Are natural antimicrobial compounds the future for delaying bread mold?

By Kacey Culliney contact

- Last updated on GMT

Essential oils hold plenty of promise in the move to develop natural, active antimicrobial preservatives for bread, say researchers
Essential oils hold plenty of promise in the move to develop natural, active antimicrobial preservatives for bread, say researchers

Related tags: Sliced bread, Shelf life, Yeast

Natural, active antimicrobial sachets containing concentrated oregano essential oil (OEO) should resonate well with consumers concerned about artificial preservation techniques, suggest researchers.

The study published in the Journal of Food Process Engineering​ investigated the antimicrobial efficiency of sachets containing different concentrations of oregano essential oil (OEO) – known for its phenolic compounds that have strong antimicrobial properties.

Researchers looked into the impact against E.coli, salmonella and penicillium on agar medium and prevention against yeasts and molds on sliced bread.

“Traditional packaging concepts are reaching their limits in enhancing food safety, quality and shelf life,”​ the researchers from Brazilian universities said.

“…Sachets containing OEO showed ​in vitro antimicrobial effect against the tested microorganisms, as well as reduced the growth rates of yeasts and molds on sliced bread.”

Mycelia of Molds on the Surface of Bread Slices Packaged Alongside with Sachets Containing 0 (A), 5 (B), 10 (C) and 15% (D) of Oregano Essential Oil, after 15 Days of Storage
Mycelia of Molds on the Surface of Bread Slices Packaged Alongside with Sachets Containing 0 (A), 5 (B), 10 (C) and 15% (D) of Oregano Essential Oil, after 15 Days of Storage

The researchers called on further research in the area of natural antimicrobial compounds to preserve sliced bread, chiefly essential oils.

They said such research is important given “the increasing demand by consumers for synthetic preservative-free, but still safe and fresh food products”.

Antimicrobial active (and natural) packaging

The packaging industry has already developed numerous technologies to improve the shelf life and inhibit mold growth in breads, including modified atmosphere packaging (MAP), irradiation, aseptic packaging and ethanol sachets.

However, the researchers said there is huge potential in natural options given consumer sentiment on preservation of fresh goods.

“Excessive amounts of synthetic preservatives have been applied to decrease fungal spoilage. Recent trends in the bakery industry comprise the demand for high-quality, minimally processed and synthetic preservative-free items, thus increasing the attention towards preservation techniques using natural compounds,”​ they said.

The active, antimicrobial OEO sachets therefore present a potential practical application for bread manufacturers looking to improve the shelf life and safety of sliced products, the researchers said.

“Directly from processing lines, one may obtain products with different flavors and extended shelf life provided by sachets included in the packaging stage. This is useful for food industries to avoid product recalls and to develop novel products, as there is an increasing understanding that innovations are essential for competitiveness.”

Sensory drawbacks?

Findings suggested that the texture of bread improved with the inclusion of the sachets in the packaging, although concentration levels are important to avoid flavor impact.

“The sachets did not affect the sliced bread texture, but imparted unpleasant sensory effects when the highest concentration was tested,”​ the researchers said.

At concentration levels above 10%, the reduction in mold and yeast growth was good but a bitter taste and strong odor impacted the bread. Concentration levels closer to 5% functioned well without the sensory impact, researchers found.


Source: Journal of Food Process Engineering
Published online ahead of print January 2014, doi: 10.1111/jfpe.12059
“Sliced Bread Preservation through Oregano Essential  Oil-Containing Sachet”
Authors: ATP. Passarinho, NF. Dias, GP. Camilloto, RS. Cruz, CG. Otoni, ARF. Moraes and N. De Fátima Ferreira Soares

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OEO concentration

Posted by Caio Otoni,

Dear Steve,

We incorporated 5, 10 and 15% of OEO in relation to the resin. As Kacey stated, these concentrations are volume/weight. To answer your question, they correspond to 0.04, 0.08 and 0.012% (v/w), respectively, in relation to bread weight.

Thanks for asking!

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Concentration level is volume / weight

Posted by Kacey Culliney,

Hi Steve - this concentration level is of the oregano essential oil itself, measured as v/w (volume/weight).

From the study: 'Sachets were prepared by incorporating 5, 10 or 15% (v/w) of OEO (Petite Marie, Itaquaquecetuba, São Paulo, Brazil) into a high-absorption polymeric resin, in accordance with Soares et al. (2008).'

Hope this helps!

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What is meant by 5% concentration level?

Posted by Steve,

I am not clear what is meant by "5% concentration level". Do you mean the bread formula contains 5% OEO? If so, is it baker's percent? This is normally how an ingredient would be expressed in a bread formula.

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