Freeze-Drying (Lyophilization) of Yellow Camellia (Camellia chrysantha) Flower Bud

Yellow camellia (Camellia chrysantha) plant is naturally distributed in Vietnam. Its flower has great ability to improve human health due to its phytochemical substances such as selens, catechin, quercetin and polyphenols. Therefore, its flower is commonly infused in dry form as tea. Freeze-drying is based on low temperatures to avoid the degradation of thermolabile constituents, preserve physicochemical and organoleptic properties. In this study, the impact of freeze-drying conditions on the quality of floral tea from Camellia bud was examined. Five different temperatures (-40,-45,-50,-55, -60 degrees C) and five working shelf pressures (0.022, 0.028, 0.034, 0.040, 0.046 mbar) were clarified. Results showed that 0.04 mbar at-55 oC were suitable for dehydration of the Camellia flower buds into functional tea. The most total phenolic content (807.4 +/- 1.3 mg GAE/100 g), flavonoid content (397.5 +/- 0.4 mg QE/100 g), DPPH free radical scavenging (206.1 +/- 0.5 mu g/mL), ABTS radical scavenging activity (45.7 +/- 0.01mM TE/g) would be maintained in the dried flower bud.