Identificação e caracterização de pontos brancos (PIPS) em doce de leite

Abstract

Dulce de leche is a food produced and marketed in Latin America and, like condensed milk, is subjected to the evaporation process. Therefore, during its manufacture, several physicochemical changes occur that can guarantee undesirable characteristics to the dulce de leche, such as the presence of white dots (PIPS). The term PIPS was chosen because the white dots refer to the typical appearance of marking dominoes. Therefore, this work aimed to identify and characterize PIPS in dulce de leche samples using different analytical techniques. With the microscopy techniques it was possible to verify the morphology of the PIPS, which is composed of a spherical center that serves as a nucleation point for the growth of a material in the shape of needles. In the X-ray energy dispersive spectroscopy technique, the presence of calcium and phosphorus atoms was identified and, with the quantitative analysis of these elements, it was possible to affirm the majority presence of calcium in the structure of the PIPS. According to the results of the elemental analysis of carbon, hydrogen and nitrogen, PIPS have the presence of organic matter and amino acids. The concentration of each amino acid present was identified through the aminogram, which highlighted the concentrations of glutamic acid, proline, leucine and aspartic acid. Infrared and Raman spectroscopy identified the presence of calcium citrate. In X-ray diffraction, calcium citrate hexahydrate was identified as the major phase. Finally, the solid state nuclear magnetic resonance spectrum of 13C showed signals consistent with chemical shift of carbon from carboxylate carbonyls, possibly amino acids. In addition to showing signs of a carbon chain of glutamic acid, aspartic acid and leucine. The 31P spectrum showed signs characteristic of chemical shifts of inorganic orthophosphates, such as octacalcium phosphate and hydroxyapatite. Thus, it was possible to conclude that PIPS have a crystal structure mainly composed of calcium citrate hexahydrate, in addition, PIPS have amino acids and a small amount of phosphates that may be related to the presence of αs1-casein.