Abstract
Coconut pulp, a by-product of coconut milk extraction, was used to prepare Pickering emulsion–stabilizing particles by modification with citric acid (CA) through dry heat treatment. The treatment temperature
(100, 120, and 140 ºC) and CA concentration (0.7, 2.0, and 3.3 % w/v) were varied. Modification at 100 ºC and high concentration of CA gave products with satisfactory appearance and surface characteristics. The product obtained by treatment at 3.3 % CA and 100 ºC had a yellowish white color with a light and porous surface, 0.08 degree of substitution (DS), 70º water contact angle, -50 mv zeta potential, and an average particle size after homogenization of 8.4 lm. Unmodified CP powders could not stabilize the oil-in-water (O/W) emulsion, and phase separation occurred rapidly at 25 ºC, while CP modified using 2.0 % and 3.3 % CA at 100 ºC could stabilize the emulsion for at least 30 d. The oil droplet size decreased as the DS of the particles increased from 77.3 to 33.3 lm and 18.6 lm for the particles with DS of 0.046, 0.072, and 0.082, respectively. The higher hydrophobicity imparted by CA modification strongly affected the oil droplet size, while the negative surface charge of particles supported the uniform dispersion of free CP particles in the interspace among the oil droplets.
Keyword:
Coconut pulp, Pickering emulsion, Stabilizing particles, Modification
