Field testing passive air samplers for current use pesticides in a tropical environment

Air was sampled for one year in the central valley of Costa Rica using an active high-volume sampler as well as passive samplers (PAS) based on polyurethane foam (PUF) disks and XAD-resin filled mesh cylinders. Extracts were analyzed for pesticides that are either banned or currently used in Costa Rican agriculture. Sampling rates for PUF-based passive air samplers, determined from the loss of depuration compounds spiked on the disks prior to deployment averaged 5.9 +/- 0.9 m3 x d(-1) and were higher during the windier dry season than during the rainy season. Sampling rates for the XAD-based passive sampler were determined from the slopes of linear relationships that were observed between the amount of pesticide sequestered in the resin and the length of deployment, which varied from 4 months to 1 year. Those sampling rates increased with decreasing molecular size of a pesticide, and their average of 2.1 +/- 1.5 m3 x d(-1) is higher than rates previously reported for temperate and polar sampling sites. Even though the trends of the sampling rate with molecular size and temperature are consistent with the hypothesis that molecular diffusion controls uptake in passive samplers, the trends are much more pronounced than a direct proportionality between sampling rate and molecular diffusivity would suggest. Air concentrations derived by the three sampling methods are within a factor of 2 of each other, suggesting that properly calibrated PAS can be effective tools for monitoring levels of pesticides in the tropical atmosphere. In particular, HiVol samplers, PUF-disk samplers, and XAD-based passive samplers are suitable for obtaining information on air concentration variability on the time scale of days, seasons and years, respectively. This study represents the first calibration study for the uptake of current use pesticides by passive air samplers.     

Colour improvement of common carp (Cyprinus carpio) fillets by hydrogen peroxide for surimi production

The preferred colour for surimi is white, but surimi prepared from light fillets of common carp (Cyprinus carpio) is slightly pink. Hydrogen peroxide (H₂O₂; 1–3% v/v) with and without sodium tri‐polyphosphate (STP; 1–2% w/v) was added to a sodium carbonate bath (pH 7.0–11.5) resulting in a final pH range of 4.4–10.1 which was injected into carp fillets. After soaking and tumbling for 30 min at 4–10 °C, the fillets were evaluated for colour and water holding capacity (WHC). Fillets tumbled with treatment solution with different pH levels (7.0–11.5), but with no H₂O₂ or STP added, had improved colour with significantly (P < 0.05) higher L* compared with untreated fillets as the control. However, the colour improvement [(L* and colour deviation (ΔE)] was not significantly different (P > 0.05) within the pH levels (7.0–11.5) trialled. With increasing H₂O₂ levels (1–3%), fillets became lighter and ΔE increased significantly (P < 0.05), especially with a 3% H₂O₂ treatment at pH of 10.5 (adjusted pH before H₂O₂ addition, actual pH after H₂O₂ addition was 8.2). The whiteness (L*?3b*) of kamaboko produced from treated (3% H₂O₂, pH 10.5) common carp light fillets was not significantly different to that of kamaboko from Alaska pollock and threadfin bream. Treatments combining H₂O₂ (3%) with STP (1–2%) significantly reduced the L* value obtained in comparison with fillets treated with only H₂O₂ (3%). Similarly, fillets treated with STP (1%) alone, resulting in lower L* values, irrespective of treatment pH (7.0–11.5). WHC, an indicator of the quality of the fillet texture, increased from 816 g/kg at pH 7.0 without STP to 841 g/kg at pH 11.5 with 1% STP. Treatment with H₂O₂ (without STP) decreased the WHC of the fillets.     

Hydrophobic Modification of Starch by Alkali‐Catalyzed Addition of 1,2‐Epoxyalkanes

An efficient method of preparing hydrophobic α‐hydroxy starch ethers using aqueous alkaline conditions is described. α‐Hydroxy starch ethers were synthesized by addition of 1,2‐epoxyalkanes to an aqueous alkaline starch gel in the presence of sodium sulfate as a co‐catalyst. The reaction, carried out in a stirred autoclave at 140 °C and 3.9 bar, was optimized with respect to the concentrations of sodium hydroxide and 1,2‐epoxyalkane. Optimum yields and molar substitutions (MS) were obtained at molar ratios of sodium hydroxide to anhydroglucose unit (AGU) of 0.5 to 1.0. The amount of molar substitution could be controlled by 1,2‐epoxyalkane concentration. Thus, a series of α‐hydroxyoctyl starch ethers with MS from 0.7 to 2.4 were synthesized in yields up to 90% by using these conditions. Starches with different amylose contents were also converted to the corresponding ethers using a threefold excess of 1,2‐epoxyoctane and an equimolar ratio sodium hydroxide : AGU. The reaction is hardly effected by the origin of the starch and its amylose content. The influence of the 1,2‐epoxyalkane chain length was investigated by performing the conversion with a series of terminal epoxyalkanes from 1,2‐epoxyhexane to 1,2‐epoxydodecane. The results indicated that the hydrophobic character of the starch ethers increased by increasing the molar substitution and alkyl chain length. All products were insoluble in water, but soluble in mixtures of methanol and methylene chloride. Furthermore the starch ethers can be converted into shaped articles by extrusion technology without the addition of plasticizers.     

Short communication: Evaluation of 5 different ELISA for the detection of bovine leukemia virus antibodies

Although Canadian dairy herds have been infected with bovine leukemia virus (BLV) for years, recent research has put new emphasis on the potential negative effects of this infection. Consequently, BLV control is becoming more favorable; however, BLV control cannot be successful without identifying infected animals. Bovicheck BLV (Biovet, Saint-Hyacinthe, QC, Canada) is currently the only assay licensed by the Canadian Centre for Veterinary Biologics. The first goal of this study was, therefore, to determine the reproducibility of the Bovicheck BLV assay for serum samples derived from Canadian cattle. The second goal was to evaluate and compare 5 different ELISA and determine their test characteristics using serum samples from Canadian herds. The considered ELISA were Bovicheck BLV, ID Screen BLV Competition (IDvet, Grabels, France), Idexx Leukosis Serum X2 Ab Test (Idexx Europe B.V., Hoofddorp, the Netherlands), Svanovir BLV gp51-Ab (Svanova, Uppsala, Sweden), and the Serelisa BLV Ab Mono Indirect (Synbiotics, Lyon, France). Eighty serum samples from Canadian cattle provided by Prairie Diagnostic Services (PDS; Saskatoon, SK, Canada) and an additional 80 serum samples from Canadian dairy and beef herds were used for the study. The Bovicheck BLV assay yielded the same results for all PDS-derived samples, implying a high level of reproducibility and robustness of this assay. Additionally, the comparison of the assays' results showed high agreement between assays, with Cohen's kappa values between κ = 0.91 and κ = 1. Furthermore, using original test results of the field samples as true status, relative diagnostic sensitivity and specificity were calculated. Relative diagnostic sensitivity of all tests was 100%. False-positive results were probable; therefore, the following relative diagnostic specificities were determined: 100% for Bovicheck BLV, Idexx Leukosis Serum X2, and Svanovir BLV; 95% for ID Screen BLV; and 97% for Serelisa BLV. When considering other test characteristics, ID Screen BLV is exceptional due to considerable practical advantages.     

Effect of temperature on raw whole milk density and its potential impact on milk payment in the dairy industry

The objective of this study was to determine the effect of temperature on whole milk density measured at four different temperatures: 5, 10, 15, and 20 °C. A total of ninety-three individual milk samples were collected from morning milking of thirty-two Holstein Friesian dairy cows, of national average genetic merit, once every two weeks over a period of 4 weeks and were assessed by Fourier transform infrared spectroscopy for milk composition analysis. Density of the milk was evaluated using two different analytical methods: a portable density meter DMA35 and a standard desktop model DMA4500M (Anton Paar GmbH, UK). Milk density was analysed with a linear mixed model with the fixed effects of sampling period, temperature and analysis method; triple interaction of sampling period x analysis method x temperature; and the random effect of cow to account for repeated measures. The effect of temperature on milk density (ρ) was also evaluated including temperature (t) as covariate with linear and quadratic effects within each analytic method. The regression equation describing the curvature and density–temperature relationship for the DMA35 instrument was ρ = 1.0338−0.00017T−0.0000122T² (R² = 0.64), while it was ρ = 1.0334 + 0.000057T−0.00001T² (R² = 0.61) for DMA4500 instrument. The mean density determined with DMA4500 at 5 °C was 1.0334 g cm⁻³, with corresponding figures of 1.0330, 1.0320 and 1.0305 g cm⁻³ at 10, 15 and 20 °C, respectively. The milk density values obtained in this study at specific temperatures will help to address any bias in weight–volume calculations and thus may also improve the financial and operational control for the dairy processors in Ireland and internationally.     

Standards for microsystems

Standardization is emerging as a very important element to be considered when larger computer systems are specified and designed. This article reviews some types of standard which might be applied and the effects of their application.     

Analysis of ultracentrifugation interference patterns with image digitizer: Application to molecular weight determination of SRM 1478 polystyrene

A new method for the analysis of ultracentrifugation interference patterns with the use of a commercial image digitizer is given. The application of the method to the sedimentation equilibrium data for SRM 1478 polystyrene leads to a weight-average molecular weight of 37 400 g mol⁻¹ having a sample standard deviation of 0.7% and an expected systematic error limit of 2%.     

Effect of the plasticizer di(2-ethylhexyl) adipate (dioctyladipate,DOA) on lipid metabolism in the rat: I. Inhibition of cholesterolgenesis and modification of phospholipid synthesis

DOA (di[2-ethylhexyl] adipate, dioctyladipate), a plasticizer used in the manufacture of polyvinylchloride plastic products, has been considered as a suitable substitute for di(2-ethylhexyl)phthalate (DEHP) in some applications. In the present studies, hepatic lipid metabolism was examined in liver mince preparations from rats fed 0.5% or 1.0% DOA in the diet for 2 weeks. By studying patterns of lipid synthesis from [¹⁴C] acetate, [¹⁴C] oleate, [¹⁴C] mevalonate, and [¹⁴C] octanoate, it was concluded that DOA feeding inhibits hepatic cholesterolgenesis and alters the pattern of phospholipids synthesized by the liver. DOA also exerted a cholesterol-lowering effect at the 1% level but did not affect plasma triglyceride levels. The results suggest that the biological effects of DOA in the rat are similar to those produced by DEHP.     

Providing lubricity in food fat systems

Lubricity, in particular mouthfeel, is an important factor in production of vegetable oil bases for food product formulations. Certain functional characteristics are necessary for good texture at various temperatures. These characteristics are dependent on degree of unsaturation, fatty acid distribution, and degree of geometrical isomerization during processing. Proper selectivity and activity of hydrogenation catalysts used in hardening of the oils are essential. Sufficient solid fat content must be balanced by necessary oxid ative stability. Products discussed include salad oils and their formulations in pourable and spoonable salad dressings, mayonnaises, frying oils, imitation dairy products, margarines and bakery shortenings. Past, present and future industry technology will be evaluated for each type of food fat product. Customer needs have greatly affected the course of research in this area.