Abstract: A method for reducing the viability of bacterial cells is disclosed. Further, a two-stage process of hypo-osmotic shock is used by exposing cells to a first solution having a water activity (a.sub.w) of 0.997 or less. In addition after the first step the cells are further exposed to a solution of a higher a.sub.w that the first solution. The solutions are applied to the cells in the form of a spray or by immersion. The solutions are applied to the bacterial cells between 5 seconds and 30 minutes to obtain a reduction in the viability of the cells being treated of which are additionally treated with a solution of lysozyme contained in the solutions or to a cold shock treatment step. The cold shock treatment is applied by exposing the cells to a temperature in an aqueous liquid at 10.degree. C. or less.