Comportamento reológico da polpa de goiaba (Psidium guajava L.).

Abstract

The aim of this paper was to determine the influence added on pectinaze enzyme on the rheological behaviour of the guava pulp. In order to reach such goal, it was used the pulp "in natura" and also the pulp added on pectinolytic enzyme (pectinaze) in proportions of the 0,001, 0,0013 and 0,001 in temperatures of 30, 40, 50, 60 and 70°C. The analyses were done in a viscometer of Brookfield model RVT shaped in concentric cylinders. In all the samples observed, the pulps showed a behaviour non-Newtonian with pseudoplastics characteristics. The experimental data were adjusted by the models of Ostwald-de-Waele (Power Law) Casson and Herschel-Bulkley. The model by Herschel-Bulkley, however, was the one which best fitted on the experimental data. The results showed that the consistency index (k) was reduced with the added pectinase enzyme content increasing and with the temperature increasing as well. The values of the flow behaviour index (n) did not show a well defined tendency which became impossible to determine a relation between the temperature and the pectinase enzyme within this parameter.