Effects of Ozone on Rheological and Emulsifying Properties of Emulsions Prepared with Ozone Treated Hazelnut Oil
Hicran Uzun, Esra Ibanoglu, Food Engineering Department, Gaziantep University
Gaziantep, Turkey.
 
Ozone is a powerful oxidant and has many industrial and consumer applications related to oxidation. In food industry, ozone can be used as a disinfecting and sanitizing purpose for food storage and processing. However, there is limited knowledge about the effects of ozone on the food components. As known, vegetable oils are sensitive to oxidation because of their unsaturated fatty acid contents and oil is one of the main constituents in many foods. The reaction of ozone with the vegetable oils occurs almost exclusively with the carbon-carbon double bonds present in unsaturated fatty acids. This reaction produces several oxygenated compounds such as hydroperoxides, ozonides, aldehydes, peroxides, diperoxides and polyperoxides. In this study, the effects of ozone treatment on rheological and emulsifying properties of emulsions prepared with ozone treated hazelnut oil were investigated. The hazelnut oil treated with ozone gas for 1, 5, 30, 60, 180 and 360 min. After ozone treatment, an increase in viscosity value of these oils was determined. The activity of emulsions prepared ozone treated oils decreased with ozone treatment time. Emulsion stability was affected negatively as ozone treatment time increased. Especially a dramatic reduction in the emulsion stability was observed with ozone treatment for 180, 60 and 30 min. However, the emulsion stability of emulsion containing ozone treated oils for 360 min. was changed with time slowly because viscosity of hazelnut oil had the highest value after ozone treatment process for 360 min. Creaming behaviour of samples were affected with ozone treatment time. Especially, a dramatic increase was observed in the creaming rate of the emulsion prepared with 180 min. ozone treated oil. The creaming was not detected in emulsions containing ozone treated oils for 360 min. due to an increase in viscosity. Dynamic  frequency  sweep  tests  were  performed  in  the  linear  viscoelastic  range  to determine the  effects  of  ozone  on  rheological  behaviour  of the emulsions prepared with hazelnut oil. It was determined that the crossover between G" and G' curves shifted towards to low frequencies when ozone treatment time increased. At frequencies bigger than the crossover frequency, a solid-like behaviour was observed where G' (elastic moduli) was higher than G" (viscous moduli) related to viscoelastic fluids.
Key words: ozone, oxidation, rheology, emulsion.