Exploring the effectiveness of natural antimicrobials as an alternative to synthetic preservatives

3 July 2025 | Annette Sansom, Section Lead - Emerging Microbiology Group

The demand for organic, vegan and clean-label food products is on the rise, resulting in an increased consumer preference for more natural and minimally processed foods.

Such a move towards more sustainable and health-conscious options is leading food manufacturers to investigate more natural ways of preserving taste and enhancing flavour, while simultaneously controlling the growth of microorganisms, including pathogens and spoilage organisms – to maintain the quality and safety of their food products.

Subsequently, we are seeing the growing use of natural antimicrobials in food.

What are natural antimicrobials?

Natural antimicrobials are compounds derived from natural sources like plants, animals and microorganisms.

As a promising alternative to synthetic preservatives, these compounds have the natural innate ability to suppress the growth or survival of detrimental microorganisms such as bacteria and fungi.

Consequently, with their ability to make food products safer and in some cases extend their shelf-life too, the use of natural antimicrobials is becoming an increasingly attractive proposition for food manufacturers.

The challenge food manufacturers face when looking to add natural antimicrobials into their food ingredients

However, while there is growing interest and opportunities in the wide range of natural antimicrobial products, there is a gap in understanding about their application and effectiveness in real-life food systems.

As a result of this, food producers and ingredient manufacturers have been requesting reliable data on the performance of these natural antimicrobials to ensure food safety and quality.

How we are addressing the knowledge gap for food manufacturers

To help tackle this, we undertook some research that would allow us to delve deeper into the effectiveness and application of natural antimicrobials. The objective of the research was to increase our knowledge of available natural antimicrobial products and enable us to establish methods to test their effectiveness, not only from initial screening but in food trials too.

The research we conducted was based on a three-stage approach.

• Phase 1
  • To expand our understanding of natural antimicrobial products, we screened 10 candidates – including fermented vinegars, fungal extracts, liquid smoke, fruit seed extract and plant-derived extracts (both individual and mixed) against a variety of microorganisms.
  • This process enabled us to evaluate which microorganisms each product was most effective against, and whether their antimicrobial activity was broad-spectrum or more targeted.
• Phase 2
  • This stage sought to determine the minimum inhibitory concentration (MIC) for selected natural antimicrobials against a relevant species or group of microorganisms.
  • Here a range of natural antimicrobials including, fungi extract, liquid smoke, fruit seed extract, and plant derived extract mix were tested with a range of concentrations against eleven Listeria monocytogenes strains.
• Phase 3
  • The final stage sought to verify the effectiveness of natural antimicrobials through in food trials.
  • A food product known to support the growth of Listeria monocytogenes was reformulated incorporating a natural antimicrobial ingredient.
  • Effectivity analysis involved microbiological challenge testing within the original and reformulated products against the target microorganism inoculated into the products.
  • Alongside, microbiological shelf-life analysis and sensory assessment of the products was conducted.

Some initial research findings

From our assessment of plant derived antimicrobial compounds, the summary results of our findings offer a strong case for the effectiveness and use of natural antimicrobial products.

Some of the strongest highlights can be seen from our assessment of a plant derived antimicrobial extract mix (S10) where:

• In our range of activity assessment – the natural antimicrobial was found to inhibit 100% (23/23) of bacteria.
• The minimum inhibitory concentration (MIC) was determined to be 1,000 ppm in a broth system.
• Our in-product assessment of pea-protein vegan patty highlighted that L. monocytogenes levels reached 8.4 log cfu/g in the control, compared to 1.4 and 1.2 log cfu/g in high (2,000 ppm) and low (1,000 ppm) antimicrobial products, respectively.

More detailed results from this research should be available soon on our website.

How we can support those wanting to add natural antimicrobials into their food products

Having attained positive results from our research, we have been able to provide a proof of concept for natural antimicrobial testing.

Subsequently, we are introducing a new Antimicrobial Assessment Service, which is ideally suited to clients looking to reformulate their product ingredients or those that have an antimicrobial product that they would like independent assessment of.

Key highlights of the new service include:

• An enhanced method for disc diffusion assay – offering analysis for a diverse range of food relevant microorganisms
• Efficacy spectrum identification including:
  • Antimicrobials with broad spectrum effectiveness
  • Antimicrobials with targeted action
• MIC analysis – food relevant conditions
• In product design and analysis
• Support for industry in the trend towards cleaner labels ensuring food quality and safety

If you have any questions about our new antimicrobial assessment service, or anything else to do with natural antimicrobials or microbiological testing, we are also offering a free 20-minute consultation with Annette.

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Disclaimer

This article is solely about the efficacy of natural antimicrobials, rather than a piece about their regulatory compliance. However, if compliance is an issue for you, our regulatory team would be very happy to discuss whether any of the natural antimicrobials outlined in this piece could be permitted for use in your products.