Tips to avoid Thermoduric grades over summer

24 Nov 2023

There is a range of visual inspections you can do to reduce the occurrence of Thermoduric grades. By doing these checks regularly, particularly during warmer months, you can catch issues quickly and increase your chances of grade-free milking.

What are Thermoduric grades?

Thermoduric bacteria (Thermo; meaning heat and duric; meaning to endure) are heat resistant and can survive pasteurisation.

There are two types of Thermoduric bacteria: environmental and hygiene. Environmental Thermoduric contamination is usually from poor-quality silage and will be indicated on your milk docket as spores. The hygiene type is found in your milking machine.

Thermodurics are normally the result of fat and protein buildup, aged milk soil or perished rubberware. Normally they would be outcompeted by other bacteria, however, they thrive in the milking system where we use hot water to kill off their competition. They are also tricky to detect because they do not smell.

Inspecting your plant:

• Jetter system: if the jetter valve is rubber, look for leaks or excessive wear and check that all unions are tight. Check rubber boots for splits, cracks in the plastic or any loose jetters onthe jetter line.

• Milk line: This is the most common place for Thermoduric bacteria to grow. Open each end and use a torch to see if there’s any dull buildup along the top of the milk line.

• Milk inlet pipe: remove the stainless-steel milk inlet pipe into the primary cooler. Use a torch to see if there is any debris, grass, or hair. If there is, we suggest you get your service agent to take apart as plate coolers are not always easy to put back together.

• Milk collection vat: if the milk silo is bottom entry, remove the taps and manually clean them. Also clean the inlet hole.

• Start up the plant: plug in the jetters, fit a new filter sock and start recirculating cold water. Wander back past each jetter and check the flow rates - a slow jetter may suggest a blockage, you may hear an air leak, or spot one that needs adjusting.

• Flushing pulsator: is it working at a minimum of 3 times and a maximum of 5 times per minute? Is the milk pump with the cold water recirculating (if it is on a controller) at full speed for at least 70% of the time? If not, the milk pump is not being fully utilised during the wash.

• Clusters/bowls: these should be opened and allowed to dry to look for protein buildup. Poor water flow when being washed will cause issues, so as a hot wash is being put through the plant, it’s suggested you visibly inspect each cluster.

• Milk pump: if it is a diaphragm type, check there are no unions on the manifolds that are leaking or weeping, as milk can get into these areas and cause a problem.

• Rubberware: check each cluster and have a look inside the claw. Run your finger around the inside of the liner lip to check for a deposit that may indicate a problem with the corresponding jetter. Inspect the rubber tube under any snap clamps as well as the tubes on flushing pulsators.

Inspecting your bulk milk collection vat

The milk vat is classified as a confined space and should never be entered - visual inspections must take place from the outside using a torch. When inspecting stainless steel, it is always better to inspect a dry surface, but we understand with night milk collections this is not possible.

• Check and clean the cleaning-in-place spray ball. With large milk silos, this is done by unscrewing the large 100mm nut on top and lifting out the spray ball. Because of the height, you may require a safety harness, or hire someone trained to work at height to do the job.

• If the spray ball is the spinning type, check the nylon that it spins on - these wear over time and the spray ball will eventually fall into the milk (it does happen!).

• Check the walls - if one area is dirty there may be a blockage in the spray ball.

• If it is dirty under the door, this may indicate the door needs to be periodically removed so it cannot cause a shadow behind and below it. Also check the interior door surface as this area also can get missed when washing occurs. Don’t forget to check the door seal itself.

• Check the inlet wash valve is working correctly by looking through the door with a torch to see the wash solution squirting out of the inlet pipe.

• Touch the non-return valve to check it is heating properly.

• Check the outlet valves (or donut if the bulk milk tank is old). Ensure they are clean and that the seals do not need replacing.

• If setup for recirculation, check the taps at the pump. If they leak the pump will suck air into the wash solution, causing cavitation that reduces the pressure at the spray ball, lessening the effectiveness of the cleaning solution.

Resolving Thermoduric grades:

It’s crucial to identify the cause of fat and protein buildup and replace any worn or damaged components that may be contributing to the issue.

A good way to properly remove buildup is to put through a hot water chlorinated alkali wash using FIL Quantum Powder alkali detergent with FIL C3 chlorinated cleaning chemical. Alkalis are designed to remove any fat and protein and are an important part of the cleaning process. Furthermore, the caustic soda removes fat and the chlorine fractionates protein deposits.

Start pre-heating the plant with hot water at 80ºC-85ºC and discard the returning cooler water. Once the returning water reaches 80ºC-85ºC, start recirculating the hot water while adding twice the amount of alkali you would normally use. Recirculate for five to seven minutes and dump at around 55ºC.

Tip: When thermoduric levels are elevated, perform a daily alkali wash to remove the food source (fat and protein). This should lower the thermoduric levels to a non-grading status while you look for the cause.

Need a hand? Your local FIL Area Manager is trained to help you combat Theromoduric grades and find a cleaning routine that works for your plant.