Green tea extract (GTE) can be successfully added to ethylene vinyl alcohol copolymer (EVOH) films to produce antioxidant active packaging, new research has found.
Spanish scientists said the green-tea containing packaging films could be used for “all types of food, from aqueous to fatty products” to reduce oxidation of sensitive products. The study was published in the Journal of Agriculture and Food Chemistry.
The team from the University of Zaragoza suggested the development of such active packaging systems could be used as a “novel alternative” to current methods such as the addition of antioxidants to foodstuffs or the use of modified atmosphere packaging systems.
They noted that while various antioxidant agents, such as oregano, and carvacrol, had already been added to polymeric films, each had drawbacks in terms of affecting the sensory properties of foods.
Substances such as flavanoids, catechin and quercetin are also “well-known” antioxidants agents. But while they have also been incorporated into polymers, they have not been approved as food additives and would therefore need this before being used in commercial packaging systems.
Green tea benefits
The paper by Pilar Hernandez Munoz et al said that green tea extract (GTE) demonstrated a number of advantages. Not only do the compounds have food additive approval they are also a “great source of flavanoids”.
Previous research has demonstrated their use as antioxidant additives in plastics is effective because “the stability provided by the addition of GTE was comparable to the stability provided by synthetic additives”.
Methodology and results
The group set out to incorporate GTE into EVOH by flat extrusion. Analysis of the material centred on its three aspects; its optical, thermal and barrier properties; its antioxidant efficiency and the release kinetics of the antioxidant agents in several food stimulants.
Using DPPH and ABTS methods, the team found the results confirmed “the high antioxidant activity of the extract, especially in ethanol”.
The films developed in the extrusion process were clear but also brown – with sugar caramalisation cited as a possible cause.
Addition of GTE increased the water and oxygen barrier at low relative humidity. Water sensitivity was also elevated.
An increase in the glass transition temperature and the crystallinity of the films, along with improved thermal resistance was observed.
The study concluded: “From these results it can be stated that green tea extract can be successfully added into EVOH by extrusion, preserving antioxidant activity.”
The substance produced by the research results in “a general purpose antioxidant solution”.
“Therefore, the materials here developed with the combination of antioxidant substances which constitute the green tea extract could be used in the design of antioxidant
active packaging of all type of foods, from aqueous to fatty products, being the compounds responsible for the protection those with the higher compatibility with the packaged product,” added the scientists.
Development of new antioxidant active packaging films based on EVOH and green tea extract by Carol Lopez de Dicastillo, Cristina Nerin, Pilar Alfaro,Ramón Catalá, Rafael Gavara, and Pilar Hernandez-Muñoz published in the online edition of the Journal of Agriculture and Food Chemistry • DOI: 10.1021/jf201246g