Comparison of physicochemical properties and oxidative stability of microencapsulated perilla oil powder prepared by freeze-drying and spray-drying.

Perilla oil is vulnerable to lipid oxidation owing to its high linolenic acid content. Microencapsulation using freeze- and spray-drying methods was applied to enhance the oxidative stability and change the physicochemical properties of perilla oil. Freeze-dried powder (FDP) possessed 11.77 to 38.48% oil content, whereas spray-dried powder (SDP) had 8.90-27.83% oil content. Encapsulation efficiency ranged from 51.22 to 85.71% by freeze-drying and from 77.38 to 90.74% by spray-drying. The oxidative stability of powders depends on the oil content and production methods. Generally, FDP had higher oxidative stability and water solubility, and lower moisture content and water activity than SDP. The particle size of FDP (154.00-192.00 µm) in volume-weight mean diameter was 2.56-24.49 times larger than that of SDP (7.84-72.03 µm). SDP had a lower volatile content at the initial time of storage than FDP, while more volatiles were observed in SDP as storage time increased. The microencapsulation method should be selected appropriately depending on the target property or usage in food applications.

Changes of molecular mobility of ascorbyl palmitate and α-tocopherol by phospholipid and their effects on antioxidant properties in bulk oil.

Molecular mobility of ascorbyl palmitate and α-tocopherol in the presence of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) were determined by NMR relaxation technique. Synergistic effects of DOPC on the antioxidative capacities of ascorbyl palmitate were evaluated in DPPH radical scavenging assay and bulk oil matrix. NMR relaxation technique can provide information on the mobility of protons. Molecular mobility of two protons in hydroxyl group of ascorbyl palmitate decreased by 85 and 78% in the presence of DOPC compared to those without DOPC. However, proton mobility of α-tocopherol increased by 41% when DOPC was present. DOPC significantly enhanced the DPPH reactivity in medium chain triacylglycerol, while this effect was not observed in α-tocopherol. Mixture of ascorbyl palmitate with DOPC showed synergistic antioxidant properties in corn oil at 60 °C. DOPC may make protons of ascorbyl palmitate in more rigid state, which can enhance hydrogen donating ability and antioxidant properties of ascorbyl palmitate in bulk oils.