| Abstract [eng] |
In this work, the properties of essential oils immobilized in hydrophobically modified starch and their application in active packaging were investigated. Eugenol, cinnamon, thyme essential oils and two types of commercial octenyl succinic anhydride-modified waxy corn starches were used in this study. Emulsions containing 5 % or 20 % of hydrophobically modified starch and 5, 10 or 15 % of essential oil were produced and the properties of these emulsions - pH, viscosity, particle size, zeta potential, stability, antioxidant properties - were investigated. The emulsions were poured on paper to form active coatings. The antioxidant activity and release in ethanol of eugenol, encapsulated in hydrophobically modified starch by spray-drying, were also investigated. Fourier transform infrared spectroscopy and scanning electron microscopy were also applied to eugenol encapsulated in hydrophobically modified starch. The emulsion containing 15 % of eugenol and 20 % of hydrophobically modified starch was found to have the highest antioxidant activity (94,4 ± 4,72 %). Emulsions containing cinnamon essential oil did not have antioxidant activity, so it would not be significant to use these emulsions as natural antioxidants in the manufacture of active packaging. Analyzing the particle size results of the emulsions, it can be seen that the particle size of the emulsions depended on both - the type of essential oil and its amount in the emulsion. The active coatings were made on paper. Depending on the type of hydrophobically modified starch, 0.7 mg/cm2 and 1.43 mg/cm2 coatings containing dry substances of emulsions were obtained. Since hydrophobically modified starch and essential oil emulsions with the highest concentration of essential oil were found to have the highest antioxidant activity, emulsions containing 15 % essential oil were used for the production of active coatings. It was found that the coating containing eugenol had the highest antioxidant activity (90,11 ± 4,5 %) after 14 days. The coating, which was prepared from an emulsion containing thyme essential oil, also had a relatively high antioxidant activity (40,07 ± 2,0 %). Coatings containing cinnamon essential oil did not have antioxidant activity. It has also been found that eugenol, immobilized in hydrophobically modified starch by spray-drying, does not lose its antioxidant activity and can be released in ethanol. The study showed that 35 % of eugenol from the theoretical possible amount was released in ethanol medium over 60 minutes. |
