Coalescence and Separation of Fish Oil Droplets in Oil-in-water Emulsions under Direct-current Fields
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Abstract:
A new electric demulsification method was proposed to more effectively process fatty fish, achieving both fish oil extraction and high-value utilization of fish protein. The coalescence and separation of fish oil droplets in oil-in-water emulsions under a direct-current field was systematically investigated. The microstructure and macroscopic phenomena during fish oil droplet coalescence, the influence of internal factors (phospholipid content and ionic strength) and external conditions (voltage and temperature) on emulsion stability, the coalescence and separation of fish oil droplets under electric field, and the impact of direct-current electric field on active ingredients in fish oil were studied. The results showed that the presence of the electrical field did not shorten the time required for fish oil separation, but enhanced the probability of oil-droplet coalescence. A certain level of phospholipid content (2 mg/mL) was found to raise the demulsification rate from 37.5% to 63.9%. Ionic strength higher than 0.02 M had a positive effect on the coalescence of fish oil droplets. Chlorine and sodium ions were better than sulfate and potassium ions, respectively, for coalescence. The volume of separated fish oil increased when the voltage magnitude was increased from 0-800 V, and remained relatively constant above 800 V. Influence of temperature was similar to that in traditional demulsification process. Additionally, treatment by direct-current electric field had virtually no impact on the active ingredients of fish oil.
