Introduction: Tea is one of the most popular and frequently consumed beverages in the world
and its consumption dates back to more than 2000 years in China and then spread to other
areas including Japan and later on to Europe (Zhao et al., 2014). Green tea is produced from
Camellia sinensis (L.) Kuntze leaf infusion and is well known for its pleasant flavour and is
associated with positive health effects.
The biological activity of green tea is related with the considerable amount of catechins and
other phenolic compounds, in particular flavonols and phenolic acids, present in its
composition (Zhao et al., 2014). These phenolic compounds prevent the oxidative damage
through their antioxidant activity and also reduce the risk of cancer, cardiovascular and
neurodegenerative diseases (Lorenzo et al., 2014).
The process of oxidation is one of the most common mechanisms of degradation of foodstuffs
and it can alter food texture and colour, decrease nutritional quality, develop off-odours and
also produce possible toxic compounds. As a consequence, the shelf-life and commercial
acceptability of the food products decrease.
Currently, one of the major concerns of the consumers is the impact of food on health. In line
with this, food industry is trying to substitute synthetic additives by natural compounds. These
can be directly added to food or incorporated in food packaging with the aim of being
controlled released throughout the product shelf life. This concept is so-called Active
packaging and allows the packaging to positively interact with foods to increase food shelf-life.
This interaction can be due to the intended release of compounds from packaging to the foods
or to their headspace, or due to the scavenging of compounds by the packaging from the
packaged foods.
Due to the antioxidant capacity of green tea, its extract can be proposed as an alternative to
synthetic antioxidants (Giménez et al., 2013). In fact, it has already been applied in active food
packaging.
Material and Methods: The present review focuses on the application of green tea extract in
active packaging. In this regard, an extensive bibliographic research was carried out in order to
evaluate the polymers already used to incorporate green tea extract, as well as the mechanical
and barrier properties and efficiency of these packaging systems in contact with foods.
Results and Discussion: The chemical composition of tea leaves on active compounds with
antioxidant activity is well documented. Bioactive constituents of the tea leaves include
catechin gallates such as epigallocatechin gallate and gallocatechin gallate (López de Dicastillo
et al., 2011). However the levels of these compounds depend on many factors, such as the
edaphoclimatic conditions and drying conditions of the Camellia sinensis leaves. Moreover the
extraction and analysis methods can also have a great influence in their content.
Green tea extract has already been incorporated into different polymers. In fact, most of them
are edible such as proteic films from distilled dry beans (Yang et al., 2016), agar (Lacey et al.,
2014), chitosan (Siripatrawan et al., 2012; Siripatrawan et al., 2010) and gelatine (Hong et al
(2009).
Green tea extract (GTE) can offers protection against oxidation, significantly reducing rancidity
and thereby extending the shelf-life of packaged foods. Moreover the sensory analysis also
demonstrated that packaged food was unaffected by GTE (Carrizo et al., 2016).
According to Yang et al. (2016), the incorporation of the GTE did not alter the physical
properties of the films. According to Siripatrawan et al. (2010), the incorporation of GTE
improved the mechanical and water vapour barrier properties.
In general, GTE provides a very positive impact in the reduction of oxidation of all types of
food, from aqueous to fatty (López de Dicastillo et al., 2011), although most of the studies
selected meat (e.g. pork, pork sausages, pork loins), or fish products (e.g. fillets of hake, salted
sardines) to test the efficiency of the active films.
Conclusion: Green tea has great potential of application in active food packaging due to its
antioxidant capacity. Therefore, in the near future, is it possible that new food packaging
based on GTE will arise in the market. However, more studies are require to elucidate about
the concentrations of GTE that do not affect or affect positively the mechanical or barrier
properties of the packaging and that are effective as oxidation inhibitors of packaged foodsThis work was supported by the research project “Development of methodologies for the evaluation of polymeric food packaging components and determination of their structural and mechanical properties” (2016DAN 1289) funded by the National Institute of Health Dr Ricardo Jorge, I.P., Lisbon, Portugal.N/
