Caracterização físico-química e espectroscópica de leite e derivados: aplicações na avaliação da estabilidade coloidal e da estrutura de matrizes lácteas

Abstract

Milk and dairy products have great nutritional, economic, and technological importance. In this context, the development of methods to optimize processing, characterize composition, and monitor structural changes is important for quality control and innovation in the dairy industry. This thesis brings together three studies focused on the application of experimental design, vibrational spectroscopy, and chemometrics to the investigation of milk and dairy products. The first study evaluated the combined effect of stabilizing salts on the colloidal stability of milk intended for UHT processing. A simplex-centroid mixture design was employed to investigate the interactions between sodium citrate and different phosphates, using pH, ionic calcium concentration, and heat stability as response variables. The results showed a synergistic effect among the salts and made it possible to define a formulation capable of increasing milk stability during thermal processing. The second study aimed to characterize the milk fat from cow, goat, sheep, and buffalo milk. The lipid fraction was extracted using the Folch method and analyzed by Raman and infrared spectroscopy associated with Principal Component Analysis (PCA). The differences observed in the spectral profiles allowed the differentiation of the animal species, demonstrating that vibrational spectroscopy can be applied to the characterization of milk fat. The third study applied Raman spectroscopy associated with PCA to compare industrial and artisanal Minas Frescal cheeses and to monitor structural changes during storage under refrigeration and at room temperature. The results revealed differences between the manufacturing processes, greater variability among artisanal cheeses, and changes mainly related to lipid phase organization and water distribution throughout storage. In addition, the study demonstrated the possibility of differentiating Minas Frescal cheeses produced by different manufacturing processes using Raman spectroscopy. Overall, the results demonstrate that experimental design, vibrational spectroscopy, and chemometrics are complementary tools for the study of milk and dairy products. These approaches made it possible to optimize formulations, characterize the fat of milk from different animal species, and monitor structural changes in Minas Frescal cheese, demonstrating their application in characterization studies, product development, and quality control.