SITA T60 tensiometer (SITA Messtechnik, Dresden, Germany) was used to measure the surface tension of encapsulation solutions by employing the maximum bubble pressure method, where the bubble pressure tensiometer produces gas bubbles at constant rate and blows these bubbles through a capillary which is submerged in the sample liquid with a known radius.
The pressure needed to form a bubble was measured (Mysels, 1990).
Measurements were taken at room temperature (20 ± 1 C) with a bubble pressure life time of 40 s.
The instrument was calibrated using water, and a surface reading of 72.8 ± 0.5 mN/m was regarded as accurately standardised.
Solutions subjected to surface tension measurement were in the same conditions as solutions used for encapsulation.