Excavation of coffee maturity markers and further research on their changes in coffee cherries of different maturity.

H NMR detection combined with partial least squares discriminant analysis (PLS-DA) was used to establish models for distinguishing between Arabica coffee immature beans and mature beans. By screening Variable importance in projection (VIP) values of the discriminant model, sugars, caffeoylquinic acids (CQAs), caffeine, trigonelline and quinic acid were confirmed as maturity markers. Response surface method (RSM) was used to filter optimal condition for the simultaneous extraction of sugars, 5-caffeoylquinic acids (5-CQA), caffeine and trigonelline and the best condition obtained was: extraction time 120 min, extraction temperature 50 °C, methanol/water 0.20, solvent/solute 274.65. Under this condition, the content of maturity markers in eight different maturity coffee green beans and pulp were analyzed, and their possible biological functions as well as impact on cupping score were further discussed.