为实现蒸煮液中蛋白质的洁净回收，同时达到净化蒸煮液以提高后续膜浓缩效率的目的，利用壳聚糖絮凝剂分离沉淀蒸煮液中的水溶性蛋白。在不同pH条件下壳聚糖与蒸煮液水溶性蛋白的絮凝过程中，通过对溶解曲线、红外光谱、分子质量分布、重金属及氨基酸含量的变化进行分析，探究了适宜的絮凝pH值和絮凝机理。实验发现，壳聚糖絮凝pH=3时絮凝效果最好，水溶性蛋白絮凝去除率达到36.23%；但选择絮凝pH=5.5时，蒸煮液的水溶性蛋白含量降低30%左右，絮凝过程简单经济，便于工业化应用。在不同酸碱环境下絮凝机理表现为不同：在酸性环境中，壳聚糖絮凝主要通过电中和作用和吸附架桥作用，形成类似蛋白-壳聚糖-蛋白的结构；在碱性环境中，壳聚糖主要通过吸附作用形成沉淀物。絮凝pH变化，影响了大分子质量水溶性蛋白与壳聚糖的絮凝作用，而蒸煮液中分子质量小于19 kDa的水溶性蛋白基本不受影响；另外，壳聚糖絮凝还具有降低蒸煮液重金属含量的作用，但不影响氨基酸含量的变化。

Engraulis japonicus cooking liquid is a by-product from fish processing. It contains various components and rich of nutrients. In order to purify the cooking liquid, chitosan was used as a safe flocculant to separate and recycle proteins from cooking liquid and help membrane concentrating efficiency in the later process. The effect of Chitosan on the flocculation of water soluble protein in cooking liquor was studied under different pH conditions. The analysis of solubility curve, infrared spectrum, molecular weight distribution, heavy metal and amino acid content showed that: the flocculation effect was the best at pH=3, and the removal rate of water soluble protein was 36.23 %. However, considering of the simplicity and economics in the industry, pH=5.5 was selected to move about about 30% water soluble protein. The flocculation mechanism of chitosan was different in different pH environment. In acidic environment, it was mainly depended on charge neutralization and bridging effects to form crosslinking structure between protein and chitosan; under alkaline conditions, the adsorption was dominant in the flocculating process. The pH affected the flocculation of macromolecular water-soluble proteins with chitosan, while the water-soluble proteins whose molecular weight was less than 19kDa remained unaffected. In addition, chitosan flocculation would reduce the content of heavy metals, but it does not affect the change of amino acid content.