Utilização da espectroscopia de infravermelho para determinação rápida do índice de maturação em queijos Pecorino, Maturado e Gouda fabricados com leite de ovelha

Abstract

The objective of this work was to explore the utility of Attenuated Total Reflectance and Fourier Transform Infrared Spectroscopy (ATR-FTIR) techniques as tools for rapid evaluation and monitoring of the maturation index of Pecorino, Ripe and Gouda cheeses produced with ewes’ milk. Maturation times of 2, 3, 4, 5 and 11 months (Pecorino), 1, 3, 6, 7, 8 and 12 months (Ripe) and 2, 3, 5 e 11 months (Gouda) have been used. Humidity and fat content analysis were carried out on the newest samples of each cheese to classify them according to the current Brazilian legislation. In relation to lipids, all varieties were classified as fatty cheeses. The water content revealed Ripe and Gouda varieties as “medium moisture” while Pecorino as “low moisture”. Protein content was also estimated. Two samples of the central part of each cheese were subjected to spectral evaluations using a MIR spectrometer (Mid-Infrared Spectroscopy) in the range of 400 to 4000 cm-1. The spectra were obtained in quadruplicate and revealed absorption bands in the region of 3700 to 1000 cm-1. In order to evaluate the ripening process of the cheeses, typical bands arising from amide (1640 and 1550 cm-1) and lipid (2922, 2852 and 1161 cm-1) groups, were studied. In general, the absorption values decreased with the development of ripening process. The whole bands of the main peaks were processed using the Principal Component Analysis (PCA). It was possible to differentiate the ripening times and to evaluate a timeline among the cheeses. The timeline was related with the IR spectral interpretations, where it could be verified the occurrence of the proteolysis and lipolysis phenomena during ripening process of cheese. Therefore, FTIR/ATR technique is a useful tool to detect molecular changes related to the ripening process.