Efeito do tipo de ácido nas características físico-químicas e na determinação da distribuição mineral da massa coalhada e do soro, durante o processo de coagulação ácida visando fabricação de requeijão

Abstract

The main objective of this doctoral thesis was to study the effect of the type of acid on milk acidification, on the physicochemical characteristics and on the mineral composition of the curd mass for the production of Requeijão. Starting from the reconstituted milk stored for 24 hours at 5°C, the acidification of the milk kept at 5°C under agitation was initiated using lactic acid (85% m/v), hydrochloric acid (37% m/v) and sulfuric acid (98% m/v) until reaching pH values of 4.55; 4.70; 4.85 and 5.00. Milk coagulation was initiated by gradually increasing the temperature from 5°C to 55°C. After coagulation, the precipitated protein agglomerate (curdled mass) was drained using a desiccant cloth coupled to a vacuum filtration system for a standardized time of 90 seconds to separate the permeated soluble phase (whey), and physicalchemical analyses were performed. The results demonstrated that the process of obtaining the curdled mass by acidifying cold milk allows the automation of production in a continuous operation for the production of Requeijão. The ionic calcium content in milk is influenced by the lowering of pH, with hydrochloric and sulfuric acids providing a greater release of calcium from the colloidal phase to the soluble phase. The acidification pH of the milk influenced the time and temperature of the start of coagulation. Production with sulfuric and hydrochloric acids at pH 4.55 had a higher adjusted yield in kg of mass/100 kg of milk, and sulfuric acid provided greater losses in production. The pH of milk acidification influenced the pH, moisture and physical characteristics of the curdled masses. The wheys obtained in the treatments with hydrochloric acid presented higher values of ionic calcium and ionic calcium at pH 4.00 and influenced the pH and physical characteristics of the wheys. The pH and acid used in milk acidification did not influence the concentrations of β-Lactoglobulin, however, there was an influence on the values of α-Lactoalbumin. In the mineral characterization of the ash samples of the curdled masses, the values of calcium, phosphorus and magnesium were lower at pH 4.55 in the three acids used. The pH of milk acidification influenced the mineral distribution of the ash samples of the wheys. Therefore, the production of curd mass using hydrochloric acid to lower the pH to 4.55 provided greater release of calcium from the colloidal phase to the soluble phase, faster onset of coagulation, higher yields and use of milk constituents in the curd mass with fewer process losses, greater release of calcium in the whey, causing the curd mass to have less calcium and consequently improving the fusion process and greater use of whey proteins in the curd mass.