模型反应中不同酚酸物质抑制PhIP形成效果分析

2-氨基-1-甲基-6-苯基-咪唑[4,5-b]吡啶(2-amino-1-methyl-6-phenyl-imidazole[4,5-b]pyridine,PhIP)是食品加工和烹饪中含量较高且有致癌风险的杂环胺类化合物。该文在以苯丙氨酸和肌酐为前体物质的模型体系中,考察阿魏酸、咖啡酸、对香豆酸3种单体酚酸以及混合酚酸对PhIP形成的抑制效果,并进一步探讨酚酸类物质在模型体系中对PhIP形成的抑制效果是否存在相互协同作用。结果表明,在单体酚酸模型中,当酚酸浓度为10^-10mg/mL或10^-9mg/mL时,从整体效果比较3种单体酚酸对PhIP形成的抑制效果,由强到弱分别为咖啡酸、对香豆酸、阿魏酸,而当酚酸浓度为10^-8mg/mL时,阿魏酸对PhIP形成的抑制效果强于对香豆酸;在混合酚酸模型中,阿魏酸+对香豆酸的组合对PhIP形成抑制效果最强,抑制率为56.37%,咖啡酸+对香豆酸的组合对PhIP形成抑制效果最弱,抑制率为13.33%。推测其反应机理可能是酚酸类物质与前体物质发生反应生成新的化合物,消耗掉前体物质的量,从而抑...     

咖啡酸激活酪氨酸酶催化反应的动力学研究

在30℃,pH6.8的Na2HPO4-NaH2PO4缓冲体系中,采用酶动力学方法研究了咖啡酸对酪氨酸酶单酚酶和二酚酶活力的激活效应.实验结果表明,咖啡酸对酪氨酸酶单酚酶和二酚酶活性均有激活作用,对单酚酶和二酚酶活力的相对激活率达到50%的咖啡酸浓度(IC50)分别为0.27mmol/L和1.35mmol/L.咖啡酸能消除单酚酶催化反应的迟滞时间,对二酚酶的激活作用表现为混合性激活,当咖啡酸浓度为0、0.50、1.0、1.50mmol/L时,米氏常数Km分别为0.31、0.25、0.20、0.15mmol/L.     

添加甘氨酸对天冬酰胺/葡萄糖模拟体系中丙烯酰胺形成的抑制作用

美拉德反应目前被认为是形成丙烯酰胺的重要途径,极探讨了甘氨酸在葡萄糖/天冬酰胺模拟体系中抑制丙烯酰胺形成的规律。模拟体系分别在90、100、110、120℃下反应4h,丙烯酰胺的生成、褐变度的增加、产物的减少以及对天冬酰胺和甘氨酸降解动力学的分析表明,甘氨酸的添加能够显著降低美拉德反应生成的丙烯酰胺,且在该反应体系中甘氨酸与天冬酰胺之间存在竞争关系。     

蓝莓花色苷对美拉德有害产物形成的抑制作用

目的 探究微波加热处理对美拉德有害产物积累情况的影响以及蓝莓花色苷对模拟体系中美拉德有害产物形成的抑制效果。方法 本研究通过构建牛血清蛋白-葡萄糖模拟体系,对其进行不同时间微波加热处理,以类黑精、晚期糖化终末产物、乙二醛、羧甲基赖氨酸、丙烯酰胺含量为指标,探讨样液中相关美拉德有害产物与加热时间的关系以及不同浓度的蓝莓花色苷溶液对美拉德有害产物的抑制效果。结果 随着微波加热时间增加,美拉德有害产物不断积累。在微波加热180 min的条件下,不同浓度的蓝莓花色苷均表现出明显的抑制美拉德有害产物生成的能力,并且0.030mg/mL的蓝莓花色苷溶液对大部分物质抑制效果最好。结论 蓝莓花色苷在食品热加工过程中,对美拉德有害物质生成有抑制作用,对未来食品安全和生物健康都具有重要意义。     

阿魏酸异辛酯抑制酪氨酸酶活性的动力学研究

在30℃,pH=6.8的Na2HPO4-NaH2PO4缓冲体系中,采用酶动力学方法研究阿魏酸异辛酯对酪氨酸酶单酚酶和二酚酶活力的抑制动力学。实验结果表明,阿魏酸异辛酯对酪氨酸酶单酚酶和二酚酶活性均有良好抑制作用,对单酚酶和二酚酶活力的相对抑制率达到50%的阿魏酸异辛酯浓度(IC50)约分别为0.24 mmol/L和0.45 mmol/L,比熊果苷抑制二酚酶活性的IC50值5.3 mmol/L小得多。阿魏酸异辛酯能明显延长单酚酶的迟滞时间,0.4 mmol/L阿魏酸异辛酯能使迟滞时间由1.1 min延长至3.6 min。Lineweaver-Burk图显示阿魏酸异辛酯对二酚酶的抑制作用表现为竞争性抑制,抑制常数(K)I为0.20 mmol/L。     

指示消费端食源性AGEs含量的美拉德反应型时间-温度指示器的研究

美拉德反应产生的晚期糖化终末产物(AGEs)与糖尿病及其并发症有潜在的关联性,因此,消费者需要一种便捷的可指示消费端食品中AGEs水平的动态标识,以指导日常合理的膳食,减少AGEs对人体健康的危害。建立了指示荧光性AGEs含量变化的美拉德反应型时间温度指示器(TTI),以指示食品模拟体系(赖氨酸/葡萄糖)在短时间加热过程中AGEs含量的变化。根据TTI活化能与食品质量变化匹配的原则,在恒温条件和变温条件下,通过计算荧光性AGEs和指示器的反应动力学参数,对TTI和荧光性AGEs变化进行匹配。结果表明:0.4 mol/L赖氨酸和0.3mol/L木糖溶于pH7.0磷酸缓冲溶液制成的美拉德反应型TTI在短时间加热过程中颜色变化明显,恒温条件下得到食品模拟体系中荧光性AGEs和美拉德反应型TTI反应活化能分别为118.18 kJ/mol和96.17 kJ/mol,两者活化能之差小于25 kJ/mol,并且在变温实验中得到两者有效温度之差小于1K,证明所构建的TTI可以用于指示食品模拟体系中荧光性AGEs的积累过程。     

Glu-Asn食品模拟体系中丙烯酰胺的形成规律

以葡萄糖和天冬酰胺为主要反应物,建立美拉德模拟体系,研究不同的反应条件和不同种类的糖对模拟体系中丙烯酰胺生成的作用规律。结果表明:温度是丙烯酰胺形成的重要因素。在120~180℃条件下丙烯酰胺含量与温度呈正相关的趋势,200℃时丙烯酰胺含量呈先上升后下降的趋势;模拟体系的初始p H值小于8时,丙烯酰胺含量随p H值升高而增加,当p H=8时其达到最大值,继续升高p H值,丙烯酰胺含量开始下降,说明高p H值条件不利于丙烯酰胺的生成;Glc/Asn物质的量比接近1∶1时反应生成的丙烯酰胺最多,且天冬酰胺过量引起的影响要小于葡萄糖过量引起的影响;半乳糖、果糖和蔗糖对丙烯酰胺的生成起促进作用,甘露醇、赤藓糖醇、山梨醇、β-环糊精对丙烯酰胺的抑制作用较为明显,前三者均有各自的最佳抑制浓度。丙烯酰胺抑制率与β-环糊精加入量呈正相关趋势。β-葡聚糖的浓度对丙烯酰胺最终形成几乎没有影响。     

南丰蜜桔幼果功能性成分的分析及酚酸的检测

南丰蜜桔幼果的功能成分中,除了VC、VE、类胡萝卜素等以外,黄酮与酚酸等酚类物质也具有重要生物活性,为了深入了解南丰蜜桔幼果的价值,以6种不同产地的南丰蜜桔幼果样品为原料,对其总酚含量、总黄酮含量进行分析。酚酸具有多种生理功能,并广泛存在于植物组织中,采用HPLC-MS测定了南丰蜜桔幼果中6种酚酸的含量,即咖啡酸、对香豆酸、阿魏酸、芥子酸、没食子酸和对羟基苯甲酸。结果显示:南丰蜜桔幼果中以肉桂酸型酚酸为主,苯甲酸型酚酸含量较少;南丰蜜桔幼果中阿魏酸是所测6种酚酸中含量最高的,其次主要是咖啡酸,且可溶性酚酸含量要远远大于束缚酚酸的含量。     

NaCl-CaCl_2处理对发芽大豆酚类物质富集及抗氧化能力的影响

为研究氯化盐是否在种子萌发过程中对酚类物质的富集发挥作用,采用水培法,研究了外源添加1. 5mmol/L NaCl、6 mmol/L CaCl_2和1. 5 mmol/L NaCl+6 mmol/L CaCl_2处理对大豆芽苗生长指标、总酚含量、酚酸含量及抗氧化能力的影响。结果表明:NaCl和CaCl_2单独处理均能促进大豆芽苗的生长,两者联合处理时促进效果更明显; NaCl-CaCl2作用下,大豆芽苗的总酚含量和酚酸含量均大幅增加,DPPH清除能力和ABTS清除能力得到提高。由此可见,NaCl-CaCl2对增强大豆芽苗的酚类物质含量及提高其抗氧化能力具有重要作用。     

土耳其科学家研究多酚类成分对美拉德模型中呋喃及丙烯酰胺形成的影响

据sciencedirect数据库消息,2013年8月土耳其研究人员在《食品化学》（Food Chemistry）杂志刊登一项多酚成分对美拉德模型中呋喃、丙烯酰胺形成的影响及储藏过程中总呋喃含量影响的研究。本研究采用葡萄糖-甘氨酸及果糖-天冬酰胺体系作为美拉德反应模型,分别研究咖啡酸、绿原酸、ECE（欧洲蔓越莓多酚提取物）、鞣花酸、表儿茶酸、橄榄苦苷、PPE（石榴皮多酚提取物）、OMWWE（橄榄多酚提取物）、安石榴苷、对羟苯基乙醇对美拉德模型及饼干焙烤过程中呋喃、丙烯酰胺形成影响。     

Study of acrylamide mitigation in model system: Effect of pure phenolic compounds

Many natural antioxidant extracts were reported to potentially reduce the acrylamide formation during Maillard reaction. In this work, the effect of pure antioxidant molecules on acrylamide net amount was investigated in an equimolar asparagine–glucose system (10 mM) during heating (200 °C). All experimentations were performed in the newly designed test cell. Cinnamic acid and six phenolic compounds (gallic, ferulic, coumaric, caffeic acids, catechin, and epicatechin), displaying different antioxidant capacity, were added at 5 mM to the model system. The results indicated no reduction effect of the tested compounds on acrylamide net amount. Moreover, in the case of ferulic acid a slight but significant promoting effect was observed. An increase of antioxidant activity was also noticed during heating of model solution spiked with caffeic acid but the acrylamide level was not affected.     

Effect of standard phenolic compounds and olive oil phenolic extracts on acrylamide formation in an emulsion system

In this work the effect of standard phenolic compounds such as trolox, phenolic acids (ferulic, gallic, protocatechuic and caffeic acid) and secoiridoids, extracted from virgin olive oil (VOO), on acrylamide formation in an emulsion system was investigated. The emulsion system was heated in an oil bath at different temperatures and for different periods of time. At 105 and 115 °C the generated amounts of acrylamide were negligible during the monitoring time. At 125 °C addition of standard phenolic compounds reduced acrylamide formation which was more pronounced at initial time of heating (20 min) reaching up to 70%. Protocatechuic and gallic acid were more effective than trolox, caffeic and ferulic acid in acrylamide reduction at the final time intervals of heating (30–60 min). On the contrary, addition of VOO extract in the emulsion system resulted in a remarkable increase of acrylamide level, which was ascribed to secoiridoids’ structure containing aldehydic groups.     

Effect of phenolic acids on glucose and organic acid metabolism by lactic acid bacteria from wine

The influence of phenolic (p-coumaric, caffeic, ferulic, gallic and protocatechuic) acids on glucose and organic acid metabolism by two strains of wine lactic acid bacteria (Oenococcus oeni VF and Lactobacillus hilgardii 5) was investigated. Cultures were grown in modified MRS medium supplemented with different phenolic acids. Cellular growth was monitored and metabolite concentrations were determined by HPLC-RI. Despite the strong inhibitory effect of most tested phenolic acids on the growth of O. oeni VF, the malolactic activity of this strain was not considerably affected by these compounds. While less affected in its growth, the capacity of L. hilgardii 5 to degrade malic acid was clearly diminished. Except for gallic acid, the addition of phenolic acids delayed the metabolism of glucose and citric acid in both strains tested. It was also found that the presence of hydroxycinnamic acids (p-coumaric, caffeic and ferulic) increased the yield of lactic and acetic acid production from glucose by O. oeni VF and not by L. hilgardii 5. The results show that important oenological characteristics of wine lactic acid bacteria, such as the malolactic activity and the production of volatile organic acids, may be differently affected by the presence of phenolic acids, depending on the bacterial species or strain.     

不同晚熟柑橘中酚类物质的含量检测及分析

采用超高效液相色谱(ultra-performance liquid chromatography,UPLC)对9种晚熟柑橘(沃柑、春见、大雅柑、不知火、默科特、红肉脐橙、伦晚脐橙、红翠2号和塔罗科血橙)中的主要酚类物质(13种类黄酮和7种酚酸)进行测定,分析比较不同品种柑橘果皮、果肉和果汁(柑橘原汁)中酚类物质种类和含量的差异。结果表明:9个柑橘品种的果皮、果肉、果汁中,类黄酮均以橙皮苷为主,酚酸以阿魏酸为主,且果皮中多甲氧基黄酮含量丰富。在9个柑橘品种果汁中,春见的橙皮苷、咖啡酸含量最高。果肉中,沃柑中阿魏酸、咖啡酸、芥子酸含量最高,塔罗科血橙的橙皮苷、对香豆酸含量最高。果皮中,默科特的芸香柚皮苷、川皮苷、阿魏酸含量最高。杂柑果皮中咖啡酸、阿魏酸及川皮苷含量高于橙类。晚熟柑橘含有丰富的酚类物质,并呈现显著的多样性。     

Antioxidant activity of hard wheat flour, dough and bread prepared using various processes with the addition of different phenolic acids

BACKGROUND: The purpose of this study was to evaluate the effect of baking process on the antioxidant activity of different phenolic acids. Antioxidant potential was determined using the β‐carotene‐bleaching activity assay, and free phenolic acid levels were determined by high‐performance liquid chromatography. Four phenolic acids, caffeic acid, ferulic acid, syringic acid and gallic acid, were mixed with wheat flour at a concentration of 4.44 µmol/g of flour. RESULTS: Type of phenolic acid and processing affected antioxidant activity. Of the phenolic acids, caffeic acid had the most pronounced antioxidant effect. The ranking of phenolic acids in terms of their antioxidant activity in fermented dough and bread was similar to that before processing, i.e. syringic acid < gallic acid < ferulic acid < caffeic acid. The content of ferulic acid was greater than that of the other phenolic acids after baking. Antioxidant activity and free phenolic acid content were reduced by mixing but recovered after fermentation and baking. Phenolic acid recovery after baking was 74–80%. CONCLUSION: Phenolic acids retain their antioxidant activity after the baking process, which has potential health benefits for consumers. Elucidation of interactions between the baking process and phenolic acids is important for the development of functional foods. Copyright © 2010 Society of Chemical Industry     

Antioxidative activity of phenolic acids on triacylglycerols and fatty acid methyl esters from olive oil

The autoxidation of kinetically pure triacylglycerols and methyl esters of olive oil (TGOO and MEOO) in the presence of four different concentrations of p-coumaric, ferulic and caffeic acids at 100 °C was studied. It was established that effectiveness and strength of the phenolic acids were greater in MEOO than in TGOO. In both lipid substates the molecules of phenolic acids participate in one side-reaction (with hydroperoxides). The rate constants of this reaction in TGOO and in MEOO are practically the same. The phenolic acids take part in chain initiation. The rate of this reaction for ferulic and caffeic acids has equal values in TGOO and in MEOO, whereas for p-coumaric acid it is twice as high in TGOO than in MEOO. The radicals of the phenolic acids participate in one reaction of chain propagation (with the lipid substrate) both in triacylglycerols and in methyl esters of olive oil. Comparison with the data published recently for sunflower oil triacylglycerols and methyl esters demonstrates the strong influence of the unsaturation type and degree of the lipid system on the kinetics and mechanism of the antioxidative action of the phenolic acids.     

Ability of Lactobacillus brevis strains to degrade food phenolic acids

The potential to degrade 15 food phenolic acids was investigated for several Lactobacillus brevis strains isolated from different sources. All the strains analysed in this study showed a similar metabolism on phenolic acids. Among the cinnamic acids assayed, only p-coumaric, ferulic and caffeic acids were metabolized by the L. brevis strains. These acids were decarboxylated to produce their corresponding vinyl derivatives. Contrarily to the results previously reported on Lactobacillus plantarum, the L. brevis strains analysed in this study were unable to subsequently reduce or metabolize these vinyl derivatives. In L. brevis, vinyl phenol, vinyl catechol, and vinyl guaiacol were the final metabolic products from p-coumaric, caffeic or ferulic acids, respectively. From the benzoic acids analysed, and similarly to L. plantarum strains, only gallic and protocatechuic acids were modified by L. brevis strains. Both acids were decarboxylated to pyrogallol and catechol, respectively. Currently, the enzymes involved in the metabolism of phenolic acids in L. brevis remain uncharacterized.     

The Use of an Extracellular Ferulic Acid Esterase from Lactobacillus acidophilus K1 for the Release of Phenolic Acids During Mashing

A purified extracellular ferulic acid esterase from Lactobacillus acidophilus K1 was successfully used during mashing for the release of free phenolic acids into sweet wort. The enzyme was produced in bioreactors and partially purified to obtain the monoenzyme preparation. Release of free ferulic and vanillic acid into the wort at 52°C (with the use of 4.09–14.60 enzyme activity units/L of the mash) and ferulic acid at 62°C (14.60 units/L) was observed. Free p‐OH‐benzoic and syringic acids were effectively released at 26°C at each enzyme concentration used. Free p‐OH‐benzoic acid was also released by the enzyme (14.60 U/L) at 52°C‐74°C. Free protocatechuic acid was effectively hydrolyzed by the enzyme preparation (8.75 U/L and 14.60 U/L) at 26°C‐52°C. Free caffeic acid (effectively released at 26°C‐62°C) originated from chlorogenic acid. No p‐coumaric acid was released due to the action of bacterial esterase during mashing. Ferulic acid esterase from L. acidophilus K1 exhibited no ability to release free phenolic acids during mashing at 62°C or at 74°C due to its low thermostability. In conclusion, L. acidophilus K1 is an attractive source for the production of ferulic acid esterase, which can be useful for the release of antioxidant phenolic acids in the early stages of mashing.     

甘蔗不同组织中游离态和结合态酚酸的分布及抗氧化活性

为了探讨甘蔗不同组织中酚酸的存在形式,本文利用反相高效液相色谱法(RP-HPLC)对蔗汁、蔗叶及蔗渣三个组织中游离态和结合态的酚酸进行了定性和定量检测分析。结果表明,甘蔗组织中的酚酸主要以结合态形式存在,但其在甘蔗三个组织中的含量和存在形式有差别。甘蔗叶、蔗渣中游离的酚酸含量最高,蔗汁较低。蔗汁、蔗叶及蔗渣中总游离态酚酸含量分别为317.18 mg/kg(干固物),1568.37 mg/kg(干基)及1504.57 mg/kg(干基);总结合态酚酸含量分别为740.32 mg/kg(干固物),2725.41 mg/kg(干基),2452.13 mg/kg(干基)。在蔗汁中,咖啡酸、没食子酸主要以游离态存在,阿魏酸、香豆酸主要以结合态存在,而在蔗叶和蔗渣中,咖啡酸、阿魏酸、香豆酸主要以结合态形式存在。甘蔗不同组织中游离态酚酸的DPPH和ABTS自由基清除活性优于结合态酚酸,不同组织中的游离态酚酸和结合态酚酸含量分别与抗氧化活性呈正相关性。     

对香豆酸、阿魏酸和低聚糖阿魏酸酯对酪氨酸酶的抑制效果

通过测定酶的稳态活力、迟滞时间和动力学参数,研究对香豆酸、阿魏酸及低聚糖阿魏酸酯对酪氨酸酶的抑制效果。结果表明,3种物质对酪氨酸酶单酚酶活性均有抑制作用,其中对香豆酸的抑制作用最强,其次为低聚糖阿魏酸酯和阿魏酸。对香豆酸、低聚糖阿魏酸酯和阿魏酸对单酚酶的IC_(50)值分别为0.75,3.20,9.30 mmol/L。对香豆酸和阿魏酸抑制二酚酶活性,IC_(50)值分别为4.3,12.7mmol/L;但低聚糖阿魏酸酯对二酚酶活力没有影响。对香豆酸能明显延长单酚酶反应的迟滞时间,阿魏酸影响很小,而低聚糖阿魏酸酯则缩短迟滞时间。动力学研究结果显示,阿魏酸和低聚糖阿魏酸酯对单酚酶的抑制作用表现为混合性抑制,而对香豆酸为竞争性抑制。