Purification and Concentration of Betalaines by Ultrafiltration and Reverse Osmosis

Abstract

ABSTRACT Beet juices prepared by solid‐liquid extractions were processed by ultrafiltration (UF) and reverse osmosis (RO) to 30°Brix at 20°C. De Danske Sukkerfabrikker (DDS) UF/RO Lab Module‐20 plate‐and‐frame system was used having a 0.72‐m 2 effective membrane area and pressures from 50‐40 bar. After prefiltering, pectinase treated juices were sequentially processed through 20,000 and 6,000 (UF) molecular weight (MW) cut‐off membranes. The UF purified products were then concentrated by RO processes on several types of cellulose acetate (CA) membranes, one with a 500 MW cut‐off and 70% NaCl permeability provided colorants that were separated from a majority of soluble solids. Addition of invertase to pectinase‐treated juices decreased flux but yielded a three‐fold increase in betalaine concentration on a dry weight basis. Betalaine concentration by UF and RO processes also halved nitrate level and greatly reduced flavor.