Milk Hygiene & Preservation: Best Methods and Practices

Milking hygiene encompasses both pre- and post-milking routines, along with ensuring the cleanliness of the milking equipment used for cows. The pre-milking procedures involve actions such as dipping, dry wiping, fore stripping, and cleaning or drying of teats and teat ends.

Upon birth, all mammals are introduced to milk. However, milk can be contaminated by the environment, milkers, and animals themselves, often harboring microorganisms. These microorganisms, some of which are detailed below, can compromise milk quality and safety.

Immediate cleaning and disinfection of milk contact surfaces are imperative after each milking session. All equipment must be maintained in a clean and operational state. Safeguarding milk from contamination during transfer and storage is vital, as is rapid cooling to curb bacterial growth.

Enteric bacteria, microscopic organisms residing in animals' gastrointestinal tracts, like cows, are frequently associated with milk production. Their presence in milk indicates fecal contamination, which may occur if proper hygiene protocols are disregarded during milking.

Examples of enteric bacteria include Salmonella, E. coli, Streptococcus faecalis, and Clostridium perfringens. Consumption of milk tainted with these bacteria can lead to foodborne illnesses in humans. Pasteurization, a process involving precise heating to eliminate harmful bacteria, is effective in rendering milk safe for consumption.

Psychrophilic microorganisms thrive in low-temperature environments, such as those where milk is stored. These microbes, including Pseudomonas, Achromobacter, and Alkaligens, can cause spoilage, altering flavor, texture, and shelf life. Proper milk handling and refrigeration are key to controlling their growth.

Certain microorganisms found in milk can generate exotoxins, toxins released outside bacterial cells, which can result in foodborne diseases upon consumption. Staphylococcus aureus is one such microorganism that can produce exotoxins. Pasteurization effectively eliminates these risks.

Adulterants in Milk:

Adulterants in milk, which include antibiotics, pesticides, and mycotoxins, pose significant health concerns. Misuse of antibiotics or inadequate withdrawal periods can lead to antibiotic residues in milk, contributing to antibiotic resistance. Pesticides and mycotoxins from moldy feed can contaminate milk, with adverse effects on human health.

Zoonotic diseases associated with milk consumption can be prevented through proper milk production techniques. For instance, Brucellosis, caused by Brucella bacteria, can be transmitted through raw or insufficiently pasteurized milk. Staphylococcus aureus, Salmonella, Mycobacterium tuberculosis, E. coli, Cholera, and Streptococcus infections are other risks linked to contaminated milk and dairy products.

How to Preserve Milk :

a). Pasteurization:

Pasteurization is the process of heating milk to a specific temperature to kill harmful microorganisms, including spoilage bacteria. The most common method of pasteurization involves heating the milk to a temperature between 63 and 72 degrees Celsius (145 and 162 degrees Fahrenheit) for about 30 minutes.

Another common method is High-Temperature Short-Time (HTST) pasteurization, where the milk is rapidly heated to 72 degrees Celsius (161 degrees Fahrenheit) for 15 seconds.

This process helps extend the shelf life of milk while retaining most of its nutritional properties. Pasteurized milk typically has a shelf life of a few days to a couple of weeks when refrigerated.

b). Ultra High-Temperature Treatment (UHT):

UHT treatment involves heating the milk at a much higher temperature, typically between 137 and 150 degrees Celsius (279 and 302 degrees Fahrenheit) or above, for a very short time, usually 2–9 seconds.

This rapid heating kills both harmful and spoilage microorganisms, making the milk commercially sterile. UHT-treated milk can be stored at room temperature without refrigeration and has a much longer shelf life compared to pasteurized milk.

When aseptically packaged, UHT milk can have a shelf life of up to 6 months.

c). Sterilization:

Sterilization is the destruction of all living microorganisms and their spores in the milk. This process involves heating the milk to a higher temperature than UHT, typically above 135 degrees Celsius (275 degrees Fahrenheit), for a longer period of time.

The result is a commercially sterile product with an extended shelf life. However, sterilization can lead to some changes in the milk's taste and nutritional properties due to high heat exposure.

d). Cooling and Refrigeration:

Cooling and refrigeration are simple and effective methods to slow down the growth of spoilage microorganisms in milk. Rapidly cooling the milk after milking prevents the multiplication of bacteria and helps maintain its quality.

Refrigeration at temperatures around 4 degrees Celsius (39 degrees Fahrenheit) or below can significantly extend the shelf life of pasteurized milk.

However, refrigeration alone may not be enough for long-term storage, as some bacteria can still survive and cause spoilage over time.

Conclusion

To ensure the safety and quality of milk, dairy farmers must adhere to proper milking and milk handling practices, including good hygiene, regular testing and monitoring for contaminants, and appropriate withdrawal periods for antibiotic treatments.

Additionally, proper storage and refrigeration of milk can help control psychrophilic microorganisms and maintain milk freshness and safety.

To protect the public's health and guarantee that milk is free from hazardous germs and adulterants, regulatory procedures and quality control are crucial.