A Comparative Study of Black Tea and Instant Tea to Develop an Instant Tea Tablet with Retained Health Promoting Properties

Abstract

The tea plant Camelia sinensis is an evergreen plant which grows under different climatic conditions in Sri Lanka and makes a significant contribution to the economy of Sri Lanka. There is a growing interest in dietary health supplements and tea can be an important source of dietary antioxidants, with its associated health benefits such as reduced risk of cardiovascular disease and cancer. Due to the fast pace of modern life there is a growing interest in ready to drink beverages and instant tea is becoming increasingly popular as a beverage. The concentration of a hot solution of an industrially produced instant tea powder which is organoleptically equivalent to a standard cup of brewed tea was determined by a thirty member sensory panel. The characteristics chosen were strength, flavour, colour, brightness and overall acceptability. A brewed tea beverage prepared by steeping 1.4 g of black tea in 140 mL of freshly boiled water for 3 minutes was found to be organoleptically equivalent to a beverage of instant tea prepared by dissolving 0.21 g of instant tea in freshly boiled water in the same volume. The total phenols and total flavonoids contents of the equivalent instant and brewed tea beverages were determined using the Folin Ciocalteu assay and the aluminium chloride colorimetric assay respectively. Phenolic content of a cup of instant tea (704.9 ± 0.7 mg gallic acid equivalents (GAE)) was much lower than a cup of brewed tea (1090.6 ± 3.8 mg GAE). The total flavonoid contents of a cup of instant tea prepared from tea powder (28.4 ± 0.8 mg quercetin equivalents (QE)) was also much lower than that of a cup of brewed tea (61.9 ± 0.4 mg QE). Similarly the theaflavins and thearubigins content determined spectroscopically were found to be lower in instant tea (1.06 and 89.32 mg/tea cup respectively) compared to brewed tea (89.32 and 322.00 mg/tea cup respectively). The in vitro antioxidant potential of the two tea beverages were determined based on their IC50 values in the scavenging of the 2,2-diphenyl-1-picrylhydrazyl (DPPFI) radical, 2,2'- azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation and by their ferric reducing antioxidant power (FRAP value). The IC50 values of brewed and instant tea obtained for ABTS (6.3 and 17.8 ig/mL respectively) are lower than the IC50 values obtained for DPPH radicals (8 .ig/mL and 20 jig!mL respectively) but is of the same order of magnitude. FRAP value of brewed tea is also higher than that of instant tea (2100 and 980 jiM Fe (II)/g respectively). These figures indicate that brewed tea has a higher antioxidant potential than instant tea in vitro. However, the in vivo antioxidant capacity of instant and brewed tea was found to be similar as measured by their effect on the serum and issues of the heart and lung in mice, at a dose equivalent to twelve cups of tea a day. The conditions for preparing a hot water soluble tablet from the instant tea powder were optimized. A series of ten formulations were prepared based on the physical properties of moisture absorption, angle of repose, compressibility index and moisture content. The formulation consisting instant tea powder (42 %), anhydrous lactose (56.3 %), microcrystalline cellulose (1.0 %), aerosol (0.2 %) and magnesium stearate (0.5 %) was chosen as the best formulation. Direct compression tablets (250 mg) were made using this formulation to obtain tablets having acceptable values for thickness, hardness, disintegration time, friability and percentage moisture absorption (5.3 mm, 5.0 kPa, 6 mm, 0.14 % and 7.62 respectively). Real time and accelerated stability studies indicate that the formulated tea tablets are microbiologically stable and retain their antioxidant potential when stored in screw capped amber glass bottles or in triple laminated aluminium foil at room temperature for one year.