【作者】 黄梅桂；

【导师】 张晓鸣；

【作者基本信息】 江南大学 ， 食品科学， 2012， 博士

【摘要】 美拉德反应广泛存在于各类食品加工中,因产生诱人的色泽、浓郁的芳香及醇厚的滋味而受到人们的关注。但褐色物质的形成有时也制约美拉德产物作为风味增强剂在食品中的应用范围,研究美拉德反应过程中的色泽调控就显得十分必要。本论文通过研究大豆肽-木糖美拉德热反应体系中色泽形成的影响因素,制备浅色型美拉德产物,考察其感官特性、相对分子质量分布及抗氧化活性,并研究各属性之间的相互关系。进一步探讨色泽抑制机理,提出高效制备肉香气浓郁、醇厚感饱满,且兼具抗氧化活性的浅色型美拉德风味增强肽的新方法。具体研究内容及结果如下:选取赖氨酸-木糖为模式体系,以A420、L*、a*、b*、ΔE及C*为指标研究了几种食品体系中广泛存在的几类物质对美拉德反应体系色泽形成的影响,结果表明具有酚羟基的化合物芦丁对色泽形成抑制作用不显著;茶多酚、NaCl以及维生素类化合物L-抗坏血酸、核黄素、硫胺素对色泽形成具有一定的抑制作用;L-半胱氨酸具有显著抑制色泽形成的作用。通过研究大豆肽-木糖美拉德色泽风味的影响因素,获得五种色泽较浅、风味协调的大豆肽美拉德增强肽(MRPs)的制备方法。通过凝胶过滤液相色谱对MRPs的相对分子质量分布分析结果显示相对分子质量分布具有显著性差异。与未添加抑制剂的体系PX相比,相对分子质量小于500的产物含量显著增大。相对分子质量500-1000的产物含量降低。产物相对分子质量1000-5000的片段含量减少,相对分子质量>5000的产物含量大幅减少。通过SPME-GC-MS对MRPs的挥发性成分进行分析,结果显示,与PX相比,除PXCC外含氮化合物含量均明显减少;呋喃类含量除PXCB、PXCN减少外,其它体系均有不同程度增加;PXCB、PXCR的酮类化合物含量显著增加,其它无显著性差异;PXC、PXCN中的醛类化合物含量显著增加,PXCB、PXCC中较低,PXCR无明显变化;酯类化合物含量除PXC外其余均不同程度地减小;PXCC的醇类含量远远高于PX,而PXCN、PXCR远低于PX,其它无显著性差异;5种风味增强肽中的含硫化合物含量均远远高于PX,酸类化合物含量PXCB、PXCC、PXCR远高于PX,其余无显著性差异。五种MRPs的感官特性具有不同的特点,5种MRPs的醇厚味、焦甜香比PX弱,肉香、持续性、鲜味及整体接受性均比PX强。PXC整体接受性及持续性都最强。PXCC体系的鲜味最强,PXCN咸味最强,PXCB具有突出的焦甜香,最强的肉香气。通过考察MRPs的DPPH自由基清除能力、抑制脂质过氧化能力、还原能力、螯合能力发现添加抑制剂的五种体系均具有较强的抗氧化活性,因此可根据MRPs的不同风味特点及抗氧化活性特征将其应用于不同食品体系中。采用PLSR对MRPs的感官指标、挥发性成分、相对分子质量分布和抗氧化活性数据的相关性进行分析,结果显示,肉香和含硫化合物具有很强的正相关性;含氮化合物、呋喃类、醛类、酯类、相对分子质量>5000的产物含量、相对分子质量1000-5000产物的含量与整体接受性呈显著性正相关;相对分子质量1000-5000段和醇厚味、持续性也具有较强的正相关性;含氮化合物、呋喃类、醛类、酯类、醇类、相对分子质量<1000的产物含量对螯合能力和DPPH清除活性成正相关;含氮化合物、酯类、醇类、含硫化合物、相对分子质量<1000的产物含量对还原能力都成正相关;呋喃类、醛类、酯类、相对分子质量>5000的产物含量对脂质过氧化能力呈正相关;含硫化合物、酸类、相对分子质量<1000的产物含量对脂质过氧化能力呈负相关。对半胱氨酸抑制大豆肽-木糖体系中颜色变化动力学进行了研究,结果表明, A420,L*,a*均符合零级反应动力学,b*和ΔE经非线性拟合符合指数方程,木糖剩余量的变化符合二级反应动力学方程,且木糖剩余量与A420,b*之间均极显著相关(p<0.01)。进一步研究半胱氨酸抑制大豆肽-木糖体系色泽形成机理结果表明,半胱氨酸是通过与氨基化合物和还原糖缩合重排形成的Amadori化合物相互作用,进而有效阻止Amadori化合物的进一步生成脱氧还原酮以及环化,抑制了呈色物质的产生。基于半胱氨酸和Amdori化合物相互作用理论,提出了一种控制色泽形成的新方法-二阶段变温美拉德反应,即在80 oC下反应60 min后添加半胱氨酸,迅速升温至120 oC反应110 min。同时比较了变温美拉德反应产物MRP-60和恒温美拉德产物PXC的相对分子质量分布、挥发性成分、感官特性及抗氧化活性(还原能力、螯合能力、脂质过氧化能力、DPPH自由基清除能力),结果显示,MRP-60的相对分子质量与PXC之间无显著性差异、香气柔和,具有更好的整体接受性,且抗氧化活性优于PXC。该方法可用于工业化生产兼具抗氧化活性、香气浓郁、滋味醇厚的浅色型美拉德风味增强肽。更多还原

【Abstract】 Maillard reaction widely present in food processing is popular with producing attractive color, aroma and taste. However, formation of browning compounds is sometimes limited to the application in food as flavor enhancers. Therefore, it is necessary to control the color formation during Maillard reaction. In this study, light-colored Maillard reaction product (MRP) was prepared through the influencing factors of color formation in soybean peptide-xylose system. Sensory properties, molecular weight distribution (MWD), antioxidant activity of MRPs and their relationship were also investigated. Furthermore, a novel method to producing light-colored MRPs with meaty aroma, mouthfulness and antioxidant activity was proposed based on mechanism of inhibiting color formation. The main content and results are as follows:Effect of few substances such as phenols, vitamins and sulfur-containing compounds on color formation was investigated in lysine-xylose model Maillard reaction system as the index of A420, L*, a*, b*,ΔE and C*. Rutin has not remarkable effect on color formation inhibition. L- ascorbic acid, riboflavin, thiamine, tea polyphenol and NaCl was effective in some extent. L-cysteine had significant effect on color formation inhibition.Through research, the influencing factors of flavor and color in soybean peptide-xylose Maillard reaction system, five light-colored MRPs with harmonious flavor was prepared. The MWD of MRPs determined using gel filter liquild chromatograph presented siginificant difference. Comparing with PX, the fraction content below 500 Da MRPs was noticeably increased. The fraction content of 500-1000Da MRPs was significantly decreased. The fraction content between 1000-5000 Da MRPs was also decreased. The fraction content above 5000Da MRPs was sharply decreased. The result of the volatile compounds of MRPs analyzed by SPME-GC-MS showed that the content of nitrogen-containing compounds was increased in PXCC, while distinctly decreased in other MRPs compared with PX. Furans content was increased in PXCC, PXCR and PXC while decreased in PXCB and PXCN. Ketones content in PXCB and PXCR was significantly increased, while that of other MRPs was not siginificantly different. Aldehydes content was remarkably increased in PXC and PXCN, decreased in PXCB and PXCC, but no changes in PXCR. Esters content was decreased in all MRPs except for that of PXC. Alcohols content in PXCC was much higher than that of PX, while that of PXCN and PXCR were much lower. Sulfur-containing compounds in five MRPs were much greater than in PX. Acids content in PXCB, PXCC and PXCR were much higher than in PX. Five MRPs has different sensory characteristics. Mouthfulness and sweetness of five MRPs were the poorest than in PX. Meaty, continuity, umami and overall acceptance were better than in PX. Overall acceptance, mouthfulnedss and continuity of PXC was the best in five MRPs. Umami of PXCC was the best. Saltiness of PXCN was the best. PXCB had prominent burnt and meaty. Five MRPs showed high antioxidant activity by DPPH scavenging activity, inhibiting lipid peroxidation activity, reducing power and chelating activity. Therefore, it might be applicable to special food according to their sensory characteristics.Analyzing the correlation of sensory characteristics, volatile compounds, MWD and antioxidant activity by PLSR, meaty and sulfur-containing compounds showed highly positive correlation. Nitrogen- containing compounds, furans, aldehydes, esters, content of above 5000 Da MRPs and between 1000-5000 Da MRPs fractions were siginificantly positive with overall acceptability. The fraction between 1000-5000 Da MRPs, mouthfulness and continuity presented highly positive correlation. Nitrogen-containing compounds, furans, aldehydes, esters, alcohols of the MRPs fraction below 1000 Da were positively correlated to chelating activity and DPPH scavenging activity. Nitrogen-containing compounds, esters, alcohols, sulfur-containing compounds and content of below 1000 Da MRPs were positively correlated to reducing power. Furans, aldehydes, esters of the fraction above 5000 Da MRPs were positively correlated to inhibiting lipid peroxidation activity. However, sulfur-containing compounds, acids of the fraction below 1000 Da MRPs were negatively correlated to inhibiting lipid peroxidation activity.Kinetics of color development on cysteine was investigated. The result indicated that A420, L*, a* followed the zero-order kinetics. b* andΔE followed exponential kinetics by non-linear fitness. Changes of xylose content followed second-order kinetics. Moreover, xylose content was extremely correlated with A420,b*.The color-inhibiting mechanism of cysteine in soybean peptide-xylose system was further investigated. Cysteine reacted with Amadori compounds formed by condensation and rearrangement between anion compounds and reducing sugar, which effectively interrupted further deoxydization and cyclization of Amadori compounds. Thus, the brown compounds formation was inhibited. Based on reaction mechanism of cysteine and Amadori compounds, a novel method to prepare light-colored MRPs by controlling color formation was proposed, namely, two stages gradient temperature-elevating Maillard reaction. The MRP-60 with light color was prepared by initially heated at 80 oC for 60 min, after added cysteine, raising temperature to 120 oC immediately and held for 110 min. Volatile compounds, MWD, sensory characteristics and antioxidant activity of MRP-60 and PXC were also compared. MWD of MRP-60 was not significant with PXC. Furthermore, MRP-60 has better overall acceptance and antioxidant activity. Therefore, it can be useful for industries in production of light-colored MRPs with attractive taste, aroma and antioxidant activity.更多还原