Essential oils are concentrated liquids of complex mixtures of volatile compounds and can be extracted from several plant organs. Essential oils are a good source of several bioactive compounds, which possess antioxidative and antimicrobial properties. In addition, some essential oils have been used as medicine. Furthermore, the uses of essential oils have received increasing attention as the natural additives for the shelf-life extension of food products, due to the risk in using synthetic preservatives. Essential oils can be incorporated into packaging, in which they can provide multifunctions termed "active or smart packaging." Those essential oils are able to modify the matrix of packaging materials, thereby rendering the improved properties. This review covers up-to-date literatures on essential oils including sources, chemical composition, extraction methods, bioactivities, and their applications, particularly with the emphasis on preservation and the shelf-life extension of food products.
Properties of fish skin gelatin films incorporated with three essential oils from various sources (basil, plai and lemon) with a gelatin/essential oil ratio of 1:1 (w/w) were determined. Films containing different essential oils had lower tensile strength and elastic modulus, but higher elongation at break and thickness, compared with the control film (without essential oils) (p \ 0.05). Lower water vapour permeability was observed when essential oils were incorporated, in comparison with the control, particularly when basil and lemon essential oils were used (p \ 0.05). Films with essential oils had varying L*-, a*-, b*-and DE*values (total colour difference) and WI (whiteness). Amongst all films, that incorporated with plai essential oil showed the highest b*-and DE*-values but lowest WI (p \ 0.05). Lower light transmittance and higher transparency value, indicating more opaqueness, were observed when films were incorporated with essential oils (p \ 0.05), especially for film added with lemon essential oil. Film containing basil essential oil showed the highest DPPH and ABTS radical scavenging activities (p \ 0.05), whilst those incorporated with lemon essential oil had the highest chelating activity (p \ 0.05). Thus, the incorporation of various essential oils from various sources determined properties and antioxidative activity of fish skin gelatin film differently.
KeywordsGelatin film Á Essential oil Á Basil Á Plai Á Lemon Á Antioxidant activity Abbreviations ABTS 2,2-Azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt DPPH 2,2-Diphenyl-1-picryl hydrazyl EDTA Ethylenediaminetetraacetic acid FFS Film forming solution RH Relative humidity TS Tensile strength
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