Abstract:
Ma-kwaen (Zanthoxylum limonella Alston) is widely spread in the Northern part of Thailand. Its fruit has been traditionally used in food and commercialized as a spice. D-limonene, alpha-phellandrene and alpha-pinene are the main compounds in ma-kwaen essential oil, which possesses smell of oranges and contributes a strong antioxidant activity. However, essential oils undergo undesirable deterioration by heat, humidity, light, and oxygen. Hence, it is beneficial to protect or prolong degradation of volatile ingredients by microencapsulation. Complex coacervation is a phase separation process resulted from electrostatic interactions. Protein (polycation) and polysaccharide (polyanion) are the most widely used wall materials. The objective of this study was to optimize the microencapsulation process of ma-kwaen essential oil by complex coacervation. Samples were prepared using three different types of polysaccharide (alginate ; ALG, gum arabic ; GAB, and xanthan gum ; XTG) together with gelatin (GEL). The resultant microcapsules were measured and analyzed for their encapsulation yield (EY), encapsulation efficiency (EE), antioxidant activities, Fourier-transform infrared spectroscopy (FTIR) analysis and scanning electron microscope (SEM) characteristics. The result showed that GEL-GAB combination formed the superior coacervate complex. Moreover, FTIR confirmed complexation between the protein-polysaccharide wall materials and no chemical reaction between wall materials and essential oil. Then, the process parameters affecting the EY and EE, such as pH (3.20-4.20), the ratio of GEL to GAB (1.00-2.00) and wall material to core material mixing ratio (wall:core ; 1.00-5.00) were optimized using response surface methodology (RSM). Conclusively, the optimum conditions were as follows: pH of 4.00, GEL:GAB of 1.55 and wall:core of 2.50. Flavor profiles of GEL-GAB microcapsule prepared by using optimal conditions showed very good preservation of the volatile compounds.