Relationship between the turbidity difference and the grade of green tea under Ca²⁺ acceleration: A preliminary study

The grade of green tea indicates its intrinsic quality and guides consumers when purchasing. Simple, accessible, and on-site determination of green tea grades is essential for consumers and regulators. In this study, we assumed that the turbidity difference in green tea might indicate its grade, and our results confirmed this hypothesis. The turbidity difference was measured in green tea infusions before and after the Ca²⁺ acceleration. For the same kind of green tea, it was found that higher grades of green tea had larger turbidity differences. Effects of brewing temperature, brewing time, Ca²⁺ concentration, and Ca²⁺ treatment time on the turbidity of green tea infusions were analyzed, and their optimal values were obtained. This study demonstrates that applying the turbidity difference and Ca²⁺ acceleration could be an accessible method for the on-site determination of green tea grades.