Production of caffeinated and decaffeinated green tea catechin powders from underutilised old tea leaves

Only the apical bud and the top four leaves are normally used to make high quality green teas, while the older lower leaves are cut and used for mulch. The aim was to determine whether the old fifth to tenth leaves could be used to make caffeinated and decaffeinated green tea catechin powders. The leaves were decaffeinated by blanching in water at 100 °C for 10 min to remove 80% of the caffeine while retaining 85% of the catechins. The leaves were then extracted in water at 80 °C and freeze drying gave 100% yields of extractable powder and catechins while spray drying gave 20–25% lower yields. Decaffeination and spray drying also increased the conversion of epistructured to non-epistructured catechins. Therefore, this study has shown that old green tea leaves, which are usually discarded, could be used as an underutilised source to make caffeinated and decaffeinated green tea catechin powders.

► Green tea catechin powders ± caffeine were produced from old waste tea leaves.
► Blanching in hot water removed 80% of the caffeine but retained 85% of the catechins.
► Freeze drying gave 100% and spray drying 75% yields for powder and catechins.
► Both freeze and spray dried decaffeinated green tea powders had low caffeine levels.
► All powders had physicochemical properties acceptable for use in the food industry.