The invention is directed to a fermented and clarified nisin-containing whey and a method of making that can be used to produce a stabilized food product by adding, for example, to the pack water of fresh mozzarella cheese. The resulting stabilized food product retards or limits below detection levels the growth of toxins from pathogenic bacterial contaminants when the nisin-containing whey is added in amounts between about 10 to about 30% to the food product. The stabilized food product improves the safety of the food by retarding the growth of Listeria monocytogenes and improves the shelf life of the product by retarding the growth of gas forming bacteria such as bacteria from the Leuconostoc species.