5 Steps to Check if Your Pasteurizer is Doing the Job it Needs to Do

By Ann Hoskins, Vita Plus calf products coordinator
Pasteurization is not sterilization.  When a pasteurizer is working properly, it will destroy 98% to 99% of bacteria.  Successful pasteurization occurs when the standard plate count (SPC) is less than 20,000 colony forming units (cfu) per mL.

Step 1 – Start with the cleanest milk possible.  Make sure all milk harvesting equipment is clean.  In systems where clean-in-place (CIP) is available, make sure the system is actually cleaning.  It should be on a maintenance schedule that follows the current milking system.

When using catch pails or other methods to collect milk, make sure those items are cleaned and sanitized according to calf equipment cleaning protocols.  If you start with milk with high bacteria counts, then the result will be pasteurized milk with high bacteria counts.

Step 2 – Make sure the machine is properly programmed to do what you want it to do.  Check those settings monthly.  Things happen – incorrect buttons get pushed and timing gets thrown off.  If protocols or routines change on the farm, adjust the pasteurizer to meet your needs.  For example, batch pasteurizers need a set amount of time to properly pasteurize.  If you move your feeding times, you need to allow the pasteurizer to do its job because you don’t want milk to sit at feeding temperature for long periods of time.

Batch pasteurizers consist of a tank with a heating element or jacket that heats milk to 145 degrees F and maintains this temperature for 30 minutes.  Milk is agitated to eliminate cold spots and ensure the milk reaches and remains at 145 degrees F for 30 minutes. These machines typically cost less, but they require manual cleaning.

HTST (high-temp-short-time) pasteurizers heat the milk and then cool it for feeding or further storage.  To achieve pasteurization, milk must reach 161 degrees F for 15 seconds.  These systems can do larger volumes of milk in a much shorter time period.  They are set up with CIP units, similar to your milking systems.  It takes a large volume of milk for them to work well.  These units require milk to be chilled at the start, so they require a chilled milk storage tank for unpasteurized milk.

Step 3 – Use a thermometer to check if the pasteurizer is working.  I suggest picking up a good digital thermometer to have dedicated to the milk system.

In a batch system, check temperatures as the machine is pasteurizing.  Verify timing and temperature readings.  Good meat thermometers are available that will catalog temperatures along the process.  This is an easy way to make sure the internal thermometer is working.

With HTST machines, testing internal temperatures is not an option because they are closed-loop systems.  You can, however, check output temperatures to make sure that sensor is working.  It is important for the milk entering these machines to be chilled and agitated.  Agitation is important to avoid milk fat separation.

Step 4 – Keep it clean!  After pasteurization is done, rinse both types of units immediately.  Do not let milk sit in them and come back to clean it later.  Read and follow the directions in the unit’s manual or talk with your equipment dealer.  Most batch pasteurizers are cleaned manually with a water rinse, followed by alkaline detergent and an acid rinse.  HTST units are often CIP.

When pasteurization is complete, immediately flush the system with water until the water runs clear.  Follow the manufacturer’s cleaning protocols to ensure a thorough cleaning.  In a more automated system, I like to mark chemical jars and barrels to make sure it is using chemicals at a consistent rate.

Step 5 – Check the milk!  Take samples and send them into your designated milk lab.  Samples should be taken pre- and post-pasteurization, and at the last calf fed.  These are three critical points to assure you have good pasteurization and to determine how much regrowth occurs during the process.  This also helps you check if any equipment is dirty.  I suggest sending samples in for testing on a weekly basis until you have a good database, and then continue monthly.

Quality goals for pasteurized samples are SPC less than 20,000 cfu per mL and coliform less than 10 cfu per mL.

Talk with your local calf specialist to follow up with an ATP meter to check surfaces for biofilms that may be missed.

A pasteurizer, like every other piece of equipment, needs to be maintained and checked for quality.  It is better to find a problem before the calves tell you the milk is not right.  Signs to look for include not drinking, head bobbing or a “weird scour” at all ages.  These are typical signs that you need to go back and check things.

A well-running, clean pasteurizer will help on the path to healthy calves.