Suitability of botanical extracts as components of complex mixtures used in herbal tea infusions—challenges and opportunities

Herbal tea is a mainstay dosage form in practically all systems of traditional medicine and widely used in modern alternative and complementary medicine. Incorporating botanical extracts into herbal tea formulations is of vital interest to manufacturers as it allows for the use of herbal ingredients that would otherwise not be suitable for the dosage form, for instance, dosing requirements, solubility in water, sensory constraints etc. Furthermore, reducing the amount of ingredients in a formula increases compliance with dosing recommendations and thus therapeutic benefit. However, formulating with botanical extracts comes with challenges, ranging from sourcing ingredients of appropriate quality, developing suitable methods for quality control with combinations of (herbal) ingredients, processing constraints such as hygroscopicity, solubility, dispersibility, homogeneity of distribution, and packaging machinability, all the way to stability required for hot-water infusion. We report on experiences with overcoming such challenges in a set of examples and provide guidance to the extract industry on how to tap into the bagged tea sector with better suited or tailor-made solutions for the formulator.

Mate (Ilex paraguariensis) tea preparations: Understanding the extraction of volatile and non-volatile compounds upon variations of the traditional consecutive infusions

Common variations of traditional consecutive infusions of mate (Ilex paraguariensis) tea were studied. Effects of tea grinding type and water temperature on the extraction of volatile and non-volatile compounds were elucidated. Extraction behavior was determined mainly by grinding type and to a minor extent by water temperature. The extraction behavior along the series of infusions is mostly driven by the way the water can access and flow through the tea mass. This processes are impaired by the formation of clogging layers which are more intense upon the increasing abundance of tea particles of sufficiently small size and high water temperatures.

Quality characteristics of infusion and health consequences: a comparative study between orthodox and CTC green teas

The present study compares the effects of two green tea processing techniques, viz. orthodox and CTC (curl, tear and crush) on the quality parameters and sensory profiles under the geographical and climatic conditions of Assam, India. The results showed that CTC green tea infusions had 13.3, 7.5, 7.1, 9.8, 5.4, 17.3, 17.1 and 18.6% more total polyphenol, total catechin, (-)-epigallocatechin-3-gallate (EGCG), (-)-epicatechin-3-gallate (ECG), (-)-epigallocatechin (EGC), (-)-epicatechin (EC), water extract and theanine level, respectively than the infusions prepared from orthodox green tea. The sensory evaluation preferred the orthodox over CTC processing mode. Risk assessment with daily consumption of five cups (10 g) of green tea reveals that the EGCG level is free from the risk of hepatotoxicity and caffeine will not inflict any health hazard.

Effect of brewing conditions using a single-serve coffee maker on black tea (Lapsang Souchong) quality

Black tea powder was used to make tea infusion using a Keuring coffee maker. Effect of tea particle size (0.30 or 0.60 mm), water volume for brewing (118, 177, or 236 ml), and the amount of tea powder (1.0, 1.5, or 2.0 g) on tea infusion quality were evaluated. The concentration of four chemical compounds (soluble sugars, total amino acids, polyphenols, and caffeine) in tea infusion was measured. In general, the concentration of the four compounds in tea infusion increased with the amount of tea powder used and decreased with increasing water volume and tea particle size. Using 2.0 g of 0.30 mm tea powder and 118 ml of water per brew, the concentration of the above four components was 412.3, 251.6, 208.9, and 205.3 μg/ml, respectively, and higher than tea infusion prepared by traditional method (312.4, 204.1, 211.6, and 175.9 μg/ml). The highest extraction efficiency (mg/cup.g) for the four chemical components per unit weight of tea powder was at using 1.0 g of 0.30 mm tea powder with 236 ml water for soluble sugars (32.3 μg/ml) and caffeine (16.3 μg/ml), at using 1.5 g tea powders for polyphenols (22.3 μg/ml) and at using 2.0 g tea powders for amino acid (13.6 μg/ml). This study suggested using a single-serve coffee maker can be a convenient and effective way to prepare the tea infusion with high quality.

Characterization and evaluation of tea bag papers

The infusion kinetics of tea bags containing black tea or green tea has been studied in detail in the past. However, the tea bag papers have never been characterized and evaluated earlier to understand their contribution towards tea bag infusion. In the present work, papers used for making tea bags were characterized for thickness, wettability, surface topography, pore size, porosity and permeance to understand their influence on infusion kinetics of tea bags. Scanning electron microscopy studies highlighted the pore structure and porous nature of tea bag papers. The porosity of tea bag paper was quantified using image processing and permeance was determined experimentally. Besides, a relationship between porosity and permeance of tea bag papers has been perceived. A general trend of increase in permeance with increasing porosity was observed. Woven nylon paper showed the highest permeance (23.9 × 10^-5 m/s) when compared with other tea bag papers. Furthermore, an initial infusion rate was determined using initial infusion data of tea bag infusion for different tea bag papers. The influence of permeance on the initial infusion rate of tea bag papers has also been investigated.

Swelling and infusion of tea in tea bags

The present study deals with swelling and infusion kinetics of tea granules in tea bags. The swelling and infusion kinetics of tea bags differing in tea loading and tea bag shapes were compared with loose tea. Increment in temperature and dipping frequency of tea bag in hot water increased the infusion kinetics of tea bags. Reduction in particle size enhanced the swelling and infusion kinetics of tea in a tea bag. The effects of tea particle size, tea bag dipping rate, loading of tea granules in tea bag and tea bag shapes on infusion kinetics were investigated. Increase in tea loading in tea bags resulted in reduced infusion kinetics. Double chambered tea bag showed the highest swelling (30%) and infusion kinetics (8.30% Gallic acid equivalence) while single chambered tea bags showed the lowest kinetics, amongst the various bags studied. The swelling and infusion kinetics of loose tea was always faster and higher than that of tea bags. It was found that overall effect of percentage filling of tea granules and height of tea bed in a tea bag affects tea infusion kinetics the most. Weibull model was found to be in good agreement with the swelling data.

Modeling of Tea Infusion Kinetics Incorporating Swelling Kinetics

Mathematical model to predict tea infusion kinetics which accounts for swelling kinetics of tea granules is presented. Swelling kinetics of tea granules has never been taken into account for models developed so far. Differential equations (DEs) for concentration of tea constituents inside tea granule with respect to radius and time were derived. Solution methodology for these DEs is developed based on Crank-Nicholson scheme. Tea infusion profile is obtained using this model by knowing the swelling kinetics, partition constant and initial contents in tea granules. Diffusivity and product of interfacial area (As) and backward rate constant (k−1) are the fitting parameters. Model prediction is fitted to the experimental data published previously (R2 = 0.90–0.98). The fitted diffusivity (3.33 × 10−10 m2/s) and Ask−1 (2 m3/(kg.s)) predicted the infusion profile of other sized tea granules very well. This model predicts the infusion during initial stage very accurately without any empirical parameter.