Polycyclic aromatic hydrocarbons in teas using QuEChERS and HPLC-FLD

Polycyclic aromatic hydrocarbons (PAHs) are food-processing contaminants considered to be carcinogenic and genotoxic. Due to its drying process stage, teas may be contaminated with PAHs. The aim of the study was to validate an analytical method involving QuEChERS and HPLC-FLD for the determination of PAH4 in teas and evaluate the contamination levels in 10 different types of teas from Brazil. Recoveries varied from 54% to 99% and relative standard deviations from 1% to 21%. Limits of detection and quantification were from 0.03 to 0.3 µg/kg and 0.1 to 0.5 µg/kg, respectively. Mate tea presented the highest PAH levels, with PAH4 varying from 194 to 1795 µg/kg; followed by black (1.8–186 µg/kg), white (24–119 µg/kg), and green teas (3.1–92 µg/kg). Teas with lowest PAH4 were strawberry, lemongrass, peppermint, and boldo. Only trace levels of PAHs were detected in tea infusions, so apparently it would not affect PAH intake by Brazilian population.     

Polysaccharides from Chinese Liupao dark tea and their protective effect against hyperlipidemia

Polysaccharides‐rich dark tea is believed to be beneficial to health in Southeast Asian. However, the hypolipidemic effect of Chinese Liupao tea polysaccharides (CLTPS) has not been investigated. Here, the potential mechanism by which the oral administration of CLTPS affects lipid metabolism was evaluated using high‐fat diet‐induced hyperlipidemia rats. In rats supplemented with CLTPS, a suppressive effect on body weight was observed after 4 weeks of intervention. CLTPS significantly improved the levels of lipid profiles, the oxidation of lipids and antioxidant enzyme activity in a dose‐dependent manner. The cholesterol‐lowering action was paralleled by the stimulation of cholesterol converted to bile acids along with a 1.5‐fold increase in faecal excretion. Besides, the prolongation of coagulation factors and the reduction in fibrinogen content showed that CLTPS regulated the coagulation initiated through the intrinsic pathway. With current findings, CLTPS may be valuable as a natural hypolipidemic nutraceutical for human consumption.     

Analysis of tea catechins in vegetable oils by high‐performance liquid chromatography combined with liquid–liquid extraction

In this study, a method was developed for the determination of various tea catechins in vegetable oils. Firstly, vegetable oils including tea seed oil, sunflower seed oil and soya bean oil were extracted by methanol/water (40:60, v/v), and then, a high‐performance liquid chromatography (HPLC) method was developed for the simultaneous determination of GA, caffeine, EGC, EGCG, EC, ECG, GC, GCG, C and CG. For the compounds detected in tested vegetable oils, LODs were in the range of 0.05–1.65 ng, both intraday and interday relative standard deviations (RSDs) were <5.0%, and the recovery rates were in the range of 96.2–100.5% with RSD <3.7%. The results showed in vegetable oils which declared to had added tea catechins in, the concentrations of tea catechins were less than that showed in package label, and the content of EGCG was the highest in all samples. Therefore, the advancement made in our study will facilitate studies of tea catechins in oil industry.     

热改性废茶叶吸附刚果红性能的研究

采用热改性废茶叶吸附刚果红染料,考察了pH、吸附剂投加量、染料液浓度和温度对热改性废茶叶吸附染料性能的影响。采用SEM和BET研究了热改性茶叶的基本物理化学特性,最后采用伪一阶动力学模型和伪二阶动力学模型拟合了改性废茶叶对刚果红染料的吸附动力学过程,并对其吸附热力学进行分析。结果表明,热改性废茶叶表面出现了形状各异的小孔,其比表面积、总孔容和平均孔径比改性前增加较多;当溶液质量浓度为50 mg/L、pH为4、吸附剂投加量为0.4 g/L、温度为35℃时,染料的吸附率达到最佳,为98.4%,吸附量为123 mg/g;热改性废茶叶对刚果红吸附动力学符合伪二阶动力学模型,吸附过程是由物理吸附和化学吸附共同决定的。热力学分析表明,吸附过程是自发进行的吸热过程。     

Bactericidal Activities of Health‐Promoting,Food‐Derived Powders Against the Foodborne Pathogens Escherichia coli,Listeria monocytogenes,Salmonella enterica,and Staphylococcus aureus

We evaluated the relative bactericidal activities (BA₅₀) of 10 presumed health‐promoting food‐based powders (nutraceuticals) and, for comparison, selected known components against the following foodborne pathogens: Escherichia coli O157:H7, Salmonella enterica, Listeria monocytogenes, and Staphylococcus aureus. The relative activities were evaluated using quantitative bactericidal activity [(BA₅₀ value, defined as the percentage of the sample in the assay mixture that resulted in a 50% decrease in colony forming units]. The BA₅₀ values were determined by fitting the data to a sigmoidal curve by regression analysis using concentration–antimicrobial response data. Antimicrobial activity is indicated by a low BA₅₀ value; meaning less material is needed to kill 50% of the bacteria. Olive pomace, olive juice powder, and oregano leaves were active against all 4 pathogens, suggesting that they behave as broad‐spectrum antimicrobials. All powders exhibited strong antimicrobial activity against S. aureus. The following powders showed exceptionally high activity against S. aureus (as indicated by the low BA₅₀ values shown in parentheses): apple skin extract (0.002%); olive pomace (0.008%); and grape seed extract (0.016%). Listeria bacteria were also highly susceptible to apple skin extract (0.007%). The most active substances provide candidates for the evaluation of antimicrobial effectiveness in human food and animal feed. Practical Application : Plant‐derived health‐promoting food supplements, high in bioactive compounds, are candidates for use as antimicrobials in food.     

混合型茯茶发酵剂的制备及其在散茯茶中的应用

目的：制备混合型茯茶发酵剂,并探讨其在散茯茶“发花”中的应用。方法：用分离于茯茶中的“金花菌”菌株制备混合型茯茶发酵剂；探讨接种量、培养时间、碳源、氮源及NaCl添加量对发酵剂中孢子数量的影响；采用响应面分析方法,建立混合发酵剂制备工艺；进而将制备的发酵剂在散茯茶生产上应用。结果：发酵剂制备组分为：蔗糖8.6%,酵母浸粉5.7%,NaCl添加量1.8%,得到干燥发酵剂中孢子数量为2.75×109 个。将该发酵剂接种于散茶进行“发花”试验,散茯茶中茶多酚和游离氨基酸显著低于自然“发花”组(CK组)(P<0.05),总黄酮含量显著高于CK组(P<0.05)。感官评审结果显示,Ⅳ-1发酵剂接种散茶“发花”后感官评价最佳。结论：优化后的混合型茯茶发酵剂中孢子数量较高,将其应用于散茯茶“发花”能有效促进散茶发花效果及其品质。本研究对提高茯茶“发花”效率具有一定的应用价值。     

Effects of the addition of green tea powder on the quality and antioxidant properties of vacuum-puffed and deep-fried Yukwa (rice snacks)

Vacuum-puffing has been found to be a very useful process for production of non-deep-fried Yukwa as it ideally produced highly porous and soft texture. In this study, we compared the effects of different green tea powder (GTP) concentrations of 0, 2, 5 and 10 g/100 g on the qualities of vacuum-puffed Yukwa and deep-fried Yukwa. The fat contents of deep-fried Yukwa were significantly higher than vacuum-puffed Yukwa at the same GTP concentrations. Yukwa bases of 10 g/100 g GTP level contained higher total catechins and caffeine contents for vacuum-puffed Yukwa than deep-fried Yukwa. Vacuum-puffed Yukwa had more total phenolics and flavonoids, and a better scavenging effect on DPPH and reducing power than deep-fried Yukwa at the same green tea concentrations. Vacuum-puffing produced more breakable expanded pellets than deep-frying. The sensory evaluation of Yukwa base showed deep-fried Yukwa added with 2 g/100 g GTP was preferred for all the examined properties.