To provide a lee-precipitator having rapid lee-precipitation rate of fermented liquid food and capable of shortening the period of time required in coagulating, precipitating and separating protein turbid materials.

This lee-precipitator is in the form of a sol in which silica microparticles having a specified zeta-potential at pH 4-6 are dispersed, in view of the fact that the zeta-potential of the silica microparticles dispersed in a sol is varied depending on the pH of the sol and the pH of a fermented liquid fluid food is normally 4-6. For effectively acting as a lee-precipitator, the silica sol must have negative zeta-potential of ≥3.5 mV absolute value. The above-mentioned silica microparticles may contain metal compound(s) such as alumina, iron oxide, titania and/or zirconia.