Abstract:
Perilla fructescens, referred to as perilla, is an annual member of the Lamiaceae family. It is an edible and medicinal plant and widely cultivated in hills and mountains of East Asia. Perilla leaves are applied in herbal medicine for symptoms of asthma and cough and its seeds support healthy immune function, prevent coronary heart disease and decrease blood clotting due to its high content of n-3 linolenic acid. Perilla seeds are a source of perilla oil containing a large amount of unsaturated fatty acid which is sensitive to light and easy to oxidise causing a nutritional loss. Microencapsulation technology is one of methods used to improve the shelf life of valuable oils by enclosing the oil droplets with protective wall materials. Through spray drying, the oxidative-sensitive oil droplet could be transformed into a solid form through rapid evaporation of solvent in the droplets. This study aimed to investigate spray drying microencapsulation of perilla seed oil (both red seed and white varieties) using a combination of wall materials including whey protein isolate (WPI), gum Arabic (GA), maltodextrin (MD) and starch sodium octenyl succinates (OSA starch). The effects of core-to-wall ratio (1:3 and 1:4), solid content (15% and 30%), wall materials and complex coacervation were conducted to see its effect on emulsions and spray-dried microcapsules. Optimisation of emulsion preparation was studied as the first step, followed by characterization of emulsions and spray-dried microcapsules. For emulsions, characteristics were investigated include average droplet size, PDI and zeta-potential. The microencapsule properties included moisture content, water activity, density, oil recovery, encapsulation efficiency (EE), morphology, reconstituted properties and oil were also studies. The oxidative stability of emulsion and spray-dried microcapsules were studied using a accelerated storage trial at 55oC without light by evaluating peroxide value (PV), p-Ansidine (AV) and DPPH antioxidant capacity. The results showed that both emulsions and microcapsules produced at core-to-wall ratio of 1:4 using OSA starch as wall material lead to the minmum changes of PV, AV and DPPH antioxidant capacity. Microencapsules in the present research produced with different wall materials, ratios of core-to-wall and solid contents had a lower water acivity (0.2 < Aw < 0.3), good moisture content (4% - 9%) for long-term storage, high EE (87% - 98%) and good reconstituted ability of spary-dried microcapsules. The microcapsules produced by feed emulsions with core-to-wall ratio of 1:4, 30% solid content using OSA starch as wall materials had the most effective formulation during accelerated storage test. And also, the oxidation stability of both emulsions and microcapsules could be improved via complex coacervation. In conclusion, the present study provided insight to microencapsulation of perilla seed oil using the spray drying method, which improved oxidative stability and inhibited oxidative deterioration.