等电点沉淀法（ISP）代替传统鱼糜漂洗法分离鱼蛋白可以显著提高蛋白回收率，目前已成为国内外水产加工领域的关注热点。然而，一些海洋鱼类的ISP分离蛋白在热凝胶过程会出现凝胶劣化现象。较之于传统鱼糜，ISP分离蛋白存在更复杂的蛋白酶系，但迄今为止的相关研究仅限于蛋白质结构变化与组织蛋白酶的影响。我们的初步研究结果表明，丝氨酸蛋白酶（SP）可能是诱导鱼分离蛋白凝胶劣化的主要原因，但其作用机理尚未解明。本课题拟以高产海水鱼蓝圆鲹为对象，开展如下研究：1）分析分离蛋白中主要内源性蛋白酶的种类以及在加热过程中对肌原纤维的降解规律；2）对SP进行分离纯化、性质分析与分子克隆，从生化角度解析SP的构象与酶学特性；3）通过免疫杂交、质构分析与电镜扫描研究SP对分离蛋白凝胶特性的影响。研究最终揭示SP对蓝圆鲹分离蛋白中肌原纤维的降解及凝胶劣化的作用机理，为ISP在鱼分离蛋白提取及鱼糜制品中的应用提供理论依据。

Isoelectric solubilization/precipitation, substituting for bleaching treatment in conventional surimi production, has been attracted increasing attentions in the field of sea-food processing due to the significant improvement of protein recovery yield. However, modori phenomenons during heat-induced gelling process were found in protein isolate prepared by Isoelectric solubilization/precipitation (ISP) from some marine fish. For that, most of present studies focus on the conformational changes of myofibrillar protein and endogenous cathepsin type proteinase. However, compared with conventional surimi, ISP protein isolate contains water soluble proteins, including proteinases, which need to be clarified. Our previous study revealed that serine proteinase (SP) might act as the major role for protein gelling during heating processing. However, studies concerning on clarifications for the mechanisms were limited. To prove the speculation, blue scad (Decapterus maruadsi) was selected to investigate the mechanism of SP on modori phenomenon of ISP protein isolate. For such purpose, present study includes: 1) autodegradation of myofibrillar proteins in ISP protein isolate during heat processing and identification of endogenous proteinase; 2) purification, characterization, molecular cloning and structural analysis of SP from blue scad skeletal muscle; 3) detection of SP induced modori phenomenon in ISP protein isolate via immunoblotting, textural analysis and scanning electron microscope. Result would elucidate the mechanisms of SP on degradation of myofibrillar protein in protein isolate and modori phenomenon. It also could provide theoretical basis for potential application of isoelectric solubilization/precipitation on surimi processing of blue scad.