Dairy Hygiene

Domestic and international consumers demand high quality dairy products. This requires dairy farmers to supply high-quality raw milk by adhering to food safety requirements, meeting trade regulations and market access requirements, meeting product specifications and accepting incentive payments or penalties based on milk quality.

Milk quality

Dairy hygiene includes all activities, processes and equipment associated with cleaning the milking machine, bulk milk vat and other milk harvesting equipment. Maintaining milking plant and dairy hygiene is critical to guaranteeing high levels of milk quality.

Poor milking hygiene can have a detrimental affect on a dairy operation. It can reduce milk quality and in turn, impact milk pricing and dairy farm profitability. That is why it is so important to get it right.

The quality of milk determines its processing capabilities and the quality of its end products. Poor quality milk can result in:

• Longer and more complex handling and processing procedures.
• Lower dairy product yields.
• Increased wastage and costs.
• Reduced flexibility in the types of dairy products it can produce.
• Off-flavours in dairy products.
• Shorter dairy product shelf life.
• Inhibition or destruction of starter cultures.
• Reduced or restricted access to markets.
• Lower sale prices for dairy products.
• Reduced customer demand.
• Negative customer feedback.

Microbial contamination is a major cause of poor-quality milk. One of the main sources of this type of contamination is associated with poor milking machine hygiene due to an ineffective cleaning program and/or cleaning method. Remember the aim of any cleaning program is simple – it should focus on the removal all milk residues from the plant between milkings and kill (sanitise) any bacteria.

Slow and ineffective cooling of the milk can also provide conditions conducive to bacteria growth, leading to high bacterial numbers and poor-quality milk.

Bacteria in milk

There are many ways to measure the quality of raw milk from the vat (not pasteurised or processed). Some are subjective, such as sensory measures (smell, taste, visual) and others are objective (composition, culturing, somatic cell count, colostrum, temperature, freezing point).

When it comes to dairy hygiene, the focus is on determining the level of bacterial contamination in the milk. There are various types of bacteria that can contaminate milk, and each can impact milk quality differently. Sources of bacteria may include:

• Inadequately cleaned and disinfected milking equipment.
• Soiled animals (especially teats and udders).
• Inadequate milk cooling.
• Cows with mastitis (rare).

Every Australian milk company has a system outlining the quality parameters used to measure a dairy farm’s supply of milk. The types of measures used, the thresholds applied, and the associated payments and penalties differ between companies. If bacterial counts are above premium limits, a thorough and systematic investigation should be carried out by an experienced person or dairy hygiene adviser. In Australia, several different tests are performed on bulk milk samples to quantify bacterial levels. The most commonly used tests are the Total Plate Count (TPC), Bactoscan and Thermoduric counts.

The Total Plate Count (TPC) measures the total number of bacteria colonies that have formed from live, viable bacteria. Bulk milk samples are incubated on agar plates at 30 degrees Celsius for 72 hours. After incubation, the colonies of bacteria are counted visually or electronically. The typical limit for premium quality is less than 20,000 colony forming units per millilitre (cfu/ml).

The Bactoscan test detects the total number of alive or dead bacteria, by electronically scanning a bulk milk supply. The typical limit for premium quality is less than 80,000 individual bacterial count per ml (ibc/ml).

The Thermoduric test measures the total number of bacteria that have survived pasteurisation and have formed colonies. Bulk milk samples are first pasteurised at 63.5°C for 30 minutes, then incubated on agar plates at 30°C for 72 hours. After incubation, the colonies of bacteria are counted visually or electronically. The typical limit for premium quality is less than 2,000cfu/ml.

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