First, prepared is a whey degradation medium to which a protease, yeast extract, and the like are added. Further, polyoxyethylene sorbitan monooleate or propylene glycol monooleate is added to the whey degradation medium. The whey degradation medium is inoculated with bacteriocin-producing lactic acid bacterium and the lactic acid bacterium is cultured while the whey degradation medium is maintained at pH of 4 to 5. After the completion of the culture, the whey degradation medium (culture solution) is centrifuged to thereby separate therefrom a concentrated cell suspension containing the lactic acid bacterium in a concentrated form. The concentrated cell suspension has very low antibacterial activity (several tens AU or less). Then, by adding the concentrated cell suspension to a yogurt mix and fermenting the same, it is possible to produce yogurt containing the bacteriocin-producing lactic acid bacterium without any delay in the fermentation.
