Sensitive ELISA and lateral flow immunoassay for the detection of walnut traces in processed food and working surfaces.

Walnut represents one of the most allergenic nuts that can be found as a hidden allergen. In this study, sandwich ELISA and lateral flow immunoassay (LFIA), based on the determination of Jug r 1, were developed to detect walnut. Cross-reactivity was only found with Pecan nut among a panel of 88 food ingredients tested. ELISA and LFIA could detect 0.25 and 0.5 µg/g of walnut protein in complex food matrices spiked with walnut extract, respectively. Furthermore, walnut was detected in blended (chocolate) and incurred foods (ice cream and bread) added with ground walnut at levels of 0.5 and 1.5 µg protein/g by ELISA and LFIA, respectively. LFIA could also detect 0.1 µg of walnut protein in working surfaces. ELISA displayed acceptable precision and high recovery (71-97 %) and both tests were robust. This study shows that developed ELISA and LFIA are reliable tools to be applied in allergen control programs.

Development of sandwich ELISA and lateral flow immunoassay to detect almond in processed food.

Almond (Prunus dulcis) represents a potential allergenic hazard that should be included in Allergen Control Plans. In this study, sandwich ELISA and lateral flow immunoassay (LFIA), using amandin (Pru du 6) as the target protein, were developed to detect almond in processed food and validated according to international guides. ELISA could detect 2 ng/mL and LFIA 30 ng/mL of pure amandin. No cross-reactivity was found on a panel of 50 food commodities with the exception of Pecan nut, Brazil nut and chestnut for which the cross-reactivity was lower than 0.02%. Furthermore, ELISA and LFIA were able to detect 0.12 and 0.70 ppm of almond protein in foods spiked with almond extract whereas 0.20 and 2.0 ppm could be detected in baked cookies incurred with almond, respectively. Both techniques could be applied for food manufacturers and control agencies for monitoring the presence of almond traces in food and working surfaces.

Twisted One-Dimensional Charge Transfer and Related Y-Shaped Chromophores with a 4H-Pyranylidene Donor: Synthesis and Optical Properties.

Three series of push-pull derivatives bearing 4H-pyranylidene as electron donor group and a variety of acceptors were designed. On one hand, one-dimensional chromophores with a thiophene ring (series 1H) or 5-dimethylaminothiophene moiety (series 1N) as an auxiliary donor, non-coplanar with the π-conjugated system, were synthesized. On the other hand, related two-dimensional (2D) Y-shaped chromophores (series 2) were also prepared to compare how the diverse architectures affect the electrochemical, linear, and second-order nonlinear optical (NLO) properties. The presence of the 5-dimethylaminothiophene moiety in the exocyclic C═C bond of the pyranylidene unit gives rise to oxidation potentials rarely low, and the protonation (with an excess of trifluoroacetic acid) of its derivatives results in the apparition of a new blue-shifted band in the UV-visible spectra. The analysis of the properties of derivatives with and without the additional thiophene ring shows that this auxiliary donor leads to a higher NLO response, accompanied by an enhanced transparency. Y-shaped chromophores of series 2 present a blue-shifted absorption, higher molar extinction coefficients, and higher Eox values compared to their linear twisted counterparts. As concerns NLO properties, 2D Y-shaped architecture gives rise to somewhat lower µß values (except for thiobarbiturate derivatives).