草鱼肉气味形成机理研究

The yield of freshwater fish has reached more than 20 million tons in China, accounting for about 40% total output of fisheries production. How to utilize freshwater fish effectively and develop highly value-added products from this valuable resource have become a major research topic. As a resource provided perfect protein, surimi processing has made significant progress which eliminated the problem of fish bone in recent years. However, the unpleasant off-flavor(earthy fish odor) has not been fundamentally resolved, restricting promotion and application of the freshwater fish processing technology. The output of grass carp has reach 4,782,000 tons in 2012 and ranked the first in china.The cultured grass carp as the research object will have great significance. The optimum conditions of extraction methods will determined by orthogonal test and response surface method to study the volatile compounds in different parts of grass carp meat (dorsal meat, belly meat and red meat). The threshold of volatile compounds in grass carp meat and the contribution to odor will determined by the aroma dilution analysis method combined with gas chromatography and mass spectrometry (GC-MS) coupled with gas chromatography-olfactometry (GC-O). The odor activity value methods were used to determine the predominant volatile compounds in different parts of grass carp odor and contribution to the overall odor of grass carp meat. And the effects of habitats，seasons, age and tempetarue of slaughter, slaughter measures, conditions after slaughter on content of nutrient, predominant volatile compounds of grass carp and endogenous enzyme activity will study. The effects of add lipoxygenase,lipase and proteases in grass carp meat on its smell will be verifed by experiment with GC-O,GC-MS, sensory experiments and electronic nose.The correlation among content of nutrient,the activity of endogenous enzyme and predominant volatile compounds in grass carp meat will be analyzed by the multiple correlation analysis. The main way of protein degradation and fat decomposition will interpretation in the odor formation of grass carp meat, and the mechanism of odor formation arise by endogenous enzyme will be confirmed. Many factors affecting the odor of grass carp will be studied and to explore the mechanism of odor formation in grass carp meat. Research results can not only enrich the theoretical knowledge of flavor chemistry, but also has significance of theoretical guidance for freshwater fish deep processing.

以草鱼为研究对象，通过正交试验和响应曲面法确定较优的草鱼肉挥发性成分萃取方法，对草鱼不同部位（背肉、腹肉和红肉）气味成分进行研究；通过香气稀释分析法结合气质联用仪、气相色谱-嗅辨仪确定各挥发性成分阈值及对气味的贡献度，利用气味活度值法确定草鱼肉不同部位气味的特征性成分及其对草鱼肉整体风味的贡献；研究产地、季节、鱼龄及致死时温度、致死方式、死后状态等对草鱼肉营养组成、特征性气味及内源酶特性影响；结合感官试验、电子鼻通过外加脂肪氧合酶、脂肪酶和蛋白酶对草鱼肉气味的影响进行验证；进而通过多元相关分析研究草鱼肉营养组成、内源酶活性与特征性气味成分之间的关系，确定脂肪分解和蛋白质降解主要途径，探明草鱼肉气味形成主要机理。项目对不同来源草鱼采用不同致死方式，深入研究草鱼肉内源酶与其特征性气味成分间的相关性，阐明草鱼肉气味形成机理，研究成果不仅可以丰富风味化学理论知识，还对淡水鱼精深加工有理论指导意义。

草鱼是我国产量最大的淡水鱼，占我国淡水鱼总产量的21%，淡水鱼的土腥味是制约淡水鱼加工利用的瓶颈，因此研究草鱼肉风味具有较好的示范意义。项目通过比较确定了SPME-GC-MS、MMSE-GC-MS和GC×GC-TOFMS方法分析草鱼不同部位肉中挥发性成分，并结合ROVA法及GC-O法确定了草鱼肉不同部位的特征挥发性成分；确定了草鱼肉中内源酶（蛋白酶、脂肪酶和脂肪氧合酶等）提取及活性的测定方法；采用GC-MS、电子鼻、电子舌、HPLC、氨基酸分析仪等系统研究了不同地域、季节、鱼龄、暂养、超高压、致死方式、冻结方式对草鱼肉不同部位的风味及内源酶的影响。结果显示上述因素对草鱼肉风味有较显著影响，并解释了不同因素对草鱼背肉、腹肉和红肉部分的影响程度；重点研究了冷藏和常温下草鱼死后僵硬过程中草鱼肉不同部位风味和内源酶活性与脂肪氧化间的相关性，并比较了不同蛋白酶水解及脱腥后挥发性成分的变化，从内源酶角度解释了草鱼肉风味的形成；选择了5种不饱和脂肪酸和模型鱼肉作为底物，添加草鱼肉提取的脂肪氧合酶（lipoxygenas,LOX），模拟脂肪自氧化与酶促氧化实验，分析氧化产生的挥发性物质，在一定程度上解释了脂肪氧合酶在草鱼肉气味形成中的作用；单独研究草鱼风味形成有时很难说明或解释一些问题，因此利用草鱼风味方面研究形成的技术拓展了研究对象和范围等，对其他鱼、虾和蟹等水产原料的风味和品质也进行了研究。因此，本项目除了按计划完成了既定的研究内容外，还进行了一部分拓展。项目确定了草鱼肉不同部位风味的特征成分，以及多种因素对草鱼肉风味的影响，从内源酶角度解释了草鱼肉特征风味的形成，丰富了风味化学的理论知识；研究结果还对草鱼肉加工和消费者日常食用草鱼提供了理论指导；所申请及授权的发明专利在水产食品加工方面具有较好的应用前景，预计在3-5年会有相关成果进行转化。