Centrifugation as pretreatment before ultrafiltration of hemicelluloses extracted from wheat bran

• Ultrafiltration of a solution containing hemicelluloses from wheat bran was studied.
• The influence of centrifugation on ultrafiltration performance was investigated.
• Centrifugation does not reduce the influence of fouling substances.
• Combining centrifugation and dead-end filtration improves ultrafiltration flux.
• Centrifugation reduces filtration resistance during dead-end filtration.

Hemicelluloses recovered by alkaline extraction of wheat bran can be isolated and purified by ultrafiltration and used to produce high-value products such as barrier films for food packaging. The flux during ultrafiltration depends to a large extent on the pretreatment of the solution. It has been shown previously that dead-end filtration with kieselguhr can increase the flux during ultrafiltration. In the present study, pretreatment by centrifugation and a combination of centrifugation and dead-end filtration was compared with dead-end filtration alone. Centrifugation reduced the turbidity and viscosity of the solution but did not significantly improve the flux during ultrafiltration. The flux of the untreated and the centrifuged solutions was about 65 l/m2 h at 1 bar transmembrane pressure. The flux after dead-end filtration was 150 l/m2 h. After combining centrifugation and dead-end filtration the flux was 200 l/m2 h. In addition to the higher UF flux, filtration resistance during dead-end filtration was markedly reduced after pre-centrifugation of the solution.