【作者】 刘晓君；

【导师】 王兴国；

【作者基本信息】 江南大学 ， 粮食、油脂及植物蛋白工程， 2011， 博士

【摘要】 浓香花生油特殊的加工工艺保留了其独特的风味和营养成分,其浓郁的风味符合东方人的饮食习惯,倍受赞誉。风味是浓香花生油的重要指标,炒籽是浓香花生油风味形成的重要加工工序。因此,研究和分析炒籽对花生油特征风味形成的影响及特征风味物质的形成路径、炒籽对花生油品质影响以及浓香花生油在煎炸过程中风味和品质变化规律,对企业生产高质量浓香花生油具有重大的理论意义和实用价值。本论文主要研究内容如下:首先,采用顶空固相微萃取法(HS-SPME)结合气相色谱-质谱联用技术(GC-MS),建立了花生油挥发性成分分析方法。通过单因素分析得出最佳萃取条件为:PDMS/DVB萃取头、搅拌状态、萃取温度50℃、萃取时间40 min和解吸时间5 min。采用HS-SPME-GC/MS对浓香花生油风味进行了初步分析,发现吡嗪类化合物含量最高,占总挥发物的32.89%,是浓香花生油顶空挥发物的主要组成。结合GC-O分析确定了浓香花生油特征风味化合物。浓香花生油特征风味组成为烘烤味/坚果味、花香味/水果香味/甜香味和脂味/青草味,其中烘烤味/坚果味为浓香花生油主体特征风味。甲基吡嗪、2,5-二甲基吡嗪、2,6-二甲基吡嗪、2,3-二甲基吡嗪、2,3,5-三甲基吡嗪、3-乙基-2,5-二甲基吡嗪、2-乙酰基-3-甲基吡嗪为烘烤味/坚果味特征风味成分,2-乙酰基吡咯、2-醛基吡咯、3-羟基-4,4-二甲基-γ-丁内酯、2,3-二氢苯并呋喃、苯乙醇、苯甲醛、间乙基苯酚、2-甲氧基-4-乙烯基苯酚为花香味/水果香味/甜香味特征风味成分,己醛、2-辛烯醛为脂味/青草味特征风味成分。HS-SPME-GC/MS、感官评定和电子鼻(EN)相结合分析了炒籽对花生油特征风味形成的影响。HS-SPME-GC/MS分析结果表明,炒籽过程中花生油风味化合物包括氮杂环化合物(20种吡嗪、5种吡啶、8种吡咯)、氧杂环化合物(11种呋喃、1种吡喃)和非杂环化合物(12种醛、12种醇、3种酮、12种酸、2种烷烃、2种烯烃以及7种酯)。炒籽30 min后氮杂环化合物含量随炒籽时间迅速增加,取代非杂环类化合物成为花生油中主要风味物质。感官评定结果表明,炒籽30 min前花生油总风味强度不大,以脂味/青草味为主,烘炒味/坚果味非常微弱;炒籽30 min后花生油总风味强度显著增强,烘炒味/坚果味对总体风味起主要贡献。风味化合物PCA分析结合感官评定结果表明,吡嗪类化合物是炒籽过程中形成风味的主要贡献化合物,赋予花生油强烈的烘炒味/坚果味。电子鼻分析结果表明炒籽时间对花生油风味具有显著影响。炒籽30 min前花生油风味特征非常接近,炒籽30 min后花生油与其他花生油风味特征差异显著。与感官评定结果一致。综上分析,炒籽时间对花生油主体特征风味形成起着非常关键的影响,其中30 min是花生油炒籽过程中重要转折点,30 min后的炒籽阶段对主体特征风味化合物吡嗪的形成非常重要。吡嗪类化合物由美拉德反应生成,炒籽30 min后温度攀升为反应提供了良好的反应条件。同时确定了花生油主体特征风味前体物质为游离氨基酸(谷氨酸、精氨酸、天冬氨酸、苯并氨酸、酪氨酸)和还原糖(果糖、葡萄糖),分别为风味化合物形成提供氮源和碳源。也系统分析了炒籽对花生油色泽、酸价、过氧化值、脂肪酸组成、微量成分和氧化稳定性等品质的影响。分析发现,经炒籽过程的花生油具有非常良好的品质:酸价和过氧化值均达到国家标准,微量脂质伴随物(维生素E、甾醇和角鲨烯)含量均未受显著影响,氧化稳定性30 min后显著升高。炒籽对花生油色泽影响较大,与炒籽后期花生中形成的大量褐变物质有关;炒籽过程中美拉德反应非挥发产物的形成减弱了花生油中以生育酚为代表的天然抗氧化成分抗氧化活性的损失。因此,花生油整体抗氧化性能得以保持或甚至随炒籽时间延长而得以提高。通过煎炸薯条模型考察了浓香花生油在食品加工过程中风味和品质的变化规律。花生油在煎炸过程中品质下降明显:酸价呈波动上升,过氧化值呈波动趋势,茴香胺值持续增长,氧化指数随煎炸进行不断增大,极性物质和反式脂肪酸含量也随煎炸进行缓慢增加,油脂色泽变深,维生素E含量煎炸初期即急剧下降消失,氧化稳定性非常差。原油中含有的吡嗪类化合物在煎炸初期完全挥发,花生油不再具有原有主体特征风味。整个煎炸过程中花生油顶空挥发物以醛类化合物为主,且醛含量随煎炸进行呈指数级增长,是花生油煎炸过程中重要的风味组成,主要由花生油中不饱和酯自动氧化形成的氢过氧化物降解生成。PCA分析结果表明,反,反-2,4-癸二烯醛是茴香胺值的重要贡献醛,其次依次为反-2-癸烯醛、顺-2-庚烯醛、反,顺-2,4-癸二烯醛、2-十一烯醛、壬醛、反-2-辛烯醛和己醛。因此,煎炸过程中醛类化合物的种类和含量可作为花生油风味和品质的重要指标。综上分析,炒籽过程中花生油特征风味形成和品质保持是由美拉德反应为主导,而在煎炸过程中花生油风味的改变和品质的降低则主要由油脂氧化反应所控制。更多还原

【Abstract】 Special production process of aromatic roasted peanut oil (ARPO) not only can generate its unique flavor but also can retain minor nutrients, which makes it award-winning among consumers. Flavor is a significant indicator of ARPO, and roasting process is the key and important production process for ARPO flavor formation. Therefore, the study on the the effect of roasting process on the formation of flavor components, the impact of roasting on peanut oil quality and the variation of ARPO flavor and quality during frying has great theoretical and practical value for the production of high-quality ARPO. The main contents of this paper were listed as follows.Firstly, an analysis method using HS-SPME technique combined with GC-MS was established for analyzing volatiles in peanut oil. Optimum HS-SPME conditions were as follows: PDMS/DVB fiber, magnetic stirring, extraction temperature of 50℃, extraction time of 40 min and desorption time of 5 min. Then volatiles of ARPO were well separated and identified using the optimized HS-SPME-GC/MS. Among these volatiles, pyrazines accounted for the largest relative percentage area (RPA) of 32.89%, which were major headspace volatile components of ARPO.Seventeen aroma-active compounds of ARPO were identified using GC-MS combined with GC-O. The ARPO aroma could be described as strong roasty/nutty, soft floral/fruity/sweet with light fatty/grassy. Methyl pyrazine, 2,5-dimethyl pyrazine, 2,6-dimethyl pyrazine, 2,3-dimethyl pyrazine, 2,3,5-trimethyl pyrazine, 3-ethyl-2,5-dimethyl pyrazine, 2- acetyl-3-methyl pyrazine were the main sources for roasty/nutty odor; 2-acetyl pyrrole, Pyrrole-2-carboxaldehyde, 3-hydroxy-4,4-dimethyl-γ-butyrolactone, 2,3-dihydro-benzofuran, benzaldehyde, benzeneethanol, guaiacol, 2- methoxy-4-vinylphenol for floral/fruity/sweet odor; hexanal, 2-octenal for fatty/grassy odor.HS-SPME-GC/MS, sensory evauation and electronic nose (EN) were combined to analyze the effect of roasting process on the flavor formation of peanut oil. A total of 95 volatiles were identified using HS-SPME-GC/MS, including N-heterocyclic compounds (20 pyrazines, 5 pyridines and 8 pyrroles), O-heterocyclic compounds (11 furans and 1 pyran) and non-heterocyclic compounds (12 aldehydes, 12 alcohols, 3 ketones, 12 acids, 2 alkanes, 2 alkenes and 7 esters). N-heterocyclic comounds increased significantly and replaced non-heterocyclic compounds to be the major flavor components of peanut oil after 30 min-roasting. Sensory evaluation results showed that peanut oil samples before 30 min-roasting owned much lower total flavor intensity, mainly presenting fatty/grassy odor; peanut oil samples after 30 min-roasting had a sharp increase in total flavor intensity, mainly presenting strong nutty/roasty aroma.? The PCA results showed that pyrazines play a major contribution to the typical flavor generated during the roasting process, presenting high-intensity roasty/nutty flavor. Also, the EN results showed that roasting time had a remarkable effect on the flavor of peanut oil. Flavor of samples before 30 min-roasting were very close to each other; after 30 min-roasting, samples had significant differences in their flavor, which were in accordance with the sensory evaluation results. In summary, it’s clearly shown that roasting time plays a critical impact on the formation of typical flavor of ARPO; 30 min is especially an important turing point during the roasting and thus the roasting stage after 30 min is very important for the formation of pyrazines. Pyrazine compounds generated by the Maillard reaction and the sharp temperature rise after 30 min-roasting provided a well reaction condition for the Maillard reaction. Also, flavor precursors of nutty/roasty flavor of peanut oil were identified as free amino acids (glutamic acid, arginine, aspartic acid, phenylalanine, tyrosine) and reducing sugar (fructose, glucose), which provided nitrogen source and carbon source respectively for the Maillard reaction.A systematic analysis was conducted to analyze the influence of roasting process on the quality of peanut oil. The results showed that peanut oil samples during the roasting process owned high quality. The acid value and peroxide value reached the national standard; minor components (vitamin E, sterols and squalene) contents were not significantly affected; OSI value significantly increased after 30 min-roasting. Also, roasting showed a great impact on oil color, which could be due to the formation of a large number of browning substances (Maillard reaction products) during the post-roasting. It can be speculated that the formation of Maillard reaction products during the roasting process weakened the loss of nature antioxidants (such as tocopherols) in peanut oil. Therefore, overall antioxidant ability can be maintaind or even improved with the roasting time extending.The flavor and quality variation of peanut oil in cooking were studied by using French fries-frying model. Peanut oil quality showed a significant decrease with the frying going on. The acid value, peroxide value, p-anisidine value, oxidative index, polar compounds and trans fatty acid content all showed different degrees of increase; oil become darker in color; vitamin E content showed a sharp decline and disappearance in the early stage of frying; and peanut oil owned very low OSI. Flavor also had great changes. Pyrazines evaporated completely in the initial frying, and peanut oil had no original nutty/roasty aroma from then on. Throughout the frying process, aldehydes were the major compounds in the peanut oil headspace, which mainly from degradation of hydroperoxide generated by autoxidation of unsaturated esters and showed an exponential growth with the frying extending. PCA results showed that E,E-2,4-decadienal showed an important contribution to the p-anisidine value, followed by E-2-decenal, Z-2-heptenal, E,Z-2,4-decadienal, 2-undecenal, nonanal, E-2-octenal and hexanal. Thus, aldehydes can be used as an important indicator of peanut oil flavor and quality during the frying process.According to the analysis above, it can be proved that the formation of typical nutty/roasty flavor and enhancement of quality during the roasting process are dominated by the Maillard reaction. However, flavor change and quality decline during the frying process are mainly affected by the autoxidation of unsaturated esters.更多还原