Improvement in separation characteristics of protein precipitates by acoustic conditioning

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Abstract
The effect of acoustic conditioning on the particle size distribution of isoelectric and calcium‐ion‐precipitated soya protein has been examined in low‐residence‐time chambers. In a previous study a beat frequency of 5 Hz obtained using a dual‐source system of opposing vibrators was determined as giving optimal improvement in particle‐settling characteristics for isoelectric soya protein precipitate. In this study the effect of amplitude of vibration, a measure of acoustic power input, and residence time of acoustic conditioning has been examined. Acoustic power input changed the flow pattern in the conditioning chamber from laminar streamline flow to a well‐mixed, turbulent pattern. Such a mixing effect promoted the rapid aggregation of fine particles, a process that was modeled on the basis of orthokinetically controlled collisions. The rate of removal of fine particles due to acoustic conditioning was shown to be proportional to a mixing effect that was releated to the acoustic power dissipated per unit volume. The consequences of fine‐particle aggregation on the centrifugal recovery of the precipitate are discussed.