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

https://doi.org/10.1016/j.jfoodeng.2012.06.022Get rights and content
Under an Elsevier user license
open access

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 500 mg kg−1 of açaí pulp for 30 min 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 0.2 μm and 0.8 μm pore sizes, and 0.0047 m2 of filtration area. The microfiltration unit was operated in batch mode for 120 min at 25 °C and the fluid-dynamic conditions were transmembrane pressure of ΔP = 100 kPa and cross-flow velocity of 3 m s−1 in turbulent flow.

The highest values of permeate flux and accumulated permeate volume were obtained using enzyme-treated pulp and 0.2 μm pore size membranes with steady flux values exceeding 100 L h−1 m−2. For the 0.8 μm 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 0.2 μm pore size membrane, it was 18%. Cake filtration was the dominant mechanism in the early stages of most of the CFMF processes. After approximately 20 min, 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.

Highlights

► Enzymatic treatment of açaí pulp examined in terms of permeate flux decay and recovery of phytochemicals. ► Analyses of fouling through resistance in series and blocking in law models. ► Recovery of phytochemicals evaluated by total polyphenols and antioxidant capacity analysis. ► Positive effect of pectin lyase on the cross-flow microfiltration of açaí pulp.

Keywords

Microfiltration
Açaí pulp
Enzymatic treatment
Polyphenols
Antioxidant capacity

Cited by (0)