Implementação de um método robusto para o controle fiscal de umidade em queijo minas artesanal. Abordagem metrológica multivariada

Abstract

Recebido em 7/2/13; aceito em 29/4/13; publicado na web em 1/7/13 IMPLEMENTATION OF A ROBUST METHOD FOR QUALITY INSPECTION CONTROL OF ARTISANAL MINAS CHEESE. A MULTIVARIATE METROLOGICAL APPROACH. This study developed and validated a method for moisture determination in artisanal Minas cheese, using near-infrared spectroscopy and partial-least-squares. The model robustness was assured by broad sample diversity, real conditions of routine analysis, variable selection, outlier detection and analytical validation. The model was built from 28.5-55.5% w/w, with a root-mean-square-error-of-prediction of 1.6%. After its adoption, the method stability was confirmed over a period of two years through the development of a control chart. Besides this specific method, the present study sought to provide an example multivariate metrological methodology with potential for application in several areas, including new aspects, such as more stringent evaluation of the linearity of multivariate methods.

Soil Organic Carbon Determination Using NIRS: Evaluation of Dichromate Oxidation and Dry Combustion Analysis as Reference Methods in Multivariate Calibration

“…The value of Durbin-Watson test calculated 1.9241 and 2.1799 when dichromate oxidation and dry combustion were reference methods, respectively, 27, No. 9, 2016 are within the acceptable limits (1.50-2.50), 27 ensuring independence of residuals. However, by applying a bias test (systematic errors test) proposed by ASTM E1655-05 13 in the residuals of validation sets for both models, it is verified that the bias presented at this residuals are significant (results in Table 1).…”

“…The figures of merit for first order multivariate calibration were described in earlier papers, 12,19,21,25,27 and are not described in detail here. The results for the figures of merit obtained from PLS models are shown in the Table 1.…”

Vitamin C Determination by Ultraviolet Spectroscopy and Multiproduct Calibration

“…These results suggest that this data set fit on a linear model. 22,27 To confirm the model linearity, Figure 4 show the histogram for the student residuals whose distribution resemble a Gaussian behavior. The Jarque-Bera test confirm that the student residuals are normally distributed at 95% of confidence level.…”

“…Considering a perfect fit of the model and that the spectral noise represent the large source of error, the inverse of the analytical sensitivity (or analytical sensitivity -1 ) allows for the establishment of a minimum concentration difference which is discernible by the analytical method in the range of concentrations where it was applied. 27 Based on this, it is possible to distinguish samples with concentration difference of vitamin C of 0.33 mg per 100 mL.…”

“…27 This parameter is more suitable for absolute comparisons and can be estimated for calibration (RPD cal ) and validation (RPD val ) as shown in Table 1.…”