Due to more stringent product specifications, particularly in relation to residues such as trichloromethane (TCM) and chlorates, it is becoming increasing difficult to achieve end-product specifications when chlorine-based products are used as part of the milking equipment cleaning protocols.

Products that contain chlorine are generally referred to as detergent sterilisers, which contain varying levels of sodium hydroxide (caustic soda) and sodium hypochlorite (chlorine).

Detergent sterilisers tend to be liquid-based products and are widely used in automatic wash units in milking parlours and bulk tanks.

Traditionally, powder-based “cold wash” cleaning protocols have been used by dairy farmers and they have proven to be satisfactory from a microbiological point of view.

The use of powder-based cleaning products is most suitable when manual washing is normally used and for small to medium plants (five to 15 units), without auxiliary equipment like milk meters.

It is less satisfactory where automatic systems are in place for cleaning both machine and bulk milk tank.

The vast majority but not all powder products contain no chlorine. Powder products contain much higher levels of caustic (76%) compared to most liquid caustic products (21 to 29%).

This is why these powder products can be used cold or hot compared to liquid products which contain the lower caustic levels and should be used with hot water.

Many milk processors are now insisting on chlorine-free wash routines. Most of these routines involve doing more hot washes and doing more acid washes.

Steps

If changing from chlorine-based detergent steriliser products to non-chlorine (caustic) products, it is critical that re-calibration of automatic detergent dosing systems for both machine and bulk milk tank is carried out.

Take-up rates may be lower for products that do not contain chlorine and that have slightly higher caustic content than products previously used.

To check if the correct quantity of product is being used, the following steps should be taken:

  • Determine the quantity of water being used in the wash trough for the main wash cycle (this may require that water is measured into the trough manually until the normal level used in the trough is reached). The recommended water usage rate is 9l per milking unit.
  • Calculate the required quantity of detergent required based on drum label. Labels normally indicate rate per 45l of water depending if hot or cold water. Higher levels of detergent are necessary when cold water is used.
  • Fill a clean container with a fixed quantity of detergent (level above what your calculations suggest) and place the automatic dosing tubes in the container prior to the next cleaning occasion.
  • Subtract the remaining quantity of detergent from the original amount to establish the amount used for the wash.
  • Should the levels be lower or higher than recommended by the manufacturer as determined on the label, then the automatic system needs adjustment (probably by the milking machine or bulk tank fitter) and the exercise repeated until the required level is achieved.
  • Sourcing advice from chemical product distributors is also an important consideration when changing products for non-chlorine cleaning as product technical personnel are best placed to advise on their own product range and routines.

    Potential risks

    There are a number of other potential risks of residues from farm dairy tasks, such as dipping clusters between individual cow milkings and disinfection of own water well source using hypochlorite products.

    Peracetic acid-based products are available which can be used as a direct replacement for hypochlorite for these tasks.

    It has to be acknowledged that mains water supplies do contain added hypochlorite but at measured levels which may contain a level of chlorates.

    Chlorine dioxide-based teat disinfectants are known to be effective against mastitis-causing bacteria.

    However, they also contain a level of chlorates which may impact on milk residues unless good teat preparation is carried out prior to milking.

  • Hot water usage is critical.
  • Increased use of acid-based products is necessary.
  • No recycling of liquid products for a further wash occasion.
  • Requirement to re-calibrate automatic dosing systems for new products.
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