Analytical Methods for Allergen Control in Food Processing.

Food allergy and food-related anaphylaxis have become a growing public health and food safety issue worldwide [...].

Comparing the effects of hydrostatic high-pressure processing vs holder pasteurisation on the microbial, biochemical and digestion properties of donor human milk.

In this study, hydrostatic high-pressure processing (HHP), a non-thermal pasteurisation method, was used to achieve the microbiological safety of donor human milk. After HHP, no bacteria were detected in human milk processed at 400 MPa for 5 min. Activities of a selection of bioactive components, including lysozyme, xanthine oxidase, lactoperoxidase, immunoglobulin A, lactoferrin, lipoprotein lipase and bile salt-stimulated lipase, did not decrease significantly. This study further investigated the gastrointestinal digestion kinetics of HoP and HHP milk compared with raw human milk, using an in vitro static infant digestion model. After 60 min of 'gastric digestion', the microstructure and protein profile of HHP milk samples were more similar to raw milk samples than HoP milk samples. Overall, HPP showed a better retention in milk nutrients and closer digestion behavior than that of HoP.

A Response Surface Methodology (RSM) Approach for Optimizing the Attenuation of Human IgE-Reactivity to ß-Lactoglobulin (ß-Lg) by Hydrostatic High Pressure Processing.

The response surface methodology (RSM) and central composite design (CCD) technique were used to optimize the three key process parameters (i.e., pressure, temperature and holding time) of the high-hydrostatic-pressure (HHP) processing either standalone or combined with moderate thermal processing to modulate molecular structures of ß-lactoglobulin (ß-Lg) and α-lactalbumin (α-La) with reduced human IgE-reactivity. The RSM model derived for HHP-induced molecular changes of ß-Lg determined immunochemically showed that temperature (temp), pressure (p2) and the interaction between temperature and time (t) had statistically significant effects (p < 0.05). The optimal condition defined as minimum (ß-Lg specific) IgG-binding derived from the model was 505 MPa at 56 °C with a holding time of 102 min (R2 of 0.81 and p-value of 0.01). The validation carried at the optimal condition and its surrounding region showed that the model to be underestimating the ß-Lg structure modification. The molecular change of ß-Lg was directly correlated with HHP-induced dimerization in this study, which followed a quadratic equation. The ß-Lg dimers also resulted in the undetectable human IgE-binding.

Intrinsic and well-defined second generation hot spots in gold nanobipyramids versus gold nanorods.

An effective strategy for regioselective modification and directional assembly of anisotropic nanoparticles is demonstrated to explore the electric field enhancement in assembled gold nanobipyramids compared with gold nanorods. The well-defined secondary plasmonic hot spots between the coupled gold nanobipyramids exhibit the capability for single molecule detection.

17ß-Estradiol residues and estrogenic activities in the Hawkesbury River, Australia.

Two highly sensitive ELISAs for the specific detection of 17ß-estradiol (E2) residues were developed, showing the limits of detection (LOD, a concentration at 15% inhibition of color development) of 0.04 ±â€¯0.02 µg/L and 0.05 ±â€¯0.03 µg/L. The average recovery rate of the river water samples spiked with E2 at 1-50 ng/L range was 111.5% (68.6-252%) with the % relative standard deviation (RSD) of 0.5-86.3%. The ELISA demonstrated a good correlation with the GC-MS analyses of the spiked river water samples (r = 0.909). Applying the developed E2 ELISA assay to the monitoring of E2 residues in Hawkesbury River (New South Wales, Australia) found that all the tested creek samples contained E2 residues less than the biologically significant level of 10 ng/L. However, 25% of the water samples tested demonstrated the estrogen activity (determined by the yeast estrogen screening (YES) assay) above the levels that have been linked to the adverse effects in fish and other aquatic organisms (> 20 E2 Eq ng/L). It was apparent that the E2 residues together with the EE2 residues (reported in our previous study) contributed to most of the observed estrogenic activity in Hawkesbury River.

A survey of 17α-ethinylestradiol and mestranol residues in Hawkesbury River, Australia, using a highly specific enzyme-linked immunosorbent assay (ELISA) demonstrates the levels of potential biological significance.

This study reports on the potential status of 17α-ethinylestradiol (EE2) and mestranol (MeEE2) residues in aquatic environments in New South Wales (NSW), Australia, based on the analysis by a specific ELISA we developed. Polyclonal antibodies were raised against the EE2 hapten with a linker attached at the C3-position to direct the antibody binding towards the ring D of EE2/MeEE2. Using this approach, an ELISA highly specific to EE2 and MeEE2 was successfully developed, showing less than 3.1% cross-reactivity (% CR) with other major steroidal sex hormones and their derivatives. The assay performed with the limit of detection (LOD) of 0.04 ± 0.01µg/L for both EE2 and MeEE2, and the limit of quantitation (LOQ) of 0.05 ± 0.01ng/L when it was coupled with the SM2-Biobeads solid phase extraction. Prior to conducting the survey study, it was validated against the gas chromatography-mass spectrophotometry (GC-MS) method, which showed high correlation with R2 of 0.934. Fresh surface water samples collected at different sites along Hawkesbury River in New South Wales (NSW) were analyzed for the EE2/ MeEE2 residues using the developed ELISA. The EE2/MeEE2 levels were found to range between 4.1 and 8.3ng/L in Emigrant Creek, NSW, where the primary activity was macadamia plantation, and higher levels between 15 and 29ng/L in South Creek, NSW, Greater Western Sydney at sites upstream and downstream of the municipal sewage treatment plants.

A Review of Methods for Detecting Melamine in Food Samples.

Melamine is a synthetic chemical used in the manufacture of resins, pigments, and superplasticizers. Human beings can be exposed to melamine through various sources such as migration from related products into foods, pesticide contamination, and illegal addition to foods. Toxicity studies suggest that prolonged consumption of melamine could lead to the formation of kidney stones or even death. Therefore, reliable and accurate detection methods are essential to prevent human exposure to melamine. Sample preparation is of critical importance, since it could directly affect the performance of analytical methods. Some methods for the detection of melamine include instrumental analysis, immunoassays, and sensor methods. In this paper, we have summarized the state-of-the-art methods used for food sample preparation as well as the various detection techniques available for melamine. Combinations of multiple techniques and new materials used in the detection of melamine have also been reviewed. Finally, future perspectives on the applications of microfluidic devices have also been provided.

Effects of Surface Epitope Coverage on the Sensitivity of Displacement Assays that Employ Modified Nanoparticles: Using Bisphenol A as a Model Analyte.

With the ever-increasing use of nanoparticles in immunosensors, a fundamental study on the effect of epitope density is presented herein, with a small molecule epitope, on the performance of the displacement assay format in an enzyme-linked immunosorbent assay (ELISA). Thiolated bisphenol A (BPA) functionalized gold nanoparticles (cysBPAv-AuNPs) and specific anti-BPA antibodies are employed for this purpose. It is shown that the displacement of cysBPAv-AuNPs bound to the immobilized antibodies was influenced by both the avidity of bound cysBPAv-AuNPs and the concentration of free BPA to displace it. The importance of surface epitope density was that it changed the number of epitopes in close proximity to the antibody-binding site. This then influenced the avidity of cysBPAv-AuNPs bound to the immobilized antibody. Furthermore, the molar epitope concentration in an assay appears to affect the degree of antibody binding site saturation. Controlling surface epitope density of the functionalized nanoparticles and molar epitope concentration in an assay leads to a decrease of the concentration of free BPA required to displace the bound cysBPAv-AuNP, and hence better assay performance with regards to the D50 value and dynamic range in the displacement assay.

Biocompatible gold nanorods: one-step surface functionalization, highly colloidal stability, and low cytotoxicity.

The conjugation of gold nanorods (AuNRs) with polyethylene glycol (PEG) is one of the most effective ways to reduce their cytotoxicity arising from the cetyltrimethylammonium bromide (CTAB) and silver ions used in their synthesis. However, typical PEGylation occurs only at the tips of the AuNRs, producing partially modified AuNRs. To address this issue, we have developed a novel, facile, one-step surface functionalization method that involves the use of Tween 20 to stabilize AuNRs, bis(p-sulfonatophenyl)phenylphosphine (BSPP) to activate the AuNR surface for the subsequent PEGylation, and NaCl to etch silver from the AuNRs. This method allows for the complete removal of the surface-bound CTAB and the most active surface silver from the AuNRs. The produced AuNRs showed far lower toxicity than other methods to PEGylate AuNRs, with no apparent toxicity when their concentration is lower than 5 µg/mL. Even at a high concentration of 80 µg/mL, their cell viability is still four times higher than that of the tip-modified AuNRs.

A testosterone specific competitive enzyme immunoassay for monitoring water quality.

Testosterone, an androgen and a primary male sex hormone, migrates through the environment in ways which could pose a threat to water quality and, subsequently, environmental and human health. This paper describes the development of a direct competitive enzyme-linked immunosorbent assay (ELISA) that is capable of measuring testosterone with high specificity. The testosterone ELISA displayed the IC20 (as the limit of detection) and IC50 values of 0.05 ± 0.01 µg L(-1) and 0.33 ± 0.18 µg L(-1), respectively. In addition, the assay showed <0.1 % cross-reactivity against structurally related steroidal compounds. However, this assay was found to be sensitive to environmental matrices such as certain metal ions, pH, and high humic acids, and sample clean-up to remove such interference was necessary before analysis. The analyses of 50 surface water samples collected in rural and urban areas in New South Wales, Australia showed that ELISA results correlated well with the androgenic activity measured by the recombinant yeast-based androgen screen assay.

Development of sensitive direct and indirect enzyme-linked immunosorbent assays (ELISAs) for monitoring bisphenol-A in canned foods and beverages.

Enzyme-linked immunosorbent assays (ELISAs) are investigated in this work for the detection of bisphenol-A (BPA), a plastic monomer and a critical contaminant in food and environment. A series of polyclonal antibodies generated in vivo using BPA-butyrate-protein conjugate and BPA-valerate-protein conjugate were evaluated on direct and indirect competitive assay formats with five competing haptens (BPA-butyrate, BPA-valerate, BPA-crotonate, BPA-acetate, and BPA-2-valerate). Two indirect ELISAs and one direct ELISA exhibiting high sensitivity and specificity for BPA were developed. The 50 % inhibition of antibody binding (IC(50)) values were 0.78 ± 0.01-1.20 ± 0.26 µg L(-1), and the limits of detection as measured by the IC(20) values were 0.10 ± 0.03-0.20 ± 0.04 µg L(-1). The assays were highly specific to BPA, only displaying low cross-reactivity (3-8 % for the indirect assays and 26 % for the direct assay) for 4-cumylphenol (4-CP), at pH 7.2. The degree of cross-reaction of 4-CP was influenced by the antibody/hapten conjugate combination, assay conditions, and the assay format. The assays were optimized for the analysis of BPA in canned vegetables, bottled water and carbonated drinks. The limits of quantification for these three evaluated sample types, based on the spike and recovery data, were 0.5, 2.5, and 100 µg L(-1), respectively.