Effect of ultrasound on different mechanisms of fouling during membrane clarification of pomegranate juice

•Ultrasound decreases the intensity of cake formation in membrane clarification.•Ultrasound decreases the cake thickness during membrane clarification.•Ultrasound increases standard blocking during membrane clarification.

Membrane processing is necessary to clarify turbid pomegranate juice. One of the most important limitations against industrialized use of membrane clarification is the fouling phenomenon. Ultrasound was applied to reduce membrane fouling and the effect of elevated temperatures was removed from the effect of ultrasonic treatment to evaluate the effect of ultrasound waves itself. Results showed that cake formation is a dominant mechanism in both ultrasonic treatment and non-ultrasonic one; however, the intensity of cake formation in the membrane process in the absence of ultrasound waves was much more than its value in the presence of ultrasound. SEM images showed that the cake layer thickness in the membrane process in ultrasonic bath was about 1.5 μm that increased to about 6 μm in the absence of ultrasonic waves.Industrial relevancePomegranate juice can be clarified by membrane filtration. Membrane fouling limits its industrial application; therefore, ultrasonic treatment was used to reduce this problem. Results showed that ultrasound waves can reduce cake layer thickness. Hence, it can increase the industrial capability of membrane process to clarify pomegranate juice.