Yeast flocculation: factors affecting the measurement of flocculence.

The physical meaning of the residual absorbance of a yeast suspension after flocculation and settling has been investigated. Starting with a dispersed suspension, agitation accelerates flocculation by increasing the probability of collision between particles. As flocculation advances, agitation also breaks the flocs. A stationary state is reached when flocculence (tendency to flocculate) is counterpoised by agitation. If the intensity of agitation is maintained constant, the free cell concentration reflects the flocculence, provided the stationary state is reached. The residual absorbance, determined after settling of the flocs, is a measure of the free cell concentration and represents an adequate parameter to characterize yeast flocculence.