Lemon Juice Aroma Concentration by Reverse Osmosis

Ethanol, a major component of lemon juice, was analyzed to indicate degree of lemon juice aroma concentration. Aroma solution was concentrated from 12.2 to 23.4% ethanol at 8.3 MPa and 19°C by reverse osmosis. Ethanol rejected by the membrane decreased from the initial 87.7% to 78% at the final aroma concentration of 23.4% ethanol. Membrane rejection of neral, geranial, and terpinene-4-ol was > 96% while rejection of the alcohols, n-propanol, 2-methyl-3-buten-2-ol, and 3-methyl-2-buten-1-ol, ranged from 6.9% to 83.5%. Sensory analysis indicated no difference between initial aroma and aroma concentrated by reverse osmosis. Mass balance determined the true recovery of total volatiles was 79.7%. Loss of volatiles was attributed to adsorption in the polymeric matrix of the membrane and some loss was attributed to cleaning.     

Geranial: the alarm pheromone in the nymphal stage of the oribatid mite,Nothrus palustris

The presence of an alarm pheromone was demonstrated in the deutonymphal stage of the oribatid mite, Nothrus palustris (C. L. Koch). The active principle was identified as 3,7-dimethyl-(E)-2,6-octadienal, geranial, and was shown to be active at doses of 10–100 ng. This is the first such pheromone identified in oribatid mites.     

Neral and geranial: Components of the sex pheromone of the parasitic wasp,Itoplectis conquisitor

A laboratory investigation of theItoplectis conquisitor sex pheromone was initiated to elucidate the structure(s) of the active component(s) of the system. Functional group tests performed on crude virgin female extract classified the pheromone as unsaturated aldehyde(s) and/or ketone(s). Isolation of active fractions by gas-liquid chromatography (GLC) suggested the existence of a multicomponent pheromone system. Analysis by gas chromatography-mass spectrometry indicated the presence of saturated and unsaturated aldehydes including neral and geranial. When mixtures of neral and geranial were bioassayed independently and in combination with other active GLC fractions, they elicited male sexual activity of intensity comparable to that released by the GLC fraction (DEGS E) from which they were isolated. The authors conclude that neral and/or geranial are components of the sex pheromone system of this species.     

Mites as Matchmakers: Semiochemicals from Host-associated Mites Attract Both Sexes of the Parasitoid Lariophagus distinguendus

The role of volatile chemicals used for mate finding was studied for males of Lariophagus distinguendus (Först.), a parasitoid of the granary weevil Sitophilus granarius (L.). In bioassays that used a static four-chamber olfactometer, males were attracted by host feces, hexane extracts from host feces, and volatile extracts of the feces obtained by closed-loop stripping (CLS). On the other hand, volatiles emitted by unmated females did not elicit any preferences in males. Both sexes of L. distinguendus responded to a synthetic mixture of neral, geranial, neryl formate, and tridecane occurring in the investigated extracts. All compounds are common constituents of astigmatid mites that are often associated with possible hosts of L. distinguendus. In the system investigated, all main compounds found in CLS extracts from larval feces of S. granarius are due to the mold mite Tyrophagus putrescentiae (Schrank) that uses neral, geranial, and neryl formate as an alarm pheromone. The possible role of host-associated astigmatid mites in mate and host finding of L. distinguendus is discussed.     

A comparative study of the exocrine products of cleptoparasitic bees (Holcopasites) and their hosts (Calliopsis) (Hymenoptera: Anthophoridae,Andrenidae)

The cephalic secretion of females of the cleptoparasitic beeHolcopasites calliopsidis contains two main volatiles, 6-methyl-5-hepten-2-one and geranyl acetone. The mandibular gland secretion of its host,Calliopsis andreniformis, on the other hand, contains the two isomeric forms of citral (neral and geranial). Neral and geranial are also produced by mandibular glands of two other species ofCalliopsis and one species in the related genusNomadopsis. The Dufour's gland ofC. andreniformis contains an oily secretion composed of hydrocarbons that are deposited on the brood cell walls and pollen balls providing a waterproof lining for both.     

以分子氧为氧化剂合成柠檬醛的研究

分子氧(或空气)是化工生产中的“绿色”氧化剂。用分子氧催化氧化醇类以合成不同的羰基化合物的研究已成为近几年来国外有机合成的一个热门研究领域。综述了以分子氧合成柠檬醛的研究。使用的Ru／Al2O3催化剂对醇-OH基的氧化具有高度的选择性并有很高的转化率。     

Variation with caste of the mandibular gland secretion in the leaf-cutting antAtta sexdens rubropilosa

InAtta sexdens rubropilosa, a strongly polyethic and polymorphic species of myrmicine ant, the contents of the mandibular gland vary with caste. Small workers of head width 0.5–1.8 mm, those generally engaged in duties inside the nest, contain chiefly 4-methyl-3-heptanone. Larger workers, those chiefly engaged in foraging, and the soldier caste contain a mixture dominated by neral and geranial, with very little of the ketone of the smaller workers. The soldiers have massive glands containing milligram amounts of neral and geranial. Virgin and mated females contain essentially only 4-methyl-3-heptanone, the amount increasing after mating, while virgin males have 4-methyl-3-heptanone and 4-methyl-3-heptanol in approximately equal proportions. Mated males have less secretion and lose the 4-methyl-3-heptanol.     

Essential Oils as Allelochemicals and Their Potential Use as Bioherbicides

Essential oils were extracted from 32 aromatic plants and evaluated for allelopathic properties. The major components of the oils were identified by gas chromatography and GC-MS. Extracts from Origanum syriacum, Micromeria fruticosa, and Cymbopogon citratus were selected for further study. The germination of several species, including wheat, was strongly inhibited by essential oils when applied at 20–80 ppm. Essential oils mixed with the top 0.5 cm of soil inhibited germination of wheat and Amaranthus seeds. This effect depended on the type of soil. The possible use of essential oils as herbicides is discussed.