Meet the Expert
Who: Greg Rachon
What: Brewing research scientist
Where: Campden BRI
Despite being effective, artificial food preservatives have received a bad rap in recent years. In fact, any ingredient that appears to have been chemically synthesised seems to be a big turn-off for consumers these days. They prefer to see ‘real food’ on the ingredients list; something that looks like it ‘should’ be in food.
Collectively, this movement is called clean label. What seemed to initially be a trend now looks to be here to stay. Consumers’ desires drive the market and they are steering it toward clean label products.
The challenge for the food industry is to source preservatives from natural ingredients that can then be incorporated into a product without negatively impacting its appeal through an off-taste or appearance etc. For example, even in an age where (as consumers) we’re quite open to novel products, adding essential oil to beer could create an unusual beverage that would likely raise eyebrows.
Finding the right antimicrobial
A food manufacturer’s first consideration when looking to use a clean label preservative should be: “what natural preservatives are available that would complement my product?”
At Campden BRI, we asked a similar question at the start of a new research project. With the aim of assessing the efficacy of natural antimicrobials against spoilage bacteria, as part of the project we performed an initial screen of potential ‘clean label’ preservatives over a wide range of pH levels, preservative concentrations and ethanol levels.
Several natural antimicrobials looked promising, including:
- lemongrass oil
- orange oil
- hop extracts, and
- British wine
The prospective preservatives were individually subjected to microbiological challenge tests in specific products, including orange juice and chicken, to find out how effective they really were when in-situ.
What did we find?
Of all our findings, the most significant included the lemongrass oil’s effectiveness against yeast in orange juice compared to orange oil and limonene. Lemongrass oil also halved the heat resistance of yeast ascospores, making this organism more susceptible to heat processes – potentially a very valuable finding for manufacturers who pasteurise fruit juices that are susceptible to yeast contamination.
The hop extract showed substantial inhibition of Alicyclobacillus in orange juice – which is significant as this organism has been found to spoil fruit juices. Bacillus cereus was another microorganism that the hop extracts were effective against; Listeria, however, was left unaffected by this ingredient.
Another surprising result was observed for the wine. Despite previous and compelling research that suggested otherwise, we did not find British red wine to have an antimicrobial effect against Campylobacter.
A future rival of artificial preservatives?
Our research has shown that if you’re willing to put the time and effort in, it is possible to find natural preservatives with a narrow spectrum of antimicrobial effects in specific products. We found a few potential applications for the drinks industry but, overall, our study highlighted the difficulty of identifying a universal natural antimicrobial with several applications.
To have an effect, we often found a high quantity of the natural antimicrobial was required. So, even though an orange cordial with hoppy notes may sound appealing, the high quantity of hop extract required for an antimicrobial effect would more likely create a beer-flavoured orange juice – perhaps not so tasty.
The trick is to source natural preservatives that can enhance the product, for example, citrus oils in fruit juices.