PROTECTIVE edible coatings on food have the potential to prolong food shelf-life, and engineers in South America have found that encapsulating active agents with β-cyclodextrin could improve their properties.
Refrigeration, freezing and controlled atmospheres are all used to help preserve fresh foods, and in recent years, some have suggested the possibility of adding an edible, preservative film made from protein, polysaccharide or lipids, which could act as barriers to moisture and oxygen. Such films could also carry other active ingredients, such as antimicrobial agents which would prevent bacterial and fungal spoilage. One of the most commonly tried is oils from herbs and spices, which are already known as edible, but are volatile, often water-insoluble, and degrade in light and oxygen.
The team, led by Silvia Matiacevich at the Universidad de Santiago de Chile, found that using encapsulating agents with the active ingredients helps to stabilise film emulsions and improves the antimicrobial properties of films.
The researchers used thyme oil as the antimicrobial agent, and alginate from seaweed as the polysaccharide to create the film. They first made an emulsion of the two components. They tested three potential encapsulation agents for the emulsion – oligosaccharide β-cyclodextrin, the disaccharide trehalose and Tween-20, a man-made polysorbate surfactant – and made films from the final emulsion, which were dried for 20 hours at 40?C. A control film with no encapsulation agent was also made.
Matiacevich and the team tested various physical aspects of the films, including stability, optical properties and antimicrobial activity. All of the encapsulation agents produced much more stable films than the control. All three had rheological properties which made them suitable for dipping or spray-coating items of food. They found that β-cyclodextrin was the most effective encapsulation agent of the three, and had the best antimicrobial properties when tested against E. coli bacteria. It also has low opacity, so would not affect the look of treated foods. Tween20 had a high opacity, and when taken in conjunction with its non-natural origin, could make it undesirable for consumers.
The researchers say that the next stage will be studying how the films made with β-cyclodextrin vary over longer periods of time.
Food and Bioproducts Processing DOI: 10.1016/j.fbp.2015.11.001
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