The new study, published in Food Hydrocolloids, compared the release properties of tea polyphenols (TP) from gelatin films using different ratios of free TP to nano-encapsulated TP to assess oxidation of a fatty food product.
Led by Fei Liu from Jiangnan University in China, the team noted that tea polyphenols – defined as a mixture of catechins from tea - can block the oxidation of food systems but that issues regarding hydrophilicity restricts their application in oils and fatty foods where the direct addition of tea polyphenols might cause unfavorable reactions with food components.
They noted that active antioxidant films are a novel alternative that may help overcome these limitations in addition to providing a route for the addition of functional ingredients in to foods.
“More recently, the demand for prolonging the shelf life of food has [also] encouraged the development of controlled-release films, where antioxidants release in a slow, but controlled manner, to maintain food quality for a longer time,” they noted.
Indeed, functional food products containing nutritional lipids such as marine omega-3’s have long been explored as candidates for additional antioxidant protection due to the high potential for oxidation of the long-chain omega-3 fatty acids leading to rancidity and off-tastes.
“We wanted to confirm if the controlled-release of TP could be obtained by varying the encapsulation efficiency of TP without the increase of content, where the free TP would release faster while the encapsulated TP release slower to extend the protection effect,” Lui and colleagues explained.
The authors developed active gelatin films made with chitosan nanoparticles with different encapsulation efficiencies to create a film with controlled-release properties.
This was achieved by adjusting the concentration of chitosan hydrochloride (CSNs), the team noted – adding that the dispersion of CSNs within the gelatin matrix was also examined to determine its influence on the final properties and applications of films.
“Nanoparticles tended to aggregate as encapsulation efficiency increased, due to the increase in surface tension of film-forming solutions,” commented Liu et al.
Tea polyphenols were released faster and greater from films in 50% ethanol (4 °C) than in 95% ethanol (25 °C) fatty food stimulant, said the team – noting that the result was due to the swelling by water.
Furthermore, they noted that controlled-release showed in both simulants – where free tea polyphenol had the largest release.
“Therefore, the free TP released at a faster rate could maintain the short-term antioxidant properties for fatty foods, whereas the encapsulated TP released at a slower rate could maintain the intermediate and/or long-term antioxidant properties,” the team explained.
“These results might open up new designs in long-term protection for fatty foods,” they concluded.
Source: Food Hydrocolloids
Volume 62, Pages 212–221, doi: 10.1016/j.foodhyd.2016.08.004
“Controlled-release of tea polyphenol from gelatin films incorporated with different ratios of free/nanoencapsulated tea polyphenols into fatty food simulants”
Authors: Fei Liu, et al