关键词: 丹凤牡丹（Paeonia ostii 'fengdan'）, 干燥方法, 真空冷冻干燥, 抗氧化活性

Abstract: In this study, Paeonia ostii ‘fengdan' flowers were used as the material. The Paeonia ostii ‘fengdan' flowers were dried by sun drying, hot air dying （40、60、80 ℃）、 microwave drying （low heat, medium heat, medium-high heat） and vacuum freez-drying. After tested by these four methods, the content of reducing sugar, protein, VC, flavonoids and polyphenols of Paeonia ostii ‘fengdan' flowers was determined. Then select 4 antioxidant indicators：DPPH scavenging abilities, hydroxyl scavenging abilities, nitrite scavenging abilities and reducing abilities to evaluate antioxidant activity of flower extract dried by these methods. The results showed that the polyphenol content of these flowers treated by vacuum freeze-drying is 11.71 mg/g, and the flavonoid content is 11.85 mg/g, which is significantly higher than any other samples processed by other drying methods. The reducing sugar content of freeze-drying treatment is 23.79%, which is not significantly different from 60 ℃ hot-air drying treatment, and is significantly higher than other drying treatments; the Paeonia ostii ‘fengdan' flower protein content of vacuum freeze-drying treatment is 63.87 mg/g, only second to sundring samples. Under the same concentration,when Paeonia ostii ‘fengdan' flower extract is processed by vacuum freeze-drying, it has the strongest DPPH scavenging abilities, hydroxyl scavenging abilities, nitrite scavenging abilities and reducing abilities of the potassium ferricyanide. Different drying methods have great effects on nutrient content, active ingredient content, and antioxidant activity of Paeonia ostii ‘fengdan' flowers. The Paeonia ostii ‘fengdan' flower protein, polyphenols, flavonoids and polyphenols processed by the vacuum freeze-drying process are high in content, and the nutrient and active ingredient of the Paeonia ostii ‘fengdan' flower are better retained. Vacuum freeze drying is a better way to dry Paeonia ostii ‘fengdan' flowers.

Key words: Paeonia ostii 'fengdan', drying methods, vacuum freeze-drying, antioxidant activity