Use of dyed solutions to visualize different aspects of vacuum impregnation of Minas cheese

The process of salting Minas cheese (a Brazilian cheese) was studied using salt solutions dyed with methylene blue, in order to visualize different aspects of the salting. Vacuum impregnation experiments were carried out in a hermetic chamber, where cheese samples were immersed in the salt solutions, after the manufacturing pressing stage, under absolute pressure ranging from 16 to 21.3 kPa. Impregnation experiments were carried out under continuous and intermittent vacuum conditions. After 1, 2 or 3 h, the chamber was opened, the impregnated cheese was withdrawn and cut, and the sections were analysed with respect to salt concentration and photographed. The pictures indicated that solute impregnation increased with the vacuum intensity and with the impregnation time. Solute penetration decreased with the force applied during the pressing step and as the cheese aged. These results could be associated with the decrease in the average size and number of the interconnected pores. The experiments showed that intermittent vacuum salting promoted a greater cheese impregnation, which can be explained by the action of deformation-relaxation mechanisms. Despite their qualitative nature, dyed solutions can be useful to study impregnation of porous foods. The experimental results for salt concentration showed that vacuum salting of Minas cheese is a simple and effective procedure for obtaining products with more homogeneous salt concentration.