Milk Processing and Storage Methods

Agric4Profits November 15, 2023November 17, 2023 0 Comments Ruminants

Almost all the milk processing methods for milk have the common objective of extending its storage or shelf life. Therefore, processing results in the conversion of raw milk into other products.

The raw milk obtained from dairy animals is highly perishable and cannot keep for long even when the quality is high. Therefore, the milk has to be converted to more stable forms in order to increase its shelf life.

Milk is very versatile and can be processed and is indeed processed to thousands of products globally depending on different traditions, habits, and customs.

Additionally, employing milk storage methods and practices, can help you to enjoy the goodness of milk while ensuring it remains safe, nutritious, and a delightful addition to your daily diet.

Whether refrigerated, frozen, or treated with advanced processing methods, the key is to maintain a balance between convenience and the preservation of milk’s natural qualities.

Milk Processing Methods

Almost all the milk processing methods for milk have the common objective of extending its storage or shelf life. Therefore, processing results in the conversion of raw milk into other products.

Whole milk, once approved for use, is pumped into storage tanks or silos where it undergoes pasteurization, homogenization, separation, and further processing into different products.

Pasteurization or heat treatment involves heating every particle of milk to a specific temperature for a specified period of time and cooling it again without allowing recontamination heating it at 63 to 66 ◦C for 30 min or 72◦ C for 15 seconds.

These conditions provide fresh-tasting milk that meets the requirements for consumer safety. Higher heat processes, such as ultra-pasteurization (137.8◦C for 2 seconds) or aseptic/ ultra-high temperature (135 – 150◦C for 4-15 seconds) or sterilization (115.6◦C for 20 min), are used to extend the shelf life of refrigerated products or allow for storage at room temperature, respectively, but may impart a cooked flavor to the milk.

The fat in milk is in globules of non-uniform size, and the non-uniform size of the globules causes them to float, or cream, to the top of the container. Pasteurized milk does not necessarily need to be homogenized.

However, homogenized milk should be pasteurized to inactivate native enzymes (lipases) that deteriorate fat and cause rancidity, which results in off-flavors and reduced shelf life in milk.

The purpose of homogenization is to reduce the milk fat globule’s size, which allows them to stay evenly distributed in milk. Homogenization is a high-pressure process that forces milk at a high velocity through a small orifice to break up the globules.

The result of homogenization is the creation of many more fat globules of a smaller size so that the fat is dispersed evenly throughout the milk, stopping the fat from floating to the top of the container to obtain a more uniform consistency.

Separation involves spinning milk through a centrifuge to separate the cream (fat-containing a portion of milk) from the milk. After separation, the cream and remaining milk are remixed to provide the desired fat content for the different types of milk being produced.

For whole milk, the cream is reintroduced until the fat content reaches 3.25-4%. For low-fat milk, the fat content is 1%. For skim milk (sometimes called solids non-fat milk) the fat content is .05%.

Milk that has gone through pasteurization and homogenization can be processed into many different forms such as whole (full cream) milk, low-fat (defatted) milk, skim milk, fortified milk (low-fat milk fortified with vitamins A and D), flavored milk (with chocolate, vanilla, etc.), condensed milk, evaporated milk, powdered (dried) milk, and filled milk (animal fat replaced with vegetable fat).

Different milk products are also produced with specific processing procedures such as yogurt (curdled milk), ice cream, butter, cheese, casein (milk protein), lactose (milk sugar), whey (liquid remaining after milk is curdled), and whey powder (dried whey).

Milk Storage Methods

Here are the the various methods for storing milk, ensuring its freshness, safety, and nutritional integrity from the farm to your table;

1. Refrigeration: The most common and effective method for storing milk is refrigeration. Maintaining a consistently low temperature slows down the growth of bacteria, preserving the freshness of the milk.

It’s crucial to store milk at temperatures below 40°F (4°C) to ensure its safety and quality. Always keep milk containers tightly sealed to prevent absorption of odors from the refrigerator.

2. Freezing: Freezing is an excellent option if you want to extend the shelf life of milk. However, it’s important to note that freezing can alter the texture of milk, causing it to separate.

To mitigate this, gently shake the milk after thawing to restore its homogeneity. Use airtight containers, leaving some space for expansion, and consume frozen milk within three months for the best quality.

3. Pasteurization for Extended Shelf Life: Certain milk products undergo a process called ultra-pasteurization, which involves heating the milk at higher temperatures.

This method extends the shelf life of the milk, allowing it to be stored for a more extended period without compromising safety or nutritional value. Look for labels indicating ultra-pasteurization if you prefer a longer shelf life.

4. UHT (Ultra-High Temperature) Processing: UHT processing involves heating milk to very high temperatures for a short duration, effectively killing bacteria and extending shelf life.

Milk treated with UHT can be stored without refrigeration until opened. Once opened, it should be refrigerated and consumed within a specified time frame.

5. Proper Container Selection: The type of container used for storing milk can impact its quality. Choose containers that are clean, airtight, and made of materials that do not impart unwanted flavors or odors to the milk. Transparent or opaque containers that protect against light exposure are preferable to maintain the nutritional content of the milk.

6. FIFO (First In, First Out): Implementing the FIFO principle is essential for ensuring that older milk is used first. When restocking your refrigerator or freezer, place the new milk at the back and move the older containers to the front. This helps prevent spoilage and ensures that you consume the oldest milk before its quality diminishes.

7. Avoiding Temperature Fluctuations: Consistency is key in maintaining milk quality. Avoid temperature fluctuations, as they can accelerate bacterial growth and compromise the milk’s safety. Keep the refrigerator at a steady temperature, and avoid leaving milk at room temperature for extended periods.

8. Monitoring Expiry Dates: Always check the expiration date on milk containers. Consume the milk before this date to ensure you are enjoying it at its freshest and safest. Expiry dates are a reliable guide to the milk’s shelf life and nutritional integrity.

In conclusion, the versatility of milk in conversion to many different products all over the world makes it one of the most important food sources globally.

Focusing on ways to improve the quality of milk products available locally in various areas could improve the well-being of those people most vulnerable nutritionally.