Ultrasonic preparation of stable flax seed oil emulsions in dairy systems – Physicochemical characterization

This study reports the incorporation of 7–21% of flax seed oil in pasteurized homogenized skim milk (PHSM) using high intensity ultrasound (US) at 20 kHz between 1 and 8 min and at varying power levels. A minimum process time of 3 min at an applied acoustic power of 176 W was sufficient to produce e...

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Bibliographic Details
Published in:Food hydrocolloids 2014-08, Vol.39, p.151-162
Main Authors: Shanmugam, Akalya, Ashokkumar, Muthupandian
Format: Article
Language:English
Subjects:
Cavitation
Droplets
Emulsification
Emulsions
Flax
Flax seed oil
Milk
Nutraceutical
Proteins
Seeds
Stability
Ultrasound
Ultraturrax
Whey protein
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Summary:This study reports the incorporation of 7–21% of flax seed oil in pasteurized homogenized skim milk (PHSM) using high intensity ultrasound (US) at 20 kHz between 1 and 8 min and at varying power levels. A minimum process time of 3 min at an applied acoustic power of 176 W was sufficient to produce emulsion droplets (7% oil) with an average mean volume diameter of 0.64 μm and they were stable at least 9 days at 4 ± 2 °C. The mechanical, cavitational and cavitation-after-effects of US are responsible for the production of smaller sized emulsion droplets and process-induced modifications of milk proteins. A very small proportion (less than 20%) of partially denatured whey proteins provided stability to the emulsion droplets. The emulsion droplets also showed a surface potential of about −30 mV due to the adsorbed proteins, which provided further stability to the emulsion droplets due to electrostatic repulsion. In order to see if other high shear techniques can generate stable emulsions, experiments were carried out using Ultraturrax (UT) at similar energy densities to that of US. UT did not produce stable emulsions until 20 min of processing suggesting the superiority of US emulsification process. [Display omitted] •Sonication for 3 min was sufficient to produce a stable emulsions of flax seed oil in milk.•Mechanical, cavitation and cavitation after-effects produced stable emulsions.•Electrostatic repulsion between droplets contributes to emulsion stability.•At similar energy densities, Ultraturrax did not produce stable emulsions.
ISSN:0268-005X
1873-7137
DOI:10.1016/j.foodhyd.2014.01.006