The new research, published online in the Journal of Food Science , indicates that antimicrobial compounds could be delivered using cyclodextrins (CDs), which function by controlling the release according to humidity levels.
And the most promising anti-microbial ingredients highlighted are essential oils, including rosemary, oregano, coriander, thyme, sage, garlic, and onion oils, state the researchers from the Centro de Investigacion en Alimentacion y Desarrollo and the Univ.
Autonoma de Ciudad Juarez in Mexico.
"Some spices contain essential oils with antimicrobial activity, such as sulfur compounds in garlic, cinnamaldehyde, and eugenol from cinnamon essential oils," added the researchers.
"The growth of different microorganisms responsible for quality loss of fruit and vegetables can be diminished using these essential oils."
Fresh-cut fruits and vegetables are a rapidly growing segment of the market, and chlorine solutions are widely used by the industry to sanitise and prolong the shelf-life.
But concerns about the potential formation of carcinogens from chlorine usage have prompted some to investigate alternative sources including essential oils and irradiation.
Unique challenges "Whole and fresh-cut produce are unique among the food products; they remain metabolically active and their shelf life and storage stability are shortened as consequences of these processes," explained the researchers.
The main problem facing the fresh-cut products is the loss of water, which promotes the growth of, predominantly, fungi and moulds that lead to spoilage.
As a result, various approaches have been proposed to prolong the shelf-life of these products, including the use of edible films and active packaging.
Cyclodextrins containing anti-microbial essential oils could provide an interesting alternative, suggest the researchers, since interactions between water and the polysaccharide lead to a weakening of the cyclodextrin-essential oil interactions.
This in turn results in a release of the 'guest' molecule and expression of its anti-microbial activity.
Some cyclodextins are already used as carriers for natural colours, flavours and vitamins, solubilisers of lipids, stabilisers of oil in water emulsions, or flavour or aroma modifiers in a variety of processed foods.
Looking ahead The Mexican researchers propose that future research should focus on optimising the microencapsulation process, identifying pre-treatments to that can better control the release according to humidity levels, and identifying the effects of the food matrix and the temperature on the release rate.
They also state that studies should be performed to quantify optimal doses, in addition to investigating the sensory qualities of the resulting fresh-cut products.
"All these studies will be useful to understand the mode of action of the system and allow offering producers a practical method to preserve fresher, more natural foods containing less artificial preservatives, maintaining and ever increasing quality by, for example, delivering natural antioxidants to increase the antioxidant capacity of fresh-cut fruits and vegetables," they concluded.
Source: Journal of Food Science (Blackwell Publishing) Published online ahead of print, 29 March 2008, doi: 10.1111/j.1750-3841.2008.00705.x "High Relative Humidity In-Package of Fresh-Cut Fruits and Vegetables: Advantage or Disadvantage Considering Microbiological Problems and Antimicrobial Delivering Systems?"
Authors: J.F. Ayala-Zavala, L. del-Toro-Sanchez, E. Alvarez-Parrilla, and G.A. Gonzalez-Aguilar