Résumé
This work aimed to characterize the impact of high shear rate generated by crossflow microfiltration on the particles size, the rheological behavior and the overall fouling propensity of fruit juices. To this end, two orange juices, with different characteristics, were circulated during a defined duration (until 120 min) under a high shear rate (22,270 s−1) in a side-stream membrane unit, without filtration. Results showed that this shearing condition was likely to induce significant changes concerning at the same time the particles size distribution (with a possible particles fractionation) and the rheological properties of the fruit juices (with a potential increase of energy of cohesion between the particles). The fouling propensity of the juices, estimated through lab-scale filtration test, was also modified by the shear rate, showing that new foulant components could be released during the circulation in the filtration loop.
Crossflow microfiltration is successfully applied to stabilize and clarify fruit juices or to concentrate their pulpy fraction. This work aimed to characterize for the first time the impact of high shear rate applied during crossflow microfiltration on the particles size distribution, the rheological behavior and the overall fouling propensity of fruit juices. This work showed for the first time that it is important to consider the impact of high shear rates on the particles size fractionation and the release of foulant compounds when carrying-out fruit juices microfiltration under high crossflow velocities. Crossflow microfiltration of fruit juices under high crossflow velocity may not be, in some cases, the most appropriate strategy to reduce membrane fouling. According to the juice characteristics, specific industrial strategies such as enzymatic treatment or mechanical actions (e.g. back-pulsing) would be more useful than crossflow velocity to enhance the overall performance of microfiltration.
•A fractionation of juice particles can take place when applying a high shear rate.•The energy of cohesion between insoluble particles is modified due to high shear rate.•The fouling propensity of orange juices can be increased under high shear rate.•Microfiltration under high shear rate may not be efficient to reduce membrane fouling.