A method for controlling microbiological contamination in a heat exchanger while using the heat exchanger to process a food product. The method includes: while processing the food product in the heat exchanger, adding a microbiological control agent to the food product at a first location; and neutralizing at least partially the microbiological control agent by adding a neutralizing agent to the food product at a second location, the second location being downstream from the first location, at least part of the heat exchanger being between the first and second locations, the neutralizing agent being operative for reducing a chemical reactivity of the microbiological control agent in the food product. The microbiological control agent controls the microbiological contamination in the heat exchanger while the food product is processed. In some embodiments, the food product is a milk product.