title: The impact of Ca2+ combination with organic acids on green tea infusions.
abstract: The effect of Ca(2+) in brewing water on the organic acid content, turbidity, and formation of tea cream and sediment in green tea infusions was studied. When the Ca(2+) concentration of the brewing water was >40 mg L(-1), the green tea infusion became more turbid. The turbidity of the tea infusion was highly negatively correlated with the contents of oxalic acid (R=-0.89, p<0.01), quinic acid (R=-0.90, p<0.01) and tartaric acid (R=-0.82, p<0.01). Oxalic acid on its own interacted with Ca(2+) at low concentrations, whereas polyphenols and protein did not. In conclusion, Ca(2+) in brewing water influences the quality of a tea infusion by inducing tea cream and sediment formation from combination of Ca(2+) and organic acids, such as oxalic acid, quinic acid and tartaric acid. Ca(2+) and oxalate are the main metal ion and anion, respectively, involved in tea cream and sediment formation on tea infusion cooling or concentrating.
authors.affiliation: Tea Research Institute, Chinese Academy of Agricultural Sciences, 9 South Meiling Road, Hangzhou 310008, China.
authors.forename: Yong-Quan
authors.initials: YQ
authors.lastname: Xu
authors.forename: Xiao-Yu
authors.initials: XY
authors.lastname: Zhong
authors.forename: Jun-Feng
authors.initials: JF
authors.lastname: Yin
authors.forename: Hai-Bo
authors.initials: HB
authors.lastname: Yuan
authors.forename: Ping
authors.initials: P
authors.lastname: Tang
authors.forename: Qi-Zhen
authors.initials: QZ
authors.lastname: Du
mesh_terms: D000143:Acids / Q000032:analysis*; D002118:Calcium / Q000032:analysis*; D028241:Camellia sinensis / Q000737:chemistry*; D003296:Cooking; D010070:Oxalates / Q000032:analysis; D013662:Tea / Q000737:chemistry*
chemical_list: D000143:Acids; D010070:Oxalates; D013662:Tea; D002118:Calcium