Reduction of solids by liquid cyclones as an aid to clarification in apple juice processing

The final step in apple juice clarification is normally carried out by pressure filtration. Since most pressure filters operate in a discontinuous manner, a reduction of suspended solids in the unclarified juice would be expected to improve filter performance. Hydrocyclones could be used prior to filtration in order to increase removal efficiency or could be employed as an alternative to high cost centrifugation, when only a partial clarification was required. The suspended solids removal capability of a conventional hydrocyclone was explored. A small diameter unit (25.4 mm) following Rietema's proportions, at two pressure drops (300 and 500 kPa), two concentrations (5 and 8% by volume), and two different conditions (with and without anti-foaming agent), was used in this work. Results indicate that hydrocyclones may be an attractive option for separation of suspended solids from apple juice. At high pressure drop, combined with anti-foaming addition, suspended solids reductions of approximately 40% were obtained. In addition, a derived dimensionless scaleup relationship showed good agreement with values reported in the literature.