Tea Testing

Amini, Tooraj, and Payman Hashemi. Journal of Chromatography B 1092 (2018): 252-257.

Caffeine (1,3,7-trimethylxanthine) is one of the most commonly consumed alkaloids, naturally occurring in coffee beans, tea leaves, and cocoa beans/leaves, and has traditionally been used daily, particularly for its stimulant properties.

Due to the widespread use of caffeine and its widespread consumption across various populations, research interest in its health impacts has increased in recent years. Studies have primarily focused on investigating the effects of caffeine on heart rate, arrhythmia, blood pressure, and serum cholesterol. Caffeine is known as a central nervous system stimulant, which can improve alertness or cause headaches and anxiety. Therefore, the determination and accurate measurement of caffeine in food, plant, biological, and pharmaceutical samples is a significant challenge.

A simple, fast, and green solvent-microextraction based on the solvent volume ratio change (SVRA) coupled with gas chromatography-mass spectrometry (GC-MS) can be used for the preconcentration and determination of caffeine in tea leaf samples.

Cina, M., del Valle Ponce, M., Martinez, L. D., & Cerutti, S. (2021). Heliyon, 7(4).

The detection of aflatoxins, ochratoxin A, and fumonisins has been reported in various tea leaves. Among these, ochratoxin A (OTA) is a harmful mycotoxin produced by several fungi. Additionally, it is considered potentially carcinogenic to humans and has been associated with nephrotoxic, immunosuppressive, teratogenic, embryotoxic, genotoxic, and mutagenic effects.

Regarding the determination and quantification of OTA, tea infusions are considered a truly complex but interesting food matrix to be analyzed, where the presence of accompanying compounds may interfere with the analysis. A novel green dispersive liquid-liquid microextraction strategy considering floating organic drop solidification (DLLME-SFO) coupled with liquid chromatography-tandem mass spectrometry detection has been used for the quantitative evaluation of OTA in tea-based beverages.

Sun, Mu-Fang, et al. Foods 11.10 (2022): 1425.

Tea leaves are rich in polyphenols, with the fresh tea leaves typically containing 18% to 36% polyphenols (on a dry weight basis), which possess strong anti-inflammatory, antioxidant, and anti-mutagenic physiological properties. Tea polyphenols, as the major secondary metabolites in tea leaves, are often used as physiological indicators for identifying tea quality, distinguishing tea cultivars, evaluating leaf maturity, analyzing processing reaction mechanisms, and assessing tea storage duration, which are of great significance in promoting tea standardization and industry development.

The determination of tea polyphenols can be divided into two main categories: the determination of total polyphenols and the determination of individual phenols in tea leaves. The analytical methods for total tea polyphenols include titration, spectrophotometry, near-infrared spectroscopy, electrochemical methods, and others. Among these, the spectrophotometric method is the most widely used, such as the application of the international standard method (ISO 14502-1:2005). For the qualitative and quantitative analysis of individual phenols in tea leaves, chromatographic methods are most commonly used.

Ye, Ting, et al. Food chemistry 405 (2023): 134969.

In daily tea consumption, little is known about the transfer of aflatoxins from tea leaves to the tea infusion during the brewing process and the actual intake amount. A validated analytical method for aflatoxins in tea infusions is of great importance for exposure assessment.

QuEChERS (quick, easy, cheap, effective, rugged and safe) is a rapid extraction and clean-up method, specifically developed for the determination of pesticides, mycotoxins and other contaminants in complex matrices. After extraction with acetonitrile or acidified acetonitrile, the extract is further cleaned-up by salting-out using primary secondary amine (PSA), C18 silica gel or graphitized carbon black (GCB), to remove organic acids, pigments, phenols and other interferences from the food matrix. Due to the extremely high content of tea polyphenols, polyvinylpyrrolidone (PVP) and PSA are considered as the priority adsorbents for cleaning up tea leaf samples.

Based on the QuEChERS principle, four approaches have been developed for the analysis of AFB1 in tea infusions. The optimal analytical method is the simultaneous determination of the four AFs (AFB1, AFB2, AFG1 and AFG2) in tea infusions.

Shi, Yating, et al. Food chemistry 199 (2016): 75-80.

Tea is the second most consumed beverage in the world after coffee, and global tea production has grown significantly in the past decade. While drinking tea has many health benefits, some studies have also reported the presence of certain organic pollutants in tea leaves that may be harmful to human health. Particularly, various polycyclic aromatic hydrocarbons (PAHs) have been detected in tea leaves. However, because of the very low levels of PAHs found in coffee and tea, as well as the intricate compositions of these samples, it is essential to properly prepare the samples before conducting instrumental analysis in order to achieve precise and reliable results.

A benign nano-adsorbent based on ionic liquid-immobilized Fe₃O₄@3-(trimethoxysilyl)propyl methacrylate@ionic liquid magnetic nanoparticles (Fe₃O₄@MPS@IL NPs) was used for the magnetic solid-phase extraction of seven high-molecular-weight PAHs from tea leaf samples, followed by HPLC-fluorescence detection.