How were heat treatment methods developed to keep milk safe and fresh, and what is the process?

Milk provides important nutrients for humans, but it is at risk of spoilage due to microorganisms. To prevent this, methods have been developed to heat treat raw milk to kill microorganisms. Pasteurization, pasteurization, and ultra-high-temperature processing are used to eliminate microorganisms, preserve nutrients, and extend shelf life.

 

Milk is a good source of nutrients for humans. It is rich in protein, fat, carbohydrates, vitamins, minerals, and other nutrients that play an important role in maintaining good health. However, when unprocessed milk, or raw milk, is sold untreated, it is at risk of rapidly growing harmful microorganisms that can cause spoilage and disease. That’s why the milk we drink every day has been heat-treated to kill microorganisms.
Heat treatment of raw milk reduces the number of microorganisms in the milk, and in general, the higher the heating temperature and the longer the heating time, the greater the reduction. However, different types of microorganisms require different times and temperatures to be killed, so it is important to know the appropriate heat treatment conditions. This is where the D-value and Z-value come in. The D-value is the time it takes to reduce the number of microorganisms by 1/10 when heat-treated at a certain temperature. If you want to reduce the population by 1/100th at the same temperature, you can do it in twice the time of the D-value. The Z-value is the additional temperature that must be raised to reduce the number of objects by 1/10 in 1/10 the time of a given D-value. Therefore, microorganisms that are more resistant to heat have larger D and Z values at a given temperature. For example, let’s say you heat treat 100 microorganisms at 63℃. If the number of individuals remaining after 360 seconds is 10, the D value is 360 seconds. If you want to reduce the number of microorganisms from 100 to 10 in 36 seconds, which is one-tenth of this D-value, and the temperature is 65°C, the Z-value is 2°C.
Based on these principles of D and Z values, several methods of heat treatment of crude oil have been developed. First, there is the pasteurization method, in which crude oil is heat treated at 63°C for 30 minutes to kill more than 99.999% of the microorganisms it contains. Pasteurization is effective in killing microorganisms, but it is time-consuming. Pasteurization is a method that has been developed to compensate for this. Pasteurization involves heat treatment of raw milk at 75°C for 15 seconds. This method has the same effect of killing microorganisms as pasteurization, but the heat treatment time is shortened by increasing the heat treatment temperature for mass production of milk.
The shelf life of pasteurized or pasteurized milk is about 5 days in refrigerated conditions. If you want to extend the shelf life of milk, you need to eliminate microorganisms that are not killed by pasteurization or flash pasteurization. In order to eliminate microorganisms that are highly resistant to heat, the “ultra-high temperature treatment method” is used, which involves heat treatment at 134℃ for 2 to 3 seconds. If the milk is sterilized and packaged, it can be stored at room temperature for more than one month.

 

 

However, milk treated with the ultra-high temperature treatment method is slightly different in terms of taste and nutrients compared to milk treated with the pasteurization method or low-temperature instant pasteurization method. Some proteins and vitamins may be lost during the ultra-high temperature process, and a distinctive heat-treated flavor may develop. Consumers recognize these differences and make decisions based on their preferences when choosing milk, which is why milk manufacturers are using a variety of heat treatment methods to provide consumers with more choices. Thanks to these efforts, we have safer, fresher, and more nutritious milk in our daily diets.
However, the heat treatment of milk is more than just a sanitizing process. It’s a complex process that involves killing microorganisms, preserving nutrients, maintaining flavor, and extending shelf life. Consumers benefit from safer and healthier milk, and the industry continues to evolve.