Plant Cleaning

The benefits of ensuring you have the correct cleaning process include:

• Maintaining milk quality. Put in place a process to ensure cleaning is done properly, so that all residues are removed and bacteria are destroyed.
• Ensuring safety issues are considered.

Cleaning must be done properly as bacteria can build up in the plant and contaminate milk. The bacteria affect milk quality by breaking down the components in milk. This reduces the shelf life of milk and milk products, and produces off flavours in cheeses and milk powders.

The plant cleaning process

Bacteria can enter the plant from cows (teat skin and infected udders) and the environment (drawn into the cluster). The milking environment is ideal for bacterial growth. Effective machine cleaning will control the presence of bacteria in the plant. The quality of the water used is very important in achieving a successful clean.

• The four key elements of the cleaning process

  Thermal

  Water which is too cool leads to redepositing of the milk residues removed, and water which is too hot denatures protein, breaks down detergents and damages seals and rubberware.

  • Aim for a temperature of 80-85°C as water exits the hot water storage cylinder.
  • Hot water washes should be dumped when wash water temperature falls to below 55°C.

  Time

  • Hot water must contact the surface for a minimum of 4 minutes; this should be extended to 7 minutes by re-circulating during an alkali wash. Pre-heating the plant will help achieve at least 5 minutes of contact time at the recommended temperature.
  • For the milking plant, 10 litres of hot water per cluster is recommended to achieve sufficient contact time.
  • For the bulk milk tank, hot water should be a minimum of 2% of the bulk milk capacity or 120 litres for 5,700 litre tanks or smaller.

  Kinetic energy

  • Air injectors and a reservoir of water at the end of the milk line can create a slug formation for cleaning the top of the milk line.
  • Small flushing pulsators used to induce turbulence are largely ineffective and regular brushing or use of a large flushing pulsator/air injector may be required.
  • Milk lines generally require turbulence created via an effective flushing pulsator to fill the line and clean the milk line or some alternate effective cleaning system.

  Chemical energy

  • Acid detergents remove mineral deposits. They can be used in hot or cold water but are more effective in hot water. Acid sanitisers commonly incorporate chemicals which also kill bacteria. These sanitisers are intended to stay in the plant after washing to provide extended protection. Acid sanitisers should always be added to the final wash.
  • Alkaline detergents remove fat and protein. If left in the plant, they can cause damage to rubberware so they must be followed with an acid wash to neutralise the alkali and leave the plant sanitised. The alkaline detergent is almost always chlorinated, or chlorine added.

Plant cleaning routines

As a minimum the following steps need to be carried out:

• Cold water rinse after every milking.
• An acid wash after every milking.
• An alkali wash at least twice weekly.
• An acid rinse after every alkali wash.

• Example of an ideal cleaning sequence

  • Cold Water Rinse
  • The post milking rinse needs to be completed immediately after milking or milk collection. It rinses most of the residual milk from the milking system and bulk milk tank.
  • Hot Water Alkaline / Acid Wash
  • The milking system should be hot washed as least once a day and twice a day during high risk periods (e.g. when grading, calving). The bulk milk tank should be hot washed after every collection. The purpose of the hot detergent wash is to remove any adhered non-rinsing milk residue. This process should alternate between acid and alkaline in some systematic way to ensure all residues are removed on a routine basis.
  • Alkaline Detergent Wash
  • A hot water alkaline wash should be carried out at least twice weekly on the milking system and bulk milk tank. The wash water should be recycled for 5-7 minutes once water discharging the plant/tank is hot.
  • Cold Water Acid Wash
  • The cold water acid wash is normally carried out at night and hot alkaline washes done after the morning milking.
  • Acid Sanitiser Detergent Wash
  • This should always be the final wash through the milking system and bulk milk tank. Acid sanitiser washes can be used hot or cold.

• Typical plant wash programme

  	Mon	Tues	Wed	Thur	Fri	Sat	Sun
  Rinse	C	C	C	C	C	C	C
  Alkaline	H				H
  Acid Sanitiser	C	H	H	H	C	H	H

  Morning wash - C = Cold wash, H= Hot wash

  	Mon	Tues	Wed	Thur	Fri	Sat	Sun
  Rinse	C	C	C	C	C	C	C
  Alkaline
  Acid Sanitiser	H	H	H	H	H	H	H

  Afternoon wash - C = Cold wash, H= Hot wash

  NB. The alkaline wash should be recycled for 5-7 minutes (if wash water falls to 55oC it should be immediately dumped).

• Typical bulk milk tank wash programme

  	Mon	Tues	Wed	Thur	Fri	Sat	Sun
  Rinse	C	C	C	C	C	C	C
  Alkaline
  Acid Sanitiser	H	H	H	H	H	H	H

  Following milk collection wash - C = Cold wash, H= Hot wash

  NB. The alkaline wash should be recycled for 5-7 minutes (if wash water falls to 55oC it should be immediately dumped).  When milk is collected every second day alkaline wash every second pickup.

Documenting cleaning procedures

A documented bulk milk tank wash procedure on a dairy wall.

All farm dairies require a written cleaning procedure that is laminated and displayed prominently in the farm dairy. Even if you are the only person working on the farm, there may be a time when someone needs to unexpectedly cover for you.

The procedures must be written clearly so that someone who has never worked in your dairy before can accurately follow the procedure.

Safety when using chemicals

• General actions to take

  • Scourer gloves are great for cleaning cluster exteriors.
  • Keep a thermometer in the dairy for checking water temperatures. Glass and mercury thermometers are not allowed for measuring temperatures in the dairy (NZFSA, 2007).

• Handling chemicals

  

  Mixing jugs.

  • Designated (and marked) chemical measuring jugs save time and chemical.
  • Always read labels before using unfamiliar products.
  • Never mix acid and alkaline detergents together.
  • Always add chemical to water, not the other way round.
  • Never mix chlorinated products with acid as this can produce a poisonous gas.
  • Never mix chlorinated products with oil or store them close together - there may be a flammable reaction.
  • Never store chemicals in unmarked containers.
  • Never store non-dairy chemicals such as herbicides and pesticides with dairy chemicals.
  • Never use a food contact hose for filling non-dairy chemical containers.

• Protective clothing

  

  Safety notice.

  Always wear protective clothing when using chemicals including:

  • safety goggles
  • apron or other waterproof clothing
  • waterproof gloves
  • gumboots.