【作者】 赵磊；

【导师】 赵晓燕；

【作者基本信息】 沈阳农业大学 ， 食品科学与工程， 2020， 博士

【摘要】 鲜切山药由于新鲜、便捷以及富含必需氨基酸、薯蓣皂苷、维生素、尿囊素等功能性成分,市场需求量大,然而在贮藏过程中常发生褐变现象。除了褐变,研究发现鲜切山药在特定条件下贮藏还会发生黄变现象,本文研究了鲜切山药黄变的形成条件并对黄变鲜切山药的品质进行评估;揭示了黄变色素的结构组成;阐明了鲜切山药黄变色素的稳定性及生物功能性。实验结果如下:（1）优化了鲜切山药黄变的最佳工艺。贮藏温度、气体组成及切分厚度影响鲜切山药的黄变,黄变现象最显著的贮藏条件为:25 ^oC贮藏,厚度0.1 cm,80%N₂、20%O₂的气调包装,贮藏时间为18 h。黄变后的鲜切山药生理品质保持良好,硬度、总酚含量、感官评价并无显著下降,电子鼻结果无显著性差异,表明黄变的鲜切山药除颜色变化外品质与未黄变鲜切山药并无显著性差异。（2）分析山药黄色素的结构组成。鲜切山药黄色素经分离纯化后通过超高液相色谱-飞行质谱（UPLC-Q-TOF-MS）鉴定表明,该黄色素主要由3个黄色物质组成,占比最大的为双去甲氧基姜黄素(C₁₉H₁₆O₄,73.7%),另外两个物质的分子式分别为C₁₉H₁₈O₃（19.2%）和C₁₉H₁₆O₃（7.1%）。（3）揭示了鲜切山药黄色素的稳定性。通过热重分析仪测定表明,鲜切山药黄色素在温度超过123 ^oC时才发生显著的降解作用,热稳定性高于花色苷、叶绿素和番茄红素等天然色素;模拟胃肠消化系统表明,鲜切山药黄色素经胃肠消化后均能发生降解作用,每小时的降解率分别为3.85%和42.3%,经肠消化后的降解率显著高于经胃消化后的降解率,且经肠降解率高于花色苷。鲜切山药黄色素具有光不稳定性,在不同波长的LED灯光源下均发生降解,不同光源的光降解作用由大到小依次为蓝光、红光、白光和绿光,其降解过程均符合一级降解动力学。（4）阐明鲜切山药黄色素的抗氧化及保护DNA免受氧化损伤的功能性。鲜切山药黄色素有较高的清除OH、ABTS和DPPH等自由基的抗氧化活性。紫外可见光谱法、荧光光谱法、粘度法、离子强度法研究了鲜切山药黄色素与小牛胸腺DNA（ctDNA）的结合方式。结果表明鲜切山药黄色素与ctDNA先通过静电相互吸引,随后以嵌插方式进行结合,鲜切山药黄色素有效的防护ctDNA的基团免受到氧化损伤。更多还原

【Abstract】 Fresh-cut yam is fresh,convenient and rich in essential amino acids,diosgenin,vitamins,allantoin and other functional ingredients.Although the market demand was large,the freshcut yam often browning during storage.In addition to be browning,it was found that fresh-cut yam would turn yellow when stored at specific conditions.In our study,the formation conditions of the yellowing fresh-cut yam were studied and the quality of it was evaluated;the structure and composition of yellow pigment（YP）were revealed;the stability and biological function of YP were clarified.The experimental results are as follows:（1）To determine the best condition of yellowing fresh-cut yam and evaluate its quality.Storage temperature,gas composition and cutting thickness affect the yellowing of fresh-cut yam.The best yellowing conditions were: 25 ℃ storage,0.1 cm thickness,80% N₂ with 20% O₂ modified atmosphere packaging（MAP）,storage time was 18 h.There were no significant difference in hardness,soluble solids,total phenol content,sensory evaluation and smell,between the yellowing fresh-cut yam and the no yellowing fresh-cut yam except for the color change,which indicated that there was no significant difference in the quality of them（2）The structure and composition of YP were analyzed.The YP was separated,purified and identified by ultra-high liquid chromatography-mass spectrometry（HPLC）.It was found that the TP was mainly composed of three yellow substances,with the largest proportion being bisdemethoxycurcumin（BDMC）（73.7%）.The formula of the other two substances were C₁₉H₁₈O₃（19.2%） and C₁₉H₁₆O₃（7.1%）.（3）The stability of YP was revealed.The results indicated that the YP had high thermal stability,when the temperature was over 123 ℃,the effect of thermal degradation was obvious.The thermal stability of it was higher than that of anthocyanin,chlorophyll,lycopene and other natural pigments.The simulated gastrointestinal digestive system indicated that the degradation of the YP would be happen after gastrointestinal digestion,and the degradation rate after intestinal digestion was significantly higher than that after gastric digestion by about 30.6 times.Gastric degradation rate of YP was lower than anthocyanin,while the intestinal degradation rate of it was higher than anthocyanin.The YP has light instability,which was easy to degrade under the LED light of different light sources.The order of degradation effect from high to low was blue light,red light,white light and green lightl,and its degradation process accords with the first-order degradation kinetics.（4）To clarify the function of YP in antioxidation and protection of DNA from oxidative damage.The binding pattern between YP and ct DNA was studied by UV-vis,fluorescence,viscosity and ionic strength.The results showed that the YP and ct DNA first attracted each other by static electricity,and then combined by intercalation.The YP prevented the group of ct DNA from oxidative damage.Key words: Fresh-cut Yam YP Ingredients Properties.更多还原