Apple juice extraction in a counter‐current diffuser

Abstract

SummaryMeasurements have been carried out on an industrial diffuser for the extraction of apple juice. Concentration profiles in the free juice and in the juice contained in the apple slices were measured at various temperatures and counter‐current flow rates. The data can be described by a theoretical model taking into account the time of plasmolysis as a function of temperature. Below around 58°C, the concentration profiles break into two parts—before and after plasmolysis—and the diffuser yield is lowered. The yield is also lowered if the water‐to‐apple volume ratio is not kept well above unity. Under optimal conditions it is possible to obtain an overall recovery of soluble matter from apple stock to final juice which is above 90%. The axial dispersion coefficient (‘eddy diffusion coefficient’) of the apple slices was also measured. At a mean speed of apple slices through the diffuser of about 0.06 m/min (holding time = 120 min), the axial dispersion coefficient was around 0.01 m2/min.