高饱和度油脂煎炸体系中极性物质的产生与生物评价

发布时间：2018-09-06 15:26

【摘要】：煎炸体系中极性物质的含量是评价煎炸油脂品质的重要指标。本论文以煎炸过程中产生的极性物质及不同极性组分为研究对象,讨论其在煎炸介质以及煎炸食品(薯条)中的分布规律,分析不同煎炸介质的脂肪酸组成对极性物质形成过程的影响,探索其在煎炸过程中的产生途径,同时,讨论极性物质对煎炸食品中丙烯酰胺含量变化的影响,以评价其对煎炸食品品质的影响。在此基础上通过小鼠喂养实验研究煎炸棕榈油及其极性物质对昆明小鼠能量代谢以及肝脏功能的影响,进一步从分子水平上研究极性物质在小鼠体内干扰脂质代谢的原因。本论文为阐明煎炸过程中极性物质的形成机制以及极性物质对动物体能量代谢过程的影响提供了理论依据,为进一步控制煎炸体系中极性物质的产生及其对煎炸食品品质的影响奠定基础。主要研究内容包括:(1)本论文以棕榈酸型(棕榈油)及月桂酸型(精炼棕榈仁油及精炼椰子油)油脂为研究对象,全面研究了煎炸过程中煎炸介质及煎炸食品中极性物质的含量与分布。结果表明:煎炸体系中极性物质及不同极性组分的含量随煎炸时间的延长而增加,极性物质含量的变化与所用油脂类型不相关。进一步研究表明极性物质在煎炸介质以及煎炸食品中的分布不同。煎炸介质中的极性物质含量略高于煎炸食品中的极性物质含量。在煎炸末期(第50 h),煎炸棕榈油,煎炸棕榈仁油以及煎炸椰子油中极性物质含量分别为31.65%,38.23%以及38.28%,但是,在对应煎炸薯条油脂中极性物质含量分别为29.42%,32.88%以及30.54%。随后,借助高效凝胶排阻色谱(HPSEC)技术进一步分析发现,极性物质中不同极性组分在煎炸介质与煎炸食品中的分布情况差别明显:氧化甘油三酯寡聚物及甘油三酯二聚物在煎炸食品中的含量高于煎炸介质中的相应组分的含量。以煎炸第50 h的煎炸棕榈油以及煎炸薯条为例,薯条中甘油三酯寡聚物及甘油三酯二聚物分别达到6.79%及6.54%,高于对应煎炸棕榈油中这些物质的含量(2.05%及5.49%)。但是氧化甘油三酯以及甘油二酯表现与之相反,在煎炸薯条中氧化甘油三酯及甘油二酯含量分别为5.55%及9.02%,这一含量低于对应煎炸棕榈油中氧化甘油三酯及甘油二酯的水平(7.41%及15.12%)。说明不同极性组分与煎炸食品中碳水化合物之间的相互作用强度不同,从而影响不同极性组分在煎炸体系中的分布。煎炸体系中极性物质及不同极性组分的含量与煎炸油脂肪酸组成中的反油酸(trans-C18:1)含量的变化呈正相关。另一方面,在棕榈酸型油脂中,极性物质及不同极性组分含量的变化还与亚油酸(C18:2)含量的变化高度相关,然而,在月桂酸型油脂中,极性物质及不同极性组分含量变化与C18:2含量变化的相关性小(相关系数低于0.8)。(2)本论文借助核磁共振(~1H NMR)的方法分析了煎炸过程中煎炸油脂的组成变化(含不饱和脂肪酸的酰基基团、醛类化合物、环氧化合物、羟基化合物以及甘油二酯等),通过电子自旋共振(ESR)方法监测高温处理条件下不同油品中自由基的产生情况,进一步阐明了煎炸过程中不同煎炸介质体系内极性物质的产生过程。结果表明:与新鲜棕榈仁油和新鲜椰子油相比,新鲜棕榈油中烯丙基酰基基团含量分别是前者中对应含量的3.04以及5.96倍,且在煎炸50 h以后,棕榈油中烯丙基酰基基团含量下降了37.05%。棕榈油在热处理过程中烷基自由基的产生更占优势。因此以其为介质的煎炸体系中首先产生非极性甘油三酯二聚物,再进一步被氧化得到氧化甘油三酯二聚物。虽然在煎炸棕榈油、煎炸棕榈仁油以及煎炸椰子油中检测到的环氧化合物以及羟基化合物含量相差不大,但是醛类化合物在煎炸棕榈油中的含量显著高于其在另外两种煎炸介质中的含量。以煎炸第30 h为例,煎炸棕榈油中醛类化合物含量分别是煎炸棕榈仁油以及煎炸椰子油的5.28以及2.88倍。而且棕榈油、棕榈仁油以及椰子油在热处理过程中能够产生强度相当的烷氧自由基。因此在以上述三种油脂为煎炸介质的煎炸体系中都存在脂质氧化产物(氧化甘油三酯单体)的聚合,而且在以棕榈仁油和椰子油为煎炸介质的煎炸体系中,氧化甘油三酯二聚物的来源主要是脂质氧化产物的聚合。(3)本论文系统研究了煎炸过程中煎炸油脂的品质对煎炸食品中丙烯酰胺含量变化的影响,以讨论其对煎炸食品品质的影响。首先,完善了煎炸食品中丙烯酰胺的快速检测方法:在预处理操作中的氮吹复溶阶段,需要预先加入一定量超纯水,以保护待测物质,防止丙烯酰胺发生聚合反应影响其回收率;同时,在丙烯酰胺色谱分析阶段,Chrome-Matrix C18色谱柱(2.6μm,2.1×100 mm)的使用不但改善了丙烯酰胺峰形,而且节约了分析时间,提高了检测效率。其次,通过测定不同食品基质中丙烯酰胺含量评价了该方法的重复性及准确度,结果表明该方法的日内精密度范围为0.04-2.38%,其日间精密度范围为2.34-3.26%。进一步研究了不同煎炸介质中煎炸食品内丙烯酰胺含量随煎炸油脂使用时间的变化:以棕榈油、棕榈仁油以及椰子油为煎炸介质的煎炸体系中,在前30 h的煎炸过程中,煎炸薯条中的丙烯酰胺含量随煎炸介质使用时间的延长而增加。与第一批次(第0.25 h)煎炸薯条中丙烯酰胺含量相比,第30 h煎炸薯条中的丙烯酰胺含量分别增长了6.63倍、0.21倍以及2.21倍。但是在第30 h以后,煎炸薯条中的丙烯酰胺含量随煎炸介质使用时间的延长而下降。与第30 h煎炸薯条中丙烯酰胺含量相比,第50 h煎炸薯条中的丙烯酰胺含量分别下降了62.28%、34.88%以及28.81%。通过分析煎炸过程中煎炸油脂中水分含量及煎炸薯条中极性物质及其组分含量的变化发现:在煎炸初期,煎炸食品中丙烯酰胺的含量与体系中水分含量相关,即丙烯酰胺含量随煎炸体系中水分含量的减少而增加,而且,丙烯酰胺的产生与煎炸油脂中游离脂肪酸的含量呈正相关。但是,在煎炸后期,随着煎炸体系中极性物质含量的增加,由于其与煎炸食品中碳水化合物的相互作用限制了煎炸体系中美拉德反应的进行,因此煎炸食品中丙烯酰胺含量明显下降。(4)本论文进一步探讨了煎炸棕榈油以及从其中分离得到的总极性物质对小鼠健康的影响,尤其是对脂质代谢以及糖代谢和肝脏的影响。结果表明,高能量摄入能够促进小鼠肝脏细胞中脂肪的堆积,但是,极性物质的摄入对小鼠肝脏中脂肪的堆积影响并不明显。另一方面,极性物质的摄入虽然没有造成小鼠肝脏中脂肪聚集,但是,其对小鼠的血脂水平、肝脏酶活力以及机体抗氧化能力的影响与其他高脂饲料喂养的小鼠表现一致,表明极性物质的摄入能够干扰小鼠体内脂质代谢过程,降低机体抗氧化能力,并且造成肝脏损伤。对小鼠肝脏中参与脂肪酸代谢的相关基因表达的测定结果显示:极性物质的摄入抑制了小鼠肝细胞中参与脂肪酸合成的相关基因(SREBP-1c)的表达,与低脂对照组相比其表达量下降了15.34%;与高脂对照组相比,极性物质喂养组小鼠肝细胞中脂肪酸去饱和酶(SCD1)的基因表达量下降了29.54%,说明极性物质的摄入影响小鼠肝脏中脂质代谢过程。另一方面,极性物质的摄入使得小鼠肝细胞中乙酰辅酶A氧化酶(ACOX1)的基因表达增强,是低脂对照组小鼠肝脏中相应基因表达量的2.07倍,表明极性物质促进小鼠肝细胞中过氧化物酶体上的脂肪酸氧化反应;但是极性物质的摄入对小鼠肝脏中肉毒碱棕榈酰基转移酶(CPT1α)的基因表达没有显著影响,说明脂肪酸在线粒体中的氧化反应并没有随极性物质的摄入而改变。极性物质对小鼠体内葡萄糖代谢过程的影响表现为:低剂量极性物质的摄入有助于改善小鼠体内由高脂饮食引起的葡萄糖耐受量变差的情况,然而,高剂量极性物质的摄入明显损伤小鼠的葡萄糖耐受量。因此高油脂基质中极性物质的摄入能够改变昆明小鼠体内的脂质代谢以及葡萄糖代谢过程。
[Abstract]:The content of polar substances in frying system is an important index to evaluate the quality of frying oil. In this paper, polar substances and polar components produced in frying process were studied. The distribution of polar substances in frying medium and fried food (French fries) was discussed. The formation of polar substances by fatty acid composition in different frying medium was analyzed. In order to evaluate the effects of polar substances on the content of acrylamide in fried food and the quality of fried food, we studied the effects of fried palm oil and its polar substances on energy metabolism and liver function in Kunming mice by feeding experiments in mice. This paper provides a theoretical basis for elucidating the formation mechanism of polar substances and the effect of polar substances on energy metabolism in mice during frying, and for further controlling the production of polar substances in frying system. The main research contents are as follows: (1) The content and distribution of polar substances in the frying medium and the frying food during the frying process were studied comprehensively with palmitic acid (palm oil) and lauric acid (refined palm kernel oil and refined coconut oil) oils as the research objects. The content of polar substances and different polar components increased with the prolongation of frying time, and the change of polar substances content was not related to the type of oil used. At the end of frying (50h), the contents of polar substances in fried palm oil, fried palm kernel oil and fried coconut oil were 31.65%, 38.23% and 38.28%, respectively. However, the contents of polar substances in corresponding fried potato chips oil were 29.42%, 32.88% and 30.54% respectively. Subsequently, high performance gel exclusion chromatography (HPSEC) was used for further analysis. It was found that the distribution of different polar components in frying medium and fried food was obviously different: the content of triglyceride oxide oligomer and triglyceride dimer in fried food was higher than that of corresponding components in fried medium. Triglyceride oligomers and triglyceride dimers reached 6.79% and 6.54% respectively, which were higher than those in the corresponding fried palm oil (2.05% and 5.49%). The levels of triglyceride and diethylene glyceride in fried palm oil (7.41% and 15.12%) showed that the interaction strength between different polar components and carbohydrates in fried food was different, thus affecting the distribution of different polar components in the fried system. The content of trans-C18:1 in fatty acid composition was positively correlated. On the other hand, the content of polar substances and different polar components in palmitic oil was also highly correlated with the content of linoleic acid (C18:2). However, in lauric acid oil, the content of polar substances and different polar components changed with the content of C18:2. (2) In this paper, the composition of frying oils (acyl group, aldehydes, epoxides, hydroxyl compounds, glycerol diesters, etc.) during frying was analyzed by means of nuclear magnetic resonance (~1H NMR), and the high temperature was monitored by electron spin resonance (ESR). The production of free radicals in different oils under different physical conditions was further clarified. The results showed that the contents of allyl groups in fresh palm oil were 3.04 and 5.96 times higher than those in fresh palm kernel oil and fresh coconut oil, respectively. The content of allyl acyl group in palm oil decreased by 37.05% after 50 h of frying. The generation of alkyl radicals was more dominant in the heat treatment of palm oil. The contents of epoxides and hydroxyl compounds in palm oil, fried palm kernel oil and fried coconut oil were similar, but the contents of aldehydes in fried palm oil were significantly higher than those in the other two media. Palm kernel oil and fried coconut oil are 5.28 and 2.88 times as strong as those of palm oil, palm kernel oil and coconut oil, and they can produce alkoxy radicals of the same strength during heat treatment. Therefore, lipid oxidation products (triglyceride monomers) can be polymerized in the frying system in which the above three oils are used as frying media, and in which triglyceride monomers are oxidized. In the frying system with palm kernel oil and coconut oil as frying medium, the source of triglyceride oxide dimer is mainly the polymerization of lipid oxidation products. (3) The effect of the quality of frying oil on the content of acrylamide in fried food during frying process was studied systematically in order to discuss the effect on the quality of fried food. A rapid method for the determination of acrylamide in fried food was developed. In the stage of nitrogen blowing and resolving in the pretreatment operation, a certain amount of ultra-pure water should be added in advance to protect the substance to be tested and prevent the polymerization of acrylamide from affecting its recovery. The method not only improved the peak shape of acrylamide, but also saved analysis time and improved detection efficiency. Secondly, the repeatability and accuracy of the method were evaluated by determining acrylamide content in different food substrates. The results showed that the intra-day precision range of the method was 0.04-2.38%, and the inter-day precision range was 2.34-3.26%. The changes of acrylamide content in fried food in different frying media with the use time of frying oil were studied. In the frying system with palm oil, palm kernel oil and coconut oil as frying media, the acrylamide content in fried French fries increased with the use time of frying media during the first 30 hours. The content of acrylamide in fried potato chips increased by 6.63 times, 0.21 times and 2.21 times at 30 h, respectively. But after 30 h, the content of acrylamide in fried potato chips decreased with the prolongation of frying time. The content of acrylamide in fried potato chips decreased by 62.28%, 34.88% and 28.81% at 50 h, respectively. Amine content increases with the decrease of water content in the frying system, and the production of acrylamide is positively correlated with the content of free fatty acids in the frying oil. The content of acrylamide in fried food decreased significantly as a result of the Rudd reaction. (4) The effects of fried palm oil and the total polar substances isolated from it on the health of mice, especially on lipid metabolism, glucose metabolism and liver, were further investigated. The results showed that high energy intake could promote the liver of mice. On the other hand, the intake of polar substances did not cause the accumulation of fat in the liver of mice, but the effects of polar substances on blood lipid level, liver enzyme activity and antioxidant capacity of mice fed with other high-fat diets were not significant. The results showed that the intake of polar substances could interfere with lipid metabolism, reduce antioxidant capacity and cause liver injury in mice. The expression of related genes involved in fatty acid metabolism in mice liver showed that the intake of polar substances inhibited fatty acid synthesis in mice liver cells. The expression of related gene (SREBP-1c) was decreased by 15.34% compared with the low-fat control group, and the expression of fatty acid desaturase (SCD1) in the liver cells of mice fed with polar substances decreased by 29.54% compared with the high-fat control group, suggesting that the intake of polar substances affected the lipid metabolism in the liver of mice. The gene expression of acetyl coenzyme A oxidase (ACOX1) was 2.07 times as high as that of the low-fat control group, suggesting that the polar substances promoted the oxidation of fatty acids in the peroxisome of the liver cells, but the polar substances increased the carnitine brown in the liver of the mice. The gene expression of palmitoyl transferase (CPT1alpha) was not significantly affected, suggesting that the oxidation of fatty acids in mitochondria did not change with the intake of polar substances. However, high doses of polar substances significantly impaired glucose tolerance in mice. Therefore, the intake of polar substances in high-fat matrices can alter lipid metabolism and glucose metabolism in Kunming mice.
【学位授予单位】：江南大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TS221

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