The gel, which scientists claim does not appear to affect food taste or appearance, could soon provide a safe, natural and environmentally-friendly alternative to conventional synthetic preservatives that are currently applied to produce after harvesting.
Daniel Valero, Ph.D., of the University of Miguel Hernández in Alicante, Spain and his associates dipped a group of common table grapes (Crimson Seedless) into Aloe vera gel and stored them for five weeks under low temperature while exposing a group of untreated table grapes to the same conditions.
The colourless Aloe gel used in this study was developed through a special processing technique that maximised the amount of active compounds in the gel.
The untreated grapes appeared to deteriorate rapidly within about seven days, whereas the gel-coated grapes were well-preserved for up to 35 days under the same experimental conditions. The gel-treated grapes were firmer, had less weight loss and less colour change than the untreated grapes, measures which correspond to higher freshness.
A sensory panel of 10 people evaluated the quality of both the untreated and the gel-treated grapes by consuming some of the grapes. They found that the gel-treated grapes were generally superior in taste.
Although a number of edible coatings have been developed to preserve food freshness, the new coating is believed to be the first to use Aloe vera.
The researchers believe that the gel works through a combination of mechanisms. Composed mostly of polysaccharides, the gel appears to act as a natural barrier to moisture and oxygen, which can speed food deterioration.
But the gel also enhances food safety. Based on previous studies by others, Aloe vera gel appears to contain various antibiotic and antifungal compounds that can potentially delay or inhibit microorganisms that are responsible for foodborne illness in humans as well as food spoilage.
Although the health effects of Aloe gel on human consumption were not directly measured in this study, the scientists are confident that coating is safe. They note that Aloe vera gel has been used as a functional ingredient in some foods and beverages for years.
In addition to preserving table grapes, which are highly perishable, the gel can be applied to other fruits and vegetables. Further testing of the gel on other types of produce is anticipated.
The gel also offers potential environmental benefits. It could provide a greener alternative to sulphur dioxide and other synthetic food preservatives that are commonly used on produce and increasingly the target of health concerns.
Valero and his associates have now filed a patent application in Spain for their gel. His findings will appear in the 5 October print issue of the American Chemical Society's Journal of Agricultural and Food Chemistry, the Society's peer-reviewed publication.
Funding for this study was provided by the Spanish Ministry of Science and Technology and the European Commission via FEDER (European fund for regional development).