Mixture Of Waxes Research Articles

Impact of binary mixtures of natural waxes in mechanical properties and microstructure of oleogels.

Solid fats are critical to obtaining a wide range of food texture and quality characteristics, but their consumption is strongly associated with higher cardiovascular disease risks. Structuring unsaturated oils with natural waxes into oleogels (OG) is an innovative solution to develop fat mimics with a healthier profile. Soy wax (SW), beeswax (BW) and carnauba wax (CW), have been used in binary mixtures of waxes, aiming to understand their interactions and influence on OG quality properties and microstructural characteristics. In the present study, OGs were produced using binary wax mixtures and analyzed for texture, color, smoke point, microstructure, Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Wax combinations led to antagonistic (mixtures with SW) and synergistic interactions (BW/CW) based on their mechanical properties. At the microstructural level BW/CW blends showed a reduction in crystal size and with a more compact structure. XRD and FTIR spectra revealed a packing of orthorhombic perpendicular subcell for most OGs, whereas SW produced samples with an arrangement with β' crystals, characteristic of edible solid fats. Additionally, when compared to commercial beef fat, BW/CW mixtures showed similar quality attributes indicating that they could act as fat mimic. The combined analysis of microstructure, spectroscopic and mechanical properties enhanced the understanding of how the nature of the interactions between waxes and lipid phases impact in the final quality of the structured oils. The study's insights indicate that binary wax combinations can efficiently replace solid fats, offering healthier alternatives at the same time as preserving desired sensory characteristics. © 2024 Society of Chemical Industry.

Faire gras à Molène: dairy products and ruminant fats detected by lipid and isotopic analysis of pottery dating to the Final Neolithic-Early Bronze Age from the island site of Beg ar Loued (Molène, western Brittany, France)

The subsistence strategies of early farming communities have been highlighted since the beginning of the Neolithic, thanks to numerous studies on lipid residues from ceramic vessels conducted in various parts of continental Europe. However, after the Early Neolithic, evidence of subsistence strategies along the northern Atlantic coast are still lacking, especially for island contexts. This paper presents the results of lipid residue analysis of 129 potsherds from Beg ar Loued (Molène, France), an island site dating primarily to the Early Bronze Age (c. 2700-2600 to 1800 BCE). Aiming to understand the use of vessels, vessel treatment and culinary practices on the settlement, analyses of visible charred residues, sherds and ceramic surfaces/coating layers were carried out using chromatographic (n = 174) and isotopic techniques (n = 24) after lipid extraction by solvent (n = 174) or acid methanolysis (n = 31). The results demonstrate the extensive use of terrestrial products (ruminant carcass and dairy) in pottery, including occasional plant products (with possible mixtures of different waxes), while the detection of aquatic products is limited. Thus, combined with evidence from faunal remains at the site, the results indicate that terrestrial resources like ruminant meat and dairy products were preferentially processed in vessels, and aquatic products mostly without the use of ceramics. These findings demonstrate the significance of lipid residue analysis for studying the role of pottery in food production and consumption at sites along the Atlantic coast.

Leaf cuticular waxes of wild-type Welsh onion (Allium fistulosum L.) and a wax-deficient mutant: Compounds with terminal and mid-chain functionalities

Plant cuticles cover aerial organs to limit non-stomatal water loss and protect against insects and pathogens. Cuticles contain complex mixtures of fatty acid-derived waxes, with various chain lengths and diverse functional groups. To further our understanding of the chemical diversity and biosynthesis of these compounds, this study investigated leaf cuticular waxes of Welsh onion (Allium fistulosum L.) wild type and a wax-deficient mutant. Leaf waxes were extracted with chloroform, separated using thin layer chromatography (TLC), and analyzed using gas chromatography-mass spectrometry (GC-MS). The extracts contained typical wax compound classes found in nearly all plant lineages but also two uncommon compound classes. Analyses of characteristic MS fragmentation patterns followed by comparisons with synthetic standards identified the latter as very-long-chain ketones and primary ketols. The ketols were minor compounds, with chain lengths ranging from C28 to C32 and carbonyls mainly on C-18 and C-20 in wild type wax, and a C28 chain with C-16 carbonyl in the mutant. The ketones made up 70% of total wax in the wild type, consisting mainly of C31 isomers with carbonyl group on C-14 or C-16. In contrast, the mutant wax comprised only 4% ketones, with chain lengths C27 and C29 and carbonyls predominantly on C-12 and C-14, respectively. A two-carbon homolog shift between wild type and mutant was also observed in the primary alcohols (a major wax compound class), whilst alkanes exhibited a four-carbon shift. Overall, the compositional data shed light on possible biosynthetic pathways to wax ketones that can be tested in future studies.

Diffusion of volatile organics and water in the epicuticular waxes of petunia petal epidermal cells.

Plant cuticles are a mixture of crystalline and amorphous waxes that restrict the exchange of molecules between the plant and the atmosphere. The multicomponent nature of cuticular waxes complicates the study of the relationship between the physical and transport properties. Here, a model cuticle based on the epicuticular waxes of Petunia hybrida flower petals was formulated to test the effect of wax composition on diffusion of water and volatile organic compounds (VOCs). The model cuticle was composed of an n-tetracosane (C24 H50 ), 1-docosanol (C22 H45 OH), and 3-methylbutyl dodecanoate (C17 H34 O2 ), reflecting the relative chain length, functional groups, molecular arrangements, and crystallinity of the natural waxes. Molecular dynamics simulations were performed to obtain diffusion coefficients for compounds moving through waxes of varying composition. Simulated VOC diffusivities of the model system were found to highly correlate with in vitro measurements in isolated petunia cuticles. VOC diffusivity increased up to 30-fold in completely amorphous waxes, indicating a significant effect of crystallinity on cuticular permeability. The crystallinity of the waxes was highly dependent on the elongation of the lattice length and decrease in gap width between crystalline unit cells. Diffusion of water and higher molecular weight VOCs were significantly affected by alterations in crystalline spacing and lengths, whereas the low molecular weight VOCs were less affected. Comparison of measured diffusion coefficients from atomistic simulations and emissions from petunia flowers indicates that the role of the plant cuticle in the VOC emission network is attributed to the differential control on mass transfer of individual VOCs by controlling the composition, amount, and dynamics of scent emission.

Hardness, plasticity, and oil binding capacity of binary mixtures of natural waxes in olive oil

In this study, olive oil oleogels structured with less than 4% binary blends of sunflower wax (SFW), rice bran wax (RBW), candelilla wax (CDW), and beeswax (BW) were characterized. Among the different binary wax oleogels, samples structured with 3% (w/w) of binary mixtures of SFW and RBW, as well as binary mixtures of CDW and BW, displayed a high oil binding capacity relative to any other mixtures. Moreover, in some binary wax oleogels, back extrusion hardness and elastic constant were significantly higher than that of oleogels prepared using the individual waxes. This was interpreted as a synergism between these waxes. Image analysis of oleogel brightfield micrographs indicated that the samples with a higher elastic constant had a lower box-counting fractal dimension and larger crystals, suggesting that this increase in the elastic constant was a consequence of the lower fractal dimension of the wax crystal network, in agreement with established fractal structural-mechanical models for van der Waals colloidal networks. The crystal structure of the individual waxes and their blends showed orthorhombic perpendicular subcell packing arrangements, which did not change upon mixing, suggesting this length scale did not play a role in the observed synergism. The melting point of binary mixtures of waxes in olive oil was in the range of 43.2 °C to 67.4 °C and pseudo-ideal mixing behavior was observed. The hardness and plasticity (brittleness) of the 2% and 3% binary wax mixtures in olive oil characterized using back extrusion, were similar to those of a commercial soft margarine, suggesting a potential use of the wax oleogels as margarine or spread replacers.

Substitution of synthetic waxes by plant-based waxes in lipsticks

The ultimate symbol of femininity, lipstick is often a brand’s most attractive makeup product. First created several thousand years ago, its composition has evolved a great deal since then, particularly in the 20th century, when petroleum and its derivatives were discovered. But today, with the emergence of Clean Beauty, customers are looking to go back to more natural compositions that respect the environment and their health. However, the total substitution of synthetic waxes has inevitably brought with its problems of product stability, lipstick solidity, sweating, incompatibilities and oxidation, which today’s ever more demanding consumers are not ready to accept. Beyond stability, the sensoriality and the performance of lipsticks can be altered by such substitution. The objective of this study is therefore to find plant-based substitutes for synthetic waxes, which do not reduce the stability and the overall quality of lipsticks. To this end, the physicochemical properties of plant-based waxes will first be measured, and the best candidates will then be introduced into an all-natural lipstick formula. Some waxes tested have a value equivalent to synthetic wax on one physico-chemical parameter but are less efficient on another. The mixtures of waxes with oils of different polarities show that no wax is as ubiquitous as petroleum wax. To conclude, none of the waxes evaluated can substitute the synthetic wax weight for weight in a formula.

Phenolics Dynamics and Infrared Fingerprints during the Storage of Pumpkin Seed Oil and Thereof Oleogel

Cold-pressed pumpkin seed oil is a valuable source of bioactive molecules, including phenolic compounds. Oleogels are designed for trans and saturated fats substitution in foods, but also demonstrate protection and delivery of bioactive compounds. Consequently, the present work aimed to assess individual phenolic compounds dynamics and infrared fingerprints during the ambient storage of pumpkin seed oil and thereof oleogel. For oleogels production, a 5% ternary mixture of waxes, composed by 3% beewax, 1% sunflower wax and 1% rice bran wax, was used. Phenolic compounds were extracted by traditional liquid–liquid extraction, followed by HPLC-MS quantification. FTIR (400–4000 cm−1) was used for characterizing and monitoring the oxidative stability of all samples and for the evaluation of intermolecular forces between oleogelator mixtures and oil. Specific wavenumbers indicated oxidative processes in stored sample sets; storage time and sample clustering patterns were revealed by chemometrics. Isolariciresinol, vanillin, caffeic and syringic acids were quantified. The main changes were determined for isolariciresinol, which decreased in liquid pumpkin seed oil samples from 0.77 (T1) to 0.13 mg/100 g (T4), while for oleogel samples it decreased from 0.64 (T1) to 0.12 mg/100 g (T4). However, during the storage at room temperature, it was concluded that oleogelation technique might show potential protection of specific phenolic compounds such as syringic acid and vanillin after 8 months of storage. For isolariciresinol, higher amounts are registered in the oleogel (0.411 mg/100 g oil) than in the oil (0.37 mg/100 g oil) after 5 months of ambient temperature storage (T3). Oxidation processes occurred after 5 months storage for both oil and oleogel samples.

Accelerated Ageing Procedures to Assess the Stability of an Unconventional Acrylic-Wax Polymeric Emulsion for Contemporary Art.

This research evaluates the stability of an aqueous emulsion of acrylic copolymers and waxes. Edelwachs, generally applied on wood, has been recently used as an unconventional medium in contemporary painting. Through Pyrolysis–Gas Chromatography–Mass Spectrometry (Py-GC-MS) and Fourier Transformed Infrared Attenuated Total Reflectance (FT-IR-ATR) analyses, the composition of Edelwachs was defined as a mixture of acrylic polymers (MA, MMA, nBA, nBMA), Carnauba and microcrystalline waxes and additives. Mock-ups-obtained mixing Edelwachs with titanium white, zinc white and ultramarine blue were subjected to UV, high temperatures, and high relative humidity accelerated ageing. The effect of the ageing procedures was evaluated through optical microscopy, colourimetric measurements, FT-IR-ATR, Thermogravimetry and Differential Scanning Calorimetry (TG-DSC) and wettability measures. FT-IR-ATR spectra do not show significant variations in terms of chemical stability, indicating a fair stability of Edelwachs as a painting binder. UV and high temperature treatments show the most relevant effects in terms of colorimetric changes (increasing of b*) and thermal stability. The TG-DSC highlights the influence of the pigments (specifically zinc white) mainly on the thermal behaviour of the acrylates. The unexpected decrease of wettability of the paint films, registered after ageing, may indicate a possible phase separation among acrylates and waxes.

Prevalence of propolis allergy in Singapore

To the Editor: Propolis is a mixture of resins, waxes (including beeswax), pollen, and organic debris produced by honeybees to repair their hives.1 It is used in personal care products and cosmetics for its antiseptic and anti-inflammatory properties and is increasingly recognized as an important allergen.1 We sought to determine the prevalence of propolis allergy in a cohort of patients.

Conversion of polyethylene waste into clean fuels and waxes via hydrothermal processing (HTP)

The exponential growth of plastic production and a low recycling rate (<9%) over the last 60 years have resulted in vast plastic waste accumulation in landfills and the environment. About 40% of the 350 million tons of global plastic waste generated in 2015 was polyethylene (PE). Converting PE waste into useful products can help reduce PE waste accumulation. Hydrothermal processing (HTP) of PE into oils was studied previously; however, comprehensive reaction pathways were not reported, and the products were not evaluated for potential fuel and wax applications. In this study, various PE wastes were converted via HTP at 425–450 °C for reaction times of 0.5–4 h into clean waxes or ultra-low sulfur fuels. Two-dimensional gas chromatography (GC×GC) and FTIR were used for determining the chemical compositions of the products. A mixture of paraffin and α-olefin waxes was obtained with a high yield, 97 wt. %, at 425 °C and 30 min. The highest oil yield, 87 wt. %, for producing fuels was obtained at 425 °C and 2.5 h. The diesel fraction (HTP diesel) met all requirements for No. 1-D ultra-low sulfur diesel and had a high cetane number of 61 and a low aromatic content of 18 vol. %. Mixtures up to 50 vol. % of HTP diesel in commercial diesel also met all requirements for No. 2-D ultra-low sulfur diesel. Comprehensive reaction pathways for PE conversion were inferred from detailed GC×GC analyses of reaction intermediates. The HTP method is more energy-efficient and has lower greenhouse gas emissions than incineration and pyrolysis, and is a promising method for reducing PE waste accumulation.

Production of Dental Inlay Wax Using Locally Sourced Materials in Enugu, Nigeria

Dental inlay wax is a mixture of several waxes, usually containing paraffin wax, ceresin wax, beeswax and other natural and synthetic waxes. It is used to prepare patterns for gold or other metallic materials in the fabrication of inlays, crowns and bridges. Inlay wax is used for the same purpose as casting wax in the formation of pattern mostly for metallic casting in Dental technology. This study aimed at producing dental inlay wax using locally sourced materials in Enugu, Nigeria. The research was carried out between July to September, 2018 in Enugu, Nigeria. The study adopted a three phased experimental approach using the same procedures but different weight compositions. Structured, pretested Product Evaluation Data Sheet was used to evaluate the product by selected Practicing Dental Technologists in Enugu State, Nigeria. The resultant wax from experiment III with the following composition: 60g Paraffin wax, 5g Beeswax, 25g Carnauba wax, 10g Ceresin wax and (35g) of green ketchup colorant gave the best result. Its properties are comparable to the conventional Dental Inlay wax. There was significant agreement among the respondents in the smoothness of the product (40%); excellent dimensional stability and product effectiveness (40%); flow and burnout of the product (35%), and color stability of the product (45%). These findings suggests that dental inlay waxes can be produced locally in Enugu, Nigeria. Therefore, more attention needs to be paid in the production process, which will facilitate easy practice of Dental Technology, and also conserve huge foreign exchange being spent in the importation of inlay wax in Nigeria.

TO THE PROBLEM OF THE GENESIS OF AMBER

The article is devoted to the analysis and criticism of the bitumen-brown coal hypothesis of the origin of amber. Common views on the genesis of amber and views of the authors of the bitumen-brown coal hypothesis are reviewed. According to this hypothesis, amber is formed from brown coal bitumen, the source of which are resin bodies, which in turn freed up during the erosion of huge areas of bituminous brown coal. To refute these views, the following is stated. Natural bitumen is a natural organic compound with a primary hydrocarbon base. Coal bitumen is a mixture of waxes and resins, which are extracted from the coal with organic solvents. Bitumen resins are retained in the coal in a dispersed state. Resin bodies can not be a source of bitumen since they are chemically inert. In the brown coal of the Dnieper Basin they are represented by resinites, the content of which in coal usually does not exceed a few percent. In addition, the resin, which underwent changes in the conditions of the regenerative environment of the swamp, could not acquire the properties of succinite. The opinion about the erosion of large volumes of coal in the Dnieper basin is also erroneous and refuted by previous studies. To compare the nature and conditions of sedimentation of fossil resins and resins extracted from brown coal bitumen the van Krevelen diagram of the atomic ratios of carbon, hydrogen, and oxygen was used. It is demonstrated that they occupy different areas on the diagram, which is an indication of a different nature and different conditions for their sedimentation.

Viscoelastic and adhesion properties of hot-melts made with blends of ethylene-co-n-butyl acrylate (EBA) and ethylene-co-vinyl acetate (EVA) copolymers

Several hot-melts (HMAs) were prepared by using blends of ethylene-co-n-butyl acrylate (EBA) and ethylene-co-vinyl acetate (EVA) copolymers - EBA/EVA. HMAs were prepared with mixtures of EVA copolymers with 18 (EVA18) and 27 (EVA27) wt% vinyl acetate contents and EBA copolymer with 27 wt% n-butyl acrylate, polyterpene resin and mixture of microcrystalline and Fischer-Tropsch waxes. HMAs made with EBA/EVA blends showed lower viscosities and reduced shear thinning than the ones made with EBA or EVA due to differences in compatibility, but both the set time and the open time were not affected as they depended mainly on the wax nature and amount. The increase of the vinyl acetate (VA) content in EVA copolymer reduced the crystallinity of the EBA/EVA blends. Even EBA copolymer was more compatible with EVA27 than with EVA18 (the α- and β-transitions shown in DMTA plots were closer) and the compatibility did not vary with the EBA content in the blends. The addition of polyterpene resin and the mixture of waxes decreased the compatibility of the EBA/EVA blends, the higher compatibility was observed for the HMAs made with only one copolymer. The tack of the HMAs depended on their EBA/EVA contents, EBA/EVA27 HMAs showed broader temperature interval with higher tack, while the tack of EBA/EVA18 HMAs blend decreased and the temperature interval with tack was shortened and shifted to lower temperatures. Adhesion to polypropylene film was improved in HMAs made with 75 wt% EBA/25 wt% EVA18 and 50–75 wt% EBA/50-25 wt% EVA27. The adhesion to aluminum film of EBA or EVA hot melts was improved only in the joints made with EBA/EVA 27 HMAs, more noticeably when they contained higher EBA content.

Evaluation of the correlation between wax type and structure/behavior of the pour point depressant

Knowledge of the lowest temperature at which a particular petroleum type is still able to flow (pour point) is important for its marketability. High pour point temperatures make transport and refining more difficult and thus can reduce demand and price. Polymer additives are an alternative to reduce the crude oil pour point. However, the relation between the type of oil and efficacy of a given additive remains obscure. We studied two model systems: one composed of commercial paraffin in toluene; and the other containing paraffins obtained in the laboratory from the distilled fraction of a crude oil, also dissolved in toluene. As pour point depressants (PPD), three samples of poly(ethylene-co-vinyl acetate) were used to determine the pour point and wax appearance temperature (WAT). The samples' behavior was also studied by rheology. The results showed that the content of linear paraffin chains with sizes larger than C30 significantly influenced the efficacy of the additives, not only in relation to the pour point, but also the viscosity of the model system below the WAT. Besides this, mixtures of the commercial waxes showed a practically linear pour point relation with the composition for the pure systems. Such linear behavior was not observed for the efficacy of the additive, which was significantly affected by the presence of a small quantity of chains with higher molar mass. Experiments conducted with the series of waxes extracted from the crude oil showed that the pour point was not influenced by linear paraffin when their concentrations were below 3wt%. In turn, in the fractions with higher concentrations of n-paraffins than this, the additive was only effective in the samples with more than half their chains having sizes under C28.

Solvent-free enzymatic production of high quality cetyl esters.

A solvent-free biocatalytic process for the synthesis of high quality cetyl laurate, myristate, palmitate and stearate has been optimized. This enzymatic procedure follows the fundamental principles of the Green Chemistry and lead to sustainable products, which can be labeled as natural and conform to the principal requirements for its use in high value-added goods. The four esters selected are the main components of spermaceti, a mixture of waxes very appreciated in cosmetic and pharmacy because of its physical properties and emolliency, which was formerly extracted from the head of the sperm whales. In this paper, the influence of the amount of biocatalyst, the commercially available Novozym(®) 435, and the temperature were studied in an open-air batch reactor before carrying out the synthesis in a high performance vacuum reactor with dry nitrogen input to shift the equilibrium towards product formation. Under optimal conditions, conversion was higher than 98.5 %. The characterization of the enzymatic cetyl esters puts in evidence that these are ultra-pure compounds, which have similar properties to the ones obtained through the conventional industrial processes with the extra benefit of being environmentally friendly.

Changes in compatibility, tack and viscoelastic properties of ethylene n-butyl acrylate (EBA) copolymer–pentaerythritol rosin ester blend by adding microcrystalline wax, Fischer–Tropsch wax and mixture of waxes

Ethylene n-butyl acrylate copolymer (EBA) instead of ethylene vinyl acetate copolymer (EVA) can be used as the base polymer for hot melts. The lower polarity of EBA should affect differently the compatibility with the wax and the tackifier as compared to EVA. In this study the compatibility, tack and viscoelastic properties of EBA copolymer–pentaerythritol rosin ester blended with waxes of different nature (Fischer–Tropsch and microcrystalline) and in different amounts were studied.An increase in compatibility of EBA-copolymer blend with microcrystalline wax was produced leading to increased tack and open time, and reduced viscosity. In contrast, the addition of Fischer–Tropsch wax decreased the compatibility and tack of the EBA-copolymer blend. The addition of a mixture of microcrystalline and Fischer–Tropsch wax caused a better balance in the rheological properties and thermal stability of the EBA-copolymer blends. Finally, an increase in the wax mixture content produced a complete removal of tack caused by dilution of the tackifier in the polymer blend rather than by differences in compatibility.

Multiphase ultra-low grade thermal energy storage for organic Rankine cycle

Up to 60% of thermal energy is wasted as low or ultra-low quality through exhaust systems. The organic Rankine cycle can be used to generate mechanical power and electricity from these low grade energy sources. A variety of organic working fluids are available to optimize the organic rankine cycle (ORC) for any target temperature range. Because the out of these sources is intermittent, it is desirable to have a storage system. Multiple types of low grade thermal energy storages have been explored including sensible, latent, and thermochemical. Targeting 86 °C, the operating temperature of our experimental ORC, multiple potential materials were explored and tested as potential phase change materials including magnesium chloride hexahydrate (MgCl2·6H2O), magnesium nitrate hexahydrate (Mg(NO3)2·6H2O), montan wax, and carnauba wax. The addition of graphite to augment heat transfer rates was also tested. Melting and solidification temperatures largely matched predictions. The magnesium salts were found to be less stable under thermal cycling than the waxes. Graphite was only soluble in the waxes. Mixtures of magnesium salts and waxes yielded a layered composite with the less dense waxes creating a sealing layer over the salt layer, which significantly increased the stability of the magnesium salts. Research into optimum heat exchangers and storage vessels for these applications indicates that horizontally oriented aluminum pipes with vertically oriented aluminum fins would be the best method of storing and retrieving energy. Fin spacing can be predicted by an equation based on target temperatures and phase change material characteristics. Copyright © 2015 John Wiley & Sons, Ltd.

Phenolic Acids, Hydrolyzable Tannins, and Antioxidant Activity of Geopropolis from the Stingless Bee Melipona fasciculata Smith

Geopropolis is a mixture of plant resins, waxes, and soil produced by the stingless bee Melipona fasciculata Smith. This paper describes the antioxidant activity and chemical composition of geopropolis produced by M. fasciculata. The total phenolic content determined with the Folin-Ciocalteu reagent was highest in the ethyl acetate fraction and hydroalcoholic extract. Antioxidant activity was assayed by the in vitro DPPH, ABTS, and FRAP assays. The hydroalcoholic extract and fractions of geopropolis, except for the hexane fraction, exhibited antioxidant activity against DPPH, ABTS, and FRAP. The phenolic compounds were identified by HPLC-DAD-MS on the basis of the evaluation of their UV-vis absorption maxima (λmax) and mass spectral analysis. Eleven compounds belonging to the classes of phenolic acids and hydrolyzable tannins (gallotannins and ellagitannins) were tentatively identified. These compounds are responsible for the antioxidant activity and high phenolic content of geopropolis produced by M. fasciculata.

Antifeedant Activity of Citrus Waste Wax and Its Fractions Against the Dry Wood Termite,Cryptotermesbrevis

The wood protective action of citrus wax, a waste from the citrus industry that is a mixture of citrus fruit epicuticular waxes and essential oils, was evaluated against the termite Cryptotermes brevis Walker (Isoptera: Kalotermitidae). The antifeedant index (AI) of the total wax and fractions was calculated. The total citrus wax exhibited an AI50 value of 24.69 mg/cm3, the wax after hydrodistillation showed the strongest antifeedant property (AI50 11.68 mg/cm3). Fractionation of the wax and gas chromatography—mass spectrometric analysis allowed the identification of coumarins and furancoumarins as the active compounds. These results suggest the potential use of these industrial residues as a natural approach to termite control.

Distribution and carbon isotope composition of lipid biomarkers in Lake Erhai and Lake Gahai sediments on the Tibetan Plateau

Lipid biomarkers and carbon isotopes of n-alkanes, n-fatty acids, and n-alkan-2-ones were used to determine organic carbon sources to surface sediments in lakes Erhai and Gahai on the Tibetan Plateau. All sediment samples contained n-fatty acids with lower concentrations of n-alkanes and n-alkan-2-ones. Long chain n-alkanes in lake sediments were characteristic of a source mixture of epicuticular waxes of higher plants and submerged littoral zone plants while n-fatty acids sources were bacteria and floating and/or submergent macrophytes; the n-alkan-2-ones had a possible source in epicuticular waxes of higher plants and/or grass from catchment which entered the lake and were reworked by the microorganisms. Sediment samples examined from Lake Erhai had heavier δ 13C values of bulk organic carbon and specific carbon compounds than samples from Lake Gahai and meadow soil. This heavier isotopic composition can be best interpreted by the enhanced productivity occurring in Lake Erhai due to its lower salinity and possibly to limited CO 2 concentrations; for the latter, this may have enriched 13C in the dissolved inorganic carbon pool of the lake water.