Differential effects of tomato (Lycopersicon esculentum mill) matrix on the volatility of important aroma compounds

Significant tomato matrix effects on the volatility of certain fresh tomato odorants were found. The concentrations of odorants such as (E,E)-2,4-decadienal, beta-damascenone, and beta-ionone, in crushed fresh tomato fruit obtained by solid-phase microextraction (SPME), resulting from a tomato matrix calibration curve were 5.5-, 2-, and 12-fold higher, respectively, than those calculated by calibration based on buffer solutions. Static headspace analyses indicated that, in most cases, the tomato matrix significantly retains the odorants relative to the buffer solution. Thus, the concentration of odorants in the headspace of tomato is lower than expected compared to a simple matrix such as buffer. CaCl(2), although needed in crushed fruit tissue to block enzymatic activity, was found to interact specifically with 2-isobutylthiazole, reducing its content in the headspace by at least 6-fold. If a matrix effect is found, analysis of the odorant molecule contents in the headspace rather than in the food is recommended in order to better evaluate their access to the olfactory receptors.     

Improved Microbial and Chemical Reduction of Direct Blue 71 Using Anthraquinone-2,6-disulfonate Immobilized on Granular Activated Carbon

The aim of this study was to evaluate the redox mediating capacity of anthraquinone-2,6-disulfonate (AQDS) immobilized on granular activated carbon (GAC) during the reductive decolorization of direct blue 71 (DB71) under microbial and chemical conditions. The immobilization of AQDS on GAC was conducted by adsorption, and it has obtained an uptake capacity of 0.227 mmol g^?1. The anchorage of AQDS on GAC improved its electron transfer capacity (ETC) up to 2.05 times higher than the raw material. Similarly, the addition of GAC-AQDS increased up to 1.75- and 1.16-fold the rate of decolorization (k _d ) of DB71 under microbial and chemical conditions, respectively, in comparison to the unmodified GAC. Surprisingly, a higher k _d value was achieved in incubations without either GAC or GAC-AQDS because of the generation of aromatic amines, from the reduction DB71, taking into account that these species may act as a catalyst in the DB71 reduction process. In contrast, adsorption of aromatic amines on either GAC or GAC-AQDS decreased its redox mediating capacity as evidenced by spectrophotometric screenings of the decolorized solution and the supporting material. The development of materials with enhanced both redox and adsorption properties, as the GAC used in this study, offers a promising way to increase the redox conversion of recalcitrant pollutants commonly found in industrial wastewaters.     

Thermal oxidation of 9'-cis-neoxanthin in a model system containing peroxyacetic acid leads to the potent odorant beta-damascenone

The potent odorant beta-damascenone was formed directly from 9'-cis-neoxanthin in a model system by peroxyacetic acid oxidation and two-phase thermal degradation without the involvement of enzymatic activity. Beta-damascenone formation was heavily dependent on pH (optimum at 5.0) and temperature, occurring over the two sequential phases. The first was incubation with peroxyacetic acid at 60 degrees C for 90 min, and the second was at above 90 degrees C for 20 min. Only traces of beta-damascenone were formed on application of only one of the two phases. Formate and citrate solutions produced a much better environment for beta-damascenone formation than acetate and phosphate. About 7 microg/L beta-damascenone was formed from 5.8 mg/L 9'-cis-neoxanthin under optimal experimental condition. The detailed pathway by which beta-damascenone is formed remains to be elucidated.     

Improvement of internal color of oranges stored in oxygen-enriched atmospheres

‘Hamlin’, ‘Parson Brown’ and ‘Pineapple’ oranges were stored for 4 weeks at 15°C in a continuous flow of (1) air, (2) 20 mg 1^?1 ethylene (C₂H₄) in air, (3) 40% O₂ + 60% N₂, or (4) 80% O₂ + 20% N₂, followed by 2 additional weeks in air. Fruits stored in the C₂H₄ atmosphere lost rind chlorophyll faster, and the rind turned orange quicker, than fruits in the other atmospheres. However, most of the fruits stored in the C₂H₄ atmosphere had paler endocarp and juice than fruits stored in the other atmospheres. Fruits stored in 80% O₂ had the palest rind, but their endocarp and juice color were the deepest orange. Color change was detectable after 2–3 weeks and continued to develop until the end of the experiments. In 40% O₂ fruit, response was intermediate.The respiration rate of ‘Pineapple’ oranges during 4 weeks of storage in the test atmospheres was highest in the fruits stored in C₂H₄, almost as high in fruits stored in 80% O₂, and lowest in fruits kept in 40% O₂ or in air. Fruits stored in the different atmospheres did not differ significantly in total soluble solids content, total acidity, or pH of the juice, and the atmospheres did not adversely affect the flavor of the juice.     

Nitrogen accumulation induced by phosphorus deficiency in citrus plants

Growth responses and nitrogen constituents were tested in young citrus trees grown on gradually decreasing amounts of phosphorus in greenhouse solution cultures. The phosphorus concentration in dry matter of minus-P leaves dropped to a third of that in control leaves and then remained steady throughout the experiment, while the total nitrogen concentration was low at the beginning and, rising gradually, reached an enormous amount. Nitrogen estimations in minus-P leaves showed the specific dynamics of the soluble nitrogen fraction: its content was low at the onset of the deficiency, and rose rapidly due to intensive accumulation of arginine in the tissues. Under conditions of acute phosphorus deficiency, arginine constituted more than 60% of the free amino acids and arginine nitrogen above 40% of the total, while in normal leaves arginine did not exceed 8% of the free amino acids, and about 1–% of the total.Similar patterns of increased nitrogen level due to arginine accumulation were found in leaves of phosphorus-deficient grapefruit and orange trees under field conditions.     

Genetic relationships and hybrid vigour in olive (Olea europaea L.) by microsatellites

The olive (Olea europaea) is one of the most important oleaginous crops of the Mediterranean basin. Increased demand for olive oil creates a need for new olive varieties to help meet the requirements of the global market. However, olive breeding has been handicapped by such varied challenges as a prolonged juvenile period, agrotechnical problems and insufficient genetic knowledge. The use of DNA markers has the potential to overcome these problems and increase the effectiveness of classical breeding programmes. In this study, co‐dominant polymorphic simple sequence repeats (SSRs) were used as markers to analyse the genetic relationships between several local and other ‘non‐native’ olive cultivars. Cluster analysis revealed four major groups among the 15 cultivars examined in this study. Table and oil cultivars were clustered in different groups. However, the clusters did not differentiate between cultivars of different geographical origins. In addition, we used the data gathered to analyse genetic relationships to evaluate the effects of heterosis in agricultural traits. Genetic distances between cultivars were determined based on the SSR genotype data and were used for evaluating the possible effects of heterosis in various F₁ populations. Interestingly, phenotypic data of F₁ progenies from crosses between different cultivars indicated the potential effects of heterosis as expressed in several traits. Genetic distance between parents was significantly correlated to F₁ performance for three traits: percentage of dry fruit weight, oil content and commercial oil production. Thus, crosses between olive cultivars exhibiting relatively extensive genetic distances one from the other are expected to result in better progeny performance in future Olea breeding programmes. Our study linked assessment of biodiversity of commercial olive cultivars with the application of this information in olive breeding programmes for selection of specific parents to generate superior new cultivars.     

Low-oxygen treatment for inhibition of decay and ripening in organic bananas

Summary

Application of a low-O₂ atmosphere for several days prior to storing organic banana clusters was effective in preventing decay development on the crown cuts, and in delaying ripening. Preclimacteric banana clusters (Musa spp. AAA group cultivar Ziv) were treated with a low-oxygen atmosphere (2%) at 208C for 24, 48 and 72.h immediately after harvest. After removal from low-O₂ stress, the bananas were stored at 128C for 21.d, and were then treated with ethylene at 188C for 24.h and transferred to shelf life at 208C for an additional 4.d. The low-O₂ treatments were compared with the commercial treatment of dipping the crown cuts in 0.2% thiabendazole (TBZ). The low-O₂ stress for 48 or 72.h was effective in preventing decay after shelf life, but less so than the TBZ treatment. Low-O₂ for 24.h was not effective enough, and the 72.h treatment markedly impaired colour development after ripening with ethylene. The 48.h low-O₂ treatment which resulted in the best decay prevention also retarded ripening processes (colour, ®rmness, respiration and ethylene production) and reduced chilling injury symptoms, without impairing the taste. The level of reducing sugars in the 48.h-treated fruit was similar to that in the control fruit after ripening and shelf life. The endogenous levels of acetaldehyde (AA) and ethanol produced by the treated fruit were lower than those in the control fruit during shelf life. It seems that there is a high potential for this physical treatment of low-O₂ stress to replace chemical treatments, as means of maintaining the quality of organic bananas.     

Differential hydrological response of biological topsoil crusts along a rainfall gradient in a sandy arid area: Northern Negev desert,Israel

Drylands are regarded as highly sensitive to climatic change. The putative positive relationship between average annual rainfall and runoff, assumed for areas between 100 and 300 mm ignores the fact that climatic change in drylands is not limited to climatic factors alone, but is often accompanied by a parallel change in surface properties. Data on rainfall, runoff and soil moisture regime were collected at five monitoring sites in a sandy area, along a rainfall gradient from 86 to 160 mm. Despite the uniform sandy substratum the frequency and magnitude of runoff declined with increasing annual rainfall. Under wetter conditions a thick topsoil biological crust develops. This crust is able to absorb and retain large rain amounts, limiting the depth to which water can penetrate, and therefore water availability for the perennial vegetation. In the drier area, the thin crust can absorb only limited rain amounts, resulting in surface runoff and deeper water infiltration at run-on areas. Our findings demonstrate the important role played by different types of biological soil crusts along the rainfall gradient considered, and question the generally held belief that higher rainfall necessarily leads to deeper water infiltration in sandy arid areas; and higher water availability for the perennial vegetation.