共查询到19条相似文献,搜索用时 62 毫秒
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通过检测苹果汁的色值(T440nm)、褐变指数(A420nnm)、氨基态氮、5- 羟甲基糠醛含量等指标研究加工过程对苹果汁褐变的影响以及在不同贮藏温度(5、20℃和37℃)下苹果浓缩汁(70.5°Brix)的非酶褐变速率。3 个贮藏温度下的苹果浓缩汁褐变速率均符合一级反应动力学模式,而且高温情况下褐变更明显。随着贮藏时间的延长,氨基态氮含量明显下降而5- 羟甲基糠醛含量上升,尤其是贮藏在37℃的苹果汁这一变化更明显。5- 羟甲基糠醛与果汁褐变效应呈指数关系,可以说明苹果汁在贮存中的褐变主因是发生美拉德反应,而且氨基态氮含量与果汁褐变效应的线性关系也验证了这一结论。在果汁的初始加工过程中,破碎、压榨、酶解、超滤、前巴氏杀菌等单元操作中美拉德反应并不明显;吸附操作可以去除果汁中的氨基态氮以及其他色素物质;而其他操作过程如浓缩和后巴氏杀菌则促进了美拉德反应,导致果汁氨基态氮含量明显下降。 相似文献
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从宁夏枸杞干制过程中色泽变化入手,测定与色泽变化相关的主要活性物质的变化,研究枸杞干制中褐变反应,以期为枸杞干制生产中的色泽保护技术提供依据。结果表明:随着干制的进行,多酚氧化酶活性逐渐降低,结合枸杞色差值的变化,确定枸杞热风干制前期有酶促褐变的发生。此外,枸杞热风干制后期,不同温度下还原糖和氨基酸态氮的含量都成下降趋势,枸杞色差值逐渐增大,且增速放缓,5-羟甲基糠醛含量逐渐下降,且温度越高越有利于美拉德反应发生。根据各非酶褐变特点,确定了枸杞热风干制后期有美拉德反应褐变存在。 相似文献
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以大枣浓缩汁中葡萄糖、酚类化合物和抗坏血酸为变量建立模拟体系,通过研究模拟体系的褐变指数(A420)和5-HMF含量(A284)的变化,并对模拟体系和5-HMF标准品全波长扫描的谱图进行比较分析,确定酚类物质、抗坏血酸、葡萄糖对大枣浓缩汁非酶褐变的影响。结果表明:随着加热时间延长,模拟体系的褐变指数(A420)和A284逐渐增大,且与模拟体系中抗坏血酸和酚类化合物的含量呈显著正相关(p<0.05),但葡萄糖发生美拉德反应的活性较小;大枣浓缩汁非酶褐变机制主要与美拉德反应和抗坏血酸氧化分解有关。 相似文献
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牛奶中共轭亚油酸含量的紫外分光光度测定方法 总被引:4,自引:0,他引:4
研究了牛乳中共轭亚油酸含量的紫外分光光度测定方法。利用紫外分光光度计,先建立标准曲线与回归公式,再将牛奶样品提取、甲酯化后,进行紫外检测。结果表明,共轭亚油酸甲酯的最大吸收波长是234nm;共轭亚油酸浓度的有效测定范围是0.00856-0.0428mg/mL;吸光度与共轭亚油酸浓度间的回归公式为Y=52.602X 0.0917(R2=0.9862);得出共轭亚油酸浓度与吸光度之间的经验公式为:共轭亚油酸浓度C(mg/mL)=0.019×吸光度(ABS);并且推出了利用紫外分光光度法测定牛奶中共轭亚油酸含量的计算公式。同时,检验了几种市售牛奶中共轭亚油酸,其平均含量为1.64mg/g。 相似文献
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Burçe Ataç Mogol Aslı Yıldırım Vural Gökmen 《Journal of the science of food and agriculture》2010,90(15):2556-2562
BACKGROUND: The Maillard reaction occurring between amino acids and sugars produces neo‐formed compounds having certain levels of antioxidant activity depending on the reaction conditions and the type of reactants. The objective of this study was to investigate enzymatic browning inhibition capacity of Maillard reaction products (MRPs) formed from different amino acids including arginine (Arg), histidine (His), lysine (Lys) and proline (Pro). RESULTS: The inhibitory effects of the MRPs on polyphenol oxidase (PPO) were determined. The total antioxidant capacity (TAC) of MRPs derived from different amino acids were in the order Arg > His > Lys > Pro. The TAC and PPO inhibition of MRPs were evaluated as a function of temperature (80–120 °C), time (1–6 h) and pH (2–12). Arg‐Glc and His‐Glc MRPs exhibited strong TAC and PPO inhibition. Increasing temperature (up to 100 °C) and time also increased TAC and PPO inhibition. Kinetics analysis indicated a mixed type inhibition of PPO by MRPs. CONCLUSION: The results indicate that the MRPs derived from Arg and His under certain reaction conditions significantly prevent enzymatic browning in actual food systems. The intermediate compounds capable of preventing enzymatic browning are reductones and dehydroreductones, as confirmed by liquid chromatographic–mass spectrometric analyses. Copyright © 2010 Society of Chemical Industry 相似文献
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Quantitative modelling approaches for ascorbic acid degradation and non-enzymatic browning of orange juice during ultrasound processing 总被引:2,自引:0,他引:2
V.P. Valdramidis P.J. Cullen B.K. Tiwari C.P. ODonnell 《Journal of food engineering》2010,96(3):449-454
The objective of this study was to develop a deterministic modelling approach for non-enzymatic browning (NEB) and ascorbic acid (AA) degradation in orange juice during ultrasound processing. Freshly squeezed orange juice was sonicated using a 1500 W ultrasonic processor at a constant frequency of 20 kHz and processing variables of amplitude level (24.4–61.0 μm), temperature (5–30 °C) and time (0–10 min). The rate constants of the NEB and AA were estimated by a primary model (zero and first order) while their relationship with respect to the processing factors was tested for a number of models, i.e., second order polynomial, different types of Ratkowsky-type model, and an Arrhenius-type model. The non-monotonic behaviour of NEB has been described more accurately by the use of a polynomial model. The rate constants of AA were described by a similar type of model having a monotonic behaviour. A synergistic effect of temperature for different amplitudes on the rate constant of both NEB and AA was observed, while an antagonistic effect of amplitude on the rate of NEB was evident. The models with the best fit were integrated to produce contour plots for the combined amplitude and temperature. The constructed contour plots illustrate that low temperatures and intermediate amplitudes, i.e., 42.7 μm, result in lower NEB and AA deterioration and consequently better quality orange juice. The overall developed modelling approaches exploit quality data in order to identify the optimal processing regions for eliminating quality deterioration of orange juice during ultrasound processing which is of high importance to the food industry. 相似文献
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美拉德反应产物的褐变、荧光吸收及抗氧化性的研究 总被引:3,自引:0,他引:3
采用以还原糖-氨基酸(木糖/葡萄糖分别与甘氨酸、赖氨酸、谷氨酰胺、半胱氨酸)模式美拉德反应(Maillard Reaction,MR)制备得到美拉德反应产物(MRPs),研究反应条件对MRPs的褐变程度、荧光吸收强度以及其抗氧化活性的影响,并分析MRPs的光学特征与抗氧化活性之间的联系。结果表明,还原糖和氨基酸的种类对MR的褐变强度有很大影响,其影响程度由强到弱分别为:Xly>Glc,Lys>Gly>Glu>Cys。随着反应时间的延长,各体系MRPs的褐变程度逐渐变强;而荧光吸收强度随着加热时间的延长而增强,然后在出现最大值后趋于平缓或者表现出下降的趋势。MRPs的抗氧化能力也随反应时间的延长而增强,抗氧化活性与褐变强度呈正相关,与荧光吸收特性没有表现出明显的关联。 相似文献