Frequently Asked Questions - Use of QACs on Farms

What is a QAC?

Quaternary ammonium compounds (QACs) are a group of chemicals widely used as biocides and disinfectants in the home, industry and in food manufacture. Products containing QACs are used to clean and sanitise the milking machine and/or vat on some dairy farms. Benzalkonium Chloride (BAC) is the specific type of QAC of most interest, and is present in a number of products registered for use on dairy farms.

Do I need to change my current practices? Why?

Some international customers have placed strict requirements on the level of BAC residues they are prepared to accept in the products they import. Consequently, some milk companies are requiring their suppliers to change the way they currently use QAC-based dairy sanitisers to ensure these high value markets remain open to them.

How do I know if the dairy chemicals I am using contain QACs?

QACs are used to kill (sanitise) bacteria in the milking machine and vat. They are found in a number of products registered for use on dairy farms. Look for the following compounds listed as one of the ‘active constituents’ on the front panel of the product label – ‘BENZALKONIUM CHLORIDE’, QUATERNARY AMMONIUM COMPOUND’ or ‘N-ALKYL DIMETHYL BENZYL AMMONIUM CHLORIDE’.

  • An indicative list of products registered with the APVMA is available here.

What do I do if my wash program is automated?

Changes to automated wash controllers should be done in association with the company supplying the controller. Your dairy chemical adviser should be able to assist with these changes too.

What alternatives do I have to change my current cleaning practices to minimise QAC residues?

There are 3 main options to minimise the risk of QAC residues – rinse the sanitiser out after use, use hot water in place of a sanitiser, or change the type of chemical you use to sanitise the milking machine and/or vat. The most appropriate option will depend on your farm situation and on your milk company’s requirements, which may vary. A decision tree has been created to help you work through the various options in association with your milk company or dairy detergent adviser.

 Decision Tree - do you use a chemical sanitiser in your vat or milking machine cleaning program

Option 1. Rinse out QAC-based sanitisers

How soon should I rinse out the plant after QAC use?

QAC-based sanitisers only need a few minutes to do their work, so can be rinsed from the plant immediately after their use, or preferably immediately prior to the next milking. Use warm or cold water at the same volume as used for the sanitising rinse. Good quality water is needed to avoid re-introducing bacteria into the milking machine or vat. Ensure the equipment is well drained so minimal water is collected with the next milk.

Option 2. Use hot water to sanitise the plant instead

How hot does the hot water need to be?

Water needs to be at or above pasteurization temperature at every point in the pipework for at least 20 seconds to effectively sanitise the pipework. This means that the hot water temperature in the wash barrel should be at 90-93oC as it enters the milking plant. Use the same volume as used for the other detergent and sanitising cycles. Hot water is unsuitable for sanitizing vats.

Option 3. Use an alternative chemical to sanitise the plant instead

What other sanitising chemicals are available?

There are many registered dairy sanitiser products available that do not contain QACs. Alternative chemicals may not suit your water quality so the decision to change over needs to be taken together with your dairy chemical adviser. Note that some alternative chemicals also need to be rinsed out after use (to avoid other residue issues) but there are some acid-based sanitisers that have been approved by the APVMA to be left in the plant ‘to drain’.

Are the alternative chemicals more expensive?

The total cost of cleaning and sanitising the milking machine and vat each day are largely determined by the costs of heating water (power costs) and the cost of the chemical. Although a drum of an alternative chemical may cost more than a drum of QAC-based chemical, in many circumstances the total costs (power+chemical) of using an alternative chemical will be similar or less than either rinsing out the QAC-based sanitiser or using hot water to sanitise the plant instead.

What do I do with any leftover QAC chemical?

If the decision is made to stop using QAC-based sanitisers, leftover chemical should not be returned to the place of purchase, stored or disposed of on farm. Existing product should be used according to the current wash program, ensuring it is thoroughly rinsed from the plant after use. This may mean some delay before the new cleaning program can be implemented.