Estudo experimental da influência da temperatura no conteúdo de vitamina c na pasteurização do suco de laranja pêra rio in natura

• Autor(a) principal: Galiassi, Gabriela Regina Rosa
• Data de Publicação: 2021
• Tipo de documento: Trabalho de conclusão de curso
• Idioma: por
• Título da fonte: Biblioteca Digital de Monografias da UFMT
• Texto Completo: http://bdm.ufmt.br/handle/1/1937
• topic: CNPQ::ENGENHARIAS; Pasteurização; Transferência de calor; Coeficiente convectivo; Vitamina C; Pasteurization; Heat transfer; Convective coefficient; Vitamin C

In Brazil, the main form of consumption of oranges is in the form of juice, which is pasteurized. The main forms of heat transfer during food cooling are convection and conduction, and the convective heat transfer coefficients can change, under normal conditions, with temperature, air humidity and air velocity. In pasteurization processes, a deviation of 1°C from the proper temperature produces a 25% error in the effect of the operation. To develop heat transfer calculations it is important knowing the thermophysical properties of foods. In the case of orange juice, some other characteristics deserve attention, such as the content of vitamin C, which is one of the most important vitamins in the human diet. This study aimed to determine the vitamin C content, density and pH of orange juice before and after pasteurization, in addition to determining the convective heat transfer coefficient in the cooling stage. The determination of vitamin C showed that there was a loss of ascorbic acid after pasteurization, making the juice not comply with the normative regulation. The pH change before and after pasteurization was minimal, and the results were consistent with the literature. As for the specific mass, the values obtained were compared with literature data and an experimental error of 3.52% before pasteurization and 0.69% after pasteurization was obtained. Small errors indicate that pasteurization does not significantly affect specific mass. The temperature profile during pasteurization was controlled inside a container with orange juice, in the heating and cooling bath. In the container containing the juice, two control regions were considered: region close to the wall and central region (in the axis of symmetry of the container). The profile obtained corresponded to that of the literature, where in heating the temperatures of the two regions are close, however, each one follows a trend, with the central region being the one with the lowest temperature, and in the cooling stage the temperature variation is the same. The literature obtained the same profile in less time, and this is due to the applied pasteurization method and the use of forced convection, since this study used natural convection. The results for the convective heat transfer coefficient indicated higher values in the region close to the wall and the data corresponded to those indicated in the literature. In the central region it was observed that h became more constant as time passed, as the central region tended towards equilibrium. In the transient conduction analysis, the Biot number was less than 0.1 throughout the cooling and showed a uniform temperature distribution. The relationship between the dimensionless of temperature and Biot*Fourier showed that there is a dependence of the dimensionless of temperature with the dimensionless Biot and Fourier. The cooling rate in the wall and central region was similar, which allowed us to assume an equal exposure of both regions to the fluid.