白酒糟制备高纯度微晶纤维素工艺优化及其结构表征

白酒糟含有丰富的纤维素和半纤维素组分,是制备食品添加剂微晶纤维素(MCC)的良好原料来源。在硝酸-乙醇法提取酒糟粗纤维的基础上,探索酸法水解制备高纯度酒糟微晶纤维素(GSMCC)的工艺参数并进行结构表征。着重考察盐酸浓度、温度、液固比和时间4个因素对GSMCC纯度和得率的影响,并通过响应面优化法确定最优工艺参数。结果表明,酒糟粗纤维在温度72.3℃,盐酸质量分数7.5%,液固比25∶1(mL/g)的最优条件下水解2 h,可制得纯度92.57%、聚合度276.39的GSMCC,得率高达89.25%;经漂白后纯度略增至93.31%,聚合度降为255.86。扫描电镜(SEM)、傅里叶变换红外光谱(FTIR)和X衍射(XRD)分析发现,GSMCC的微观形貌呈不规则颗粒状,具有典型纤维素的红外光谱特征,纤维素晶型为Ⅰ型,结晶度为67.49%。热重分析(TGA)表明GSMCC热稳定性良好。本试验结果说明利用白酒糟制备食品添加剂微晶纤维素的工艺可行且具有良好结构特性。

Preparation Process Optimization and Structure Characterization of Microcrystalline Cellulose from Grains Stillage

Grains stillage,rich in cellulose and hemicellulose,is a favorable resource of raw materials for the preparation of microcrystalline cellulose(MCC).In order to make full use of the cellulose components in grains stillage,the preparation parameters of high purity MCC from grains distillers(GSMCC)were investigated based on acid hydrolysis method,followed by the extraction of crude fibers by nitric acid-ethanol method,and the structural characterization during isolation of GSMCC were determined.The technological parameters,such as hydrochloric acid concentration,temperature,liquid-solid ratio and hydrolysis time,were optimized by response surface method with the index of purity and yield.The results showed that the optimal preparation conditions of GSMCC were as follows:time of 2 h,temperature of 72.3℃,hydrochloric acid mass fraction of 7.5%and liquid-solid ratio of 25∶1(mL/g).Under the optimal conditions,the yield,purity and degree of polymerization(DP)were 89.25%,92.57%and 276.39,respectively.The purity of GSMCC was increased to 93.31%after bleaching,and the degree of polymerization was reduced to 255.86.The results of structure characterization by using SEM,FTIR and XRD showed that the microstructure of GSMCC is irregular granular type,which has a typical functional group of cellulose with characteristics of celluloseⅠcrystal.The degree of crystallinity is 67.49%.TGA shows that the heat stability of GSMCC is nice,indicating that the preparation of food additive microcrystalline cellulose from grains stillage is feasible.