havebeendevelopedto removelayersof deposit at millimetre level(Liuet al.,
2002).Theforce required to disrupta surfacefilmcan be determined by
drawing a probeacross the film, and the effectivenessof removalfollowedboth
by filming the processand examiningthe surfaceafterward. The methodwas
developedto studybiofilms (Chenet al., 1998),but has beenextendedto study
foods.
The forcerequired to removethe deposit is measured by drawing the micro-
manipulationprobeacross the surface of the deposit. The apparentadhesive
strength of a fouling sample,(J/m^2 ), definedas the workrequired to remove
the sample per unit area, is given by
Fig. 29.3 Comparisonof the energyrequiredfor partialand totalremovalof depositsof
(a) bakedtomatopaste;(b) milkproteins(Liuet al., 2005).
484 Handbookof hygiene controlin the foodindustry