| Summary: | 碩士 === 國立中興大學 === 食品暨應用生物科技學系 === 96 === Abstract
Litsea cubeba, also named as “Makauy”, is a plant commonly found in medium-high altitude area in Taiwan. It is usually used as cooking condiment or tea brewing for aborigines. The component analysis of Litsea cubeba essential oil, and microencapsulation of the oil by using cyclodextrin (CD) were studied; meanwhile, the better condition for the microencapsulation of Litsea cubeba essential oil and the antioxidant activities and antibacterial effect were also investigated.
The main content in Litsea cubeba essential oil is limonene and citral, after analyzing by Headspace GC-MC, the results show that d-limonene takes about 23.74% whereas citral takes about 57.98% of the total content. While proceeding with encapsulation, by using β-CD, and the optimal ratio of β-CD to Litsea cubeba essential oil is 8:1. By water distillation to recover the oil in the capsule, the result shows the encapsulating rate of essential oil is around 82%.
The antioxidant activities of Litsea cubeba essential oil were determined. For DPPH free radical scavenging effect, pure essential oil is 66.25%, IC50 value is 63.22 mg/mL, while β-CD shows no DPPH free radical scavenging effect. For reduction power, Litsea cubeba essential oil is 98.64%, IC50 value is 27.74 mg/mL, yet β-CD has no reduction power. For total antioxdation effect test (TEAC), the result shows the higher content of the essential oil, the better capability of antioxdation effect. The content at 44 mg/mL (50% of the essential oil) has about the same antioxdation effect as Ascorbic acid at 0.1 mg/mL, TEAC’s IC50 value is 0.15 mg/mL. While the concentration is 880 mg/mL, Litsea cubeba essential oil’s chelating effect is 75.79%, that is more than EDTA’s chelating effect at concentration of 1 mg/mL which IC50 value is 111.45 mg/mL. Regarding the analysis of total phenolic compound, the total phenols content increases with the elevation of Litsea cubeba essential oil concentration. When the oil concentration at 27.5 mg/mL, comparatively to gallic acid at value 0.207+0.061 (mg/mL), which is equivalent to 7.51mg of GAE/g.
The inhibitory activities of Litsea cubeba essential oil has on Escherichia coli, Bacillus cereus, Lister monocytogenes at 0.1 mg/mL concentration were apparent. The result implies that the three bacteria are relatively sensitive to Litsea cubeba essential oil. The minimum inhibition concentration of the essential oil on Staphylococcus aureus, Salmonella enterica and Vidrio alginolyticus are 0.41 mg/mL, 0.83 mg/mL and 0.41 mg/mL respectively. Microencapsulated Litsea cubeba essential oil can inhibit Staphylococcus aureus within 24 hours. Adding same concentration of Litsea cubeba essential oil into the broth contains Staphylococcus aureus, the result shows Litsea cubeba essential oil has germicidal effect. Obviously, microencapsulated Litsea cubeba essential oil can release the essential oil in the capsule gradually.
The Litsea cubeba essential oil has good inhibition effect on bacteria. Furthermore, the microencapsulated oil can not only lessen the evaporation rate but also protect certain content such as limonene which is prone to oxidize by light or heat. In conclusion, Litsea cubeba essential oil is suitable to develop into natural bacterial inhibition material for food industry. And with the microencapsulation process, the inhibition time period can be prolonged. Litsea cubeba essential oil is therefore also suitable to make into natural preservatives.
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