芝麻籽细胞壁多糖在焙炒过程中的解离机制

Roasting pretreatment, as a key step during the process of fragrant sesame seed oil, has complicated various chemical reactions, which made the fragrant sesame oil have rich aromas and characteristic colors as well as antioxidant activities. Many sugar compositions, which provided by the dissociation of cell wall polysaccharides in sesame seeds during the roasting pretreatment process, were the important precursors for sugar chemical reactions including the Maillard reaction and caramelization. Therefore, the dissociation of the cell wall polysaccharides in sesame seeds was a key scientific problem during investigation the mechanism of Maillard reaction and caramelization which occurred in the process of sesame seeds roasting pretreatment. In the project, the structure and bonding of cell wall polysaccharides in sesame seeds were investigated firstly. Before characterization of the cell wall polysaccharides, a high efficiency method for fractionation and purification of cell wall polysaccharides in sesame seeds has been established, and then the chemical structure and bonding of the purified polysaccharides have been characterized by various techniques. Furthermore, the effect of roasting pretreatment on the chemical structure and bonding of polysaccharides in sesame seed cell wall will be investigated, and the dissociation mechanism of the polysaccharides in the sesame cell wall during the roasting pretreatment process was analyzed. The aim of the project is to elucidate the cell structure and bonding of cell wall polysaccharides in sesame seeds and reveal the dissociation mechanism of the polysaccharides during the process of roasting pretreatment. When the project was completed, the results could effectively promote the structural characterization of cell wall polysaccharides in sesame seeds, and provide a theoretical basis for Maillard reaction and caramelization investigation during the roasting pretreatment of sesame seeds.

焙炒预处理作为芝麻香油加工过程中的关键步骤，发生着复杂的化学反应，从而赋予了芝麻香油浓郁的香味、特征色泽和抗氧化能力。其中糖参与了其中最重要的美拉德反应与焦糖化反应，在焙炒过程中，芝麻籽细胞壁多糖的解离为这些糖化学反应提供了重要的前体物。因此，焙炒过程中芝麻籽细胞壁多糖的解离机制是研究美拉德化学反应和焦糖化反应机理的关键性科学问题。本项目从芝麻籽细胞壁多糖的结构入手研究，首先构建一套芝麻籽细胞壁多糖高效分步分级的提取方法，对纯化后的细胞壁多糖的糖单元及其链接结构进行解译；进而研究在焙炒过程中这些细胞壁多糖的结构变化规律，对比分析得出芝麻籽细胞壁多糖在焙炒过程中的解离机制。本项目旨在阐明芝麻籽细胞壁多糖的糖单元及其链接结构在焙炒过程中的解离规律。研究成果可有效的推动芝麻籽细胞壁多糖的结构解译，而且可为芝麻籽焙炒预处理中美拉德反应和焦糖化反应的研究提供理论支持。

芝麻经高温焙炒发生着复杂的化学反应，从而赋予了芝麻香油浓郁的香味、特征色泽和抗氧化能力。其中糖参与了其中最重要的美拉德反应与焦糖化反应，在焙炒过程中，细胞壁多糖的解离为糖化学反应提供了重要的前体物。本项目先对针对芝麻的籽粒结构特性，分别对芝麻皮与芝麻仁中的结构性多糖进行了提取，然后对获得的不同结构性成分的糖单元及其链接结构进行了研究，通过研究在不同焙烤条件下这些结构性成分的结构变化规律，对比分析得出芝麻籽细胞壁结构性多糖成分在焙烤过程中的解离机制。从芝麻仁中提取得到水溶性杂多糖组分，并纯化得到3种和5种多糖片段，主要含半乳糖醛酸、半乳糖、阿拉伯糖，核磁与甲基化的结果表明连接方式主要有T-L-Araf(1→，→5)-L-Araf(1→，→3)-D-Galp(1→等。在焙炒过程中芝麻皮中的脂肪酸组成、氨基酸组成和单糖组成未发生改变；芝麻皮焙炒之后具有芳香气味，其来源于美拉德反应和焦糖化反应过程中产生的呋喃、糠醛、嘧啶、噻唑、吡咯和吡啶等物质；芝麻皮中丝氨酸、苏氨酸、精氨酸、半乳糖醛酸、鼠李糖、阿拉伯糖和木糖可能作为重要的前体物质参与美拉德反应以及焦糖化反应。焙烤过程中芝麻皮半纤维素中的半乳糖、木糖和鼠李糖单元比其他糖单元更容易降解；纤维素的结晶态未发生明显的降解，然而非结晶态发生了降解；果胶的RG-Ⅰ区域以及侧链结构糖单元更容易发生降解；果胶多糖中鼠李糖、阿拉伯糖、半乳糖、岩藻糖、木糖和葡萄糖醛酸发生了降解，与纤维素多糖相比，芝麻皮中的半纤维素多糖和果胶多糖更容易发生降解，其降解产物作为重要前体物质参与美拉德反应和焦糖化反应，进而影响芝麻香油的风味和色泽。研究成果可有效的推动芝麻籽细胞壁多糖的结构解译，而且可为芝麻籽焙炒处理中美拉德反应和焦糖化反应的研究提供理论支持。研究成果可有效的推动芝麻籽细胞壁多糖的结构解译，而且可为芝麻籽焙炒预处理中美拉德反应和焦糖化反应的研究提供理论支持。

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