Indicator displacement assay for freshness monitoring of green tea during storage.

[Display omitted] • IDA sensor showed high sensitivity for EGCG detection. • IDA elements were composed of low-cost accessible pH dyes and metal ions. • IDA provided qualitative discrimination of green tea freshness. • IDA provided quantitative prediction of catechins in green tea during storage. Aging of green tea leads to reductions in its flavor and health value, yet in situ testing methods for green tea freshness are lacking. A novel sensitive indicator displacement assay (IDA) sensor was constructed and applied for monitoring of green tea freshness during storage. Low-cost pH dyes and metal ions were used as indicators and receptors, respectively, for the targeted detection of catechins in tea samples. The feasibility of the IDA reaction was verified using images and UV–vis spectroscopy, respectively. IDA combined with supervised algorithms achieved accurate identification of green tea freshness with an accuracy of 86.67%, and acceptable accuracies in the prediction of catechin monomers and total catechins with ratio of prediction to deviation values over 1.5. Thus, the developed IDA sensor is capable of qualitative and quantitative monitoring of the green tea freshness during storage, providing a new option for quality evaluation and control of green teas. [ABSTRACT FROM AUTHOR]