Pasteurization - Preserving Food or Destroying Nutrients?

In primeval times, people in Europe mainly ate raw plant parts, wild vegetables, and fruit. With the advent of hunting and fishing, meat, fish, and seafood enriched their diet. Methods such as salting, smoking, or drying helped preserve food, i.e., to conserve it and build up provisions for lean times. Only in modern times were various methods developed to preserve food, including pasteurization. For foods such as dairy products or beverages, the pasteurization process is best known. 

What happens during this process? And what are the advantages and disadvantages of pasteurization? How does pasteurization affect Kombucha? You can find the answers to these questions in this article.

These methods preserve food

Pasteurization

The simplest method to extend the shelf life of food is heat treatment. This kills harmful microorganisms or pathogenic bacteria, such as salmonella. In this way, products are gently preserved. However, pasteurized foods are not indefinitely shelf-stable, as they are not germ-free, but only low in germs. This method extends shelf life; depending on temperature, duration, and food, the content of individual heat-sensitive ingredients can change.

During pasteurization, the food is heated for a short time (from a few seconds to a few minutes) to a temperature of at least 60 °C. The core temperature of pasteurization varies depending on the process - but never reaches 100 °C. The pasteurization process was named after its developer, the French chemist Louis Pasteur. In the mid-19th century, he recognized that germs could be rendered harmless by briefly heating food, thus making it last longer.

Many types of cheese, for example, are made from pasteurized milk; others from raw milk.

Sterilization and UHT treatment

Heating above 100 °C is sterilization. After this heat treatment, food can be stored much longer. However, this method means a loss of taste and nutrients. The difference between "UHT" and "sterilized" milk lies in the heating process and thus also in the minimum shelf life of unopened packages.

UHT milk, also known as long-life milk, is briefly heated to at least 135 °C and filled aseptically. It is sealed and has a shelf life of at least six to eight weeks.

Sterilized milk is heated to about 110 °C for 20 to 30 minutes. It is sealed and has a shelf life of up to one year. This method is used significantly less often because the vitamin loss is much higher than with UHT milk. It is also inferior in taste to UHT milk. Sterilization is not required to be labeled. You can only assume this due to the long shelf life of the pasteurized milk.

Homogenization

During homogenization, particles of different sizes in a liquid are reduced – this makes them easier to combine. Homogenization prevents, for example, a cream layer from forming on milk. In this process, the milk is pressed at high pressure through a fine nozzle. This breaks down the milk fat into tiny globules and distributes it homogeneously (evenly) in the milk liquid. Homogenization is often used in combination with pasteurization, sterilization, or UHT treatment.

Fermentation

Fermentation is a biological form of food preservation. Another advantage of the fermentation process is the formation of probiotics, healthy yeasts and acids, as well as many other nutrients.

About a third of our food is produced by fermentation. These include, for example, bread, fermented dairy, meat, and sour vegetable products such as sauerkraut or kimchi, kombucha, or alcoholic beverages such as beer and spirits. The advantages of fermentation include the formation of aromas and flavors, the breakdown of harmful ingredients, and the extension of shelf life. The principle: organic substances are converted into acid, gases, or alcohol. Raw material enzymes as well as microorganisms – such as bacteria or yeasts – are used for this.

Which foods are pasteurized?

Pasteurization is suitable for liquid foods. This process is best known for milk and dairy products. But also liquid eggs, fruit and vegetable juices, canned fruit, and prepared meals undergo such heat treatment. Pasteurization is often combined with other preservation methods. For beverages, this is done, for example, by lowering the pH value and by light-protective, airtight packaging. As long as these are not opened, additional cooling is not necessary. Examples include fruit and vegetable juices or other beverages, such as lemonades or even kombucha.

Pasteurized Kombucha vs. Raw Kombucha

With Kombucha, there is an important difference in processing. Some manufacturers pasteurize their Kombucha after fermentation to microbiologically stabilize it.

Heat treatment inactivates heat-sensitive living microorganisms. In contrast, with raw and unpasteurized Kombucha, living cultures can still be present in the finished drink.

Pasteurization thus primarily changes the microbiological state of the drink. Other components such as tea, organic acids, or flavor components do not automatically disappear.

Those who value living cultures should therefore look for indications such as raw, unpasteurized, or active cultures when buying.