Checking Temperatures to Stay Out of Hot Water

The most common reason for producers running into quality problems can be related to milking equipment cleaning. In order to provide high quality milk to the marketplace a pipeline milking system must clean up perfectly after each milking. The four basics of cleaning are time, temperature, chemical concentration and physical action. Of these four important factors in each cycle of a clean-in-place (CIP) system, failure to maintain proper temperatures is probably the biggest culprit when it comes to cleaning problems.

Step 1- Pre-rinse cycle

The pre-rinse removes 90 to 95% of milk solids and warms up the milk lines, which will help maintain temperature in the wash cycle. Water temperature should start at 43°C to 60°C (110°F to 140°F). If water temperature drops below 38°C (100°F) milk fat will solidify back onto the milk line. Likewise, too high a pre-rinse temperature can bake on milk proteins making them much more difficult to remove in the subsequent wash cycle. Check temperatures at the beginning and end of the cycle to be sure. A hand held thermometer, similar to that used by the Bulk Tank Milk Grader to measure milk temperature, can be a useful tool to confirm wash cycle temperatures.

Step 2- Hot chlorinated alkaline wash cycle

Hot water is critical to softening fat and breaking up protein. The alkali in the cleaner breaks down milk fat into components that are suspended in the cleaning solution. The chlorine breaks up the proteins which are suspended in the wash solution.

Start temperature should be 71°C to 76°C (160°F to 170°F). Residential water heaters will not provide hot enough water, however they can be retrofitted to meet hot water requirements for CIP cleaning. Water temperature at the end of the wash cycle must be absolutely no less than 43°C (110°F), and ideally no less than 49°C (120°F) with a circulation time of 6 to 10 minutes. Note that maintaining adequate end wash temperature is more important than precise wash solution contact time given that low temperatures will allow milk solids to re-deposit on pipeline surfaces. Again, check temperatures at the beginning and end of the wash cycle to be sure.

A sufficient supply of hot water is one of the first items to investigate if encountering a bacterial problem. The water heater needs to be adequately sized for your requirements. The actual amount of hot water available from a tank is about 70% of its capacity. Using hot water for other uses, e.g. mixing milk replacer, can reduce the availability of hot water for pipeline washing. Recovery rates will vary depending on your specific heater. The time between a pipeline wash and a bulk tank wash needs to be sufficient to allow the water heater to recover.

Water heater problems can go undetected for a long time if wash temperatures are not monitored. Calcium and magnesium salts can accumulate in water heaters and reduce heating capacity. A burnt out bottom element is a frequent problem. Buildups in water pipes and screens can restrict flow of hot water to the wash sink, leading to long fill times and resultant heat losses.

Systems with air leakage can cool wash water very rapidly and may cause poor slugging. Maintain water level in CIP sink so that suction lines never draw air. The pipeline must be free of air leaks at joints and milk inlets. If your system has an air injector, proper adjustment is essential. The air injector open time determines slug travel distance. The open time should be just long enough to cause the slug to travel to the receiver jar before it breaks up. The air injector closed time determines the amount of water drawn in and initial slug length. Slug volume should be about one third the volume of the receiver.

Wash temperatures as well as chemical concentrations can be adversely affected by residual water from previous cycles. All secondary drains, especially from the receiver, must be large enough to drain completely before the next cycle. All milk lines and wash lines need adequate and continuous slope to allow for complete drainage between cycles. Wash sink drains not closing properly can result in hot water loss and detergent loss.

The amount of detergent used depends on volume of water and water hardness. Your chemical supplier should provide a wash procedure chart, detailing the types and amounts of cleaners required for each cycle of your equipment wash system.

Step 3 - Acid rinse cycle

Acid neutralizes alkaline residues and dissolves mineral deposits for easy removal. This final rinse cycle leaves the pipeline with an acid pH, which suppresses bacterial growth. Water temperature is not critical in this cycle but should comply with label recommendation as posted on the wash chart.

Step 4 Sanitize cycle

The sanitize cycle eliminates bacteria that may grow on equipment surfaces between milkings even when well cleaned and acid rinsed. A warm solution at 43°C (110°F) containing about 200 ppm chlorine should be used just prior to milking. Cycle time is usually 3 to 4 minutes. Ensure all sanitizer is sufficiently drained from the system prior to milking. Do not follow the sanitizing cycle with a clear water rinse since any bacteria present in the milk house water supply could contaminate the milking system.

Bulk Tank CIP Systems

Bulk tank CIP cleaning involves the same cycles and temperatures as pipeline cleaning. However, bulk tanks are often more difficult to clean than pipelines. Frequent bulk tank cleaning problem areas include:

• Outlet and valve
• Plug and plunger rod
• Under the bridge and lid
• Dipstick and dipstick socket
• The corners of a square tank
• Agitator paddles

A hand held thermometer and strong flashlight are valuable tools in trouble shooting bacterial problems. A little investment of your time to routinely observe your wash system in operation, and check equipment cleanliness afterwards, can go a long way towards ensuring high quality milk production.

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