Casein derivative delivery systems were developed by the use of a modified
pH-induced gelation method with GDL (Nag et al.,
2011). Five percent (w/v) of casein derivative solution was mixed
with DHA dissolved in ethanol and 2% (w/v) GDL solution followed by stirring for
10 min. Final concentration of DHA in casein derivative solution was 25 mg/100
mL. To form delivery system, 10 mL of casein derivative solution including GDL
and DHA was added to 40 mL of soybean oil (Sajo Haepyo, Seoul, Korea). It was
mixed thoroughly for 5 min in magnetic stirrer and then held for 60 or 70 min to
allow to form gel matrix. After holding for 60 and 70 min, pH of sodium
caseinates solution reached to 5.0 or 4.8, respectively and aqueous phase
(sodium caseinate solution) was turned into micro-sized particles by
acid-induced gelation. Casein derivative-based delivery systems formed in water
phase were collected by centrifugation at 15,000×g for 1 min and oils at
top layer were discarded. After washing 3 times with deionized water to remove
residual oil, casein derivative delivery systems were collected and then
freeze-dried.