3.1. Emulsion gel characterization
3.1.1. Microscopy
Microscopic images showed that inulin concentration significantly
influenced morphologies of emulsion gels prepared with 3% psyllium husk
(Fig. 2).
(Place for figure 2)
Fig.2. microscopic observation (500X) of ultrasonic-treated and
untreated 3% psyllium husk emulsion gel with different concentration of
inulin. Dark arrow indicates length of 20 μm.
At 0% inulin concentration, emulsion droplets in close proximity to
each other were large and polydispersed, which increased the
flocculation rate. High flocculation of emulsion droplets indicates low
emulsion stability (Yvonne and Victoria, 2018). The oil droplets in the
emulsion gels became smaller and uniform with increased inulin
concentration suggesting that the husk-emulsions were stable at higher
inulin concentration. A similar result was reported previously (Xu et
al., 2020), where the particle size of oil-in-water emulsion decreased
with increasing inulin concentration. The droplet decrease may be due to
high inulin concentration that forms a secondary interfacial layer
enhancing surface coating of oil droplets to prevent against droplet
aggregation and coalescence; and this result in smaller oil droplets and
highly stable emulsion (Sarkar et al., 2018). These results were further
confirmed by the particle analysis and SEM image.
The ultrasonic-treated emulsions showed higher stability with smaller
particle size compared to untreated emulsion. Reduction of droplet size
by ultrasound can be attributed to shear force generated by the
cavitation of the ultrasonic wave breaking droplets into smaller sizes
(Guo et al., 2014).