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Plant extracts – the preservatives of the future?

The food industry is always searching for new ingredients or additives that give a product a certain added value. Nowadays, this added value is not just measured by whether the product ingredients or additives can provide it with food technological advantages. Thus factors such as naturalness, purity and sustainability also play an important role alongside taste, quality, consistency and durability.
 

Food should be produced in a more healthy and sustainable way

The research project “Healthy nutrition and sustainable food production” (www.nfp69.ch), published in the autumn of 2013 by the Swiss National Science Foundation, is a step in this direction. Studies are being carried out on unknown antimicrobial substances from bacterial strains, which could be used for the preservation of food, and on the impact of different influencing factors, such as higher concentration levels of cooking salt, curing salt, sugar or lactic acid on the formation of staphylococcal enterotoxin of the staphylococcus. A further research field outside of the project consists of functional plant ingredients, in particular those substances that work against germs and thus have the potential to be used in maintaining food safety.
 

Longer shelf-life using natural substances - Possible approach in practice?

The antimicrobial effectiveness of rosemary extract has already been studied in detail. It works against yeast, mould and bacteria by paralysing their energy production. It was already established in the 80’s that the alcoholic extract from rosemary had the ability to inhibit the germination and toxic formation ofClostridium botulinum. Further studies showed that rosemary negatively affects the growth of Listeria monocytogenes, Yersinia enterocolitica, Aeromonas hydrophila and even Escherichia coli, Staphylococcus aureus as well as Salmonella typhimurium. The well-known antioxidant characteristics of this substance are complemented by its antimicrobial potential. 
Another interesting, natural substance is Alfalfa protein extract. Alfalfa is already known throughout the world for being a very valuable plant nutritionally. However, people are now also becoming aware of it due to its antimicrobial efficacy. The saponins and prosaponins it contains show a growth-inhibiting effect on different yeasts, moulds, gram-positive and gram-negative bacteria. They are directed in particular against gram-positive bacteria, such as Bacillus cereus, B. subtilis, Staphylococcus aureus and Enterococcus faecalis. 
Furthermore, for example, antimicrobial efficacy is also attributed to the flavonoids in garden peas (Pisum sativum L.), peanuts (Arachis hypogea) and fenugreek (Trigonella foenum-graecum), as well as a multitude of quinones and manzamines from different plant-based natural substances or marine sponges.
The question of suitability as a food ingredient is an interesting topic for research. Of course, the effects on the rheology and sensory properties of the products would need to be examined.
 

UFAG LABORATORIEN as strong partner for durability tests

Whilst the oxidative stability of food can be easily identified from the occurrence of aldehyde from fat oxidation, for example, (here hexanal presents an indicator substance of choice), the easiest and most reliable way to establish the antimicrobial activity is through direct comparative studies between conventionally produced products and those that have the addition of functional plant substances. During storage, the microbiological status of different active ingredients changes at different speeds. Studies are carried out according to this principle at the UFAG laboratories within the framework of routine microbiological controls. 

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