Utilization of spectroscopy in the infrared region (FTIR) and chemometry in the identification of adulterated toasted and ground coffee. / UtilizaÃÃo da espectroscopia na regiÃo do infravermelho (FTIR) e quimiometria na identificaÃÃo do cafà torrado e moÃdo adulterado.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

In this work the potentialities of the chemometric techniques and the eases in the obtaining of spectra presented by the spectroscopy techniques in the infra-red region with Fourier transform (FTIR) through the attenuated total reflectance (ATR), drift reflectance (DRIFT) and transmittance, aiming at the identification of barley (substance used as an adulterant) in a ground and toasted coffee are combined. The analyzed spectral region was the medium infrared region. Arabic coffee samples of hard beverage were utilized. The coffee beans were toasted with standard commercial toasting and ground next. To the toasted and ground coffee was added barley at the ratios of 0%, 0,5%, 3%, 5%, 7%, 10%, 15% and 20%. Three replicates of each one amounting to 24 samples were done. The adulterated samples were submitted to freeze-drying to avoid the interference of the water bands into the spectrum and left in a dissecator with silica gel for 24 h. Next, the spectra were obtained. The data were organized into matrices and centered on the mean. The chemometric methods employed were: principal component analysis (PCA), hierarchical clustering analysis (HCA), by utilizing euclidean distance for calculation of the distance and the complete linkage method and partial least squares regression (PLS) with cross validation. The R software was utilized for the treatment of the data with adequate functions. The employed methods allowed to separate the coffee with barely from the pure coffee using the diffuse reflectance (DRIFT) and attenuated total reflectance (ATR) with the exception of the samples containing 0.5% of barley. The chemometric methods also allowed to distinguish samples with 20% of barley through the techniques of attenuated total reflectance (ATR) and diffuse reflectance (DRIFT). The transmittance technique was not effective in identifying barley in toasted and ground coffee. In the partial least squares regression analysis, satisfactory results were obtained only for the ATR technique, finding a good adjust between the true values and the estimated values of barley. A correlation coefficient of 98% was found.

ASSUNTO(S)

infrared atr spectroscopy espectroscopia coffee quimiometria cevada chemiometry cafà barley ciÃncias agrÃrias infravermelho atr

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