Effect of arabic gum and xanthan gum on the stability of pesticide in water emulsion

The effect of arabic gum (AG) and xanthan gum (XG) on the physicochemical properties of 2% pesticide avermyctin in water emulsions was systematically investigated by measuring creaming stability, droplet size, zeta potential, and rheology. Addition of AG and XG had significant influence on the physicochemical properties of emulsions. Emulsions showed high stability throughout the storage time in the AG concentration range of 0-0.14%. In contrast, addition of XG induced the apparent creaming of emulsion as the XG concentration increased from 0.011 to 0.15%, which might be well explained by the depletion flocculation of droplets. The droplet diameter increased progressively with increasing AG concentration; however, it sharply grew initially with XG concentration and reached a maximum, followed by a gradual decrease. Zeta potential increased gradually as AG concentration was lower than 0.081%, followed by a slight decrease, whereas it reduced dramatically as XG concentration increased from 0.011 to 0.040% and then remained almost unchanged. In the AG concentration range of 0-0.14%, the emulsion exhibited typical Newtonian flow behavior and the viscosity decreased a little. The XG emulsion exhibited Newtonian flow behavior at low XG concentrations (≤0.019%), whereas, non-Newtonian flow behavior was displayed at relatively high XG concentrations (>0.019%), wherein viscosity value and yield value increased gradually as XG concentration increased. In addition, the curves of shear stress versus shear rate for XG emulsion and solution were well fitted by a power law model and the Herschel-Bulkley model; the Herschel-Bulkley model fitted much better. The present study would provide useful information for the reasonable application of AG and XG in making stable pesticide emulsion.     

Conjugation of sodium caseinate and gum arabic catalyzed by transglutaminase

Conjugation of the milk protein sodium caseinate and a protein-containing polysaccharide, gum arabic, was achieved through the use of the cross-linking enzyme transglutaminase. The extent of conjugation was monitored by size exclusion separation coupled with a multiangle laser light scattering detector. The elution times of gum arabic solutions incubated with transglutaminase were unchanged over time, whereas incubation of sodium caseinate with transglutaminase resulted in shorter elution times as reaction time increased, indicating the formation of cross-linked caseinate polymers. However, when mixtures of caseinate and gum arabic were incubated with transglutaminase, the elution times were decreased markedly, indicating conjugation between the protein and polysaccharide. The molecular masses of the conjugates increased from approximately 950 to 1600 kDa. This method of protein-polysaccharide conjugation offers noticeable advantages over previously used methods, and the conjugates produced may exhibit unique functional properties.     

Origin and thermodynamic properties of the instability of synthetic azo colorants in gum arabic solutions

The instability of some industrially important synthetic azo colorants, including sunset yellow, azorubine, and allura red, toward gum arabic in aqueous solution has been a long-standing problem for the beverage and confectionery industries. Precipitation of these colorants causes the deterioration of product appearance and properties. This work examines the origin and nature of the problem by analysis of the precipitate and thermodynamic studies of gum arabic-colorant interactions using isothermal titration calorimetry (ITC). The presence of divalent alkaline earth metals in gum arabic samples, that is, calcium and magnesium, is shown to be responsible for the precipitation of the azo colorants. There is no direct interaction between gum arabic and the colorant molecules, and the precipitate is formed likely due to the mediation/bridging by the divalent cations. The thermodynamic knowledge gained from the ITC studies, for example, binding affinity, stoichiometry, and enthalpy, enables interpretation of many industrial observations.     

Effect of partial replacement of gum arabic with carbohydrates on its microencapsulation properties.

Gum arabic solutions (10% w/v) were emulsified with soy oil at oil/gum ratios of 0.25-5.0. At oil/gum ratios <1.0, it was established that gum arabic could be partially replaced with a nonsurfactant carbohydrate. To assess different carbohydrates as replacers for gum arabic, emulsions and spray-dried emulsions of soy oil and mixed solutions (10% w/v) of gum arabic and a range of carbohydrate wall materials (oil/gum = 0.5) were prepared and analyzed. Maize starch and glucose were ineffective as partial replacers of gum arabic, but maltodextrins of various dextrose equivalence values (5.5-38) successfully replaced 50% of the gum arabic. The microencapsulation efficiency of the gum arabic/maltodextrin stabilized powders was further increased by increasing total solids of the feed to the dryer and by increasing the atomizer nozzle diameter.     

New insights into the structural characteristics of the arabinogalactan-protein (AGP) fraction of gum arabic

The structural characteristics of the gum exudate of Acacia senegal (gum arabic) have been investigated by monitoring the composition and physicochemical properties before and after treatment with proteolytic enzyme and various alkaline systems. Molecular mass ( M w) and radius of gyration ( R g) measurements were performed using gel permeation chromatography (GPC) coupled to refractive index, UV absorbance, and multiangle light scattering detectors and indicated that the macromolecules present have a compact structure. It was found that treatment with proteolytic enzyme caused the arabinogalactan-protein component (AGP) with average molecular mass approximately 2 x 10 (6) Da to degrade, yielding material of molecular mass approximately 4 x 10 (5) Da, whereas the bulk of the material corresponding to the protein-deficient arabinogalactan component (AG) with molecular mass 4 x 10 (5) remained unaffected. Barium hydroxide was found to hydrolyze the polysaccharide component (AG) itself in addition to the proteinaceous component as demonstrated in control experiments using dextran. However, sodium borohydride/sodium hydroxide treatments were unable to hydrolyze dextran and were assumed to hydrolyze only the proteinaceous component of gum arabic. The AGP component was completely degraded, yielding material of molecular mass approximately 4.5 x 10 (4) Da. It has been concluded, therefore, that the enzyme did not fully hydrolyze all of the protein present and that the AGP component of gum arabic consists of carbohydrate blocks of approximately 4.5 x 10 (4) Da linked to a polypeptide chain consistent with the wattle blossom structure. Because the AGP was degraded to differing extents using a mild and more severe sodium borohydride/sodium hydroxide treatment, it was concluded that the polysaccharide moieties were linked through both O-serine and O-hydroxyproline residues. The gum arabic sample was deglycosylated by treatment with anhydrous hydrogen fluoride and revealed the presence of two putative core proteins of approximately 3 x 10 (4) and approximately 5 x 10 (3) Da, respectively, which correspond to proteins of approximately 250 and 45 amino acids in length. A new model for the structure of the AGP component has been proposed.     

Using multiple composite fingerprints to quantify source contributions and uncertainties in an arid region

Purpose

Developing targeted protection measures at a watershed scale requires spatially distributed information of sediment sources. Therefore, the objectives of this study are to (1) test and evaluate the ability of multiple composite fingerprints (MCF) to quantify sediment provenance using multiple particle size classes in an arid region; (2) quantify uncertainty of the estimated proportional contributions of sediment sources; and (3) provide decision support information for sediment control in the Danghe Reservoir Watershed.

Materials and methods

In total, 66 samples were collected from north alluvial fan, south alluvial fan, and high mountains, and all samples were divided into six particle size groups. A multistep test was used to remove the tracers that were non-conservative, unable to differentiate sources, or highly variable within a source. Based on geochemical properties of distributed source samples and a linear mixing model, a MCF method with multiple particle size tracking was used to estimate proportions of three potential source contributions. More importantly, the uncertainty of sediment source contributions was quantified using the Gaussian first-order approximation.

Results and discussion

The results showed that the MCF method with multiple particle size tracking could obtain relatively accurate estimates of the contributions with an overall mean absolute relative error of 3.5% and a relatively narrow 95% confidence interval. The major contributions were consistently coming from the high mountains for all six particle groups. During these runoff events, the overall estimated mean proportions were 49.0%, 26.5%, and 24.5% from the high mountains, south alluvial fan, and north alluvial fan, respectively. Furthermore, the Gaussian first-order approximation revealed that more than 60% of the total uncertainty contribution was a byproduct of the downstream sediment mixture, while each individual sediment source produced less than 15% of the absolute uncertainty.

Conclusions

Acquiring watershed scale sediment source information is challenging and the MCF method proved accurate. A majority of the contribution uncertainties were associated with the downstream sediment mixture, which is because the sediment sink inherited both spatial and temporal variations of all contributing sources. Consequently, a larger sample size is recommended for sediment mixtures, compared to each sediment source, in order to increase the accuracy of the source proportion estimation.

     

Using summed individual species models and state-of-the-art modelling techniques to identify threatened plant species hotspots

Reliable identification of hotspot areas with high numbers of threatened plant species has a central role in conservation planning. We investigated the potentiality of identifying the distribution, richness and hotspots of threatened plant species at a 25 ha resolution using eight state-of-the-art modelling techniques (GLM, GAM, MARS, ANN, CTA, GBM, MDA and RF) in a taiga landscape in north-eastern Finland. First, the individual species models developed based on occurrence records of 28 species in the 1677 grid squares and derived from different statistical techniques were extrapolated to the whole study area of 41 750 km². Second, the projected presence/absence maps were then combined to create species richness maps, and the top 5% of grid cells ranked by species richness were classified as hotspots. Finally, we created an overall summary map by combining the individual hotspot maps from all eight modelling techniques and identified areas where the individual hotspots maps overlapped most. There were distinguishing differences in projections of the geographic patterns of species richness and hotspots between the modelling techniques. Most of the modelling techniques predicted several hotspot locations sporadically around the study area. However, the overall summary map showed the highest predictive performance based on Kappa statistics, indicating that the locations where the hotspot maps from the eight models coincided most harboured highest observed species richness. Moreover, the summary map filtered out the patchy structures of individual hotspot maps. The results show that the choice of modelling technique may affect the accuracy and prediction of hotspot patterns. Such differences may hamper the development of useful biodiversity model applications for conservation planning, and thus it is beneficial if the conservation decision-making can be based on sets of alternative maps and overlaying of predictions from multiple models.     

Hapten synthesis and development of polyclonal antibody-based multi-sulfonamide immunoassays

This paper reports the synthesis of five sulfonamide derivatives, the production of broad-specificity polyclonal antibodies for immunoassay of sulfonamides, and the analysis of milk samples by developed assay. The three-step synthesis procedure reported in most of the literature was adopted and modified in this study. In the procedure, the purification of the intermediate was avoided and the time of synthesis was shortened from >20 to 6-9 h with improved yields. This method is generally applicable to the synthesis of haptens containing the common structure of sulfonamides. Three haptens were coupled to keyhole limpet hemocyanin, and polyclonal antibodies were obtained from rabbits immunized with these conjugates. Using the antibodies obtained, from one of these was developed an enzyme-linked immunosorbent assay (ELISA) based on the competition between free sulfonamides and the hapten-horseradish peroxidase (HRP) conjugates. The hapten-HRP conjugate giving the best competitive results and 11 structurally different sulfonamides showed 50% inhibition at concentrations of <100 ng mL(-1). After removal of the protein with acetone, milk samples were analyzed by ELISA directly; a matrix effect could be avoided when a 1:20 dilution with phosphate-buffered saline was used, and 104-131% recoveries of spiked samples were obtained. The developed immunoassay is suitable to determine sulfisozole, sulfathiazole, sulfameter, sulfamethoxypyridazine, sulfapyridine, and sulfamethizole below the maximum residue limit in milk (100 ng mL(-1) of total sulfonamides) rapidly and reliably.     

Suppressive effect of saturated acyl L-ascorbate on the oxidation of linoleic acid encapsulated with maltodextrin or gum arabic by spray-drying

6-O-Palmitoyl L-ascorbate was added to linoleic acid at various molar ratios of the ascorbate to the acid, the mixtures were emulsified with a maltodextrin or gum arabic solution, and the emulsions were spray-dried to produce microcapsules. At higher molar ratios, the oil droplets in the emulsions were smaller, and the oxidative stabilities of the encapsulated linoleic acid were higher for both the maltodextrin- and gum arabic-based microcapsules. 6-O-Capryloyl, caproyl, and lauroyl L-ascorbates, which were synthesized through lipase-catalyzed condensation in acetone, were also used for the microencapsulation of linoleic acid. Except for capryloyl L-ascorbate, the addition of a saturated acyl ascorbate, especially caproyl ascorbate, to linoleic acid was effective for preparing oil droplets of small particle diameter and for suppressing the oxidation of the encapsulated linoleic acid.     

Effect of a novel edible composite coating based on gum arabic and chitosan on biochemical and physiological responses of banana fruits during cold storage

The composite effects of gum arabic (GA) (5, 10, 15, and 20%) and chitosan (CH) (1.0%) on the biochemical and physiological characteristics of banana fruits stored at 13 ± 1 °C and 80 ± 3% relative humidity (RH) for 28 days and afterward for 5 days at simulated marketing conditions (25 °C, 60% RH) were investigated. Significant (P ≤ 0.05) differences were observed for the entire GA plus CH treatments as compared to the control. However, the results showed that after 33 days of storage, the weight loss and soluble solids concentration of fruits treated with 10% GA plus 1.0% CH composite coating were 24 and 54% lower, whereas fruit firmness, total carbohydrates, and reducing sugars were 31, 59, and 40% higher than the control, respectively. Furthermore, the composite edible coating of 10% GA plus 1.0% CH delayed color development and reduced the rate of respiration and ethylene evolution during storage as compared to the control. Similarly, sensory evaluation results also proved the effectiveness of 10% GA plus 1.0% CH composite coating by maintaining the overall quality of banana fruits. Consequently, the results of scanning electron microscopy also confirmed that the fruits coated with 10% GA plus 1.0% CH composite edible coating had very fewer cracks and showed a smooth surface. These findings suggest that 10% GA plus 1.0% CH as an edible composite coating can be used commercially for extending the storage life of banana fruits for up to 33 days.     

ITS1-rDNA-based methodology to identify world-wide hake species of the Genus Merluccius

Species-specific DNA-based tags are valuable tools for the management of both fisheries and commercial fish products. In this study, we have developed a two-step molecular tool to detect the presence of hake DNA (Merluccius spp.) and to identify the exact hake species present in an blind sample. The first test involves PCR amplification of an ITS1-rDNA fragment of 193 bp using nested primers that are interspecifically conserved in Merluccius spp. and Atlantic cod, Gadus morhua. The second test consists of the PCR amplification of a 602-659 bp DNA fragment spanning part of the ribosomal cluster 18S-ITS1-5.8S and digesting it with four restriction enzymes whose targets map at interspecifically nonconserved sites of the ITS1. Alternatively, the identification of hake species can be achieved by FINS or BLAST, using the nucleotide sequence of either the whole ITS1 sequence or its nested fragment of 193 bp. Because of their high reproducibility and ease of execution, these procedures allow for routine analysis and constitute high reliable tools for the rapid identification of 12 species of hake.     

Approaches to quantify progressive soil development with time in Mediterranean climate—I. Use of field criteria

Soil‐chronosequence studies are useful to assess relationships between land‐surface ages and stages of soil formation. Such relationships may then be applied to establish relative chronologies of development of land surfaces of unknown ages, contributing to landscape‐history reconstruction. For this purpose, it is important to identify those soil properties that are most closely related to soil age. This article reviews soil‐chronosequence studies from Mediterranean regions in Europe and California. Soil properties described in the field and soil‐development indices based on field criteria that have been used in the studies are evaluated. The properties total texture, rubification, clay films, dry consistence, and soil thickness are identified as useful and easy‐to‐obtain soil parameters, which are generally closely related to soil age. Most soil properties exhibit their greatest changes during certain phases of soil development, e.g., soil structure in soils < 10,000 y and rubification in soils > 100,000 y. The specific time spans of major changes of soil properties need to be considered, when looking for appropriate parameters to study a particular chronosequence. Indices, which combine several soil properties having their greatest changes in different phases of soil development, are useful to study soil chronosequences comprising large time spans, e.g., from Holocene to Middle Pleistocene. It is important to be aware that soil chronofunctions obtained from Pleistocene soils integrate rates of soil‐forming processes over periods of very variable climate and environment, and that soil development crossed internal and external pedogenic thresholds that are not reflected in soil chronofunctions.     

Development of monoclonal antibody-based immunoassays to the N-methylcarbamate pesticide carbofuran

To produce monoclonal antibodies (MAbs) to the pesticide carbofuran, three compounds with carboxylic spacer arms of different lengths introduced at the carbamate group of the analyte structure were synthesized, conjugated to proteins, and used as immunizing haptens in mice. MAbs were subsequently characterized for affinity and specificity in the conjugate-coated format and in the antibody-coated format using newly synthesized compounds as heterologous assay haptens. Depending on the immunoreagent combination and assay format, competitive assays with I(50) values in the 1.2-10.2 nM (0.27-2.27 ng/mL) range were obtained. LIB-BFNB67 MAb in combination with the hapten BFNH, coupled either to horseradish peroxidase or to ovalbumin, was used to develop a direct and an indirect enzyme-linked immunosorbent assay, respectively. Optimized immunoassays displayed very similar analytical characteristics, with an I(50) value around 0.7 ng/mL and a limit of detection around 0.08 ng/mL. Both immunoassays were able to tolerate the presence of methanol up to a 15% concentration. Compounds very similar in structure to carbofuran (benfuracarb, furathiocarb, bendiocarb, and carbofuran-hydroxy) exhibited cross-reactivity values in the 18-37% range, but major N-methylcarbamate pesticides were not recognized by the MAb. These immunoassays should reasonably allow the rapid, low-cost, and sensitive determination of carbofuran in food, in soils, and in the environment at levels of regulatory and practical importance.     

Use of nondestructive sensors to quantify ornamental kale nitrogen status

Greenhouse production of ornamental kale is popular for fall sales. The objective of this study was to evaluate if nondestructive handheld sensors could be used to quantify nitrogen (N) status in Brassica oleracea ‘Nagoya Red’. Topdressed fertilizer treatments of 0, 2.5, 5, 10, 15, and 20 g of 16-9-12 controlled release fertilizer (CRF) were utilized. Individual plants were scanned from 10 pots per treatment for Normalized Difference Vegetative Index (NDVI) values using a prototype NDVI pocket sensor, the recently released commercial GreenSeeker? handheld, and a Soil-Plant Analyses Development (SPAD) chlorophyll meter at three different rating dates starting 25 d after fertilizer treatment application (DAT). Linear and quadratic trends were observed within sampling dates. All three sensors showed correlations with leaf N depending on sampling time. Results indicated that 10 g CRF would be recommended for potted production.     

Synthesis of haptens and protein conjugates for the development of immunoassays for the insect growth regulator fenoxycarb.

Sensitive and selective enzyme-linked immunosorbent assays (ELISAs) in the immobilized antigen format were developed for fenoxycarb (1), an insect growth regulator (IGR). The parent molecule [ethyl 2-(4-phenoxyphenoxy)ethylcarbamate] was derivatized at several positions to obtain haptens (2-5) that were used to produce protein conjugates and rabbit polyclonal antisera. Amino derivatives of fenoxycarb at the terminal and internal rings (2 and 3, respectively) were linked to carrier proteins by azo coupling. Carboxyalkyl-spacer groups were attached to the ethyl group and the nitrogen atom of the target compound (1) to obtain haptens 4 and 5, respectively. Hapten-homologous ELISAs based on protein conjugates of compounds 2 and 4 determined fenoxycarb in the mid-ppb range (IC(50), 102 and 95 ppb, respectively). A more sensitive hapten-heterologous ELISA (IC(50), 17 ppb; detection limit 0.5 ppb) involved the antiserum raised against a conjugate of hapten 2 and the plate-coating antigen obtained from compound 3. These assays displayed no significant interferences with photodegradation products of fenoxycarb, the IGRs methoprene and pyriproxyfen, and a variety of pesticides including the pyrethroids fenvalerate and cypermethryn, the phenoxyacetic acid herbicide 2,4-D, DDT, and the nitrodiphenyl ether herbicides acifluorfen and fluorodifen.     

Applying species distribution modelling to identify areas of high conservation value for endangered species: A case study using Margaritifera margaritifera (L.)

The development and implementation of a population supplementation and restoration plan for any endangered species should involve an understanding of the species’ habitat requirements prior to the release of any captive bred individuals. The freshwater pearl mussel, Margaritifera margaritifera, has undergone dramatic declines over the last century and is now globally endangered. In Northern Ireland, the release of captive bred individuals is being used to support wild populations and repatriate the species in areas where it once existed. We employed a combination of maximum entropy modelling (MAXENT) and Generalized Linear Mixed Models (GLMM) to identify ecological parameters necessary to support wild populations using GIS-based landscape scale and ground-truthed habitat scale environmental parameters. The GIS-based landscape scale model suggested that mussel occurrence was associated with altitude and soil characteristics including the carbon, clay, sand, and silt content. Notably, mussels were associated with a relatively narrow band of variance indicating that M. margaritifera has a highly specific landscape niche. The ground-truthed habitat scale model suggested that mussel occurrence was associated with stable consolidated substrates, the extent of bankside trees, presence of indicative macrophyte species and fast flowing water. We propose a three phase conservation strategy for M. margaritifera identifying suitable areas within rivers that (i) have a high conservation value yet needing habitat restoration at a local level, (ii) sites for population supplementation of existing populations and (iii) sites for species reintroduction to rivers where the mussel historically occurred but is now locally extinct. A combined analytical approach including GIS-based landscape scale and ground-truthed habitat scale models provides a robust method by which suitable release sites can be identified for the population supplementation and restoration of an endangered species. Our results will be highly influential in the future management of M. margaritifera in Northern Ireland.     

Use of scaling to quantify variability of heavy metal sorption isotherms

Sorption isotherms of heavy metals in soil often vary strongly from place to place in the field. Scaling might be useful to quantify the variability of such functional relations. Application of scaling to sorption isotherms requires a rule. In this paper the derivation of a scaling rule for sorption isotherms, based on a hypothesis of 'sorption similarity’, and its application to cadmium sorption isotherms measured in 25 fields on sandy soils are reported. Scale factors are calculated by least squares procedures. Scaling reduced the variation of the Cd isotherms, expressed as sum of squares about an average, by about 86%, preserving the variation through the calculated scale factors. Scaling of sorption isotherms requires no specific equation to fit the sorption data. The aforementioned average should be calculated as scale mean because of the theoretical stringency of this approach.     

The use of remote sensing techniques to identify potential natural areas in oregon

Approaches in identifying terrestrial natural areas in Oregon are reviewed. Remote sensing techniques using high altitude colour infrared photography were applied to locate and describe candidate natural area reserves on state-owned land in seven Oregon countries. Land units totalling 25, 700 ha were catalogued as potential natural areas, based on the natural quality and character of the vegetation cover. The characteristics and uses of high altitude colour infrared photography are discussed with reference to natural area inventory.