Abstract: Systems and methods are provided for pasteurizing milk or other fluids, and for cleaning and disinfecting processing passageways prior to and after the milk processing. The disclosed pasteurization systems and methods have very low impact on the characteristics of raw, unpasteurized milk (e.g., texture, flavor, and/or nutritional value). For example, some systems and methods utilize a pump that operates at a very low flow rate (e.g., about 1 gallon per minute (GPM)) to prevent mechanical adulteration of the raw milk. Disclosed systems and methods for cleaning and disinfecting the fluid passageways also utilize a low-flow rate, and can use the same low flow pump that is utilized during pasteurization. A pressure pulser allows pressure to build up within the fluid passageways despite the low flow, and then releases the pressure to purge air from the passageways and to cause their interior surfaces to contact the cleaning fluid.