Abstract
The aim of this study was to evaluate the potential of Fourier transform infrared (FTIR) spectroscopy coupled with chemometric methods to detect fish adulteration. Muscles of Atlantic salmon (Salmo salar) (SS) and Salmon trout (Onconrhynchus mykiss) (OM) muscles were mixed in different percentages and transformed into mini-burgers. These were stored at 3 degrees C, then examined at 0, 72, 160, and 240 h for deteriorative microorganisms. Mini-burgers was submitted to Soxhlet extraction, following which lipid extracts were analyzed by FTIR. The principal component analysis (PCA) described the studied adulteration using four principal components with an explained variance of 95.60%. PCA showed that the absorbance in the spectral region from 721, 1097, 1370, 1464, 1655, 2805, to 2935, 3009 cm 1 may be attributed to biochemical fingerprints related to differences between SS and OM. The partial least squares regression (PLS-R) predicted the presence/absence of adulteration in fish samples of an external set with high accuracy. The proposed methods have the advantage of allowing quick measurements, despite the storage time of the adulterated fish. FTIR combined with chemometrics showed that a methodology to identify the adulteration of SS with OM can be established, even when stored for different periods of time.

Abstract
Food fraud is a growing problem and happens in many ways including mislabelling. Since lack of consumers' knowledge about mandatory food labeling information and different types of food fraud may impact public health, the present work assesses consumers' knowledge about these issues. Principal component analysis was performed to obtain a smaller number of uncorrelated factors regarding the usefulness and confidence of information displayed in food labels and the perception of food fraud. Results indicated that information displayed in food labels is useful, however the way it is presented may decrease consumer interest and understanding. Regarding respondents' confidence in foodstuffs, over half of them stated that information provided in food labels is reliable. However, a lack of confidence about food composition is observed in those processed foodstuffs such as meat products. Food fraud is recognized by more than half of respondents with a higher perception of those practices that imply a risk to public health than those related to economic motivation. Age and education of consumers influenced the perception of the information displayed in the food labels, their confidence and knowledge about food fraud. Implementation of education programs to increase consumer knowledge about food labelling and fraud is essential. Respondents' perception results could be use as guidelines by the food industry to improve food label design in order to enhance consumer understanding.

Abstract
Fiber optic-based refractometers is a thoroughly researched field, with many different configurations being used. However, most designs require external calibration using substances of known refractive index (RI) and their fabrication process might be impractical and time consuming, creating the need for a quick and accurate method of measuring RI of different substances. A simple method for simultaneous measurement in real-time of RI and thickness of polymer thin films is presented, allowing dynamic measurements in the presence of changing environmental parameters, such as temperature or humidity. This method, which does not require previous calibration, is based on an inline Fabry-Perot (FP) cavity, created by dipping the tip of a cleaved optical fiber (OF) in a polymer solution. The procedure consists of using the equations of the low finesse FP interferometers to directly extract information from the structure created, such as RI and cavity length, by working in the spectral window from 1500 to 1600nm. The method was validated by creating FP cavities with liquids of known RI, for which a typical precision of 3 x 10(-3) was achieved, along with errors lower than 0.6% and 1% for RI and cavity length determination, respectively, The procedure was then used to monitor three different curing processes, namely the temperature curing of Sylgard (TM) 184, the UV curing of Norland Optical Adhesives (TM) 65 and the mixing and curing of Ceys (TM) Araldite epoxy glue. Both RI and cavity length were compared to reference values, showing excellent agreement with the experimental results for a method that does not require external calibration.

Abstract
A strategy for the detection of H2O2 as a milk adulterant using a single shot membrane sensor, is presented. Direct quantitative evaluation of H2O2 in raw, skimmed, semi-skimmed and whole milk was carried out based on a chemiluminescence reaction with luminol. For H2O2 water solutions a linear response was attained from 0.0001% to 0.007 %w/w, with a limit of detection of 3x10(-5) %w/w. A coefficient of determination, R-2, greater than 0.97 was achieved, with a relative standard deviation (RSD) not exceeding 10%. In the analyzed milk samples, the lowest H2O2 concentration detected was 0.001% w/w for raw and for skim milk and 0.002%w/w for, semi-skimmed and whole milk. The presented method is original, sensitive, rapid, and cost-effective. Due to the achieved sensitivity the method has great potential to be used for H2O2 detection in diverse areas, such as environmental monitoring and food quality.

Abstract
Biogenic amines (BAs) are compounds found in a vast range of food products. In recent years, there has been a crescent awareness toward food safety, followed by an increase in food regulations. Long-period fiber gratings (LPFGs) coated with titanium dioxide (TiO2) were used to monitor the optical properties of a layer of poly(ethylene-co-vinyl acetate) (PEVA) doped with maleic anhydride (MA), which was polymerized on top of TiO2. This hydrophobic polymeric structure is permeable to BA, which causes a steady increase in its effective refractive index (RI) causing a wavelength shift in the coated LPFG attenuation band. LPFG wavelength shift was observed and measured for the monoamine tyramine (TYR), to the diamines, putrescine (PUT), cadaverine (CAD), histamine (HIS), and tryptamine (TRYP), and to the polyamines, spermidine (SPED), and spermine (SPEM). It was determined that, while PEVA-coated devices present a residual sensitivity to BA, the MA greatly increases it. In fact, for PEVA only coated LPFGs, the sensitivities of 1.45 +/- 0.11, 0.97 +/- 0.05, 0.46 +/- 0.08, and 0.94 +/- 0.09 nmM-1 for PUT, CAD, HIS, and TYR, respectively, were measured. However, for PEVA-doped MA-coated LPFGs, the sensitivities are 3.34 +/- 0.13, 3.06 +/- 0.11, 2.62 +/- 0.14, and 3.65 +/- 0.23 nmM-1 for PUT, CAD, HIS, and TYR, respectively. Thus, the RI of PEVA increases with BAs in- diffusion, and MA doping further enhances the PEVA sensitivity to BA. The proposed sensor is expected to play a part in the further development of a biosensor for the quantification of BA in real foodstuff, providing a methodology for quality control.

Abstract
The precise production of 4.5 µm off-axis first order FBG in an SMF-28e fiber through femtosecond laser direct writing is demonstrated. The off-axis FBG potential as sensing head for torsion sensing was successfully explored. © 2021 The Author(s).