影响乙酸乙酯对茶多酚和儿茶素萃取效果的研究

利用乙酸乙酯（EtAc）萃取茶多酚（TP）和茶儿茶素类（TC），系统探讨了茶汤浓度、pH值、离子强度和萃取温度时茶多酚和儿茶素萃取效果的影响。采用正交试验方法确定了EtAc萃取TP和TC的最佳工艺组合为：茶汤浓度4％，离子强度6％，茶汤温度30℃和pH5，按照该工艺组合萃取TP和TC具有可操作性和实用性，时工业生产有指导意义。     

应用响应面法优化木聚糖酶的双水相萃取条件

采用响应面分析法优化短小芽孢杆菌木聚糖酶在PEG2000/K2HPO4双水相体系中的萃取条件。确定最佳萃取条件为NaCl 6%、PEG 2000 18%、K2HPO4 10%。在最佳萃取条件下得木聚糖酶分配系数为3.38,蛋白分配系数为0.13,纯化倍数为7.93,回收率为84.24%。考察了萃取酶液的部分酶学性质,其最适温度为50℃,最适pH为7.0。     

茶叶末中天然抗氧化剂提取工艺条件的研究

比较了乙酸乙酯、乙醇、丙酮、甲醇等不同的有机溶剂萃取绿茶多酚的提取率。以乙酸乙酯、乙醇为提取剂时 ,初提物中茶多酚纯度相对较高 ,乙醇初提物的相对提取率最高达80 % ,乙醇浓度与浸提温度对茶多酚提取率影响最显著 ,茶叶末中天然抗氧化剂提取最佳工艺条件为 :乙醇溶液浓度 70 %、浸提温度 4 5℃、浸提时间 1h     

无花果蛋白酶在双水相体系中分配行为

双水相萃取(ATPS)是近年来发展起来的新型、廉价酶纯化方法。为了扩展该方法应用领域,对PEG(polyethylene glycol)/(NH4)2SO4 双水相体系萃取无花果叶中无花果蛋白酶的实验条件进行研究,考察PEG 相对分子质量、成相物质量分数、pH 值、温度对无花果蛋白酶在两相体系中分配系数(K 值)的影响。结果表明：当两相体系中PEG 相对分子质量为1000、PEG 质量分数为20%、(NH4)2SO4 质量分数为19%、pH 值为6、温度室温(25℃)时蛋白酶在两相体系中分配系数最高可达3.6。     

利用双水相萃取栀子黄废液中的栀子苷酶法生产栀子蓝色素的研究

研究有机溶剂/ 磷酸氢二钾双水相体系对栀子黄废液中栀子苷的萃取条件,并将萃取后的栀子苷用于栀子蓝色素的生产。根据分相后上下相中栀子苷的分配系数及两相体积比,选择合适的双水相体系,并改变溶剂与废液的体积比、磷酸氢二钾加入量、废液pH 值以及萃取温度等参数,研究萃取栀子苷的最佳条件。实验结果表明,乙醇/ 磷酸氢二钾为合适的萃取体系。当双水相体系总量为10ml 时,乙醇与栀子黄废液的体积比为6:4,加入磷酸氢二钾1.0g,体系分相完全后栀子苷分配系数(K)为4.56,两相体积比(R)为6.38,栀子黄废液pH 值及萃取温度在正常条件下对K 值及R 值影响不大。放大实验表明,以乙醇/ 磷酸氢二钾体系萃取栀子黄废液中的栀子苷,所得栀子苷纯度可达62.12%,收率可达96.32%。萃取后的栀子苷经β- 葡萄糖苷酶水解精氨酸显色后得到栀子蓝色素,色价E1% (590nm)65.92。     

用茶末及废茶枝叶提取高纯茶多酚的研究

本文研究了以茶末和废枝叶为原料提取茶多酚的工艺。工艺流程为:(1)原料经微沸水浸提后加入碳酸氢铵调pH至中偏酸性后用硫酸锌沉淀纯化;(2)然后用硫酸解析溶解沉淀,加入乙酸乙酯进行萃取,分相后,水相(硫酸锌溶液)循环供沉淀纯化用,有机相(乙酸乙酯 茶多酚)真空分离、干燥制取高纯茶多酚,萃取剂乙酸乙酯回收循环使用;茶末、废茶枝叶和碳酸氢铵、硫酸进行茶多酚的浸提和纯化后,以有机多元复肥形式回收综合利用。茶多酚的综合提取率大于13%,质量达到GTP-l(大于95%)要求。     

绿茶萃取物对N-亚硝基二乙胺体外合成的影响

目的研究绿茶萃取物对N-亚硝基二乙胺体外合成的影响。方法采用分级萃取法获得绿茶二氯甲烷萃取物、乙酸乙酯萃取物、正丁醇萃取物和水提物,利用高效液相色谱法研究各萃取物主要成分,并在模拟胃液条件(37℃,pH 3)下萃取物与20 mmol/L亚硝酸钠、40 mmol/L二乙胺进行反应,分析其体外对N-亚硝基二乙胺(N-nitrosodiethylamine,NDEA)合成和NO_2~-清除的影响。结果二氯甲烷萃取物主要成分为咖啡碱,剩余水相中主要成分为多糖、蛋白质和氨基酸,2种萃取物对NDEA的合成无显著影响;乙酸乙酯萃取物和正丁醇萃取物主要成分为茶多酚,能有效阻断NDEA的合成,在4 mg/mL条件下阻断率分别为51.9%和45.7%,其中EGCG含量与其阻断率呈显著正相关,酸性降低和温度升高有利于其阻断作用;乙酸乙酯萃取物在浓度低于1.6 mg/mL时可促进NDEA生成。结论绿茶萃取物的主要有效成分为茶多酚,能有效阻断NDEA合成,在高浓度、强酸性环境和升温条件下阻断作用更强。     

PEG/（NH4）2SO4双水相体系萃取果胶酶

采用PEG/(NH4)2SO4双水相系统对果胶酶进行萃取分离,研究了PEG分子量、pH、成相物质浓度、NaCl浓度、温度等因素对果胶酶分配系数的影响,结果表明:双水相体系质量组成为PEG100027%,(NH4)2SO419%,NaCl0.002%,pH5.0时果胶酶的萃取效率较好,实验中分配系数最高可达为14.0。     

离子沉淀法制备茶多酚的工艺研究

探讨了离子沉淀法提取茶多酚的最佳工艺。通过正交试验确定了最佳浸提方案,进而确定以Zn2+做沉淀剂,选用NaHCO3溶液调pH=7,沉淀浓缩液中的茶多酚;酸溶沉淀后以乙酸乙酯萃取,提取率可达21.71%。     

菱角梗、菱角壳提取物抑菌活性及其活性成分分析

采用滤纸片扩散法研究菱角梗、菱角壳乙醇提取液及其不同溶剂萃取物的抑菌活性,并考察不同温度、pH、紫外辐照对菱角梗、菱角壳乙酸乙酯萃取物抑菌活性稳定性的影响,最后,采用高效液相色谱法和超高效液质联用法对菱角梗、菱角壳乙酸乙酯萃取物中的成分进行鉴定。结果表明：菱角梗、菱角壳乙酸乙酯萃取物对金黄色葡萄球菌、大肠杆菌和酿酒酵母菌的最小抑菌浓度分别为0.391、0.391、3.125 mg/mL和0.098、0.195、1.563 mg/mL,抑菌效果显示,菱角壳乙酸乙酯萃取物优于菱角梗乙酸乙酯萃取物,二者萃取物均对革兰氏阳性菌具有显著抑菌作用,且效果强于革兰氏阴性菌,对真菌的抑菌作用最弱;菱角梗、菱角壳乙酸乙酯萃取物在温度20~100℃、pH5~9和紫外光处理10~40 min时,均表现出良好的抑菌稳定性。经鉴定,菱角梗乙酸乙酯萃取物中含量最高的是没食子酸和1,2,6-三-O-没食子酰-β-D-葡萄糖,含量为45.87%,菱角壳乙酸乙酯萃取物中含量最高的是1,2,3,6-四-O-没食子酰-β-D-葡萄糖、槲皮素-3-O-半乳糖苷和1,2,6-三-O-没食子酰-β-D-葡萄糖,含量为57.84%。本文为菱角梗、菱角壳提取物作为抑菌剂的实际应用提供了参考。     

芦荟多酚氧化酶特性的研究

研究了芦荟多酚氧化酶的基本性质。以邻苯二酚为底物,采用分光光度法在4 10nm处测定芦荟多酚氧化酶的活性,研究了温度、pH值、底物浓度以及酶浓度对其活性的影响,并建立了酶促褐变反应动力学方程。实验结果表明,芦荟多酚氧化酶的最适温度为4 0℃,最适pH值为6 5 ,其酶促褐变反应动力学符合米氏方程所描述的单底物酶促反应动力学,相应的动力学参数Km=0 2 8mol/L ,Vmax=2 32×10 -2 U/min。文中还研究了利用蛋白酶抑制褐变的方法,以芦荟多酚氧化酶液(mL)∶木瓜蛋白酶(mL ,浓度0 5mg/mL) =5∶1的比例向芦荟多酚氧化酶粗酶液中添加木瓜蛋白酶,在5 5℃、pH5 7条件下,水解10min可较好地抑制多酚氧化酶的活性,从而抑制芦荟的酶促褐变。     

槲皮素及其乙酸乙酯衍生物的平衡溶解度和油水分配系数的测定

通过测定槲皮素及其酯化物的平衡溶解度和油水分配系数,检测酯化后的槲皮素衍生物脂溶性是否提高。采用高效液相色谱法测定槲皮素及3,7,3’,4’-O-四乙酸乙酯槲皮素在水、不同缓冲盐溶液中的质量浓度;采用摇瓶-液相色谱法,测定二者在正辛醇-水、缓冲液体系中的油水分配系数。37 ℃时,槲皮素在水中的平衡溶解度为23.02 μg/mL,而3,7,3’,4’-O-四乙酸乙酯槲皮素在水中的平衡溶解度更小,为10.23 μg/mL。随着溶剂pH值的增大,槲皮素的平衡溶解度增大,3,7,3’,4’-O-四乙酸乙酯槲皮素变化并不显著。槲皮素、3,7,3’,4’-O-四乙酸乙酯槲皮素在正辛醇-水体系条件下的油水分配系数分别为1.819、3.696。酯化修饰后的3,7,3’,4’-O-四乙酸乙酯槲皮素脂溶性高于槲皮素。     

Temperature-dependent uptake rates of nonpolar organic compounds by semipermeable membrane devices and low-density polyethylene membranes

The effect of temperature on sampling rates and sampler-water partition coefficients of semipermeable membrane devices (SPMDs) and low-density polyethylene (LDPE) strips was studied in an experimental setup under controlled flow conditions. Aqueous concentrations of chlorobenzenes, polychlorinated biphenyls (PCBs), and polyaromatic hydrocarbons (PAHs) were maintained by continuous circulation of the water over a generator column. Sampling rates for standard design SPMDs (460 cm2) were in the range of 20-200 L d(-1). No significant differences were observed between sampling rates of SPMDs and LDPE strips, but the latter samplers reached equilibrium faster because of their smaller sorption capacity. Sampling rates at 30 degrees C were higher than at 2 degrees C by a factor of about 3. Sampling rate modeling indicated boundary layer-controlled uptake for compounds with log octanol-water partition coefficients smaller than 4.4 and aqueous boundary-layer controlled uptake for more hydrophobic compounds. SPMD-water partition coefficients did not significantly change with temperature, but LDPE-water partition coefficients were larger at 2 degrees C than at 30 degrees C by a factor of 2. For field application of SPMDs, the results imply that temperature is not a key factor that controls uptake rates unless large geographical and temporal scales are involved. The results confirm that water flow velocity has a profound effect on sampling rates.     

C.I.活性红268染料在高温下的水解反应及其稳定性

采用反相离子对高效液相色谱法(HPLC)研究了双一氟均三嗪活性染料C.I.活性红268在130℃、p H值为7.0~8.0条件下的水解反应及其稳定性。计算了该条件下染料的双一氟均三嗪形式和一氟一羟基双均三嗪形式的水解速率常数k1和k2。130℃下,随着p H值的增大,染料2种形式的水解速率均不断变大,p H值在7.5和8.0下的准一级反应的水解速率常数k1相对7.0而言分别增加了8.8倍和30.2倍。但与70、80℃,p H值为11.0条件相比,高温(130℃)下双一氟均三嗪染料形式和一氟一羟基双均三嗪染料形式在水解反应性上的差距显著减小。作为水解反应的副产物,130℃下染料降解产物的量与80℃时相当,表明母体染料在高温下仍具有较好的稳定性。     

Partition coefficients in food/packaging systems: a review

Food contamination can result from various interactions between food and packaging materials. Migration of volatiles, additives, monomers and oligomers from packaging materials into food or adsorption of volatile compounds from the food by the polymer are important considerations from safety, hygienic and economic points of view. The term 'migration' includes two phenomena (partition and diffusion) that can be important in determining the concentration of contaminants in a food system at any time. An estimation of the partition coefficient, K, in food/packaging systems has been the major objective of numerous different studies. Various parameters can influence K such as temperature, pH, the chemical structure of the migrant, molecular size and structure, fat content, and degrees of crystallinity. Some theoretical approaches such as the quantitative structure-property relationship method could be of interest in the near future.     

酶法提取石榴皮多酚工艺研究

为研究酶法提取石榴皮中多酚的最佳工艺,采用单因素试验考察不同浓度的纤维素酶、果胶酶、复合酶(不同质量比的纤维素酶和果胶酶)、酶解时间、酶解温度及酶解液pH值对石榴皮多酚得率的影响,并运用二次通用旋转回归组合设计优化酶法提取石榴皮多酚的最佳工艺参数。试验结果表明,对石榴皮多酚得率影响次序依次为酶解时间>酶浓度>pH值>酶解温度。当复合酶(纤维素酶和果胶酶质量比为2:1)质量浓度为0.25mg/mL,酶解时间150min,酶解温度50℃,初始酶解液pH6.0时,多酚得率达(23.87±0.08)%(n=5),与理论计算值23.96%的相对误差仅0.376%。酶法提取石榴皮中多酚的提取率比溶剂浸提法高出16.84%。     

Accumulation of persistent organic pollutants in canopies of different forest types: role of species composition and altitudinal-temperature gradient

Leaves from the dominant tree species in three different alpine forests were sampled along an altitudinal gradient and analyzed for HCB, alpha- and gamma-HCH, and PCBs. The mean canopy concentration was calculated, considering the relative abundance of each species in the respective forest. Compound fractionation occurred in the vegetation along the altitudinal/temperature gradient. Results were compared with air concentrations and in-field plant/air partition coefficients (K(PA)) were calculated for each species; this showed differences between broadleaves and needles. The mean canopy/air partition coefficient (K(CA)) was also calculated by averaging results from single species. The variability of persistent organic pollutants distribution in canopies is discussed considering two main factors, the altitudinal/temperature gradient and the species composition. The latter is responsible for most of the concentration variability of the more volatile compounds. A model to calculate dry gaseous deposition to different forest canopies is presented.     

Quantification of solute-solute interactions using negligible-depletion solid-phase microextraction: measuring the affinity of estradiol to bulk organic matter

The interaction of trace organic contaminants with bulk organic matter has implications for the transport and behavior of organic trace contaminants within the aquatic environment as well as water and wastewater treatment processes. Partition coefficients (K(OM)) of the steroidal trace organic contaminant estradiol were quantified for environmentally relevant concentrations of bulk organic matter (12.5 mg C/L) using a full mass balance form of solid-phase microextraction (SPME). The results indicated that the method is successful and can be used at environmental concentrations. Estradiol had the greatest affinity for bulk organic matter that contained phenolic and benzoic acid ester groups, namely tannic acid, compared to organics containing predominately carboxylic functional groups. The solution chemistry (pH) was found to influence the interaction, as estradiol had a lower affinity for negatively charged and hydrophilic bulk organic matter. The partition coefficients determined using SPMEwere consistentwith partition coefficients derived using solubility enhancement and fluorescence quenching measurements, confirming that SPME is a powerful technique to quantify the affinity of estradiol for low concentrations of bulk organic matter and trace contaminants. Further, this novel method can be applied to a range of trace contaminants.     

Prediction of pH Change in Processed Acidified Turnips

The acetic acid uptake by turnips was studied during an acidification process in containers. The process was successfully described by a Fickian diffusion, using a correlation for the buffer effect. Diffusion coefficients (0.629 to 3.99 × 10^-9 m²/sec) and partition coefficients (0.8 to 1.1) were obtained by optimization of the fit between experimental and theoretical values, using the simplex method. The partition coefficient did not show an evident dependence on temperature, while diffusivity followed an Arrhenius type behavior. The relationship between acid concentration and pH was described using a cubic model with parameters independent of temperature. Results showed that the combination of these models describing the acid diffusion into the food and the buffering effects of the food allowed accurate prediction of pH evolution in the acidification process.     

砀山酥梨膜结合态与可溶态多酚氧化酶性质比较

为探究砀山酥梨膜结合态多酚氧化酶（mPPO）性质,本文以砀山酥梨为原料,研究其mPPO催化特性及热失活动力学,并与可溶态多酚氧化酶（sPPO）性质进行比较。结果表明:以邻苯二酚为底物时,mPPO与sPPO催化特性及热失活动力学性质不同。mPPO比活力及对底物亲和力高于sPPO。mPPO在pH4.50时酶活最高,而sPPO最适pH为5.00。mPPO酸碱稳定性高于sPPO,mPPO在pH3.50～4.50环境中保持24 h后酶活大于原始酶活。砀山酥梨mPPO在35～45 ℃温度区间内活性最高,且mPPO在55～75 ℃区间热稳定性高于sPPO。热失活动力学分析结果表明,热处理对sPPO及mPPO的钝化均符合一级反应动力学,动力学参数E_a值及Z_T值分析表明mPPO比sPPO催化反应对温度的依赖性更小,热耐受性更高。