Pasteurization - Preserving Food or Destroying Nutrients?

In prehistoric times, people in Europe primarily ate raw plant parts, wild vegetables, and fruits. With the advent of hunting and fishing, meat, fish, and seafood enriched their diet. Methods such as curing, smoking, or drying helped to preserve food, meaning to conserve it and build up stores for leaner times. Only in modern times were various methods developed to preserve food, including pasteurization. The pasteurization process is best known for foods such as dairy products or beverages. 

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

Pasteurizing

The simplest method to extend the shelf life of food is heat treatment. This kills harmful microorganisms or pathogenic bacteria, such as salmonella. This gently preserves products. However, pasteurized foods do not have an unlimited shelf life, as they are not sterile, 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, 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 realized that short-term heating could neutralize germs and thus make food last longer.

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

Sterilizing and Ultra-High Temperature Processing (UHT)

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

Ultra-high temperature processed milk, so-called UHT milk, is briefly heated to at least 135 °C and filled aseptically. It can be stored unopened for at least six to eight weeks.

Sterilized milk is heated to about 110 °C for 20 to 30 minutes. It can be stored unopened for up to a year. This process is used significantly less often, as the vitamin loss is much higher than with UHT milk. It is also inferior in taste to UHT milk. Labeling for sterilization is not required. You can only infer this from the long shelf life compared to pasteurized milk.

Homogenizing

Homogenization involves reducing the size of differently sized particles in a liquid – this allows them to combine better. Homogenization, for example, prevents a cream layer from forming on milk. In this process, milk is forced through a fine nozzle at high pressure. The milk fat contained therein breaks down into tiny globules and distributes homogenously (evenly) in the milk liquid. Homogenization is often used in combination with pasteurization, sterilization, or ultra-high temperature processing.

Fermenting

Fermentation is a biological method for preserving food. During fermentation, various microorganisms, organic acids, and other natural fermentation products can arise depending on the culture.

About one-third of our food is produced through fermentation. This includes, for example, bread, fermented dairy, meat, and pickled vegetable products, such as sauerkraut or kimchi, kombucha, or alcoholic beverages like 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. This uses raw material-specific enzymes and microorganisms – such as bacteria or yeasts.

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 fruits, and prepared meals are subjected to 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.

Through heat treatment, heat-sensitive living microorganisms are inactivated. In contrast, with a raw and unpasteurized kombucha, living cultures can still be present in the finished drink.

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

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