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Authors: Radi Aly and Uzi Ravid

Virgin olive oil (VOO) quality depends on many factors, including duration of storage of the fruits before processing, olive oil color, and storage conditions. We characterized here a Souri virgin olive oil cultivar and evaluated some chemical and physical characteristics during 3 years in different storage conditions. Samples of VOO were collected from the first cold pressing of olives and stored in different storage containers: polyethylene, glass, and stainless steel. Samples (100 ml) were then subjected to colorimetric and chemical measurements. VOO stored in polyethylene containers for 3 years showed higher increases in acidity (2.43%) compared to 1.36 and 1.64% found in oil stored in glass bottle and stainless containers, respectively. VOO color represented by O.D. 450-600 nm, was diminished significantly in polyethylene containers (0.67) as compared to O.D. (1.41 and 1.72) in stainless steel and glass containers, respectively, during the storage period. The majority of volatile compounds detected were acids, alcohols, and aldehydes. The concentrations of hexanal, hexanol, E-2-hexanal, and E-2-hexen-l-ol decreased significantly after 12 months of storage in polyethylene containers as compared to fresh oil. These data led to the conclusion that color and acidity could be used as a marker for VOO quality and freshness. An unexpected volatile compound (styrene 2.4%) was detected only in olive oil samples stored in polyethylene containers. Styrene is an oily organic compound, widely used to make plastics and rubber, and considered to be harmful to human health. Therefore, VOO is not recommended to be stored in polyethylene containers.

In: Israel Journal of Plant Sciences

The chemotaxonomic significance of the enantiomeric composition of monoterpenes was investigated in selected species of Origanum, Salvia, and Rosmarinus genera. The combination of SPME-chiral-GC-MS analysis and two-dimensional hierarchical cluster analysis provided a fast, easy, and reliable method to discriminate between species with similar morphological appearance or between different cultivars in the same species.

Using the enantiomeric ratio of monoterpenes instead of the relative percentage of compounds in total volatiles permitted us to distinguish clearly between the closely related Israeli aromatic plants O. dayi and O. ramonense, and between three selected R. officinalis commercial cultivars.

In: Israel Journal of Plant Sciences

Khat (Catha edulis Forsk., Celastraceae) is a perennial shrub that was introduced to Israel by Yemenite immigrants. Its young leaves are chewed for their psycho-stimulating properties. Young khat leaves contain the phenylpropylamino alkaloids (-)-cathinone [(S)-α-aminopropiophenone], (+)-cathine [(1S)(2S)-norpseudoephedrine], and (-)-norephedrine [(1R)(2S)-norephedrine] as the main active principles. A novel GC-MS analysis method for the quantitative determination of phenylpropylamino alkaloids and their putative biosynthetic precursor 1-phenylpropane-1,2- dione in khat leaves was developed. We utilized an alkaline-organic extraction, coupled with gas chromatography and a chiral permethylated beta cyclodextrin phase, to allow a full separation between the two diastereoisomers (1S)(2S)-cathine and (1R)(2 S)-norephedrine. We found a marked diversity in the phenylpropylamino alkaloid content and composition in three different locally grown accessions and the commercial cultivar ‘Mahanaim’.

In: Israel Journal of Plant Sciences

Petals of 11 rose cultivars were analyzed by solvent extraction for the presence of key scent volatiles. Two different cultivars--'Fragrant Cloud', a very fragrant cultivar, and 'Golden Gate', a non-fragrant cultivar--were further analyzed by the headspace technique during flower opening. The 'Fragrant Cloud' headspace is composed of a variety of volatiles, including monoterpene alcohols, acetates, and terpene hydrocarbons, while the 'Golden Gate' headspace is composed mainly of orcinol dimethylether, a compound that is scentless to the human nose but that is perceived by honeybees, as judged by proboscis extension experiments. In both cultivars, the level of volatiles increased during flower development, while the ratio of different major volatiles remained constant.

In: Israel Journal of Plant Sciences