A voltammetric e-tongue tool for the emulation of the sensorial analysis and the discrimination of vegetal milks

[EN] The relevance of plant-based food alternatives to dairy products, such as vegetable milks, has been growing in recent decades, and the development of systems capable of classifying and predicting the sensorial profile of such products is interesting. In this context, a methodology to perform the sensorial analysis of vegetable milks (oat, soya, rice, almond and tiger nut), based on 12 parameters, was validated. An electronic tongue based on the combination of eight metals with pulse voltammetry was also tested. The current intensity profiles are characteristic for each non-dairy milk type. Data were processed with qualitative (PCA, dendrogram) and quantitative (PLS) tools. The PCA statistical analysis showed that when using three first principal components, which covered 77% of variance, the eight samples can be differentiated, and the preparation method (artisanal milks or commercial) is one of the main differentiation factors, together with raw material type. The PLS statistical analysis allowed models to be created to predict all 12 sensorial parameters. The goodness of the predictions depends on the parameter being particularly accurate for the body, the granularity in the wall of glass and homogeneity of colour. The results strongly suggest the potential feasibility of using electronic tongues as systems for easy, rapid and effective sensorial assessments of vegetable milks. (C) 2018 Elsevier B.V. All rights reserved.The authors thank the financial support from the Spanish Government (Project MAT2015-64139-C4-1-R) and the Generalitat Valenciana (Project PROMETEOII/2014/047).Pascual, L.; Gras Romero, ML.; Vidal Brotons, DJ.; Alcañiz Fillol, M.; Martínez-Máñez, R.; Ros-Lis, JV. (2018). A voltammetric e-tongue tool for the emulation of the sensorial analysis and the discrimination of vegetal milks. Sensors and Actuators B Chemical. 270:231-238. https://doi.org/10.1016/j.snb.2018.04.151S23123827

Application of mesoporous silica materials for the immobilization of polyphenol oxidase

[EN] The ability of a number of mesoporous silica materials (SBA-15, SBA-3, and MCM-48) to immobilize polyphenol oxidase (PPO) at different pH has been tested. Pore size and volume are the structural characteristics with higher influence on the PPO immobilization. Mesoropous material SBA-15 adsorbs a larger quantity of PPO at pH 4.00 and offers an inhibition of enzymatic activity close the 50% in apple extracts.AEGB acknowledges support from the Swedish Research Council (Grant Number 621-2012-3375), the ARC Centre of Excellence for Nanoscale BioPhotonics (CE140100003), and an ARC Future Fellowship (FT150100342)Corell Escuin, P.; Garcia-Benett, A.; Ros-Lis, JV.; Argüelles Foix, AL.; Andrés Grau, AM. (2017). Application of mesoporous silica materials for the immobilization of polyphenol oxidase. Food Chemistry. 217:360-363. https://doi.org/10.1016/j.foodchem.2016.08.027S36036321

Highly active hydrogenation catalysts based on Pd nanoparticles dispersed along hierarchical porous silica covered with polydopamine as interfacial glue

New catalysts based on Pd(0) nanoparticles (Pd NPs) on a bimodal porous silica of the UVM-7/polydopamine (PDA) support have been synthesized following two preparative strategies based on the sequential or joint incorporation of two components of the composite (Pd and PDA). We analyzed the role played by the PDA as 'interfacial glue' between the silica scaffold and the Pd NPs. The catalysts were tested for the hydrogenation of 4-nitrophenol using (NEt4)BH4 as the hydrogenating agent. In addition to the palladium content, the characterization of the catalysts at the micro and nanoscale has highlighted the importance of different parameters, such as the size and dispersion of the Pd NPs, as well as their accessibility to the substrate (greater or lesser depending on their entrapment level in the PDA) on the catalytic efficiency. Staged sequential synthesis has led to better catalytic results. The most active Pd(0) centers seem to be Pd NPs of less than 1 nm on the PDA surface. The efficiency of the catalysts obtained is superior to that of similar materials without PDA. A comprehensive comparison has been made with other catalysts based on Pd NPs in a wide variety of supports. The TOF values achieved are among the best described in the literature

Fish Freshness Decay Measurement with a Colorimetric Array

The development of rapid non-destructive techniques to determine fish quality and shelf-life is vital to guarantee food safety. The aim of this study was to evaluate a new optoelectronic nose composed by eight sensing materials prepared by the incorporation of pH indicators and chromogenic reagents selective to metabolites into inorganic materials (aluminium oxide and silica gel) in the shelf-life assessment of fresh sea bream in cold storage. Physico-chemical and microbial analyses were carried out periodically throughout the cold storage, as well as colour measurements on the colorimetric array. The results obtained using the chromogenic array were in accordance with those obtained from physico-chemical and microbial analyses, which showed a clear loss of freshness from day 4 to day 7. This confirms the potential usefulness of colorimetric reagents for detection of sea bream spoilage.Zaragozá Torres, P.; Ribes, S.; Fuentes López, A.; Vivancos, J.; Fernández Segovia, I.; Ros-Lis, JV.; Barat Baviera, JM.... (2012). Fish Freshness Decay Measurement with a Colorimetric Array. Procedia Engineering. 47:1362-1365. doi:10.1016/j.proeng.2012.09.409S136213654

An optoelectronic sensing device for CO detection in air based on a binuclear rhodium complex

The design, fabrication and validation of an optoelectronic sensor implemented in an easy-to-use portable device for the selective and sensitive detection of CO in air is reported herein. The system is based on the colour changes observed in the binuclear rhodium complex of formula [Rh2[(C6H4)P(C6H5)2]2(O2CCF3)2](CF3CO2H)2(1) upon coordinating CO molecules in axial positions. Complex 1 is used supported on cellulose chromatography paper. In this support, colour changes to the naked eye are observed for CO concentrations above 50 ppm. The probe is also implemented in a simple portable optoelectronic device.The cellulose support containing probe 1 in this device is placed inside a small dark chamber, is illuminated with a tricolour LED emitting at 624, 525 and 470 nm, respectively corresponding to red (R), green (G) and blue (B) light, and reflected light is detected by a photodiode. With a transimpedance amplifier, the current generated by the photodiode is transformed into a voltage compatible with the 10-bit analogue-to-digital converter (ADC) port. Colour changes are measured as the distance d between the R, G and B data of the blank (probe without CO) and that for a certain CO concentration. Typical calibration curves are fitted using a bi-exponential equation. This system offers a typical response time of a few minutes (ca. 7 min) and a limit of detection of 11 ppm. The probe in the cellulose supports is also highly reversible.The optoelectronic device is portable (dimensions 14 × 8.5 × 3.5 cm; weighs approximately 270 g) and is powered by AA batteries. In addition, no variations in experimental parameter d upon exposure to CO2, N2, O2, Ar, water-saturated air and vapours of chloroform, hexane, ethanol, acetone, methane, toluene or formaldehyde are observed. Besides, colour changes are found for acetonitrile vapour, NO and NO2, but only at high concentrations. For validation purposes, the device was used to determine the CO present in the 4-shed accumulated smoke of two cigarette types after passing smokers lungs.We thank the Spanish Government (Project MAT2012-38429-C04-01), Generalitat Valenciana (Projects PROMETE02009/016 and ISIC/2012/005) and the UPV (Project INNOVA-04-10) for support. M.E.M thanks the Spanish Ministry of Education for a Doctoral FPU Fellowship.Moragues Pons, ME.; Montes Robles, R.; Ros-Lis, JV.; Alcañiz Fillol, M.; Ibáñez Civera, FJ.; Pardo Vicente, MT.; Martínez Mañez, R. (2014). An optoelectronic sensing device for CO detection in air based on a binuclear rhodium complex. Sensors and Actuators B: Chemical. 191:257-263. https://doi.org/10.1016/j.snb.2013.09.107S25726319

Synthesis and evaluation of fluorimetric and colorimetric chemosensors for anions based on (oligo)thienyl-thiosemicarbazones

A family of heterocyclic thiosemicarbazone dyes (3a-d) containing thienyl groups has been synthesized, characterized and their chromo-fluorogenic response in acetonitrile in the presence of selected anions studied. Acetonitrile solutions of 3a-d show absorption bands in the 338-425 nm range which are modulated by the groups attached to the thiosemicarbazone moiety. The fluoride, chloride, bromide, iodide, dihydrogen phosphate, hydrogen sulfate, nitrate, acetate and anions were used in the recognition studies. Only sensing features were observed for fluoride, cyanide, acetate and dihydrogen phosphate anions. Two different chromogenic responses were found, (i) a small shift of the absorption band due to coordination of the anions with the thiourea protons and (ii) the appearance of a new red shifted band due to deprotonation of the receptor. For the latter process changes in the color solutions from pale-yellow to orange-red were observed. Fluorescence studies showed a different emission behavior according to the number of thienyl rings in the π-conjugated bridges. Stability constants for the two processes (complex formation + deprotonation) for receptors 3a-d in the presence of fluoride and acetate anions were determined from spectrophotometric titrations using the HypSpec program. The interaction of 3d with fluoride was also studied through 1H NMR titrations. Semiempirical calculations to evaluate the hydrogen-donating ability of the receptors were also performed.Fundação para a Ciência e a Tecnologia (FCT) , Acções Integradas Luso-Espanholas/CRUP, Generalitat Valenci