Effect of pH on cream particle formation and solids extraction yield of black tea

Effect of pH on tea solids extraction yield was significant in increasing i nstant tea yield. Solids extraction yield was doubled when tea was extracte d at pH 1.2 compared with that extracted in boiling distilled water with pH 6.8. H+ encouraged black tea cream particle formation by either releasing more solids into the infusion or stimulating polyphenols to interact with p olysaccharides and nucleophilic groups on protein in tea infusions. HPLC re sults revealed that theaflavins and tea catechins were leading substances a ffecting the formation of cream particles and infusion colour. Theaflavins and some tea catechins, such as EGCG, ECG and EGC, were dissociated or degr aded under alkaline conditions and thus tea cream particles tended to disso lve and tea infusion became dark in colour. Feasibility of stepwise extract ion of instant teas used for iced tea and normal drinking tea, by controlli ng temperature and pH, is also considered in the present paper. (C) 2001 El sevier Science Ltd. All rights reserved.