Pasteurization Process And Related Instrumentation Involved In Dairy Plant

Pasteurization Process 

Pasteurization is a process that kills pathogens in milk. Pasteurizer is the equipment used for HTST pasteurization. Pasteurizer is also known as plate heat exchanger. Pasteurization process achieved by heating the milk in the pasteurizer to a temperature of minimum 72 °C, holding it at that temperature for 15 seconds and rapidly cooling below 4 °C.

Pasteurization involves heating liquids at high temperatures for short amounts of time. Pasteurization kills harmful microbes in milk without affecting the taste or nutritional value (sterilization= all bacteria are destroyed).

The process of pasteurization involves heating milk to 71.7°C for at least 15 seconds (and no more than 25 seconds). Because of the nature of the heat treatment it sometimes referred to as the 'High Temperature Short Time' (HTST) process. Once the milk has been heated, it is then cooled very quickly to less than 3°C.

Top 4 Methods of Milk Pasteurization

High Temperature Short Time

In the United States, the most common method of pasteurization is High Temperature Short Time (HTST). This method involves using metal plates and hot water to raise the temperature of the milk to at least 161 °F (71 °C) for no less than 15 seconds, or 145 °F (62 °C) for 30 minutes, followed by rapid cooling. 

Higher Heat Shorter Time

Similar to HTST pasteurization, Higher Heat Shorter Time (HHST) uses slightly different equipment and higher temperatures for a shorter time. Using HHST, milk can be heated anywhere from 191 °F (89 °C)  – 212 °F (100 °C) for its specified time (see chart below).

Ultra High Temperature

Another popular method of pasteurization is Ultra High Temperature (UHT). This process involves heating the milk using commercially sterile equipment and filling it under aseptic conditions into hermetically sealed packaging. The milk must be heated to 280 °F (138 °C) for at least two seconds, then rapidly cooling it down. UHT kills more bacteria (good and bad) and gives it a much longer shelf life. UHT milk does not need refrigeration, until opened, and is shelf stable for at least six months.

Ultra Pasteurized

Not to be confused with UHT, Ultra Pasteurized (UP) milk is heated using commercially sterile equipment, but it is not considered sterile because it is not hermetically sealed. Milk is heated to 280 °F (138 °C) for at least two seconds, then rapidly cooling it down. Since the milk is not hermetically sealed, it must be refrigerated with an average shelf life of 30 – 90 days.

Pasteurization Process and related instrumentation involved in dairy plant

HTST Pasteurization Systems [High-Temperature, Short-Time]

High-temperature, short-time (HTST) pasteurization—also known as flash pasteurization—is the most commonly used pasteurization technique in the United States. It is typically utilized for dairy products, such as milk, cream, cheese milk, and yogurt, but can be employed for other low-viscosity to medium-viscosity food and beverage products, such as hot- and cold-brewed coffee, tea, juice, sports drinks, soups, and sauces.

HTST Pasteurization Systems Work

HTST pasteurization equipment uses Sanitary Plate Heat Exchangers utilizing hot water or steam to raise the temperature of products. This heating stage is then followed by a rapid cooling stage. The pasteurization temperature and time depend on the product. For example, milk must achieve a minimum of 161° F for at least 15 seconds. However, if the product’s fat content is at or above 10%, the product’s total solids content is 18% or greater, or the product contains sweeteners, the pasteurization temperature should be 5° F greater. If a product needs to be ultra-pasteurized, it must be heated to a minimum of 280° F for two seconds.

All of the products that undergo HTST pasteurization have longer shelf lives than their unpasteurized counterparts. However, they are not shelf-stable. They must be refrigerated before and after opening.