Selected microorganisms extend the shelf-life of foods, thereby contributing to a reduction in food waste. In a study of the literature, Agroscope highlighted the important role of protective cultures and fermentation.
Preserving foods through fermentation is probably the oldest method of extending their shelf life, having been used for millennia. In the beginning, preserved foods were produced by spontaneous fermentation. In addition to extending their keeping qualities, this also altered their textural and sensory properties.
Fermentation makes foods more nutritious and digestible
A further side-effect of this fermentation was a reduction in anti-nutritional properties, which rendered the foods more digestible. In addition, these microorganisms also produced valuable metabolites such as vitamins.
With time, humans learned to ‘control’ these fermentation processes by first of all using fermented material at the start of the subsequent fermentation (‘back-slopping’). After Pasteur succeeded in tracing fermentation back to microorganisms, people began isolating the responsible microorganisms and cultures were deliberately added for fermentation. At the same time, however, other methods of preservation such as pasteurization were introduced, and fermentation for the sole purpose of preservation was largely forgotten. Microorganisms were also increasingly tarred as ‘bad’, and in principle to be avoided.
Bioprotection and biopreservation – microorganisms protect and preserve our food
In recent years, terms such as ‘protective cultures’, ‘bioprotection’ and ‘biopreservation’ have appeared with increasing frequency. These terms refer to the process of adding specific microorganisms to foods that inhibit the spread of dangerous microorganisms such as listeria or salmonella, or even clostridia, in said foods. The cultures are specifically selected to inhibit harmful bacteria of this sort, but without altering the properties of the food. This latter characteristic is the only difference from the traditional understanding of fermentation. The cultures used in this manner form part of the ‘hurdle concept’, and are usually isolated from the relevant foods, i.e. they can also be found in our natural surroundings.
Protective cultures for raw and ready-to-eat products
Unlike previously, however, such protective cultures are nowadays also suggested for use in foods not traditionally considered as fermented. This applies in particular to raw and ready-to-eat products. Here, the use of protective cultures is intended to either delay or prevent spoilage, or to halt the growth of pathogenic bacteria without altering the product. The study delves deeper into the subject of biopreservation, as well as highlighting the possible mechanisms of action. It also describes several protective cultures that are already commercially available.
*The so-called hurdle concept was introduced as a term for the cumulative inhibitory effect achieved in food preservation by combining several (chemical, physical, biological) preservation measures.
- Protective cultures are microorganisms that are deliberately used to protect foods from spoilage.
- As a rule, isolates of the natural microflora of the food in question are used.
- Food waste can be reduced through the use of protective cultures.
- The activity of the microflora of raw foods can also be termed fermentation, which can be favourably influenced by the deliberate addition of protective cultures.