Liquid ‘hold-up’ on stainless steel surfaces: I — Effect of surface finish

The effect of stainless steel surface finish on the ‘hold-up’ of a representative food liquid (sucrose solution) was studied for drainage angles between 0·46° and 3·7°. Surface finish was found to have a significant effect on ‘hold-up’, but no correlation was found between the Ra value and ‘hold-up’.An explanation of the results is proposed based on the effect of the nature of surface roughness rather than its magnitude (as measured by the Ra value) on wetting and contact angle.The orientation of grain direction had only a small effect on ‘hold-up’ and was dependent on the surface finish.It is suggested that electro-polishing may give the most cost-effective finish for stainless steel food contact surfaces. Drainage angle was found to have a considerable effect on ‘hold-up’ and it is recommended that the minimum drainage angle for food plant should be 2°.