茶多酚脂质体的制备和物化性质研究

本文采用薄膜超声分散法制备茶多酚脂质体以提高茶多酚的生物利用率.在制备工艺研究中运用响应面分析,确定其最佳工艺条件:药脂比为1∶8,卵磷脂与胆固醇比为4∶1,缓冲液pH值为6.62,超声时间为3.5 min.理论最佳包埋率60.36％,实际包埋率为60.09±.69％.并对其理化性质进行了考察,平均粒径为160.4 n...     

茶多酚的功效特性及其在军用食品中的开发应用

茶多酚具有抑菌、抗病毒、免疫调节、抗氧化等诸多功能,可在军用食品中开发保健食品、抗氧化剂、防腐剂、食用色素及稳定剂等,应用前景广阔。     

Preparation and Oxidation Stability Evaluation of Tea Polyphenols‐Loaded Inverse Micro‐Emulsion

Compared to synthetic antioxidants, tea polyphenols (TPs) has its own advantages in edible oil industry, however, the hydrophilic properties have restricted its applications. In this study, the ternary phase diagram of TPs‐loaded micro‐emulsion (ME) system was constructed, in which glyceryl monooleate (GMO), Tween80, linoleic acid as the surfactants, ethanol as the co‐surfactant and soybean, corn, sunflower oil as the oil phase, have been used for the preparation of ME. The results indicated that a composition of ME (57.5% oil, 18% Tween80, 18% GMO, 4% Linolic acid, and 2.5% water+ethanol) could dissolve maximum water and could stable for 2 mo at room temperature with an average diameter of 6 to 7 nm, as detected by means of dynamic light scattering (DLS). The loaded of TPs into ME led to an increase of particle size to 15 to 16 nm, due to increased polarity of the water phase. The antioxidant capacity of TPs in ME was characterized by the peroxide value (POV) method. The addition of 1% water phase with 0.1 g/mL TPs could retain the POV at low value for 30 d at accelerating temperature 50 °C. Meanwhile, comparing the three edible oil, ME with corn oil has lower conductivity and higher value of POV during the storage. This work provides an efficient and environmentally friendly approach for the preparation of TPs‐loaded ME, which is beneficial to the application of TPs in edible oil.     

类分子印迹纳米多孔膜修饰电极制备三聚氰胺电化学传感器

采用电化学法在充蜡石墨电极上,原位修饰了一种基于三聚氰胺/纳米银/聚槲皮素的类分子印迹-纳米多孔膜。场发射扫描电镜、X-射线光电子能谱、红外光谱和电化学验证了该类分子印迹-纳米多孔膜为三维网状结构。该纳米多孔膜修饰电极对三聚氰胺显示良好的选择性富集作用,氧化峰(0.17V)电流和三聚氰胺的浓度在1×10-7～1×10-5mol/L范围内,呈良好线性关系,检出限为1×10-8mol/L(3σ)。该修饰电极有较好的抗干扰能力,可用于牛奶样品中三聚氰胺的测定。     

茶叶中茶多酚和生物碱的测定及聚类和线性判别分析

目的：建立一种反相高效液相色谱方法,测定绿茶、乌龙茶、红茶、白茶和普洱茶中儿茶素[(+)-catechin,C]、表儿茶素[(-)-epicatechin,EC]、表儿茶素没食子酸脂[(-)-epicatechin gallate,ECG]、表没食子儿茶素[(-)-epigallocatechin,EGC]、表没食子儿茶素没食子酸脂[(-)-epigallocatechin gallate,EGCG]、没食子酸(gallic acid,GA)、咖啡因(caffeine,CAF)、可可碱(theobromine,THEO)的水平。以这8 种组分为指标对茶叶进行聚类分析和线性判别分析,建立区分绿茶、红茶和乌龙茶的方法。方法：茶叶提取后采用HPLC 法测定儿茶素和生物碱含量,色谱柱为C18 柱,流动相由甲醇(A)、2% 的乙酸(B)等度洗脱,A、B 相的体积比为25:75,流速为1mL/min,柱温30℃。采用PDA 检测器在278nm 检测,参考波长为210nm。采用SPSS 14.0 对实验数据进行了聚类分析和线性判别分析。结果：在选择的分析条件下,样品中的8 种组分获得了理想分离, 加标回收率在8 7%～ 112.8%之间,并采用外标法对8 种组分进行定量。以这8 种组分的含量为指标,聚类分析和线性判别分析能对39 种茶叶样品进较好的区分。     

荷移光度法测定茶及茶饮料中茶氨酸含量

通过实验得到了适宜茶氨酸测定的荷移剂--四氯苯醌,并对四氯苯醌荷移光度法测定茶氨酸的条件进行探讨。最佳测定条件为：茶氨酸水溶液与四氯苯醌乙醇溶液反应,温度50℃,pH8～9,时间50min,能得到n茶氨酸:n四氯苯醌=2:1 的紫红色荷移络合物,其稳定常数K(293K)= 3.9 × 103,Gibbs 自由能ΔrGm(293K)= － 20.14 kJ/mol;在工作波长λ=331nm 处,表观摩尔吸光系数ε = 1.98 × 104 L/mol·cm,在5 × 10-6～9 × 10-5 mol/L 内符合比尔定律,线性方程为A=0.028 × 10-6C － 0.02 (r=0.9958)。该法对市售的茶叶和茶饮料中茶氨酸含量测定的结果与HPLC法一致,回收率在98.7%～102.6% 内,RSD 为1.2%～4.2%。此方法操作容易掌握,灵敏度高,结果较为满意,但样品的预处理稍繁琐。     

Spectrophotometric Trace Determination of Iron in Food, Milk, and Tea Samples using a New Bis-azo Dye as Analytical Reagent

A newly synthesized bis-azo dye, 2,6-bis(1-hydroxy-2-naphthylazo)pyridine (PBN) was used as a sensitive reagent for iron. To determine the metal ion using a spectrophotometer in the concentration range between 0.3 and 2.76 ppm (molar absorptivity of 2.65 × 10⁴ l mol⁻¹ cm⁻¹ at 550 nm). In a phosphate-buffered medium, none of the transition metals, except Fe(II), Co(II), Ni(II), Cu(II), and Hg(II), produced color with the reagent; however, colors produced by Co(II), Ni(II), Cu(II), and Hg(II) could be masked using thiosemicarbazide, therefore, making the reagent highly selective for iron determination. The reagent was applied for the estimation of iron levels in milk, food grains, and tea samples and the results were compared with the iron levels found in those samples using AAS.     

甘薯块根多酚高效测定技术优化与应用

摘要 通过建立高效、准确、适宜批量测定甘薯块根多酚含量的方法,为筛选评价高多酚含量甘薯种质提供技术支持。对提取溶剂、福林酚、碳酸钠等浓度及反应时间进行系统优化,并对建立的甘薯多酚高效检测方法的稳定性、可靠性进行评价;采用优化的方法对国内83个甘薯品种的多酚含量进行测定。结果表明,以乙醇做提取剂,最佳浓度为70%,最佳福林酚浓度为15%,碳酸钠浓度为5%,最佳反应时间60 min;采用酶标仪及96孔板可同时检测30份样品;该方法的平均加标回收率为98.4%,3次重复测定相对标准偏差为2.4%,表明建立的方法准确度高,重复性好;83份甘薯样品的多酚含量在0.22~2.00 mg/g鲜样之间,且紫肉品种中的多酚含量显著高于其它品种。     

茶多酚对海藻酸钠/玉米淀粉复合膜的影响及保鲜应用

以海藻酸钠(sodium alginate,SA)、玉米淀粉为基材,茶多酚(tea polyphenols,TP)为功能性添加剂,通过溶液共混法制备茶多酚/海藻酸钠/玉米淀粉复合膜,考察不同TP浓度对复合膜的抗氧化能力、抑菌能力、机械性能等理化性质的影响,以挥发性盐基氮值(total volatile base nit...     

茶叶、茶鲜叶及茶汤中啶虫脒残留的检测

建立了茶叶、茶鲜叶、茶汤中的啶虫脒残留量的液相色谱检测方法。茶叶样品经乙腈提取,碱性NaCl饱和溶液萃取,Envi-Carb/NH2固相萃取柱净化,10 mL乙腈洗脱,液相色谱-紫外检测器检测,茶叶,茶鲜叶啶虫脒的添加浓度为0.1～1.0mg/kg时,其平均回收率为68.5%～103.6.0%,相对标准偏差(RSD)≤13.6%。茶汤啶虫脒的添加浓度为0.033～0.333 mg/L时,其平均回收率为:73%～103.8%,相对标准偏差(RSD)≤7.6%。用该方法最低检出浓度为分别为:0.07、0.09 mg/kg、0.002 mg/L,符合农药残留分析要求。该方法可用于茶叶中啶虫脒的常规检测和啶虫脒在茶叶生产中应用的安全性评价研究。     

Tea Polyphenols as Inhibitors of Furan Formed in the Maillard Model System and Canned Coffee Model

In this article, the effects of sugars and amino acids on furan formation via the Maillard reaction in low‐moisture model systems were investigated. Glucose and alanine are important furan precursors, and the effects of the heating temperature, heating time, and molar ratio of glucose to alanine on furan formation were studied in glucose/alanine model system by response surface methodology. The heating temperature greatly affected furan formation. The maximum furan concentration was obtained with a glucose‐to‐alanine molar ratio of 0.83:1.00, by heating at 151 °C for 41 min. Tea polyphenols effectively inhibited furan formation in the glucose/alanine model and a canned coffee model. A high inhibition rate of 42.4% ± 1.5% was obtained in the canned coffee model during sterilization procedure with addition of 84 mg (the mass fraction is 12.1%) of tea polyphenols (99%). However, the content of aromatic components in the canned coffee model was significantly reduced at the same time. This study provides evidence for a good furan inhibitor that can be used in food processing.     

Rapid Identification and Comparison of Compounds with Antioxidant Activity in Coreopsis tinctoria Herbal Tea by High‐Performance Thin‐Layer Chromatography Coupled with DPPH Bioautography and Densitometry

A simple and efficient method based on high‐performance thin‐layer chromatography coupled with 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) bioautography (HPTLC‐DPPH) was established for the screening and comparison of antioxidants in different parts of Coreopsis tinctoria herbal tea from different origins and other related herbal tea materials, which used Chrysanthemum morifolium cv. “Gongju” and “Hangju” in this study. Scanning densitometry after DPPH derivatization was applied for the determination of antioxidant capacities of isolated compounds in each sample. It is considered that ethanol extracts of C. tinctoria had stronger antioxidant activity and more characteristic bands than those of 2 compared samples, C. morifolium cv. “Gongju” and “Hangju.” Chemometric analysis results showed that the combination of hierarchical clustering analysis and principal component analysis based on determined antioxidant capacities could be used for the discrimination of different parts of C. tinctoria and C. morifolium. Results showed that 7 compounds made up the major contributions of antioxidant activity in C. tinctoria, including okanin, isookanin, marein, flavanomarein, 5,7,3′,5′‐tetrahydroxyflavanone‐7‐O‐glucoside, 3,5‐dicaffeoylquinic acid, and chlorogenic acid. Therefore, 7 compounds were identified as major antioxidant biomarkers for quality control of C. tinctoria. Results demonstrated that the established method could be applied for the identification of C. tinctoria, and were beneficial for the bioactivity‐based quality control of C. tinctoria.     

鸡蛋中氟苯尼考质控样品的研制及稳定性评价

采用空白鸡蛋基质中添加不同含量氟苯尼考的方式自主研制质控样品,按照CNAS-GL003:2018《能力验证样品均匀性和稳定性评价指南》,采用GB/T 22338—2008《动物源性食品中氯霉素类药物残留量测定》液相色谱-串联质谱法为参比方法对质控样品的均匀性和稳定性进行评价,同时对影响质控样品稳定性的因素进行研究,并通过6 家实验室间联合定值的方式确定质控样品的参考值,结果表明自主研制的非冻干（液态）和冻干（固态）2 种状态质控样品均匀性良好,不同样品状态、不同贮存温度对质控样品稳定性有影响,冻干质控样品在－18 ℃条件下贮存12 个月稳定性良好,3 个添加量的冻干质控样品最终定值结果为0.23、0.39 μg/kg和1.92 μg/kg,可推广应用于快速检测领域和实验室日常检测的质量控制。     

Polyphenol oxidase activity in grass and its effect on plant‐mediated lipolysis and proteolysis of Dactylis glomerata (cocksfoot) in a simulated rumen environment

Little is known about the level or activity of polyphenol oxidase (PPO) in grasses and its potential impact on proteolysis and lipolysis. Six grass species were initially screened for PPO activity (740.6, 291.9, 213.6, 119.0, 16.3 and 6.5 U g^?1 fresh weight (FW) for cocksfoot, hybrid ryegrass, Italian ryegrass, perennial ryegrass, timothy and tall fescue respectively). Cocksfoot, which expressed the highest activity, was then used to determine the effect of PPO on plant‐mediated proteolysis and lipolysis in a simulated rumen environment. Sourced cocksfoot was macerated and incubated in an antibiotic‐containing anaerobic medium with or without ascorbate to deactivate PPO in the dark at 39 °C over five time points. At each time point (0, 1, 2, 6 and 24 h), six replicate samples were destructively harvested; three of the replicates were used for lipid analysis and the other three for protein, free amino acid and bound phenol determination. Characterisation of the herbage showed PPO activities of 649.6 and 0 U g^?1 FW, which were reflected in the extent of phenol (derived from quinones) binding to protein after 24 h of incubation, namely 65.1 and 29.6 mg bound phenol g^?1 protein (P < 0.001) for cocksfoot and cocksfoot + ascorbate respectively. Proteolysis, measured as free amino acids released into the incubation buffer, was significantly reduced (P < 0.001) with increasing PPO activity, with values after the 24 h incubation of 0.03 and 0.07 mmol L^?1 g^?1 FW for cocksfoot and cocksfoot + ascorbate respectively. Lipolysis, measured as the proportional decline in the membrane lipid polar fraction, was likewise reduced (P < 0.001) with increasing PPO activity, with values after the 24 h incubation of 0.43 and 0.65 for cocksfoot and cocksfoot + ascorbate respectively. Changes that occurred in protein and the lipid fractions (polar fraction, monoacylglycerol + diacylglycerol, triacylglycerol and free fatty acids) during the incubations are also reported and discussed. These results support the selection of forages high in PPO activity to reduce protein and lipid losses in silo and potentially in the rumen. Copyright © 2006 Society of Chemical Industry     

茶叶中儿茶素类测定方法的优化

目前对茶叶中的5 种儿茶素进行分离测定一般采用GB/T 8313-2008《茶叶中茶多酚和儿茶素类含量的检测方法》中的方法,但在实际测定过程中,发现测定结果的重复性较差,空白、标准溶液与样品的溶剂不一致,标准溶液配制过程中标准品不能完全溶解,对国标中儿茶素的测定方法进行改进,用10 mL预热过的体积分数70%甲醇溶液在70 ℃条件下重复提取3 次,合并提取液,用水定容。利用高效液相色谱仪在波长278 nm处进行检测。流动相A为体积分数0.1%乙酸溶液,流动相B为乙腈,洗脱程序为A的初始比例为95%,5 min内A的比例降至90%,保持至15 min,15～20 min内A的比例降至80%,20～25 min内A的比例升至90%,25～30 min内A的比例恢复至95%。结果表明：采用本方法测定茶叶中5 种儿茶素含量可以保证标准溶液与样品溶剂的一致性,提取较完全,减少了因操作带来的误差,重复性较好,其相对标准偏差为0.75%～4.50%,分离度为0.58～4.35,方法的回收率为81.4%～113.0%,其相对标准偏差均在1.21%～7.71%之间。     

茶叶中有机氯和拟除虫菊酯同时分析的简易前处理方法研究

本文对茶叶中的11种有机氯和拟除虫菊酯类农药残留量进行了同时快速分析。通过简单的样品前处理方法,将茶样与吸附剂充分研磨后,进行柱层析净化预分离,最后经气相色谱检测。文中分别对吸附剂、层析柱和洗脱剂等条件进行了详细考察,优化的方法为:1.0 g茶样浸润后与4.0 g中性Al_2O_3吸附剂充分研磨,混合物装入预填2.0 g无水Na_2SO_4+2.0 g Florisil+0.1 g活性炭的自制层析柱净化预分离,以20 mL乙酸乙酯:正己烷(2:3,V/V)洗脱;该法线性范围为0.1~2.0 mg/L,相关系数(r)大于0.9962(除了氟氯氰菊酯和氯氰菊酯),检出限(LOD)在0.0000321~0.1451379 ng之间,样品加标回收率(R)在68.44%~119.20%,不同加标级别回收率结果的相对标准偏差值(RSD)均低于14.73%。此外,对茶样的基质干扰(ME)问题进行了详细讨论,并采用基质匹配校准曲线法(MC)有效解决ME问题。经实验验证,该方法快速、准确、简便、环保,适用于茶叶中农残的同时、快速分离与分析。     

Effect of plant polyphenols and ascorbic acid on lipid oxidation,residual nitrite and N‐nitrosamines formation in dry‐cured sausage

The effects of green tea,grape seed polyphenols and ascorbic acid on pH, water activity (a_w), microbiological counts, TBARS, residual nitrite and N‐nitrosamines were determined in dry‐cured sausages during the ripening period. Results showed that TBARS increased gradually during ripening (P < 0.05), but were significantly reduced with plant polyphenols and ascorbic acid (P < 0.05). Green tea polyphenol (GTP) was most effective (P < 0.05) in reducing TBARS. Plant polyphenols and ascorbic acid significantly decreased residual nitrite, ascorbic acid being most effective (P < 0.05). The amount of N‐nitrosamines increased during ripening, but was significantly reduced with plant polyphenols and ascorbic acid (P < 0.05). Plant polyphenols had no significant effects on moisture content, a_w, pH or microbiological counts in dry‐cured sausage during ripening (P > 0.05). It was concluded that plant polyphenols and ascorbic acid were effective in maintaining the quality and safety of dry‐cured sausages.