【摘要】 采用盐析法从柚皮果胶提取液中盐析沉淀果胶.研究了盐析剂种类对果胶沉淀得率及盐析过程中pH值对果胶沉淀得率和果胶灰分含量的影响,并探索了适宜盐析条件和盐析机理.实验结果表明:以硫酸铝钾为柚皮果胶盐析剂,适宜盐析条件为:pH值5.8,盐析温度25℃,盐析时间30 min,果胶沉淀得率可达91.4%;采用三氯化铁盐析果胶,则pH值宜控制在4.0,于60℃下盐析60 min,果胶沉淀得率达95.8%.两种盐析方法所得果胶灰分均低于5.0%.铝盐盐析的果胶为白色,铁盐盐析的果胶颜色呈浅黄色,加入脱铁助剂Aid-4后可以获得较好的脱色效果.铁盐和铝盐盐析果胶的机理相似,都是果胶中的羧基离子取代金属水合物中的羟基,与金属离子发生配位反应,生成沉淀实现果胶从溶液中的分离.更多还原

【Abstract】 Salting-out processes were applied to precipitate shaddock-peel pectin from shaddock-peel pectin extracts.Effects of salting-out agents and pH value on pectin precipitation yield and pectin ash content were investigated;suitable salting-out conditions and mechanism were also discussed.Results from experiments show that if aluminum potassium sulfate is used as salting-out agent,the suitable conditions are pH value 5.8,temperature 25℃ and salting-out time 30 minutes,which ensure the precipitation of white pectin with a 91.4 % yield;that with ferric chloride,the conditions are pH value 4,temperature 60℃ and salting-out time 60 minutes,which bring about the precipitation of light yellow pectin with a 95.8% yield;that when either aluminum potassium sulfate or ferric chloride is used under their respectively suitable conditions,pectin ash contents are less than 5 %;that Aid-4 is an effective iron-removing aid for pectin salting-out with ferric chloride;and that the salting-out mechanisms both for ferric and aluminum cations are alike: carboxyls in pectin substitute the hydroxyls in metal cation hydrates,reacting complexly with metal cations and forming pectin-metal cation precipitation.更多还原