Quimiometria: De los algoritmos clásicos a los genéticos

In this paper the fundamentals of Chemometrics are presented, by means of a quick overview of the most relevant techniques for data display, classification, modeling and calibration. Two emerging techniques such as Genetic Algorithms and Artificial Neural Networks will also be presented. Goal of the paper is to make people aware of the great superiority of multivariate analysis over the commonly used univariate approach. Mathematical and algorithmical details are not presented, since the paper is mainly focused on the general problems to which Chemometrics can be successfully applied in the field of Food Chemistry.En este artículo se muestran los aspectos fundamentales de la Quimiometria por medio de una revisión rápida de las técnicas más relevantes para mostrar los datos, modelar y calibrar. Se describen dos técnicas emergentes como los algoritmos genéticos y las redes neuronales. El objetivo del articulo es que la comunidad científica tome conciencia de la gran superioridad del análisis multivariante sobre el análisis univariante. No se describen los detalles matemáticos y algorítmicos porque el articulo está dirigido a problemas genéricos en los que la Quimiometría puede ser aplicada con éxito dentro del campo de la Química Analítica

A Preliminary Color Study of Different Basil-Based Semi-Finished Products during Their Storage

open6: Basil-based semi-finished products, which are mainly used as an intermediate to produce the typical pesto sauce, are prepared and exported all over the world. Color is a fundamental organoleptic requirement for the acceptability of these semi-finished products by the manufacturers of the pesto sauce. Some alternative formulations, which adjust the typical industrial recipe by both changing the preservative agent (ascorbic acid, citric acid, or a mixture of both) and introducing a preliminary thermic treatment (blast chilling), were evaluated. In this work, a fast and non-destructive spectrophotometric analysis, to monitor the color variations in these food products during their shelf-life, was proposed. The raw diffuse reflectance spectra (380–900 nm) obtained by a UV–visible spectrophotometer, endowed with an integrating sphere, together with the CIELab parameters (L*, a*, b*) automatically obtained from these, were considered, and elaborated using multivariate statistical analysis (principal component analysis). From this preliminary study, blast chilling, together with the use of ascorbic acid, proved to be the best solution to better preserve the color of these products during their shelf-life.openTurrini, Federica; Farinini, Emanuele; Leardi, Riccardo; Grasso, Federica; Orlandi, Valentina; Boggia, Raffaella;Turrini, Federica; Farinini, Emanuele; Leardi, Riccardo; Grasso, Federica; Orlandi, Valentina; Boggia, Raffaell

Intra-source provenance study on Monte Arci (Sardinia) obsidian by pXRF: Role of the data acquisition and analysis tools

In this work, a detailed study of Monte Arci obsidian sub-sources using the increasingly accessible technique of pXRF is presented based upon a large dataset of 68 geological samples, for the development of X-ray fluorescence-based analytical standardless procedure. In addition, a non-conventional (for obsidian provenance study) direct application of multivariate analysis on XRF spectra (continuous variables), rather than absolute concentrations or intensity ratios (discrete variables) is proposed. Results from different softwares and data analysis approaches (bi-/trivariate versus multivariate) were compared. In a blind test, the bi-/trivariate approach led to the correct assignment for the main SA, SB, and SC sub-sources, taking into account averaged values of intensity ratios with their standard deviation obtained from three independent measurements. A high intra-source variability for the SB subgroups was detected (almost 13% of error in the assignment, 9 samples out of 68). A non-conventional application of multivariate analysis was carried out directly on the XRF spectra and correct assignments were obtained for SA, SB1, SC groups, while 71% of the SB2 samples were correctly identified. The non-destructive analysis on 14 archaeological samples from Su Carroppu (Carbonia, southwestern Sardinia) rockshelter and from the Middle Neolithic (MN) 422 structure of the open-air dwelling site at Cuccuru is Arrius (Cabras, central-western Sardinia) permitted to test the method and hypothesise their provenance. The comparison with visual characterization or previous analyses by Particle Induced X-Ray Emission (PIXE) permitted to verify the correct provenance assignment of all artifacts for the bi-/trivariate method, and for 12/14 samples in the case of the multivariate one. The standardless analytical approach proposed in this work can represent a more general method exploitable for other obsidian sources, other glassy materials, besides other materials of archaeological interest

Chemometrics: from classical to Genetic Algorithms

none1R. LEARDILeardi, Riccard

Oxidative stability of virgin olive oil enriched with carnosic acid

The aim of this study was to evaluate the effect of the addition of carnosic acid on the oxidative stability of virgin olive oil. Two different amounts of carnosic acid (0.01 and 0.1 g/100 g oil) and two different temperatures (accelerated aging temperature, 60 °C; deep frying temperature, 180 °C) were considered. The influence of carnosic acid and heating time on the stability of the oils was studied by experimental design. The results obtained at 60 °C showed a dose dependent inhibition in the formation of primary and secondary oxidation products and a dose dependent enhancement of radical scavenging activity, which was only less significantly influenced by heating time. On the contrary, at 180 °C no protective effect against lipid oxidation was observed and the radical scavenging activity was practically zeroed by heating, probably as a consequence of a fast decomposition of carnosic acid

Empirical modelling of interferences in electrothermal atomization atomic absorption spectrometry

none3noneM. GROTTI; R. LEARDI; R. FRACHEGrotti, Marco; Leardi, Riccardo; Frache, Robert