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化皮过程是阿胶生产中的重要环节,该文采用近红外光谱技术结合多变量数据分析快速测定驴皮化皮液中的总氮含量,并提出化皮过程终点判断方法。以近红外透反射光谱采集模式采集化皮液光谱,以凯氏定氮法测定值为参比,采用偏最小二乘回归建立化皮液近红外光谱与其总氮含量间的校正模型,并对建模波段及主成分数等模型参数进行优选。使用所建定量模型快速测定化皮液的总氮含量,并以其为依据确定化皮次数。所建总氮定量模型性能良好,验证集相关系数和预测误差均方根分别为0.991 3,0.807 g·L-1。根据模型测得的总氮含量以及预设的总氮含量限,可以快速判断化皮过程的进度,确定合理的化皮次数。结果表明,近红外透反射光谱可快速准确地测定化皮液中的总氮含量并判断化皮工艺终点,避免了不合理的化皮次数带来的能耗或原料浪费。
Skinning process is an important link in the production of donkey-hide gelatin. In this paper, the total nitrogen content of donkey hide skin fluid is rapidly determined by near-infrared spectroscopy combined with multivariate data analysis, and the judgment method of the end of crusting process is proposed. Near infrared transmission spectrum acquisition mode was used to collect the skin fluid spectrum. The Kjeldahl method was used as a reference to establish the calibration model between near infrared spectroscopy and total nitrogen content by partial least-squares regression. Mode band and the number of main components and other model parameters are preferred. The quantitative model was used to quickly determine the total nitrogen content of the skin fluid and to determine the number of skinning based on it. The built nitrogen quantitative model has good performance, the correlation coefficient of the validation set and the root mean square of prediction error are 0.991 3,0.807 g · L -1. According to the total nitrogen content measured by the model and the preset limit of total nitrogen content, the progress of the skinning process can be quickly determined and a reasonable number of skinning steps can be determined. The results show that near infrared transmission spectroscopy can determine the total nitrogen content in the skin fluid quickly and accurately and determine the end point of the skinning process, avoiding the energy consumption or waste of raw materials caused by the unreasonable skinning times.