Avaliação do processo de obtenção da cajuína por resinas de troca iônica

Abstract

The cajuína is a refreshing drink, very consumed and appreciated because of its characteristic flavor, which is slightly astringent, free of turbidity due to the low level or absence of tannins, obtained from the cashew apple. Traditionally, the tannins are removed by non-standardized and/or rudimentary techniques, thus reducing the quality of the final product. Thus, this study aimed to remove the cashew apple juice tannins through the ion exchange process for obtaining the clarified cashew apple juice (cajuína). For that, two strong base resins were used, and a macroporous and other gel type. Equilibrium studies were carried out in batch and from them were evaluated operating parameters: temperature (25 to 50 °C), the resin ratio:juice (1:3, 1:6 and 1:9), stirring speed (50 and 122 rpm), maintaining the contact time constant. Based on the results, the optimized conditions were observed and from that heat treatment was conducted to obtain the cajuína. Were carried out physical and chemical analysis (pH, acidity, soluble solids - SST) as well as analysis of thermal and rheological properties of cajuína and other products from cashew (nectar and pulp). Studies in fixed bed (continuous system) were also performed using two systems: standard solution (catechin + vitamin C + sucrose) and cashew apple juice. The modeling of the process has been carried out using Langmuir, Freundlich, Sips, Toth and Radke-Prausnitz models. The experimental results showed that the macroporous anionic resin presented a removal of tannins around 80% in optimal conditions (30 °C, 1:6, 122 rpm, 1 h). The cajuína obtained after the ion exchange process was clear and translucent, with low astringency, acidity and soluble solids (°Brix), according to Brazilian legislation. The physicochemical characterization for cajuína, nectar and cashew pulp presented in accordance with Brazilian legislation. For the thermal properties, the cajuína showed lower density (ρ = 1.035 ± 0.005 g / cm3), and higher thermal conductivity values (k = 0.58 ± 0.02 W/m °C), thermal diffusivity (α = 1.44 ± 0.02 × 10 -7 m2/s) and specific heat (Cp = 3834 ± 109 kJ/kg °C) when compared with the other cashew products. Rheological studies showed that cajuína behaved like a non-Newtonian fluid and presented a dilatant behavior at all tested temperatures, and that the Ostwald-de-Waelle model was the best fit to the experimental data for cajuína. Through the fixed bed of studies it was observed that vitamin C and sucrose showed no influence on the removal of catechin by macroporous resin. Regarding the cashew apple juice, even if these juices have shown differences in the amount of initial tannins, juice 1 (15 ± 1 mg/100g) and juice 2 (115 ± 1 mg/100 g) before passing through the fixed bed, the results showed that it is possible to obtain a completely clarified juice with the process of ion exchange column, presenting itself as a good alternative for obtaining the cajuína. Among the models evaluated, Sips, Freundlich and Radke-Prausnitz presented the best fitting with high R2 (0.9999; 0.9982; 0.9979, respectively), the Sips model presented the best fit to the experimental data. Thus, it was observed that the use of ion exchange resin strong base macroporous proved to be viable, being an important alternative for the production of cajuína.