摘要
为了对发酵桑叶茶工艺条件进行优化并探究桑叶茶经发酵后抗氧化活性的变化,该试验通过响应面分析法确定发酵桑叶茶在发酵温度、发酵时间和黑曲霉接种量3种变量条件下的最佳工艺条件,并测定发酵桑叶茶生物活性物质含量及其抗氧化性.结果表明,最佳工艺条件为发酵时间5d16h,发酵温度30℃,接种量16.55％,此条件下所制发酵桑叶茶感官评分高达90分,且其总黄酮、总多糖、多酚、游离氨基酸、芦丁、槲皮素含量比桑叶绿茶分别升高了 14.39％、12.67％、2.90％、3.46％、81.13％、19.35％,还检测到 了含量 7.55％±0.37％的茶褐素.此外,1/1000(g/mL)浓度下发酵桑叶茶对羟基自由基、DPPH自由基、超氧自由基的清除率和对二价铁离子的螯合率分别是桑叶绿茶的1.16倍、1.07倍、1.06倍和0.82倍,该研究结果为今后桑叶的进一步开发与应用提供理论基础和参考.
Abstract
In order to optimize the fermentation process conditions of mulberry leaf tea and explore the changes in antioxidant activity of mulberry leaf tea after fermentation.This experiment used response surface analysis to determine the optimal process conditions for fermenting mulberry leaf tea under three variable conditions:Fermentation temperature,fermentation time,and inoculation amount of Aspergillus niger.The content of bioactive substances and antioxidant properties in fermented mulberry leaf tea were determinated.The findings indicated that 5 days and 16 hours of fermentation duration,30 ℃ of fermentation temperature,and 16.55％of inoculation amount were the ideal process parameters,and that the fermented mulberry leaf tea scored as high as 90 on the sensory scale under these conditions.In addition,the content of total flavonoids,total polysaccharides,polyphenols,free amino acids,rutin,and quercetin in fermented mulberry leaf tea increased by 14.39％,12.67％,2.90％,3.46％,81.13％,and 19.35％,respectively,compared to mulberry leaf green tea.Tea brown pigment with a content of 7.55％±0.37％was also detected in fermented mulberry leaf tea.In addition,the scavenging rate of hydroxyl radicals,DPPH radicals,superoxide radicals and the chelating rate of divalent iron ions of fermented mulberry leaf tea at the concentration of 1/1000(g/mL)were 1.16,1.07,1.06 and 0.82 times higher than that of mulberry leaf green tea,respectively.The results of this study provide theoretical basis and references for further development and application of mulberry leaf in the future.
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