INFRARED SPECTROSCOPY AND FLOW ANALYSIS FOR THE DETECTION OF ADDITIVES/CONTAMINANTS IN FOOD PRODUCTS

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Application of mid- and near-infrared spectroscopy for the control and chemical evaluation of brine solutions and traditional sea salts

Publication . Galvis-Sánchez, Andrea C.; Santos, Inês C.; Mesquita, Raquel B. R.; Lopes, João A.; Rangel, António O. S. S.; Delgadillo, Ivonne

Mid- and near-infrared spectroscopy methodologies were explored for the analysis of brine solutions and traditional sea salt samples. Brine solutions from different salt pans, corresponding to different stages of sodium chloride crystallisation, were collected. A total of 61 dried and non-dried traditional sea salts were also analysed. Partial least squares regression with leave-one-out cross-validation strategy was applied for the calibration of inorganic constituents Ca2+, Mg2+ and K+, alkalinity as HCO (3) (-) , SO (4) (2-) , NO (2) (-) and NO (3) (-) and phosphate in brine solutions. Promising results were obtained with the near-infrared (NIR) methodology for brine solutions with coefficients of determination R (2) > 0.90 for Mg+2, K+, HCO (3) (-) and SO (4) (2-) . Using mid-infrared, the calibration for H2PO (4) (-) was R (2) = 0.85. In relation to the sea salt samples, the strategy adopted was the re-sampling based cross-validation using different spectral pre-processing treatments. In this case, the calibrations using the two IR methodologies fell bellow acceptable levels for the techniques; however, by comparing the R (2) coefficient, the results were slightly better when using the NIR spectra of dried sea samples. In general, these results open a new possibility for the IR applications and also bring an opportunity for continuing with the NIR characterization for dried sea salt samples.

2013Journal article

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Monitoring sodium chloride during cod fish desalting process by flow injection spectrometry and infrared spectroscopy

Publication . Galvis-Sánchez, Andrea C.; Tóth, Ildikó V.; Portela, Ana; Delgadillo, Ivonne; Rangel, António O. S. S.

In order to adapt to the market trends that are moving towards ready-to-use products cod !sh industry is including into their industrial operations as the desalting step. The desalting process is a high cost and time demanding operation. The optimization of the desalting process is of vital importance for the !sh industry in order to assure the homogeneity and predictable concentration of sodium chloride in the !nal hydrated cod !sh product. On the other hand, consumers are more aware about the necessity to bring sodium consumption down to healthy levels to prevent cardiovascular diseases. The application of rapid and simple analytical methodologies that permit the control of the process and ensure food quality is essential in the food industries. This work reports the optimization and application of two analytical methodologies with the objective of monitoring the variation of sodium chloride concentration during cod desalting process. A "ow injection analysis system was developed based on the reaction between chloride and silver nitrate, and the formed precipitate was assessed spectrophotometrically as a turbidity change. A Fourier-mid infrared spectroscopy attenuated total re"ection method was also applied. Different chemical and physical parameters of the "ow injection system were studied and the analytical characteristics of both systems were compared.

2011Journal article

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An experimental approach to perform solid liquid extraction in flow systems

Publication . Santos, Inês C.; Rangel, António O. S. S.; Galvis-Sánchez, A.

2015Conference object

Open access

NMR water transverse relaxation time approach to understand storage stability of fresh-cut ‘Rocha’ pear

Publication . Fundo, Joana; Galvis-Sanchez, Andrea; Madureira, Ana Raquel; Carvalho, Alexandra; Feio, Gabriel; Silva, Cristina L. M.; Quintas, Mafalda

Fresh-cut fruit is an important segment in fruit market due to the increasing demand for healthy/ convenient foods. However, processing promotes a decrease in fruits stability with faster physiological and microbiological deteriorations. Food stability is strongly attributed to its molecular dynamics and “water availability”. Understanding changes in water location/mobility is of utmost importance, since water dynamics profoundly influences physic-chemical and microbiological quality of foods. Nuclear magnetic resonance spectroscopy (NMR) is a methodology used to study the food constituents' molecular dynamics. The aim of this study is to use NMR to evaluate changes in water mobility that occurred in fresh-cut pear tissues during storage, by measuring the transverse relaxation time (T2) parameter. Results showed the existence of three water classes in the cells after processing, with T2 values of 10 ms, 187 ms and 3s for cellular wall, cytoplasm and vacuole, respectively. Also, the obtained results demonstrated that T2 was affected by processing and storage. Moreover, a relationship between T2, microstructure and the quality parameters was established. T2, maximum value increased with pear hardness as well as water activity. On the contrary, a decrease in total colour difference (TCD) was found with T2. Results demonstrate the usefulness of the application of NMR relaxometry in food studies.

2016Journal article

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Fourier transform near-infrared spectroscopy application for sea salt quality evaluation

Publication . Galvis-Sanchez, Andrea C.; Lopes, João Almeida; Delgadillo, Ivonne; Rangel, António O.S.S.

Near-infrared (NIR) spectroscopy in diffuse reflectance mode was explored with the objective of discriminating sea salts according to their quality type (traditional salt vs "flower of salt") and geographical origin (Atlantic vs Mediterranean). Sea salts were also analyzed in terms of Ca2+, Mg2+, K+, alkalinity, and sulfate concentrations to support spectroscopic results. High concentrations of Mg2+ and K+ characterized Atlantic samples, while a high Ca2+ content was observed in traditional sea salts. A partial least-squares discriminant analysis model considering the 8500-7500 cm(-1) region permitted the discrimination of salts by quality types. The regions 4650-4350 and 5900-5500 cm(-1) allowed salts classification according to their geographical origin. It was possible to classify correctly 85.3 and 94.8% of the analyzed samples according to the salt type and to the geographical origin, respectively. These results demonstrated that NIR spectroscopy is a suitable and very efficient tool for sea salt quality evaluation.

2011Journal article

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