Comportamento reológico de dispersões coloidais aquosas de polissacarídeos na presença de ácidos orgânicos em diferentes temperaturas

Abstract

Polysaccharides are molecules of high weight which the property to confer viscosity when it is in solution state. With different origins and shapes, each polysaccharide shows different rheological properties, once its solubility can suffer influence from divers factors, like temperature, storage period and medium components. This work had, as objective, the evolution of rheological behavior of liquid polysaccharides solutions in the presence of organic acids in different temperatures. Fourty-eight colloidal dispersion were prepared with variation of acid (ascorbic, citric and tartaric acids), also polysaccharides (CMC gum, guar gum and xanthan gum). Each sample was analyzed in four temperatures: 10, 25, 40 and 90°C. The rheological behavior was evaluated through Brookfield’s viscosimeter, (Brookfield Engineering Laboratories / model LVT). With Spindle number SC4-31, where an amount of an 8mL sample was used and the viscosity was observed according to speed (1 to 100 rpm) in cycles of 20 minutes. The rheological behavior varied from 0 to 19375 mPa.s. All samples presented pseudoplastic behavior. The temperature and the acids influenced on the viscosity of the samples. The sample viscosity showed it self inversely proportional to the temperature. The viscosity for all thickenings was larger in liquid solutions, followed by the citric acid and tartaric acid. The lowest viscosities were observed in the samples with addition of ascorbic acid.