羊脂酶解-调控氧化定量预测模型的构建及其模式下羊肉特征风味形成机制的研究

The contents of hip (tail) fat were significant abundant in fat sheep, a characteristics livestock resource in Xinjiang, because of the special natural environment. Currently, some problems, such as the technical lack of fat preparation, the unobvious characteristic and instable flavor of meat flavor prepared from controlled fat oxidized fat, have become the bottlenecks restricting the development of fat resource industry. Based on the previous research achievements, in this project, partial least squares regression (PLSR) was applied to quantify the relationships among volatile compounds with active-odor (identified by GC-MS-O), chemical parameters and electronic nose responses for different enzymatic hydrolysis-controlled oxidation of suets, and then establish the quantitative predictability models of thermal reaction precursors; Quantitative discriminant model of natural mutton flavor was performed by partial least squares regression-discriminant analysis (PLS-DA). Further, changes in the aroma characteristics of mutton process flavors (MPF) prepared under different reaction conditions or/and different reaction bases were assessed using PLS-DA combined with descriptive sensory analysis (DSA) in order to confirm a desirable precursor for the sensory characteristics of MPF, which can be used for finding the potential flavor precursors and characteristic aroma compounds related to mutton flavor; Meanwhile, the formation pathways of mutton characteristics flavor were performed by using isotope labeling combined with the process and law interpretation of the compounds formed from Maillard reaction and fat oxidization. On the basis, the results of this study will serve as a theoretical base for the improvement of stability and overall flavor, and the directional preparation of characteristic flavor compounds. Thus, this research has profound significance in the utilization of the by-products of meat processing industry and upgrading the quality of products.

区域特殊自然环境造就了臀(尾)脂肪含量显著的新疆特色肥羊畜产资源。目前其脂肪制备产品技术匮乏、现有调控氧化肉味料特征风味不明显及品质不稳定等问题，已成为制约区域脂肪资源产业发展的瓶颈。本项目在前期研究成果总结分析的基础上，采用GC-MS-O技术分析不同酶解-氧化状态羊脂样本香气成分，结合PLSR分析建立其与化学参数及E-nose响应间的量化关系，构建羊脂热反应前体定量预测模型；采用天然羊肉风味PLS-DA判别模型，结合描述性感官分析和多元回归分析确定酶解-氧化羊脂美拉德反应最适前体状态，挖掘与羊肉风味形成与呈现相关的潜在风味前体物质及特征香气成分；同时通过同位素标记及美拉德反应与脂肪氧化历程规律诠释，研究羊肉特征风味形成途径，深入解析羊脂参与羊肉模拟风味形成机制。预期为脂肪氧化香精稳态化、整体风味的提升及特征风味物质的定向制备提供理论基础，对特色副产物资源利用及相关产品升级具有深远意义。

羊肉加工副产物资源极其丰富，但其深加工利用技术匮乏。目前国内羊肉香精产品普遍存在天然感差、留香时间短、特征风味不明显等问题，严重制约羊肉香精产业化的发展。基于上述原因，本项目开展了以下相关研究，主要内容如下：.采用SPME-GC-MS结合GC-O对不同批次的羊肉样本中的挥发性成分进行分析鉴定，共筛选获得32种共有风味物质作为羊肉特征风味评定的关键化合物，以此为分类变量，结合五种常见肉类样品中相对应化合物的种类和含量，构建用于鉴别天然羊肉风味PLS-DA模型。.对不同酶解-氧化条件下获得的羊脂的化学指标和各种挥发性化合物成分的变化进行了研究。利用PLSR分析建立了各种挥发性化合物与化学指标之间的相关性模型，掌握了羊脂的氧化规律；建立了基于电子鼻与羊脂定量氧化理化指标之间的相关预测模型，该模型拟合效果较好，可为实施羊脂的定向调控氧化提供依据。.考察不同反应条件对Maillard制备的MPF的影响，结果表明pH、反应温度和反应时间对于MPF样品整体风味具有显著的影响，过高或过低的pH和反应温度以及过短或过长的反应时间均不利于MPF整体风味的呈香。采用均匀设计实验优化了制备MPF风味基料的模式Maillard反应体系反应配方和最优条件。.通过DSA和GC-MS分析，比较了不同氧化状态羊脂的Maillard反应产品，结果表明，在热反应过程中氧化羊脂对于模拟或加强羊肉特征风味具有重要作用，通过温和酶解-氧化羊脂制备的羊肉风味基料表现出明显的羊肉味、肉味、脂肪香和高的仿真度。通过电子鼻响应值、感官分析数据和重要化合物的相关性分析，同时结合PLS-DA风味品质评定模型，确证了温和酶解-氧化羊脂作为Maillard反应的前体可以产生羊肉特征风味。.通过GC-MS-O技术对酶解-氧化羊脂及上述热反应产物中的挥发性物质进行分离和鉴定，通过回归系数的显著性分析，筛选羊脂反应前体所提供的潜在风味前体物质和羊肉特征香气成分。结合相应脂肪氧化规律及其作为前体物质参与Maillard反应历程中可能的形成途径，初步明确了酶解-氧化羊脂作为反应前体对于羊肉特征风味形成途径。