Olive Seeds Research Articles

IN VITRO GERMINATION OF STONELESS SEEDS AND ISOLATED EMBRYOS OF 14 SICILIAN CULTIVARS OF OLEA EUROPAEA L.

Olive seeds are characterized by an orthodox behaviour and exhibit a state of dormancy caused by different factors such as the hard covering structures (sclerified endocarp) and the inhibitory germination substances contained both in the teguments and in the endosperm and within the embryo. For these reasons, olive seed germination percentages and rates are usually low. To speed up olive seedling development can be very advantageous in breeding programmes as well as in rootstock production for grafting of hard-to-root cultivars. In this study, the in vitro germination potential of stoneless seeds (seeds without the sclerified endocarp) without teguments and of excised embryos of fourteen Sicilian olive cultivars was evaluated. For the in vitro germination of excised embryos, three different media (presence/absence of plant growth regulators, different carbon source concentrations) have been evaluated. Differences in the seed and in isolated embryo germination percentages due to culture media were recorded. In vitro germination of isolated embryos can be a useful method for increasing the efficiency of germination. In fact, according to these results, embryo culture can increase the efficiency and shorten the time for starting initial progeny evaluation of olive breeding programmes.

Microwave-integrated extraction of total fats and oils

An improved process of Soxhlet extraction assisted by microwave, called microwave-integrated Soxhlet (MIS) is proposed for the extraction of oils and fats from different food matrixes such as oleaginous seeds, meat and bakery products. Optimal conditions for extraction were obtained using a response surface methodology and reached from a central composite design allowing us to conclude in a previous paper that the proposed process ensures complete, efficient and accurate extraction for lipids determination from olives. In this paper, the peak areas of the main fatty acids extracted with MIS from olive seeds were considered as response variables and submitted to an analysis of variance in order to determine if there was a significant link between the extraction of fatty acids and the variables required in extraction procedures. Results have shown that MIS parameters do not affect the composition of the extracts. For the generalization of the study with several food matrixes, MIS extraction results obtained were then compared to conventional Soxhlet extraction in terms of crude extract and fatty acid composition and shown that the oils extracted by MIS were quantitatively and qualitatively similar to those obtained by conventional Soxhlet extraction. MIS labstation can be considered as a new and general alternative for the extraction of lipids by using microwave energy.

Green procedure with a green solvent for fats and oils’ determination: Microwave-integrated Soxhlet using limonene followed by microwave Clevenger distillation

Here is described a green and original alternative procedure for fats and oils’ determination in oleaginous seeds. Extractions were carried out using a by-product of the citrus industry as extraction solvent, namely d-limonene, instead of hazardous petroleum solvents such as n-hexane. The described method is achieved in two steps using microwave energy: at first, extractions are attained using microwave-integrated Soxhlet, followed by the elimination of the solvent from the medium using a microwave Clevenger distillation in the second step. Oils extracted from olive seeds were compared with both conventional Soxhlet and microwave-integrated Soxhlet extraction procedures performed with n-hexane in terms of qualitative and quantitative determination. No significant difference was obtained between each extract allowing us to conclude that the proposed method is effective and valuable.

Characterization of olive seed storage proteins

At present little is known about olive seed storage proteins (SSPs). A better understanding of olive SSPs will be important for future biotechnology efforts. In the present study, we first developed a protocol relied on chloroform for preparing protein samples free of lipids from lipid-rich olive seeds. Then, we characterized olive SSPs by SDS-PAGE, N-terminal sequencing and immunoblot. Two smaller subunits (20 and 21.5 kD) of SSPs were purified to homogeneity and used for antibody production or N-terminal sequencing. N-terminal sequencing confirmed that major olive SSPs are 11S globulins. Moreover, the components and size distribution of SSPs are identical among several olive cultivars examined, suggesting that their synthesis is highly conserved in this species. Olive SSPs are soluble in aqueous alcohol, with limited solubility in water and dilute salt. Thus, despite their homology with globulins, olive SSPs are similar in solubility to prolamins and different from globulins in other dicot plants. Finally, the accumulation of olive SSPs during fruit maturation was examined. Our results revealed that the accumulation of SSPs is time-dependent and tissue-specific, and only 105 days after pollination (DAP), did individual components of SSPs synthesize substantially, and accumulate rapidly in large quantities over a short period of time. Our results suggest that a 36 kD protein is the precursor of olive SSPs, and 90–105 DAP seems to be a crucial transition period (from a precursor to mature subunits) for the accumulation of SSPs.

Phenolic Compounds and Antioxidant Activity of Olea europaea L. Fruits and Leaves

Extracts of leaves, fruits and seeds of olive tree cultivars of Trás-os-Montes e Alto Douro (Portugal) were analysed by reverse phase HPLC with diode array detection and mass spectrometry (MS). This methodology allowed the identification of some common phenolic compounds, namely, verbascoside, rutin, luteolin-7-glucoside, oleuropein and hydroxytyrosol. Moreover the hyphenation of HPLC with MS enabled the identification of nüzhenide in olive seeds. An oleuropein glucoside was also detected in olive tree leaves. The total phenolic content was determined with the Folin Denis reagent and the total antioxidant activity with the ABTS method. There is a correlation between total antioxidant activity and total phenolic content with the exception of the seed extracts analysed. The apparent high antioxidant activity of seed extracts may be due to nüzhenide, a secoiridoid that is the major phenolic component of olive seeds. These results suggest a possible application of olive seeds as sources of natural antioxidants.

Erosion‐corrosion of laser and thermally deposited coatings exposed in fluidised bed combustion plants

AbstractCoated low alloyed steel tubes were exposed in two combustion power plants of the type Circulating Fluidised Bed (CFB) and Pressurised Fluidised Bed Combustion (PFBC). The power plants were fired with wood chips and coal with a small addition of olive seeds, respectively. In addition to laser coating two thermal spray techniques were used; arc‐spray (air as carrier gas) and High Velocity Oxy Fuel (HVOF). The sample locations in the PFBC plant were at the highest and lowest loops of a platen immersed in the fluidising bed. The material temperatures in each loop were 450 °C and 400 °C, respectively. The exposure lasted over two firing seasons for a total time of 8089 h. In the CFB plant a probe was located at the cyclone entrance where the material temperature was 630 °C for an exposure time of about 2100 h before being reduced to 480 °C for a further 920 h. The material wastage was determined from metallographic studies on cross‐sections of rings cut from the exposed tubes. The nature and chemical composition of the corrosion products and deposits formed were determined by SEM/EDX, Auger spectroscopy, XPS and XRD. Cobalt based coatings show the best performance in both the PFBC plant and the CFB plant, while nickel based coatings are resistant to a corrosive atmosphere but very sensitive to erosion. The degree of corrosion is much larger in the CFB plant as is clearly seen from the chromium carbide containing coating, which totally degraded in this environment. Contrary the performance of the same coating was excellent in the fluidised bed due to its high erosion resistance. The material wastage of a coating with a specific composition is independent of the deposition method. No significant differences in spallation behaviour occurred among coatings deposited with the different techniques.

Surface runoff and seed trapping efficiency of shrubs in a regenerating semiarid woodland in northern Ethiopia

In forest restoration areas in northern Ethiopia, natural regeneration of Olea europaea ssp. cuspidata only occurs under pioneer shrubs. To assess the impact of erosion on the spatial distribution of Olea recruits, secondary dispersal of olive seeds by surface runoff was determined in and near the micro-environment of two important pioneers ( Acacia etbaica and Euclea racemosa). We hypothesized that (1) Olea seeds deposited under the protective crowns of shrubs are less likely to be lost by surface wash than seeds in the bare inter-plant areas and (2) that seeds in the latter are more prone to be translocated by runoff to microsites under shrubs than to open areas. Runoff experiments were conducted in August–September 2003 in ten 3 × 3 m 2 plots laid out around isolated shrubs in two sites. Twenty-eight marked tracer seeds were dropped at the upper end of each plot at 0.10 m intervals. Ten seeds marked in another way were deposited under the crown in each plot simulating seed dispersal by birds. The seeds were collected after the rainy season and their positions recorded. In a third experiment, mulch under shrubs was removed and ten marked seeds were deposited under each crown. Rainfall simulation experiments were conducted with a maximum intensity of 120 mm h − 1 for a 10 min duration. For all experiments, seed movement was analyzed in relation to slope and shrub variables. Seed movement was limited in one site, where only 21% of the seeds were translocated. Movement was significantly higher in the other site (61%) although it had a lower slope gradient. The number of seeds moved by surface runoff was not significantly related to shrub species, slope gradient or slope roughness. There was a strong linear relationship between the distance parallel to the contour from the shrub center to the seed and the extent of the downhill translocation. No seeds moved to a position under a shrub crown and no shrub lost a seed deposited under its crown. Simulated rainfall after mulch removal resulted in a seed loss of nearly 33%. Micro-topographic structures under shrubs, especially under E. racemosa, cause some soil and sediment retention, but more importantly divert runoff water and concentrate flows to rills alongside shrubs. From an eco-geomorphological point of view, shrubs show poor seed trapping efficiency contradictory to expectation. Seeds in sediment flows are deposited in the bare inter-plant areas. However, seeds under shrubs are not likely to be lost by surface wash. Surface runoff has little effect on the general pattern of the primary seed rain. Since Olea recruits were exclusively found under shrubs and not in the spaces between shrubs in the studied field sites, it appears plausible that seeds deposited in the open field are almost without doubt lost to post-dispersal seed predation, unsuccessful germination or seedling predation and mortality. Recovery of O. europaea in degraded shrubland communities therefore depends upon directed dispersal of seeds under shrubs by frugivorous birds.

A macroscopic study of the retention capacity of copper b polyaniline coated onto silica gel and natural solid materials

Synthesised polyaniline coated onto silica gel and other natural materials such as peanut, almond, nut shells, apricot and olive seeds, etc., have been tested for the ability to retain metallic pollutants. Two adsorbents have been tested, namely silica gel and peanut shells, with copper as the metallic pollutant. In the absence of the polymer, both adsorbents have shown an extremely low capacity of retention, inversely to the case where they are coated with polyaniline, where the retention is very important. In fact the kinetic study of metal retention has shown that both polyaniline coated sorbents exhibit a rapid phase of adsorption before saturation is reached. However it should be noted that the peanut shells have shown a more rapid kinetic of retention than silica gel. The influence of different parameters like the contact time between the liquid and solid phases and the solution pH, on the capacity of retention, has been considered. The main result obtained from this study is that, macroscopically, the introduction of polyaniline onto the surface of silica gel and peanut shells, has largely improved the retention capacity of copper, practically from a zero value to nearly hundred per cent.

Fast ultrasound-assisted method for the determination of the oxidative stability of virgin olive oil

A method for accelerating the determination of the oxidative stability of virgin olive oil by use of ultrasound energy is proposed. The most influential variables on the acceleration of the process were those characteristic of the ultrasound probe, namely irradiation time, duty cycle and pulse amplitude, and they were exhaustively optimized. The ultrasound device, a cylindrical titanium alloy microprobe (3 mm diameter), was immersed into the olive oil sample contained in a 5 cm long test tube where the ultrasound waves were applied directly. The oxidation process was monitored at 270 nm. Twelve samples of virgin olive oil with known oxidative stability, ranging between 19 and 129 h, calculated by the Rancimat method, were analyzed and the results obtained showed an excellent correlation ( r=0.9961) with those provided by the Rancimat method. The proposed method drastically decreased the time required for the determination of this parameter, e.g. a virgin olive oil with oxidative stability 129 h, as calculated by the Rancimat method, required only 50.5 min, thus decreasing the determination time 110 times. The method was applied to the determination of the stability of five extra virgin olive oils from different varieties of olive seeds. The values obtained were interpolated in the correlation plot for the calculation of the values corresponding to the Rancimat method. They coincided with those calculated previously with this method, thus demonstrating the validity of the proposed method.

Role of olive seed in the biogenesis of virgin olive oil aroma.

Results obtained in a set of experiments point to an effective participation of olive seeds in the biosynthesis of olive oil aroma through the lipoxygenase pathway during the extraction process to produce virgin olive oil. Data showed that olive seeds should contain enzymatic activities metabolizing 13-hydroperoxides other than hydroperoxide lyase, giving rise to a net decrease in the content of C6 unsaturated aldehydes during the olive oil extraction process. Olive seeds seem also to supply this process with alcohol dehydrogenase activity, being more specific for saturated C6 aldehydes and not acting on C5 alcohols. Moreover, olive seeds would be responsible for the biosynthesis of 30-50% esters during the olive oil extraction process of intact fruits. Thus, olive seeds would afford a load of alcohol acyltransferase activity that might be quite unspecific in terms of substrate, producing any kind of esters.

The Germination of European Type Olive Seed as Affected by Different Sowing Methods

The Germination of European Type Olive Seed as Affected by Different Sowing Methods

OLIVE SEED SET AND ITS IMPACT ON SEED AND FRUIT WEIGHT

Pistillate olive flowers bear at anthesis four viable equally sized ovules. In spite of that, olive fruit is typically a one-seeded drupe. Preliminary observations, however, disclosed that some cultivars sometimes form fruits containing two seeds. In this study we compared seed set on five olive cultivars and we found maternal (cultivar) and paternal (pollen) effects on seed set. Up to 14% of Hojiblanca fruits from open-pollination were two-seeded while only 4% and 1% were found in Arbequina and Sevillano. No biseeded fruits appeared in Picual and Frantoio. On the contrary, Sevillano produced 46% of fruits with aborted seeds. Paternal effects on seed set could also be verified. In general, a higher percent of biseeded fruits developed under cross-pollination while empty endocarps were more often found under self-pollination. Presence and number of seeds per fruit affected fruit and seed size on cv Hojiblanca. Fruits containing two seeds were heavier due to heavier pulp as well as heavier endocarp and seeds. Though total resource allocation in seed development was higher in two-seeded fruits, each seed from biseeded fruits weighed less than single seeds. Results reveal pollination as a useful tool to improve not only fruit set, but also fruit size and fruit uniformity in olive.

Production of activated carbon from acorns and olive seeds

Production of activated carbon from acorns and olive seeds

Characterization of seed storage proteins and their synthesis during seed development in Olea europaea

SDS-PAGE analysis showed that seed storage proteins (SSPs) in olive mainly consisted of two hydrogen-bonded subunits, Solea I (41 kDa) and Solea II (47.5 kDa). When reduced, Solea I and II yielded 3 and 2 disulfide-bonded polypeptides, respectively. N-terminal sequencing confirmed that both Solea I and II shared a high similarity with II S proteins. Additionally, time-course of protein synthesis in olive seeds was investigated from 25 days after anthesis (DAA) until seed ripening. Before 105 DAA, young seeds contained only trace amounts of detectable proteins. Only from 105 DAA onwards, seed proteins began to be massively synthesized. Seeds of 105 DAA and more exhibited no significant difference in protein profiles with mature seeds, especially in terms of Solea I and II.

Production of activated carbon from acorns and olive seeds

This study has been designed to produce activated carbon from acorns and olive seeds. The starting materials are low in cost and they are the cause of solid waste pollution problems in Jordan. A chemical procedure is used to produce the required activated carbon. The results indicate that activated carbon produced from acorns compares favorably with that from olive seeds which rank second, along side commercial type activated carbon which comes last with respect to adsorption capacity. However, the optimum activation temperature is 800°C and the optimum regeneration temperature is also 800°C.

Early effects of rodent post‐dispersal seed predation on the outcome of the plant–seed disperser interaction

We analysed two potential effects of post‐dispersal seed predation on recruitment of the wild olive tree (Olea europaea var. sylvestris), a Mediterranean bird‐dispersed tree: (a) the limitation of abundance and distribution of seedlings after dispersal, and (b) the selection of certain seed characteristics of the recruited plants. An observational approach was used to compare seed rain among microhabitats, and how it was affected by seed predation. The relation of microhabitat, scrub density, and seed size with predation risk was explored by a field experiment. Seed density ranged from 0 seeds/m2 in open places to 93.2 seeds/m2 under O. europaea. The overall predation rate was low, as shown in the observational approach (35%). The mean percentage of predation in the experimental approach was 51%, ranging across microhabitats between 28% and 88%. It was higher in dense scrub patches (67%) than in sparse ones (33%), and lower for large seeds (42%) than for medium and small ones (57% and 55%, respectively). Finally, seed density near seed depots did not increase their probability of being detected by rodents or the predation rate. Although predation rates were low, wild olive seeds could be frequently found by rodents due to their spatial ubiquity and local abundance. Together with the efficient foraging strategy of predators (92% of experimental seed depots were found), this allowed a widespread post‐dispersal predation, but it did not modify the relative distribution of seeds among microhabitats. Thus, in our study, the seed dispersal pattern of the wild olive tree was not reshaped by post‐dispersal predation, because (1) rodents did not alter significantly its initial spatial distribution and (2) mice did not seem to limit the number of recruits. Finally, our results indicate that, as a consequence of seed size preferences of rodents, large seeds have a higher probability to survive post‐dispersal predation. Thus, seed size may be a key trait to determine the identity of the future recruits in the wild olive tree, at least affecting the characteristics of the seeds that reach the soil seed bank.

Germination of seeds of olive (Olea europaea L.) and ethylene production: Effects of harvesting time and thidiazuron treatment

SummaryThe germination of mature seeds of olive (Olea europaea L.) from six cultivars was examined by recording the percent germination, rate of germination and the ability to produce ethylene. The effects of various treatments, namely thidiazuron (TDZ), a compound with cytokinin-like activity, 1-aminocyclopropane-l-carboxylic acid (ACC), and aminoethoxyvinylglycine (AVG), on these variates were also evaluated. The main characteristics of seed development were also defined in both ‘Moraiolo’ and ‘Canino’, following harvest on three dates, by determining the course of the dehydration process and the ability of the seeds to produce ethylene; the effect of maturity state on germination and ethylene production was clarified. In general, there were wide variations between the cultivars with no positive correlations between the examined parameters. Germination of untreated seeds (control) from all the cultivars was always accompanied by an increase in ethylene synthesis. The presence of ACC was not always effective in a concomitant stimulation of germination and ethylene production. Instead, TDZ influenced the germination process in almost all the cultivars even if it did not always enhance ethylene production. In all cultivars tested, the presence of AVG in general reduced the stimulatory effect of TDZ on the percent germination and on ethylene production. The findings are discussed in relation to the possible role of ethylene production in the germination of olive seeds.

A multivariate study of the performance of a microwave-assisted Soxhlet extractor for olive seeds

The operating variables affecting the performance of a conventional Soxhlet extractor modified for application of focused microwaves on the sample chamber has been evaluated. An experimental approach based on a central composite design (CCD) and olive seed samples was used. The new variables introduced by means of the modification are irradiation power and time, and cycle number, which were chosen for evaluation. Statistical treatment of the results provided by the CCD revealed that the selected parameters were all significant; also, their optimum values were used in order to assess the predictive ability of the model relative to both the central points of the design and the conventional Soxhlet. The extraction time is reduced from 8 h to 20–25 min; also, the proposed method is less-labour intensive (the official method entails halting the extraction twice to grind the sample). Another achievement of the proposed method is that 75–80% of the extractant is reclaimed which makes it a nearly clean approach.

In vitro germination of embryos for speeding up seedling development in olive breeding programmes

The germination potential of olive seeds without the sclerified endocarp (stoneless seeds) and growth of the seedlings were compared with germination and growth of excised and in vitro cultured embryos of ten olive cultivars. The number of empty stones and the number of stones with two seeds were also determined for each of the cultivars. Isolated embryos of all the cultivars germinated uniformly within 10–14 days in culture, while the mean germination time of stoneless seeds was 55–95 days depending on the cultivar. The percentage of embryo germination was 3–15 fold higher than that of stoneless seeds according to cultivar. Root growth was more rapid in plants originating from seeds than from excised embryos. The growth of plantlets derived from in vitro germinated embryos in the greenhouse was normal. Thus, embryo culture would increase the efficiency and shorten the time for starting initial progeny evaluation of olive breeding programmes.

Dormancy and germination of olive embryos as affected by temperature

Olive seeds do not germinate promptly when placed under favourable conditions, which is a problem in raising young plants for breeding or experimental purposes. In a series of experiments an investigation of the role of temperature in the germination of olive embryos was conducted. Naked, unchilled olive embryos (Olea europaea L. cv. Chalkidikis), cultured in vitro at 20°C, had a germination capacity of 73%, whereas that of embryos which had previously been chilled at 10°C for 2 or more weeks reached 96%. Intact seeds did not germinate at 20°C unless they had previously been subjected to 10°C for 3 or 4 weeks. Embryos chilled while in the intact seed and excised just before transfer to 20°C, reacted in a similar way to naked embryos, but reached their maximum germination capacity after 4 weeks at 10°C. Under constant temperature conditions the highest germination percentage of embryos was observed at 10 and 15°C and the highest germination rate at 15°C, while a moderate capacity and rate of germination occurred at 20°C, and a very low percentage and rate at 25 and 30°C. Prechilling at 10°C did not affect germination at 15°C, but improved the percentage and the rate of germination at 20, 25 and 30°C. The germination percentages of embryos chilled for 1 or 2 weeks at 10°C and then transferred to 25°C were lower than those of similarly chilled embryos transferred to 20°C. The chilling effect could not be reversed at 25°C when the embryos had been chilled for 3 or more weeks. The results show that olive seeds exhibit a state of dormancy that is caused by factors residing partly in the endosperm and partly within the embryo.