烫漂过程中荠菜过氧化物酶失活动力学模型研究

采用一级动力学模型、Weibull分布模型、Logistic模型对荠菜烫漂过程中过氧化酶失活动力学模型进行拟合。以决定系数（R2）、卡方（x2）、均方根误差（RMSE）、精确因子（A_f）、偏差因子（B_f）等为评价指标,分析模型的拟合效果。利用模型预测不同烫漂温度的烫漂工艺条件,同时以维生素C的含量为指标,评价不同烫漂工艺对维生素C含量的影响。结果表明:Logistic模型拟合烫漂过程中荠菜过氧化物失活动力学效果好,拟合精度高,拟合值与实测值偏差小,其决定系数R2为0.9980,x2为0.96×10?4,RMSE为0.0097,A_f为1.1304,B_f为1.0070。在过氧化物酶95%失活的条件下,依据Logistic模型预测,100 ℃下烫漂20 s,80 ℃下烫漂287 s,POD相对酶活在0.050±0.001之间;烫漂后维生素C含量也存在显著性差异,高温短时烫漂后的维生素C损失较少。POD失活动力学模型预测烫漂工艺条件,可以减少维生素C等热敏性营养成分损失。     

草莓漂烫过程中过氧化物酶和V_C的失活动力学

探讨了草莓在75、80、85、90、95℃漂烫过程中过氧化物酶和V C的变化规律,建立热降解动力学方程。结果表明:草莓漂烫过程中过氧化物酶和V C热降解均符合一级动力学模型,草莓中的过氧化物酶热降解活化能为74.05 kJ/mol,其动力学模型预测值与真实值的平均误差1.53%。而草莓中Vc热降解活化能为54.68 kJ/mol,其动力学模型预测值与真实值的平均相对误差为2.9%,两个模型合理可信。     

几种蔬菜烫漂后过氧化物酶活性的测定

几种蔬菜烫漂后过氧化物酶活性的测定程宏侯金铎刘浪（吉林职业师范学院，长春，１３００５２）０前言烫漂是许多速冻蔬菜生产时的一个必不可少的工艺环节，它关系着速冻蔬菜的质量。烫漂的主要目的之一是破坏蔬菜中酶类的活性，使蔬菜在冻藏中其营养价值及原来具有的感官...     

高温短时蒸汽漂烫对鲜玛咖过氧化物酶活性的影响

为探索高温蒸汽漂烫对鲜玛咖过氧化物酶(POD)钝化的最佳工艺参数,解决鲜玛咖加工中的褐变问题,采用响应面分析法建立处理时间、蒸汽温度和载物量对POD相对酶活影响的二次多元回归数学模型。结果表明:鲜玛咖的最佳漂烫条件处理时间54s、蒸汽温度130℃、载物量170g时,POD相对酶活为4.90%;未处理鲜玛咖破碎放置7d后,褐变变化率为52.66%,芥子油苷、水溶性生物碱、VC和总酚的损失率分别为45.68%、13.71%、20.27%和15.13%,而经高温蒸汽漂烫的鲜玛咖褐变变化率仅为8.56%,与未处理的样品相比,芥子油苷、水溶性生物碱、VC和总酚的损失率分别为23.46%、11.29%、6.76%和10.26%。表明在响应曲面法(RSM)优化条件下,鲜玛咖经高温蒸汽漂烫处理后,其褐变可得到有效控制,营养成分得到很好的保留。     

微波烫漂对杏鲍菇POD酶活的影响

研究微波烫漂对杏鲍菇POD酶的灭活效果,并与沸水和蒸汽烫漂两种常规灭酶模式效果进行比较。为获得微波烫漂的优化条件,采用响应曲面分析法建立微波功率和微波时间对POD相对酶活影响的二次多项数学回归模型。结果显示：杏鲍菇最适宜的灭酶条件为微波功率570W,微波时间59s。在此条件下处理的杏鲍菇游离氨基酸含量损失少,感官品质佳。     

速冻毛豆钝化过氧化物酶及胰蛋白酶抑制因子的安全烫漂时间研究

以不同成熟度的毛豆为试材,研究了钝化过氧化物酶及胰蛋白酶抑制因子的安全烫漂时间。结果表明,6～7成熟度的带荚毛豆烫漂时间为2.5min,7～8成熟度的为3min;烫漂液含有3.5%的食盐的6～7成熟度的带荚毛豆烫漂时间为2min,7～8成熟度的为2.5min。     

黄花菜烫漂过程中Vc降解动力学研究

对黄花菜在烫漂过程中的Vc含量变化及降解动力学进行了研究,结果表明,随漂烫温度的升高和烫漂时间的延长,漂烫后的黄花菜中维生素C含量大幅度降低,并推得其降解反应级数为一级,降解反应活化能为68.64（kJ·mol-1·K-1）。      

漂烫对速冻苹果丁过氧化物酶活性及品质的影响

为了优化速冻苹果丁漂烫工艺,以新鲜富士苹果(切分为1.5 cm×1.5 cm×1.5 cm的小丁)为研究对象,采用响应曲面法,建立漂烫时间、漂烫温度、料液比对POD相对酶活影响的二次多元回归数学模型,并分析漂烫对其品质的影响。结果表明:抑制速冻苹果丁POD酶活性的最佳漂烫条件为:漂烫时间4.5 min、漂烫温度92℃、料液比1∶11(g/m L);未漂烫速冻苹果丁的ΔE值升高了36.10,感官品质降低了34.46,可溶性固形物、可滴定酸及VC损失率分别为28.25%、17.67%、20.13%,漂烫后速冻苹果丁的ΔE值升高了5.57,感官品质降低了7.27,可溶性固形物、可滴定酸及V_C损失率分别为24.42%、10.85%、12.16%。表明漂烫处理较好地保持速冻苹果丁的品质。      

高温蒸汽瞬时漂烫对黑牛肝菌酶活和品质影响的研究

研究了高温瞬时蒸汽对黑牛肝菌的过氧化物酶(POD)和多酚氧化酶(PPO)活性的影响,并研究了对黑牛肝菌几种重要营养成分的影响,包括总酚、可溶性总糖、VC以及可溶性蛋白。通过时间(s)、物料量(g)、蒸汽压力(MPa)的单因素试验,设计正交试验,对POD、PPO、总酚、总糖、VC、可溶性蛋白进行综合评价分析,得出最佳的试验条件:高温蒸汽瞬时漂烫时间为30 s、物料量300 g、蒸汽压力0.3 MPa,综合评分值最高。高温蒸汽漂烫最优结果与最佳的热水漂烫处理进行比较,体现了高温蒸汽漂烫的优势。     

PA/PE复合膜对鲜切莴笋保鲜效果的影响

为了验证尼龙-聚乙烯（polyamide/polyethylene,PA/PE）复合膜对鲜切莴笋的保鲜效果,将新鲜莴笋切片真空包装后在4 ℃条件下冷藏,不加任何包装的鲜切莴笋同样条件下作空白对照。贮藏期间评价菌落总数、色差、pH值、汁液流失率、VC含量、感官等指标。结果PA/PE组贮藏期达24 d,而不加包装的对照组只有4 d。可见对于鲜切莴笋的贮藏,PA/PE复合膜结合真空包装可明显延长其贮藏期。     

莴笋叶渣吸附Cu2+研究

采用二次回归正交旋转组合设计方法对莴笋叶渣吸附Cu2+条件进行优化,建立加入量(X1)、质量浓度(X2)、时间(X3)、pH值(X4)、温度(X5)5个因素与吸附率(Y)的回归模型为:Y=85.45862+11.80098X1-6.85546X2+0.24918X3+2.14203X4+1.12124X5-4.75315X12-2.40953X22-2.23141X32-1.49228X42-3.40533X52+3.84570X1X2+0.61717X1X3-3.15888X1X4-0.26948X1X5-0.29760X2X3+0.77899X2X4-0.01867X2X5-0.23965X3X4-1.45840X3X5+0.94533X4X5。各因素对莴笋叶渣吸附Cu2+影响顺序为:加入量>质量浓度>pH值>温度>时间,在加入量0.9g、Cu2+质量浓度30mg/L、时间5h、pH3、温度40℃条件下,莴笋叶渣对Cu2+吸附率最高可达98.40%。验证值为97.96%,与理论值基本一致。对于60mg/L Pb2+溶液,莴笋叶渣为吸附剂时的最佳固液比为12g/L;莴笋叶渣对中低质量浓度Pb2+溶液的吸附效果好于活性炭。     

Kinetic Parameters for the Thermal Inactivation of Peroxidase and Lipoxygenase in Precooked Frozen Brassica Species

Thermal inactivation of peroxidase (POD) and lipoxygenase (LOX), both enzymes present in broccoli and Brussels sprouts, is required before freezing, to obtain high‐quality precooked frozen vegetables. Rate constants of a 1st‐order biphasic model for the heat‐labile and heat‐resistant POD and LOX isoenzymes were determined at different temperatures (75, 80, and 90 °C) and the corresponding activation energies were estimated using nonlinear regressions. In the case of Brussels sprouts, the activation energies for the resistant and labile fractions were 56.3 and 62.5 kJ/mol for POD and 63.7 and 65.8 kJ/mol for LOX, respectively. For Brussels sprouts, different precooking times were tested to analyze the effect of residual enzyme activity on quality parameters and sensory attributes, after a frozen storage of 4 mo at ?20 °C. A significant reactivation of enzyme activity after frozen storage was observed (especially in the case of POD) for short precooking times (<6 min) leading to low‐quality parameters at the interior zone of the vegetable. A precooking time of 6 min at 90 °C allowed an adequate inactivation of LOX and POD obtaining a high‐quality final frozen vegetable. A sensory analysis confirmed the global acceptability of the product. The obtained results are relevant to define the precooking stage conditions in the production of frozen cruciferous vegetables.     

Blanching, Freezing and Frozen Storage Influence Texture of White Asparagus

We studied effects of three methods of blanching in conjunction with freezing, on texture of white asparagus as defined by three measures: maximum shear force, cutting energy, and total fiber content. We also assessed shelf life of asparagus kept in frozen storage at -22°C. Methods of blanching were total immersion in hot water, progressive immersion in hot water and steam. An increase in total fiber content was found throughout frozen storage. This increase correlated with lignification of vascular bundles in the basal segment of spears, even during frozen storage. This was reflected in an increase in maximum shear force and cutting energy required. The shelf life of frozen asparagus was 12 mo using total fiber content as a criterion.     

Thermal Inactivation Kinetics of Peroxidase and Lipoxygenase from Broccoli, Green Asparagus and Carrots

ABSTRACT: Thewermal inactivation curves for peroxidase (POD) and lipoxygenase (LOX) in broccoli (florets), green asparagus (tip and stem), and carrots (cortex and core) extracts were determined in the range of 70 to 95 °C for 0 to 600 s. The capillary tube method was used to obtain quasi-isothermal conditions. The kinetics of both enzymes showed a biphasic first-order model, while at 70 °C, LOX in asparagus showed a monophasic first-order behavior. LOX activity was not detected for carrots. Kinetic parameters, k and Ea , were determined for heat-labile and heatresistant isoenzyme fractions. Additionally, initial and residual activities for both enzymes within tissue sections showed a different distribution and heat stability.     

Purification and Kinetic Characterization of Peroxidase from Tomato Cultivated under Different Salinity Conditions

By including hydrophobic chromatography in the purification scheme, 2 homogeneous tomato fruit peroxidase isoenzymes were obtained. The expression of these 2 peroxidases, one acid and the other basic, was determined in tomato fruits grown under different salinity conditions. Increased salinity modified the isoenzyme profile of tomato peroxidase. In tomatoes grown under highly saline conditions, there was an increase in the expression of the acid form with respect to the basic, the acid/basic ratio rising from 4.5 in tomatoes grown under normal saline conditions to 70 in those grown in highly saline conditions. Kinetic studies using 2,2'-azinobis(3-ethylbenzo-thiazolinesulfonic acid) as reducing substrate showed that increased salinity in the growth medium did not modify the kinetic parameter of tomato peroxidase over both hydrogen peroxide or reducing substrate.     

橄榄多酚氧化酶和过氧化物酶的抑制剂筛选及其热失活动力学

本项目研究了七种抑制剂(分别为亚硫酸钠、明矾、O-异抗坏血酸、EDTA-2Na、Ca Cl2、多聚磷酸钠、柠檬酸亚锡二钠)对橄榄多酚氧化酶和过氧化物酶活力的影响,并采用两段模型分析了高温处理对橄榄果实多酚氧化酶(PPO)和过氧化物酶(POD)的钝化动力学。结果表明,橄榄中酚类化合物氧化分解与POD和PPO活性有关,在特定的环境条件下,O-异抗坏血酸和柠檬酸亚锡二钠抑制橄榄PPO酶和POD酶活性效果最好,譬如,其浓度为0.20 g/L时,可完全抑制橄榄PPO酶和POD酶活力;热烫时间和温度对橄榄果实PPO和POD活性影响较大,并随着热烫时间和热烫温度的增加,橄榄果实PPO和POD活性呈现先下降后处于平稳的趋势,故高温处理对橄榄PPO和POD的钝化过程符合两段模型。     

Kinetics of Peroxidase Inactivation in Carrot Juice Treated with Pulsed Electric Fields

Peroxidase activity accounts for quality losses in many plant‐based foods. The paper provides insight into the inactivation kinetics of peroxidase (POD) in carrot juice treated with pulsed electric fields (PEF). Juice samples were subjected to electric field intensities of 20 to 35 kV/cm for 300 to 2000 μs. Up to 93% of the initial activity was inactivated after treating at 35 kV/cm for 1500 μs. POD activity inactivation correlated well with the increase in energy density input. A first‐order fractional conversion model best fitted the experimental results. Other kinetic approaches such as the Fermi's model can be used to estimate residual POD activity values in treated juices as a function of electric field strength. Practical Application : Pulsed electric fields (PEF) are a processing technology that can be used for the pasteurization of liquid food products. Peroxidase activity inhibition is required in carrot juices to prevent undesirable quality losses, such as discoloration, flavor changes, and loss of nutrients. The most significant processing parameters ruling POD inactivation in PEF‐treated carrot juice are identified and mathematical modeling of experimental data is conducted.