【作者】 张清；

【导师】 沈群；

【作者基本信息】 中国农业大学 ， 粮食、油脂及植物蛋白工程， 2014， 博士

【摘要】 本文研究了大豆油在180℃下加热、煎炸面团和煎炸鸡胸肉这三种煎炸体系中的特征性理化性质,包括煎炸油脂的颜色、黏度、脂肪酸组成及其含量、挥发性成分及其含量、红外指纹图谱和组分分子量分布的变化情况；探讨了产生这些代表性产物的可能的化学反应途径。油样的颜色和黏度分别采用色差仪和流变仪进行测定。三种处理过程中油样的颜色变化分别是：由浅黄色变为深黄色；浅黄色变为红黄色和浅黄色变为深黑色。三种处理过程中油样的黏度变化是：由新鲜大豆油的0.052Pa.s分别增大到油样7-8h时的0.142、0.312和0.146Pa.s。油样的脂肪酸组成采用GC-MS进行分析。脂肪酸变化在不同的处理下呈现出显著的差异。食物组分的引入加剧了大豆油中的多不饱和脂肪酸在高温下的氧化分解,其中鸡胸肉成分导致的多不饱和脂肪酸减少程度更大,这与鸡胸肉中脂肪含量相对较高有关。油样中挥发性成分采用SPME-GC-MS进行定性和定量分析。加热时大豆油的挥发性成分包括烷烃、烯烃、炔烃、醇、醛、酮和其他类物质,其中醛类含量最多。煎炸面团时,大豆油中红挥发性成分的数量减少、相对含量降低。煎炸鸡胸肉时,大豆油中的挥发性成分含量相对较低,尤其是醛类物质,同时在油样中检出了含氮物质。三种热处理过程中都检出了邻苯二甲酸酯类,这可能是大豆油多不饱和脂肪酸热氧化分解反应产物的反应产物。对油样红外图谱进行处理,含有O-H、C=C、C-H、C=O和C-O键的基本成分在三种处理过程中的含量随时间的变化都得到了很好的描述性分析。利用图谱所包含的全部信息,结合聚类和判别分析,对合格玉米油、花生油、菜籽油和大豆油掺入煎炸废油进行了良好的定性分析。通过分析代表性吸收波段间的峰面积比和其波数随掺入比例的变化规律,得到四种掺假方式在这两个参数下的检测限分别为6.6、7.3、5.1、4.3与8.3、9.1、7.4和5.7%。大豆油组分的分子量采用MALDI-TOF-MS进行分析,质谱图呈现三个明显的分布区域。A区(m/z853～1001)代表甘油三酯及其氧化单体。B区(m/z613-853)主要代表甘油二酯及其氧化单体、氧化甘油二酯与小分子分解产物的化合产物。C区(m/z1001～2907)主要代表甘油三酯二聚体及其氧化单体、氧化甘油三酯二聚体与小分子分解产物的化合产物、甘油三酯三聚体及其氧化单体。在三种处理下,油样的分子量呈现出不同的分布情况。大豆油组分在三种处理中发生的变化主要是不饱和甘油三酯的含量降低,生成含量逐渐增多的小分子酸类、挥发性成分、甘油二酯及其氧化单体、氧化甘油三酯单体、甘油三酯二聚体及三聚体等。食物组分的引入加剧了高温作用下发生的化学反应强度,促使甘油三酯含量减少、产物含量增多。煎炸鸡胸肉的情况比煎炸面团时表现出数量更多的产物及更为复杂的化学反应。基于所检测的产物种类和结构类型,大豆油在煎炸食物过程中发生的主要化学反应为不饱和甘油三酯的氧化分解反应,其次是水解反应、热聚合反应、美拉德反应和焦糖化反应。具体的化学反应类型有自由基反应、官能团位置异构化、立体异构化、环氧化和环化、缩合及协同反应等,其中自由基反应是最主要的化学反应。更多还原

【Abstract】 The changes of color, viscosity, fatty acids and volatile compounds composition and their amounts, the infrared spectra and the component molecular distributions of the soybean oil (SO) heated or fried with wheat dough (WD) and chicken breast meat (CBM) at180℃were comparatively analyzed in this study. The proposed production reaction mechanisms of these typical products found during the treatment were also investigated according the yeilds and the molecular structures of these products.The color and viscosity of the treated oil samples were determined by colorimeter and rheometer, respectively. The color of the heated, WD-fried and CBM-fried SO were changed from pale yellow to deep yellow, reddish yellow and aterrimus, respectively, as the processing time increased. After the treatment of7days and8h/day, the viscosities of the heated, WD-fried and CBM-fried SO sample were increased from0.052Pa.s of the fresh SO to0.142,0.312and0.146Pa.s, respectively.The fatty acid (FA) profiles were detected by GC-MS. The changes in amount of the FAs were different under the different frying ways. The introduction of the food components increased the intensity of the oxidation occurred in the polyunsaturated FAs. The impact on the changes of FAs resulted from the constituents of CBM was the most significant, which was related with the relative high content of fat contained in CBM.SPME-GC-MS was used to isolate and investigate the volatile compounds in the headspase of the oil samples. A series of alkanes, alkenes, alkynes, alcohols, aldehydes, ketones and the other type of compounds were found in the heated SO samples. Aldehydes were the main volatile compound from the viewpoint of relative concentration. The number of the volatile compounds was reduced and the relative conteration of the volatile compounds were lower in the WD-fried SO samples compared to those in the heated SO samples. The concentrations of the detected typical volatile compounds (especially the aldehydes) found in the CBM-fried SO samples were the lowest among the three frying ways. However, the nitrogen-containing volatile compounds were only found in the CBM-fried SO samples. Phthalates which might be the reaction products of the oxidative decomposition products derived from the polyunsaturated FAs were found in relative low concentration in all the treated SO samples.The contents of the basic components with O-H, C=C, C-H, C=O, and C-O bonds were well descriptively analyzed with the proceeding of the heating and food deep-frying by thoroughly proceesing the FTIR spectra of the treated oil samples. By combining the whole imformation contained in the FTIR spectra and the cluster and discriminant analysis, the qualified corn oil, peanut oil, rapeseed oil and SOs adulterated with the used frying oil were all well quanlititively analyzed. Furthermore, by using the varying patterns of the area ratio (A19/A20) and the wavenumber shift of the typical bond (band19) along with the increace of the mixed proportion of used frying oil, the limit of detections (LODs) of the four adulteration situations were6.6,7.3,5.1,4.3and8.3,9.1,7.4,5.7%under the two parameters, respectively.MALDI-TOF-MS was used to study the molecular distribution of the constituents of the treated SO samples. Three districts of the molecular distribution named as District A, District B and District C were clearly shown from m/z600to3000for the constituents of the treated SO samples. Constituents in the District A (m/z853-1001) included the triacylglycerols (TAG) and their oxidation monomers (oxidized TAG). Constituents in the District B (m/z613-853) included the diacylglycerols (DAG) and their oxidation monomers (Oxidized DAG) and the combined compounds between the oxidized DAG and the small-molecular-weaght decomposition compounds produced from the thermaloxidation of the unsaturated TAGs. Constituents in the District C (m/z1001-2907) included the TAG dimers and their oxidation products (oxidized TAG dimers), the combined compounds between the oxidized TAG dimers and the small-molecular-weaght decomposition compounds, the TAG trimers and their oxidation products (oxidized TAG trimers) and so on. Different molecular distribution patterns were shown under the condition of different frying systems.The constituents of SO were changed significantly during the heating and food frying process. The content of the polyunsaturated TAGs was significantly decreased. Consequently, the concentrations of the small-molecular-weight acids, volatile compounds, DAGs, oxidized DAGs, oxidized TAGs, TAG dimers, and TAG trimers were correspondingly increased. The introduction of the food components intensified the chemical reactions occurred under the conditions of high temperature and prompted the decrease in content of the TAGs and the increase in amount and concentration of these products. More products and more complex reactions were found in the CBM-fried SO samples than those in the WD-fried SO samples.According to the types and structure features of the products, the main chemical reaction occurred during the heating and food frying of SO is oxidation decomposition of TAGs. In addition, hydrolysis, thermal polymerization, Maillard reation and caramelization were also found during these frying ways. The specific chemical reaction type include free radical action, Location of heterogeneous reaction and stereoisomerism of the functional groups (such as C=C bonds), epoxidation, cyclization, concerted reaction, and condensation reaction and so on.更多还原