脂质光氧化反应解析传统腌腊鱼制品优良日晒风味的形成机制

Cured fish processed by traditional technique of sun-drying is highly appreciated due to its better aroma quality compared with that processed by modern industrial techniques such as cold-air or hot-air drying. So far, the underlying reason or mechanism of this phenomenon has not yet been elucidated. Some researchers deduced that it might be related to the lipid photo-oxidation reaction mainly mediated by myoglobin in fish meat. In this study, two groups of grass carp samples will be firstly salted and then aged under the light and dark conditions respectively for different time periods, among which the aroma components and lipid oxidation indexes will be determined, the characteristic sunlight flavor components (CSFCs) subsequently identified and the significance that lipid photo-oxidation reaction contributing to CSFCs formation eventually verified. Furthermore, several test systems on lipid photo-oxidation reaction will be elaborately designed. Due to these test systems, the conformation changes and transformation rules of different types of myoglobin could be studied, and their lipid oxidation stimulating abilities could also be evaluated according to yield of singlet oxygen and several other indexes. Meanwhile, the relationship between lipid components degradation and CSFCs formation will also be analyzed, which could not only confirm the targeted substrates of lipid photo-oxidation reaction but also further deduce the possible pathways of CSFCs formation. Based on lipid metabolomics means, the formation mechanism of CSFCs in conventional cured fish by lipid photo-oxidation would be finally elucidated and its reaction kinetics equation will also be established. The results of the present project will provide some necessary scientific references for both improving conventional flavor qualities of industrial processed cured fish and controlling its quality and safety as well in the future.

现代腌腊鱼干普遍采用冷风或热风干制技术进行工业化加工，但其香味远逊于人们追寻的传统日晒制品，该现象发生缘由或机制未见报道，推测可能与本体中肌红蛋白等介导的脂质光氧化反应有关。针对上述科学问题，本项目拟分析光照和避光成熟过程中鱼品香气成分与脂质氧化指标动态变化规律，鉴别传统腌腊鱼品固有的“特征日晒风味物(CSFCs)”身份，确证脂质光氧化对CSFCs形成的重要性。另方面，构建多样化试验体系，研究光氧化过程中各类肌红蛋白空间构象变化与相互转变规律，结合单线态氧生成量等指标评估其促脂质氧化特性差异；探究光氧化过程中脂质成分降解与CSFCs生成的关联性，确认脂质光氧化反应的靶向底物，推断CSFCs可能的形成路径。在此基础上，借助脂质代谢组学分析手段解析基于脂质光氧化反应的传统腌腊鱼制品特征日晒风味形成机制并构建反应动力学模型。旨在为工业化生产腌腊鱼品的传统风味改良与质量安全控制提供必要的科学依据。

本研究初步阐明了腌腊鱼干制加工过程中肌红蛋白介导脂质发生光氧化反应产生关键香气物质的机制。主要取得以下三方面的研究结果：（1）分析了不同干制工艺（自然日晒、热风光照、热风避光、冷风光照和冷风避光）下制得腌腊鱼制品的香气成分，确定了庚醛、辛醛、壬醛、壬烯醛、1-辛烯-3-酮可能是传统腌腊鱼的“优良日晒风味物”；（2）分析了腌腊鱼干制加工过程中脂质氧化指标变化情况，研究了脂质与脂肪酸动态变化规律，探讨了关键气味活性物质与不饱和脂肪酸间的相关性，证实亚油酸和花生四烯酸等多不饱和脂肪酸（PUFA）是产生腌腊鱼关键香气成分的重要风味前体物，且游离脂肪酸是最易发生氧化降解的脂质成分；（3）构建了不同的浓度氧合肌红蛋白（OMb）和高铁肌红蛋白（MMb）模拟反应体系，解明了上述体系中肌红蛋白构成、脂质及脂肪酸组成、关键香气成分的变化规律。干制过程中OMb主要发生了变性作用（构象改变），而MMb主要发生了降解作用（结构破坏），证实了OMb促脂质氧化能力强于MMb，前者体系中生成的香气物质总活性值是后者的1.5倍以上。本研究可为工业化生产腌腊鱼的传统风味改良与质量安全控制提供理论支持，对火腿等传统肉制品加工业也有一定的借鉴意义。