淡水鱼加工过程中油煎促进其脂肪氧化型香味物质形成机制研究

Previous research indicated that frying could promoted the formation of flavor compounds especially those formed from lipids oxidation, of which mechanism was unknown and should be studied further. Therefore, the Promotion mechanism of frying to formation of flavor compounds from lipids oxidation during processing of freshwater fish will be stuied in this project taking grass carp etc as research objects. Firstly, the effect of frying condition on fatty acids composition and formation of flavor compounds in fish filets will be studied with the application of GC-MS, thin-layer chromatography(TLC) and so on, and relenvance between frying condition, fatty acids composition, oxidation degree of fat, and formation of flavor in filets during frying will be discussed. Then, TLC, specific enzyme, LC-MS etc will be emploied to analyze primary oxidation products and the oxidation sites of lipids in filets after fying. After free fedical captured from fried filets by 1,1-diphenyl-2-picrylhydrazyl radical 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl (DPPH), the LC-DAD-MS and NMR will be used to identified the combination of DPPH-free redical to analysis sites of lipids degradation and to explore the formation rule of flavor compounds from lipids oxidation promoted by frying. Finally, the Promotion mechanism of frying to formation of flavor compounds from lipids oxidation will be proposed according to fundamental theory of oil chemistry based on the analysis of precursor substance of flavor, primary oxidation products of lipids, intermediate products of lipids degradation, and flavor compounds formed during frying. With the research conducted, the theory of food flavor chemistry will be enriched, which could be used to guide to produce safe food with good flavor.

前期研究表明，淡水鱼加工过程中油煎可促进鱼肉形成香味物质尤其是脂肪氧化型香味物质，但其促进机制还不清楚，有待深入研究。本项目拟以草鱼等为研究对象，经大豆油煎后，借助GC-MS、TLC等技术，研究油煎条件对鱼肉脂肪酸组成、香味物质等的影响，探明油煎条件-脂肪酸组成-脂肪氧化程度-香味物质形成四者间的相关性规律；利用TLC、专一化酶、LC-MS等手段，精确测定脂肪初级氧化产物及其反应位点，探索油煎促进鱼肉脂肪氧化的本质；应用DPPH捕获自由基，采用LC-DAD-MS与NMR进行鉴定，探究脂肪氧化分解的关键中间产物及其分解位点，探清油煎促进脂肪分解形成香味物质的内在规律。基于上述研究，应用油脂化学等理论，从香味前体物质变化、初级氧化产物、氧化分解中间产物及香味物质形成规律入手，探明油煎促进鱼肉脂肪氧化型香味物质形成的分子机制。研究将丰富食物风味化学理论，为生产风味良好、安全的鱼制品提供科学依据。

项目以草鱼肉为对象，通过分析油煎过程中鱼肉理化性质、风味物质形成规律、风味前体物质及油煎鱼肉中脂肪的初级氧化产物和氧化分解中间产物，结合主要脂肪酸标品氧化实验以及氧化产物结构的鉴定，推断油煎鱼肉主要脂肪氧化型风味物质形成机理。结果显示：鱼肉经油煎后形成了大量的风味物质，包括醛、醇、酮、芳香族化合物、呋喃、吡嗪等，经PLS-DA线性回归，发现油煎鱼肉中主要风味物质为己醛、庚醛、辛醛、壬醛、2-壬烯醛、1-戊烯-3-醇、2-辛烯-1-醇、3-壬烯-1-醇、1-辛烯-3-醇、2, 3-辛二酮、2, 4-癸二烯醛，是典型的脂肪氧化产物。风味前体物质研究发现，脂肪酸分解是油煎鱼肉风味形成的主要原因，其中花生四烯酸（ARA）和油酸(OA)是最重要的两种前体物质。生鲜鱼肉及油煎鱼肉检测出大量脂肪氧化初级产物（氢过氧化物和羟基脂肪酸）以及氧化分解中间产物（醛酮化合物），包括4种HOME，3种HPOME，3种HODE，3种HPODE，6种HOTrE，5种HPOTrE，6种HETE，6种HPETE，4种HEPE，5种HPEPE，2种HPDPE和5种HPDHA，其中ARA的氧化产物（HETE和HPETE）含量最高，且在油煎过程中显著下降，其氧化产物基本呈现先上升后下降的趋势，进一步说明ARA是最重要的前体物质。经脂肪酸标准品氧化初级产物与终产物（风味物质）的鉴定结果的分析，除1-戊烯-3-醇未找到相应的前体脂肪酸外，前体主要脂肪氧化型风味物质的形成路径可推测如下：己醛主要经亚油酸氧化形成13-HPODE发生β-均裂产生；庚醛由OA经氧化形成11-HOME在 C11-C12 位置发生β-均裂产生；庚醇的前体物质也为OA，经氧化形成9-HOME，通过C9-C10 β-均裂以及随后脱去羟基自由基产生；辛醛由OA经氧化形成11-HOME后在C10-C11 位置发生β-均裂产生; 壬醛由OA经氧化形成9-HOME在C8-C9 位置发生β-均裂产生；2, 4-癸二烯醛：2, 4-癸二烯醛由ARA经11-HPETE在C10-C11位置发生β-均裂产生；2-庚烯醛由ARA经氧化形成14-HPETE后发生β-均裂产生；1-辛烯-3-醇：1-辛烯-3-醇由ARA经氧化形成12-HPETE后在C13-C14 发生β-均裂产生；2-壬烯醛由ARA经氧化形成11-HPETE后在C11-C12位置发生β-均裂产生。