Abstract: The invention relates to a process of preparing concentrated bacterial cultures for direct vat inoculation of milk batches in which harmless lactic acid-producing bacteria are cultured in an aqueous medium including fermentation nutrients to obtain a fermented aqueous culture of the bacteria cells together with residual nutrients including casein, whereby the bacteria cells are recovered and concentrated by subjecting the bacterial culture to centrifugation while having dissolved therein prior to or after fermentation a combination of from 0.05% to 0.20% based on the weight of the culture of a water--soluble food--acceptable polyphosphate salt selected from the class consisting of tripolyphosphate and hexametaphosphate containing from 4 to 22 phosphate groups per molecule and from 0.25% to 0.50% based on the weight of the culture of a water--soluble food--acceptable citrate salt.