Pasteurization is one of the most widely used forms of food preservation. Pasteurization involves treating food with mild heat to destroy all disease-causing microorganisms and spoilage enzymes. The process is named after the French scientist, Louis Pasteur.

It all started in the 1860s when Napoleon III, emperor of France, requested to determine the cause of souring and contamination of wine. Pasteur then demonstrated that microorganisms caused it. And it could be prevented by heating the wine at 120°F (50°C) to 140°F (60°C) for several minutes. This mild thermal process eventually became what we know today as pasteurization. Today, pasteurization applies to foods such as eggs, fruit juices, beers, and milk.

Generally, pasteurization involves heating packaged or non-packaged with mild heat of less than 212°F (100°C). However, pasteurization comes in several types today. And one of them is flash pasteurization, also called high-temperature short time (HTST) pasteurization. In the United states, HTST is the most common method used, especially for milk.

During flash pasteurization, the product is treated with mild of heat of 162°F (72°C) to 165°F (74°C) for 15 to 20 seconds and then followed by rapid cooling.

In flash pasteurization of milk, the product is heated with mild heat of 161°F (71.7 °C) for 15 seconds to destroy Coxiella burnetii. Coxiella burnetii is the most heat-resistant pathogen in raw milk. The process is a standard US protocol for flash pasteurization of milk, which was first introduced in 1933. Flash pasteurized milk may last 16 to 21 days.

In processing of fruit juices, the product may be heated rapidly for about 1 minute and then filled into containers. The containers are sealed airtight under cover steam to sterilize the seal and then cooled. This process may be used for apple juice, orange juice, grape juice, etc.

ADVANTAGES OF FLASH PASTEURIZATION

The common applications of flash pasteurization include milk, beer, and fruit juices. Because flash pasteurization involves mild heat, it holds several advantage over other forms of heat treatment:

• There is minimal change in flavor, color, and nutrients
• It economically saves time and space
• Heats product uniformly, reducing cooked taste to a minimum
• Beneficial enzyme inactivation is obtained

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OTHER TYPES OF PASTEURIZATION

Ultra high temperature (UHT)

Ultra high temperature (UHT) pasteurization involves heating, usually milk, in commercially sterile equipment and pouring it into hermetically sealed packaging under aseptic conditions. The process involves heat of 284°F (140°C) for 4 seconds. The product is “shelf stable,” which means it doesn’t need to be refrigerated until it’s opened. And it can last up to 6 months or even longer. This type of pasteurization is also called aseptic processing.

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Low temperature long time (LTLT) pasteurization

Low temperature long time (LTLT) pasteurization, as the name suggest, involves low temperature and long time for pasteurization. In this type, the product is heated at 145°F (63°C) for 20 to 30 minutes. LTLT does not alter the structure as well as the taste of the milk. But prolonged holding time may change the milk protein’s structure and the taste. This type of pasteurization is called batch pasteurization.

References:

M. Shafiur Rahman (2007). Handbook of Food Preservation (2nd edition). CRC Press.

P. Fellow (2000). Food Processing Technology (2nd edition). CRC Press.

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