence of chronic degenerative diseases and higher life expectancy. These health benefits have been partially attributed to the dietary consumption of extra virgin olive oil (EVOO) by Mediterranean populations, and more specifically the phenolic compounds naturally present in EVOO. Studies involving humans and animals (in vivo and in vitro) have demonstrated that olive oil phenolic compounds have potentially beneficial biological effects resulting from their antimicrobial, antioxidant and anti-inflammatory activities. This paper summarizes current knowledge on the biological activities of specific olive oil phenolic compounds together with information on their concentration in EVOO, bioavailability and stability over time.     

Biotransformation of hop aroma terpenoids by ale and lager yeasts

Terpenoids are important natural flavour compounds, which are introduced to beer via hopping. It has been shown recently that yeasts are able to biotransform some monoterpene alcohols. As a first step towards examining whether yeasts are capable of altering hop terpenoids during the brewing of beer, we investigated whether they were transformed when an ale and lager yeast were cultured in the presence of a commercially available syrup. Both yeasts transformed the monoterpene alcohols geraniol and linalool. The lager yeast also produced acetate esters of geraniol and citronellol. The major terpenoids of hop oil, however, were not biotransformed. Oxygenated terpenoids persisted much longer than the alkenes.     

Antagonism between olive oil phenolics and nitric oxide on lymphomonocyte cytosolic calcium

Some biological actions of olive oil phenolics (inhibition of platelet aggregation, decrease of LDL-oxidation, inhibition of bacterial growth and hypertensive action) have been attributed to NOS stimulation in endothelial cells through an increase of cytosolic calcium, notwithstanding the scavenging activity of phenolics on NO and superoxide. In this paper, we determine the concentration of cytosolic calcium in human lymphomonocytes incubated with high concentrations of NO-donors (CysNO) and we evaluate the effects of olive oil phenolics on this parameter. CysNO induces a marked decrease of cytosolic calcium; both olive oil phenolics oppose this action of CysNO. The effects of phenolics and CysNO are independent and additive. (Mol Cell Biochem xxx: 181–184, 2005)     

一株油脂降解菌的筛选鉴定及降解效果分析

为了筛选分离得到一株具有油脂降解能力的菌株,同时探究菌株的特性和降解能力。以屠宰场污染土作为菌源,通过梯度驯化法最终筛选分离得到能够将橄榄油作为单一碳源生长的降解菌。随后通过形态特征观察、Biolog生理生化测试以及16S rRNA基因序列比对分析鉴定,实验菌株为革兰氏阴性菌,属于无色杆菌属（Achromobacter sp.）,在构建的系统发育树上与Achromobacter pulmonis聚为一支。综合运用紫外分光光度法和高效液相色谱法检测,测得实验菌株培养4~5 d时对橄榄油的降解率可以达到90%,同时测得菌株降解油脂的最适pH和最适温度分别为7.5和35 ℃,该菌株在盐浓度低于40 g·L-1环境中降解率较高。此外实验结果表明,实验菌株对各类型油脂均具有较高的降解效率,具有广泛的应用前景。