HP-β-CD-functionalized hydrogel SERS fingerprinting for rapid storage-year discrimination of white tea

Accurate discrimination of white tea storage years is important for quality evaluation, authenticity control, and market regulation. In this study, an HP-β-CD-functionalized hydrogel surface-enhanced Raman scattering (SERS) substrate was developed for rapid storage-year discrimination of white tea. Hydroxypropyl-β-cyclodextrin-functionalized silver nanoparticles (HP-β-CD/Ag NPs) were incorporated into an agarose hydrogel to construct an HP-β-CD/Ag NPs/AG substrate. HP-β-CD was designed to promote the local capture of aromatic and polyphenolic tea components near SERS-active Ag hotspots, while the agarose hydrogel improved nanoparticle dispersion and signal uniformity. The optimized substrate retained distinguishable SERS responses for epigallocatechin gallate and quercetin at 10^-7 mol L^-1 and showed good signal uniformity, with a relative standard deviation of 6.96%. White tea samples from seven storage years between 2011 and 2023 were analyzed, including 10 independent samples per year and 10 spectra per sample. Principal component analysis showed that the first three principal components explained 98.94% of the spectral variance. Under 50 repeated tea-sample-level splits, machine-learning models achieved stable internal storage-year discrimination, with sample-level accuracies ranging from 97.62% to 100.00%. A sample-level permutation test further indicated that the classification performance was unlikely to result from random label association. These results suggest that the proposed hydrogel SERS strategy can provide a rapid and fingerprint-based approach for white tea storage-year discrimination, although further external validation using more diverse samples is still required.