Research On The Preparation And Stabilized Mechanism Of Citral Nanoemulsion

Citral is one of the most important flavor compounds in fresh juice and lemon oil. It contributes to a strong, pleasant and lemon-like aroma with very high consumer acceptance. Unfortunately, citral is chemically unstable and degrades over time in aqueous solutions due to acid catalyzed and oxidative reactions. This leads to loss of desirable flavour and formation of off-flavours. In this research, the preparation of citral nano-emulsions was optimized in order to cut off the touch of the citral with the acidic system. Antioxidants were added to decrease the oxidation reaction of citral by increasing the proximity of citral with antioxidants, in order to make it possible for citral in the acidic system.1) The best formulation were 0.5% citral,1.0% emulsifier (mass ratio of gelatin to tween-20 was 3:1),5.0% oil phase,800 bar high pressure, and homogenization 2 times. The average particle size of the citral nanoemulsion was 476.73 nm, and the dispersion coefficient was 0.285. After one month storage at room temperature, the nanoemulsion with particle size of 480.83 nm and dispersion coefficient of 0.257 was still stable without turbidity.2) The physical stability was significantly improved, and still remain stable after long-term storage. After two weeks'storage under the temperature of 40?, the citral content of blank control group was only 8.82% of the initial content. While the citral of the nanoemulsion added mixture emulsifier still had 21.25% citral left. Emulsifier can significantly improve the chemical stability of citral under acidic conditions. And in the citral nanoemulsions, the chemical stability of trans-citral was more stable than cis-citral. Meanwhile, the citral degradation products can be inhibited in the acidic environment. The content of p-cymene, p-cresol, and p-methyl acetophenone were significantly decreased.3) With the addition of antioxidants into the nanoemulsion, the average particle size of the emulsion obviously increased. However, the appearance of the emulsion was homogeneous and stable after being stored for two weeks under the condition of 40?. Water soluble antioxidants can significantly improve the chemical stability of citral in the acidic environment. Isoascorbic acid and sodium erythorbate behaved best, there still had 69.26% and 77.42% citral left after storage. As for oil soluble antioxidants, there is still a certain inhibitory effect on the citral degradation in the acidic environment.