Estudo do desempenho do processo de microfiltração tangencial com membranas cerâmicas aplicado à retenção de bactérias e redução de sólidos suspensos de uma bebida à base de açaí / Performance study of the crossflow microfiltration process with ceramic membranes applied to the bacteria retention and suspended solids reduction of the beverage based on açai

AUTOR(ES)

Renata Natsumi Haneda

DATA DE PUBLICAÇÃO

2010

RESUMO

In this doctoral research, the crossflow microfiltration process utilizing ceramic membranes was investigated aiming at the bacteria retention (Escherichia coli) and reduction of suspended solids of beverage based on açai (Euterpe oleracea Mart.). The selected commercial membranes of alfa-alumina (AL IND.2O IND.3) had nominal pore sizes of 0.8 and 1.2 müm and were manufactured by Andritz Group from Austria. The membrane nominal value of 1.2müm is larger than the width of the Escherichia coli (0.8müm). Therefore, as the microrganisms are subjected to pass through the pores of this membrane, it was submitted to silver impregnation. This procedure aimed to verify the silver influence as a bactericide material to assist in retention or elimination of bacteria during the microfiltration process. In this way, the microporous structure was chemically treated with a silver citrate solution and then, subjected to burning until 600 Celsius degrees to eliminate organic compounds and consequent impregnation of nanoparticles of metallic silver in the membrane pores. The morphology characterization, composition, and impregnation of silver in membranes were analyzed by Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray fluorescence (EDX) spectrometer. The same techniques were utilized to characterize the physicochemical phenomenon of polarization layer formation on the membrane surface. The analysis of bacteria retention was performed by the counting of colony forming units (CFU/mL) in Petrifilm Plates EC POT.TM. The performance of the membranes in the retention of solids in suspension was analyzed by Ultrasound Spectroscopy - APS100 and Optical Microscopy. The variations of the anthocyanin concentration and the total polyphenol content were investigated by spectrophotometry, showing direct relationship with the membrane pore size and flow regime. Therefore, fluid-dynamical parameters, such as Reynolds number, transmembrane pressure, and permeate flux were characterized for a large range of turbulent flow and analyzed with the resistance-in-series model. The experimental results of this research indicated that the microfiltration process is a suitable alternative to retain microrganisms and simultaneously decrease suspended solids of the beverage based on açai.

ASSUNTO(S)

bebida à base de açaí beverage based on açaí cake layer camada polarizada ceramic membrane membrana cerâmica microfiltração microfiltration prata silver

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