Effect of enzymatic treatment on the cross-flow microfiltration of açaí pulp: Analysis of the fouling and recovery of phytochemicals

Abstract

This study aimed to investigate the effects of pectinase enzyme treatment of açaí pulp on cross-flow microfiltration (CFMF) performance and on phytochemical and functional characteristics of their compounds. Analyses of fouling mechanisms were carried out through resistance in series and blocking in law models.The enzymatic treatment was conducted using Ultrazym® AFPL (Novozymes A/S) at 500mgkg−1 of açaí pulp for 30min at 35°C. Before microfiltrations, untreated and enzyme-treated açaí pulps were previously diluted in distilled water (1:3; w/v).CFMFs were conducted using commercial α-alumina (α-Al2O3) ceramic membranes (Andritz AG, Austria) of 0.2μm and 0.8μm pore sizes, and 0.0047m2 of filtration area. The microfiltration unit was operated in batch mode for 120min at 25°C and the fluid-dynamic conditions were transmembrane pressure of ΔP=100kPa and cross-flow velocity of 3ms−1 in turbulent flow.The highest values of permeate flux and accumulated permeate volume were obtained using enzyme-treated pulp and 0.2μm pore size membranes with steady flux values exceeding 100Lh−1m−2. For the 0.8μm pore size membrane, the estimated total resistance after the microfiltration of enzyme-treated açaí pulp was 21% lower than the untreated pulp, and for the 0.2μm pore size membrane, it was 18%. Cake filtration was the dominant mechanism in the early stages of most of the CFMF processes. After approximately 20min, however, intermediate pore blocking and complete pore blocking contributed to the overall fouling mechanisms.The reduction of the antioxidant capacity of the permeates obtained after microfiltration of the enzyme-treated pulp was higher (p<0.01) than that obtained using untreated pulp. For total polyphenols, on the contrary, the permeates obtained after microfiltration of the enzyme-treated pulp showed a lower mean reduction (p<0.01) than those from the untreated pulp. The results show that the enzymatic treatment had a positive effect on the CFMF process of açaí pulp.