Essential oils have boomed in popularity as alternatives for synthetic cleaning products, anti-mosquito sprays and even medicines.

Why not use them to preserve food in a way that will appeal to the natural medicine crowd? 

Essential oils have been used therapeutically for centuries, mostly for mood altering and also for preservation. Today, they are being studied by tobacco companies, the cosmetics industry and, of course, food chemists. A study in the Journal of Agricultural and Food Chemistry reports the development of new edible films containing oils from clove and oregano that preserve bread longer than commercial additives.

Nilda de F. F. Soares and colleagues note that the search for new ways to keep packaged food from spoiling has led some scientists to essential oils, which can keep bacteria and mold at bay. Oils from clove and oregano had already been incorporated into edible films. But scientists still needed to optimize the effectiveness of these films and test them under real-life conditions for other uses.  

This will be necessary to get broad uptake. Currently, essential oils are not standardized so people could be buying something useless from alternative medicine and homeopathy charlatans. Aromatic substances are also difficult to use for blinded studies and for conventional medicine there needs to be confirmation what causes the outcome, but for food preservation things are a little easier. 

Soares's team tested how well different edible films with clove and oregano essential oils could maintain bread's freshness and see how they measured up against a commercial antimicrobial agent. Bread is a common staple around the world and is often kept fresh with calcium propionate, which is completely natural but a few papers have suggested negative side effects and that has been fodder for the anti-science nutrition crowd.

The scientists bought preservative-free bread and placed slices in plastic bags with or without essential oil-infused edible films. To some slices, they added a commercial preservative containing calcium propionate.

After 10 days, the latter additive lost its effectiveness, but the edible films made with small droplets of the oils continued to slow mold growth.