桑枝皮中果胶的提取工艺优化

摘要

One-factor-at-a-time combined with orthogonal array design method was used to optimize process conditions for pectin extraction from mulberry stalk bark by ammonium oxalate-oxalic acid hydrolysis and subsequent ethanol precipitation.The effects of solid-to-liquid ratio,pH,temperature and time on pectin extraction rate were investigated.Pectin extraction rates from the bark of different stalk positions of mulberry cultivars Husang 32,Yu 711,Nongsang 8 and Nongsang 14 at different growth stages were compared.The optimal conditions for extracting pectin from mulberry stalk bark were solid-to-liquid ratio（g/mL） 1：14,pH 2.0,temperature 90 ℃,and extraction time 120 min,and the addition of activated carbon at 1 g/100 mL for decolorization at 60 ℃ for 30 min resulted in the best decolorization.Under these conditions,the pectin extraction rate was roughly 12%.Cultivars,harvest periods and stalk bark positions showed a difference in the extraction rate of pectin.Among the four cultivars investigated,Husang 32 revealed the highest pectin extraction rate.In summer a higher pectin extraction rate from mulberry stalk bark was observed than in spring and autumn.In spring and autumn,the bark of the middle position of mulberry stalk exhibited a higher pectin extraction rate than that of the top and bottom.In summer,the pectin extraction rate from the bark of one-year-old mulberry stalk was higher than that of newly grown mulberry stalk.In addition,an increase in pectin extraction rate was found from fresh mulberry stalk bark as compared with its dried counterpart.%以桑枝皮为原料,采用草酸铵-草酸水解、乙醇法沉淀提取果胶,研究料液比、pH值、提取温度和提取时间对果胶提取率的影响,并分析湖桑32、育711、农桑14和农桑8桑树品种在不同时期和不同部位的桑枝皮中果胶的提取率。结果表明,提取桑枝皮中果胶的最佳工艺条件为料液比1：14（g/mL）、pH2.0、提取温度90℃、提取时间120min,脱色条件为温度60℃、时间30min、活性炭与浸提液比例1：100（g/mL）,在此条件下果胶提取率可达12%左右。不同桑树品种、不同采摘时期、不同部位的桑枝皮中的果胶提取率都有所差异,其中湖桑32号、夏伐桑枝皮、春秋季中部位桑枝皮及夏伐一年生桑枝皮中果胶提取率较高。湿桑枝皮中果胶提取率比烘干后的桑枝皮中的提取率高。