Rheological behavior of mixed nectars of pineapple skin juice and tropical fruit pulp
2017
Rodrigues, A. M. | Braga, A. C. C. | Peixoto Joele, M. R. S. | Silva, D. C. S. | Lourenço, L. F. H.
This study aimed to evaluate the rheological behavior at different temperatures of mixed nectars containing pineapple skin juice and fruit pulp (cupuaçu, taperebá, and guava), which then underwent microbiological and physicochemical analyses according to the current legislation. The rheological data were obtained using a rotational viscometer with concentric cylinder geometry. The formulations had low pH at 3.44 to 3.85, acidity between 0.71 and 0.87 (% citric acid), °Brix/acidity ratio ranging from 12.60 to 15.41, vitamin C content between 1.23 and 7.56 mg/100 g, and fiber content between 0.46 and 0.68%. The microbiological analyses showed no coliforms at 35°C or Salmonella sp. The mixed nectars showed a non-Newtonian behavior at the temperature range studied. The Power Law model fitted the experimental data and was shown to be appropriate to describe the behavior of the mixed nectars according to the statistical fitting parameters assessed (R2, x², and RSS). The products showed behavior indices below 1, which characterizes the pseudoplasticity of the beverages. Formulation F1 had the highest consistency index (K), however, the index of F2 and F3 decreased as temperature increased. Temperature impacted the nectars’ shear stress and apparent viscosity with the lowest values being observed at 60°C. The effect of temperature on the rheological behavior of the nectar was described by an equation analogous to Arrhenius equation and discussed in terms of activation energy (Ea). Ea values were 3.92 (F1), 4.61 (F2), and 5.19 kcal.g.mol-¹(F3), which match the data in the literature for juices and nectars.
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