Citrus essential oils could be anti-fungal additives for food

By Stephen Daniells

02-May-2008 - Essential oils from citrus like mandarins and lemon could be natural anti-fungal agents for food, tapping into the search for natural alternatives to synthetics, suggests new research from Spain.

The tide is currently turning against chemical-based anti-fungal additives for food use, opening up opportunities for alternatives from natural sources. The reasons for this are manifold and include general consumer preferences for natural foods, legislative changes, and the isolation of antibiotic resistant pathogens.

"It seems that citrus essential oils could be considered suitable alternatives to chemical additives for use in the food industry, attending to the needs for safety and satisfying the demand of consumers for natural components," wrote the researchers from Miguel Hernandez University in Alicante.

The study, published in the journal Food Chemistry, reports that essential oils of lemon, mandarin, grapefruit and orange all exhibited antifungal activity against the common food moulds Aspergillus niger, Aspergillus flavus, Penicillium chrysogenum and Penicillium verrucosum.

According to the researchers, essential oil from orange was the most effective against A. niger (50 per cent reduction). The mandarin produced the best effects against A. flavus (65 per cent reduction), and grapefruit came out on top against P. chrysogenum and P. verrucosum (48.1 and 48.3 per cent, respectively).

The protective effects against growth were proposed to be due to toxic effects of the essential oil on the functionality and structure of the cell membrane in the mould.

The researchers also note that other studies have indicated that inhibition may also be due to the monoterpenes content of essential oils. "These components would increase the concentration of lipidic peroxides such as hydroxyl, alkoxyl and alkoperoxyl radicals and so bring about cell death," they said.


Potential for essential oils

"The main advantage of essential oils is that they can be used in any foods and are considered generally recognized as safe (GRAS), as long as their maximum effects is attained with the minimum change in the organoleptic properties of the food," wrote the Alicante-based researchers.

Indeed, the search for natural alternatives to synthetic additives has increased the attention on essential oils. Katie Fisher and Carol Philips of the University of Nottingham's School of Health, UK, reviewed the potential of essential oils as inhibitors of both gram-positive and gram-negative bacteria.

The review, published in Trends in Food Science and Technology, noted that the antimicrobial properties of citrus essential oils have only started to be explored quite recently.

Fisher and Philips sounded a note of caution, however: "Should essential oils be applied to food they may be able to inhibit a wide range of organisms, but they could also cause an imbalance in gut microflora," they wrote.

Thus, while more research is conducted on the effect of certain essential oils throughout the whole intestinal tract, they recommend that a good starting point for the food industry would be to look at using those citrus oils that are already being used as food flavours.

Source: Food Chemistry
Published online ahead of print, doi: 10.1016/j.foodcont.2007.12.003
"Antifungal activity of lemon (Citrus lemon L.), mandarin (Citrus reticulata L.), grapefruit (Citrus paradisi L.) and orange (Citrus sinensis L.) essential oils"
Authors: M. Viuda-Martos, Y. Ruiz-Navajas, J. Fernandez-Lopez, J. Perez-Alvarez
http://www.foodnavigator.com/news/ng.asp?n=85051-citrus-essential-oils-mould

Candle Power

Candle Power February 11, 2006
News release
From the University of Southampton
Ref: 04/89 16 June 2004
Candle power wipes out bugs
In recent years the consumer market for candles has grown dramatically, as candles of all shapes, sizes, colours and fragrances have been used increasingly in homes and restaurants to create atmosphere and enhance mood.
Now two researchers at the University of Southampton have taken the potential uses of fragranced candles one step further, by demonstrating that they can also have valuable and effective bactericidal properties.
The researchers, Dr Lindsey Gaunt and Sabrina Higgins, have discovered that adding essential oils to the candle can destroy bacteria such as Escherichia Coli and Staphylococcus aureus on surfaces. Working with Professor John Hughes in the Bioelectrostatics Research Centre, Lindsey and Sabrina have been testing different essential oils, such as orange, thyme, and eucalyptus, which when dispersed into the air and combined with the ions produced in the candle flame, all have a powerful bactericidal effect.
Where candle use would not be appropriate, for example in a kitchen, the same bactericidal effect can be produced by using plug-in devices combining the appropriate essential oils and ions generated by an electrical discharge.
According to Lindsey Gaunt, the candles and electrical devices could be as effective as liquid disinfectants, together with the added benefit of being able to penetrate porous surfaces and fabrics in a room with very little personal effort.
This unique combination of essential oils and electrical ions has demonstrated a remarkably powerful bactericidal action, with up to nearly 100 per cent bacteria kill.
Lindsey Gaunt and Sabrina Higgins will be presenting the results of their research in Tokyo in November at the annual joint international conference of the Institute of Electrostatics Japan and the Electrostatics Society of America.