Enhanced cleaning of whey protein soils using pulsed flows

Enhancement of alkali-based cleaning-in-place (CIP) of whey protein deposits by flow pulsing was investigated using low frequency (≤2 Hz) fluid pulses with amplitudes an order of magnitude greater than the steady flow velocity. Flow pulses were generated using (i) a bellows unit and (ii) a piston device. The effect of pulsing was studied at a steady flow Reynolds number of 580, where pulsing at 2 Hz was found to increase heat transfer by up to 100%. Whey protein deposits were generated in a tubular heat exchanger and cleaned using 0.5 wt% NaOH at 50 °C. Enhancement of cleaning rates varied up to 250% and depended on the initial amount of deposit present, the pulsing frequency and pulse amplitude. The increase in cleaning rate was most sensitive to the difference in pulse and steady flow velocities and the presence of reverse flow. Simultaneous protein removal and heat transfer resistance measurements showed that flow pulsing strongly affected the cleaning behaviour after the initial deposit swelling stage, breaking down the swollen deposit matrix by some fatigue mechanism.