All costs were calculated per litre of permeate juice,
taking into account the raw material, investment, energy
and average labour costs. Costs of raw material and
enzymatic preparation were estimated at, respectively,
US$ 0.50 per litre for passion fruit and US$ 100 per litre
of Rapidase Pomaliq 2F. Investment costs were evaluated
at US$ 10 000 per square metre of tubular ceramic
membrane installed and the depreciation period was
assumed to be 3 years (about 6000 h of processing, not
including cleaning cycles). Energy consumption was
calculated on the basis of 3 kWh for each square metre
of membrane installed, considering that the pumps must
move the retentate through the tubular membrane system
at a cross¯ow velocity of 7 m sÿ1. An average price
per kWh of US$ 0.20 was assumed. Labour costs were
estimated at 0.1 man hour per square metre and US$
3.00 per man ho