Impregnation and drying to develop a melon snack enriched in calcium.

Melon fortification with calcium by impregnation techniques using a vacuum and/or ultrasound and drying were combined to obtain a snack product. For the impregnation step, samples were immersed in a 2 g 100 mL-1 calcium chloride solution at 25 °C. The samples were dried at 60 °C and an air velocity of 2 m s-1. The influence of the impregnation method on drying kinetics, mass variation, calcium content, water activity, color, and texture was evaluated. All dried samples had reduced water activity. The vacuum impregnated (VI) melons presented higher mass gain and drying time. It resulted in the highest calcium incorporation, increasing up to 13 times the calcium concentration of the samples. The samples dried after submitted to VI showed the greatest differences in color and hardness. However, VI was the most effective technique for calcium incorporation, being the only one capable of producing fortified dried melon.

Aplicação da espectroscopia de infravermelho próximo e calibração multivariada para previsão do teor de lipídios em queijos de coalho comercializados em Pernambuco / Application of next infrared spectroscopy and multivariate calibration for forecasting the content of lipid in “coalho” cheese marketing in Pernambuco

O queijo de coalho é um dos produtos lácteos mais tradicionais produzidos no Nordeste brasileiro. A Espectroscopia na Região do Infravermelho próximo (NIRS) tem sido utilizada em análise de alimentos para a determinação de vários constituintes. O objetivo deste trabalho foi prever o teor de lipídios utilizando NIRS associada à calibração multivariada em queijos de coalho comercializados em Pernambuco. Para tanto, 80 amostras de queijo de coalho foram submetidas às análises de referência (Gerber para lipídios) e espectroscópicas. Foi possível verificar que o Erro Médio Quadrático de Previsão para lipídios de 1,39%, evidenciando que o modelo PLS obteve resultados de previsão satisfatórios, embora para outras variedades de queijos, apresentaram-se significativamente menores.

Authenticity assessment of banknotes using portable near infrared spectrometer and chemometrics.

Spectra recorded using a portable near infrared (NIR) spectrometer, Soft Independent Modeling of Class Analogy (SIMCA) and Linear Discriminant Analysis (LDA) associated to Successive Projections Algorithm (SPA) models were applied to identify counterfeit and authentic Brazilian Real (R$20, R$50 and R$100) banknotes, enabling a simple field analysis. NIR spectra (950-1650nm) were recorded from seven different areas of the banknotes (two with fluorescent ink, one over watermark, three with intaglio printing process and one over the serial numbers with typography printing). SIMCA and SPA-LDA models were built using 1st derivative preprocessed spectral data from one of the intaglio areas. For the SIMCA models, all authentic (300) banknotes were correctly classified and the counterfeits (227) were not classified. For the two classes SPA-LDA models (authentic and counterfeit currencies), all the test samples were correctly classified into their respective class. The number of selected variables by SPA varied from two to nineteen for R$20, R$50 and R$100 currencies. These results show that the use of the portable near-infrared with SIMCA or SPA-LDA models can be a completely effective, fast, and non-destructive way to identify authenticity of banknotes as well as permitting field analysis.

Standardization from a benchtop to a handheld NIR spectrometer using mathematically mixed NIR spectra to determine fuel quality parameters.

The interest in performing in field measures using portable instruments is growing increasingly. Calibration transfer techniques can be used to enable models, predicted values or spectra obtained in a benchtop instrument be used in portable instrument, saving money and time required for a complete recalibration. Most of the calibration transfer methods require a set of transfer samples which spectra have to be acquired in both spectrometers. The present work evaluates the use of virtual standards as transfer samples in the reverse standardization (RS) method in order to standardize very dissimilar spectral responses of fuel samples (gasoline and biodiesel blends) from a high-resolution benchtop Frontier FT-NIR (PerkinElmer) spectrometer and a handheld MicroNIR™1700 (JDSU). These virtual standards can be created by mathematically mixing spectra from the pure solvents present in gasoline or diesel/biodiesel (D/B) blends, to avoid volatilization and changes in the composition of the compounds during storage and/or transportation of the real transfer fuel samples. Virtual standards were created using ten and five pure solvents for gasoline and D/B blends, respectively. Partial least squares regression (PLS) models were built for five quality parameters of gasoline (distillation temperatures at 10%, 50%, 90% and final boiling point (FBP) volume recovered and density) and one of D/B blends (biodiesel content). The RMSEP values obtained after the standardization approaches were equivalent to the reproducibility of the reference methods, except for density and biodiesel content parameters obtained for the virtual samples standardization approach. RS procedure provided promising results showing that it is possible to transfer gasoline or D/B blend spectra acquired with a high-resolution benchtop instrument to the handheld MicroNIR using virtual standards as transfer samples.

A comparative study of calibration transfer methods for determination of gasoline quality parameters in three different near infrared spectrometers.

This work presents a comparative study of calibration transfer among three near infrared spectrometers for determination of naphthenes and RON (Research Octane Number) in gasoline. Seven transfer methods are compared: direct standardization (DS), piecewise direct standardization (PDS), orthogonal signal correction (OSC), reverse standardization (RS), piecewise reverse standardization (PRS), slope and bias correction (SBC) and model updating (MU). Two pre-treatment procedures, namely standard normal variate (SNV) and multiplicative scatter correction (MSC), are also investigated. The choice of an appropriate number of transfer samples for each technique, as well as the effect of window size in PDS/PRS and OSC components, are discussed. A broad set of gasoline samples representative of the Northeastern states of Brazil is employed in the investigation. The results show that the use of calibration transfer yields prediction errors comparable to those obtained with complete recalibration of the secondary instrument. Overall, the results point to RS as the best method for the analytical problem under consideration. When storage and/or physical transportation of transfer samples are impractical, MU is more appropriate. The comprehensive investigation carried out in the present work will be of value for practitioners involved in networks of fuel monitoring.

Analytical curve or standard addition method: how to elect and design--a strategy applied to copper determination in sugarcane spirits using AAS.

In most instrumental analysis, the analyte concentration is usually obtained the by Analytical Curve Method (ACM) or Standard Addition Method (SAM). Thus, it is important for the analyst to select the most appropriate method, to seek the best conditions of analysis, and to provide parameters of analytical performance. A strategy to do so is proposed in this paper in conjunction with MATLAB software to implement it. The proposed strategy was applied to copper determination by atomic absorption spectrometry in Brazilian sugarcane spirits termed 'Cachaça' and SAM was chosen as the most appropriate method. To select the best experimental design for SAM, the influence of some factors, such as the number of standard additions and concentration levels, the location of the levels and the average concentration of the standard additions were demonstrated. The design with six standard additions, four concentration levels located near the inferior and superior levels and the average concentration of the standard additions closer to zero yielded SAM with an adequate compromise between precision, cost and time of analysis. The uniform distribution of concentration levels, usually used in routine analysis, is not a good design regarding precision. On the other hand, it is adequate when the linear range is unknown. Generally, the proposed strategy can be applied to different instrumental techniques and samples, which aim to improve their analytical performance.