Study On Ultrafiltration Technology For Cleaning Applle Juice

Membrane separation, emerged some 20 years ago, has developed at a quick pace. Since it does not require heating, it will not result in transformation of the processed matters, can save energy and reserve the original characteristics of the matter. It is therefore extensively used in food processing industry, particularly in juice clarification.In consideration of the requirements for juice clarification, a hyperfiltration system is developed with a dual-circulation structure. The entirely new structure allows separate control over flow and pressure and has an improved performance. Through single factor and multi factor experiment on the basic operating parameters of the ultrafilter, the relationships between operating pressure, flow rate of slurry and temperature and separating capacity (permeation rate) has been determined. The permeation rate of membrane will increase with pressure, velocity and temperature. The maximum permeation rate arrives at 63 L/m2h, a higher level by national standard. To solve the problem of concentration polarization, the membrane module structure was carefully selected, the fruit juice properly treated (by removal of macromolecular substance such as pectine), the working parameter during hyperfiltration optimized, and reasonable purging method and criteria established, resulting in reducing concentration polarization. The working performance of membrane was effectively maintained and the up-time prolonged. The normal purging interval is between 20 and 24 hours.The clear juice obtained with ultrafiltration well preserves its nutritional value and flavor. It has a clear and transparent appearance, with hygienical indicators at or over the specifications stipulated by the corresponding national standards. By the addition of antioxidant and preservative and the adoption of aseptic package, the shelf life is as long as 180 days.