Development of a 'millimanipulation' device to study the removal of soft solid fouling layers from solid substrates and its application to cooked lard deposits

A mm-scale scraping device was developed to study the removal behaviour of soft solid fouling layers (thickness 0.5-10 mm) from solid substrates. A blade is dragged through the circular or rectangular samples at controlled speed and the resistance forces measured. Tests with a viscous liquid (honey) and viscoplastic material (a Vaseline®-carbon black paste) indicated that cohesive deformation dominated the measured force. Two model food soils were: (i) unbaked lard and (ii) lard baked for different times with and without added ovalbumin. The cohesive strength of the baked lard, and its removal behaviour, changed noticeably following autoxidative polymerisation. Ovalbumin delayed the onset of polymerisation.