Juice Membrane Filtration Flux Keeps Dropping? It Is Not Damaged Membranes, But Poor Pretreatment

Many juice processors face a common issue: membrane systems run well at the start, but flux gradually falls after hours of operation. Many operators assume membrane elements are broken and replace them directly. In fact, over 70% of such flux loss comes from improper pretreatment instead of defective membranes. Blind membrane replacement only raises operating costs.

Pectin, fine pulp fibers, starch and polyphenol‑protein complexes in raw juice are major fouling sources. Pectin forms dense gel layers on membrane surfaces under pressure, causing fast flux decay that simple CIP cleaning cannot fully remove.

Common pretreatment mistakes

1. Skip enzymatic hydrolysis and only use crude filtration. Soluble pectin remains in juice and pollutes membranes rapidly.

2. Wrong security filter precision, leading to either particle leakage or frequent filter clogging.

3. Remove centrifugation to save budget, letting membranes bear heavy solid‑liquid separation load.

4. Keep fixed pretreatment parameters regardless of seasonal raw‑material quality changes.

Recommended pretreatment workflow

1. Enzymatic hydrolysis with pectinase to decompose pectin and lower juice viscosity.

2. Centrifuge or plate‑frame filtration to remove bulk pulp residues.

3. Two‑stage security filtration to protect downstream membrane elements.

Quick on‑site troubleshooting

When flux drops, do not rush to change membranes.

1. Check enzymatic hydrolysis conditions and security filter status.

2. Test raw juice turbidity and viscosity.

3. Run full standard CIP cleaning. If flux recovers after cleaning: optimize pretreatment.