Abstract:
This research aimed to microencapsulate macadamia oil by spray drying to prevent oxidation reaction and rancid odor. Firstly, the optimum condition for preparing emulsion using response surface methodology was studied by varying the ratio of sodium caseinate (NaCas) to maltodextrin DE18 (1:3-1:5), ratio of wall material to core material (50:50-70:30) and homogenizing pressure (100-300 bar). The oil droplet size and viscosity of emulsion were measured. The result showed that the appropriated condition of emulsion was the ratio NaCas to maltodextrin of 1:4, ratio of wall material to core material of 60:40 and homogenizing pressure of 200 bar and the oil droplet size and viscosity of this emulsion were 0.64±0.01 µm and 37.81±0.63 mPa.s, respectively. Secondly, the conditions of spray drying were investigated by varying the feed rate (1-2 kg/h) and inlet temperature (160-200 ℃) and measuring various properties of microcapsules obtained after spray drying. It was found that the appropriated condition of spray drying was the feed rate of 1.1 kg/h and inlet temperature of 167 ℃. The microcapsules were sphere with wrinkle surface, particle size was not uniform, and the structures inside microcapsules were multi-core and simple core. The properties of the microcapsules were the average particle size of 9.75±0.03 µm, moisture content of 1.00±0.05 %, bulk density of 0.36±0.01 g/cm³, surface oil of 7.33±0.59 %, microencapsulation efficiency of 88.75±0.45 %, free fatty acid of 0.170±0.001 % oleic acid and peroxide value of 0.198±0.004 meq.O₂ / kg oil. The microcapsules of macadamia oil were kept at 30 ℃-55 ℃ and packed in laminated pouch (non-nitrogen and nitrogen gas flushing) to study the oxidation reaction by analyzing the peroxide value and evaluating the rancid odor during storage for 2 months. The results showed that peroxide value of microcapsules kept at 30 ℃, both non-nitrogen and nitrogen gas flushing did not change significantly (p>0.05). However, the microcapsules kept at 45 ℃ and 55 ℃ had higher peroxide value after 50 days and the samples in non-nitrogen gas flushed package had higher peroxide values than nitrogen gas flushed one. The microcapsules kept at all conditions did not show rancid odor.