Previous research has shown that thyme and basil have antimicrobial potential. Building on this research, scientists at Ghent university in Belgium opted to investigate the antimicrobial impact of thyme and basil essential oil and their major constituents towards Shigella.
According to the researchers who published their findings in the February issue of Food Microbiology, thyme essential oil and its major constituents thymol and carvacrol decontaminated Shigella inoculated lettuce.
They also found that thyme and basil essential oil, and their major compounds thymol, estragol, carvacrol, linalool and p-cymene, inhibited Shigella in an agar diffusion method.
The researchers determined the antimicrobial effect of basil and thyme essential oil and its major constituents thymol, p-cymene, estragol, linalool, and carvacrol by using an agar well diffusion assay.
Thyme essential oil, thymol and carvacrol showed inhibition of Shigella sp. in the agar diffusion method. The potential of thyme essential oil, thymol and carvacrol at 0.5 per cent and 1 per cent v/v for decontamination of lettuce was evaluated.
According to the findings, the researchers noted a decrease of the shigellae after washing with 0.5 per cent while at 1 per cent Shigella numbers dropped below the detection limit. The antimicrobial effect on a subsequent lettuce sample in the same decontamination solution was significantly decreased. In addition, application of thyme essential oil or thymol or carvacrol for decontamination is hampered by sensoric properties of the lettuce (browning, strong odour), note the researchers.
"In this study, it was shown that essential oils and their compounds have potential to be used for decontamination of minimally processed vegetables," write the authors of the paper.
More research into the use of essential oils as food preservatives is needed, concluded the scientits.
Used since antiquity for their antimicrobial potential, herbs and spices have played a role in food protection for thousands of years.
According to the researchers, in recent years, two consumer-driven demands have arisen in the food industry. The first is the provision of fresh, natural foods requiring minimal preparation and the second is the control of food safety. But only a few studies have evaluated the potential role of essential oils and their components as food preservatives.
With the natural trend still on a steep, upward curve, the recent findings from Belgium suggest that the food industry should start to invest more time and money into discovering the full potential essential oils could play in food preservation.
Full findings are published in the February issue (Volume 21, Issue 1 , February 2004, Pages 33-42) of Food Microbiology.