The most important influencing variables include: Type of juice to be filtered, process temperature, sugar content (measured in °Brix), and filter aids used.
Here, during cross-flow filtration using ultrafiltration modules, the rule of thumb is: the higher the sugar content, the lower the expected flow rate. In addition, the achievable flow rates also tend to be higher for light-colored juices (with the exception of juices from citrus fruits such as lemons or limes) – dark juices, although filtered more “openly” for the purpose of color retention, tend to be at the lower end of the scale here.
A practical example is the clear filtration of (raw) apple juice, which must first undergo enzymatic pretreatment and be depectinized before ultrafiltration. The process temperature during UF should be approx. 50 °C with a sugar content between approx. 10 and max. 20 °Brix. Usually the Brix is adjusted between 13° and 14° to allow constant high flow rates > 90 l/m²h. A reduction or increase in the sugar content here has a direct effect on the achievable flow rate, so that in the best case up to 120 l/m²h are possible.
Our application experts have rich experience in ultra- and microfiltration of various fruit juices. Please contact us, we are looking forward to your project!