Packaging has always plays an important role in protecting the food products from the external environment with as aim to increase the shelf life of product and satisfy consumer requirements of safe food for consumption. In recent times a lot of research work is going on advances in packaging technologies and active packaging of food is one of the technology gaining popularity and wide acceptance for maintaining the quality attributes along with increasing the shelf life of food products.

Active packaging system make use of active materials or ingredients such as ethylene emitters (KMnO₄, Titanium dioxide), CO₂ emitters (citric acid, sodium bicarbonate) and O₂scavengers (gallic acid, glucose oxidase); biological active molecules from plants like polyphenols, flavonoids and essential oils that helps in prolongs the shelf life and maintain the wholesomeness of food products. In recent times, researchers are focusing more on essential oils extracted from different parts of plant such leaves, roots, bark, stem, bud, flowers etc. The bioactive compounds in essential oils are reported to have antimicrobial and antioxidant properties that make them suitable for incorporating in packaging material for enhancing the shelf life of food products.

Essential oils (EO):

Essential oils are secondary metabolites of plants and are volatile, aromatic in nature with a peculiar and strong aroma inherent to oil. The EO are colorless, hydrophobic and liquid at ambient temperatures and most of the EO possess Generally Recognized as Safe (GRAS) status by American Food and Drug Administration (FDA). EO have a wide spectrum of biological activity due to the presence of constituents such as alkaloids, terpenes, flavonoids, ketones,  phenols (eugenol, thymol), aldehydes (citral, benzaldehyde, cinnamaldehyde), flavones (isoflavones), and alcohols (menthol, terpineol, linalool). These active compounds are responsible for the antioxidant, antifungal, antimicrobial activities of EO. The mechanism of antimicrobial activity of EO is due the ability of EO to pass through the lipid bilayers of cell membrane there by causing electrolyte leakage and interfering the transport mechanism of ATP synthesis in mitochondria resulting in cells lysis and eventually the cell death. The other use of EO is exploited for use as an alternative to chemical additives for preserving the food from bio chemical and microbial decay. The major EO incorporated in biodegradable films and edible coatings are oregano, lemongrass, tea tree, sage, clove, cinnamon, peppermint, rosemary, thyme, lavender etc. are used for wrapping and coting of various food matrixes such as fruits and vegetables, fish and meat products, dairy products. The essential oil along with their bioactive components are listed in Table 1.

Applications of EO in food packaging system:

The active packaging system consisting of polymeric films, biodegradable films and edible coatings that can act as carrier for bioactive compounds of EO and help in slow release of active compounds in food matrixes, thereby improving the food safety and stability from the food borne pathogens during storage of food products (Fig.1).

The addition of EO in films not only improves the antimicrobial, antioxidant properties but also lowers down the water permeability of film thereby modify the film characteristics. The films and coatings incorporated with essential oils for preserving food products from food born pathogen is listed in Table 2:

Limitations of using essential oil for active food packaging:

EO have an inherent strong aroma that may have a negative effect on the sensory properties of the food products. Moreover the EO are highly volatile and possess stability issues such as poor solubility and unstable to light conditions which in turn reduces the efficacy of EO during its incorporation in packaging materials. To overcome these problems nano technological interventions such as nano encapsulation, nano emulsion and nano fibres are used for improving the efficacy of EO without affect the organoleptic properties of food products.

Future prospects

Active Packaging system consisting of EO have demonstrated the potential of improving the antioxidant, antimicrobial properties of the packaging films and coatings. The incorporation of EO in packaging films have prolonged the shelf life of food products due to the presence of bioactive components that are responsible for preventing chemical and microbial decay. Beside the advantages of EO, there is need of more researches on nano technological approaches for improving the stability of EO without effecting the organoleptic properties of the food.

References:

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