authentication and classification of black tea from narrow-geographic origins based on thecombination of uv-vis fingerprinting and chemometric methods

Tea is the second most consumed beverage in the world, and its characteristic flavor is due to thechemical components such as catechins, vitamins, amino acids, caffeine, and volatile aromacomponents derived from tea leaves. the chemical composition of tea leaves determines theirquality characteristics. the geographical features and environmental factors such as slope aspect,altitude, soil characteristics, temperature, rainfall, and sun exposure mainly influence thisparameter [1]. the combination of uv-vis spectrophotometry by multivariate data analysismethods for authentication of food products has been recently proposed as an efficient techniquein food science and technology [2]. this study investigates the feasibility of uv-vis spectroscopycoupled with chemometric methods to authenticate tea samples based on their geographical originsin a narrow longitudinal strip (200 km). black tea samples were obtained from five geographicalareas in the northern provinces of iran, including ramsar, lahijan, shaft, leilakooh, and oshiyan.samples of 0.1 g of tea were used to perform the extraction process. 40.0 ml of 20% methanolaqueous solution was added to a 0.1 g tea sample and then heated at 80 °c for 20 min in a sealedbeaker. the sample was heated on a hot-plate magnetic stirrer equipped with a thermometer. thespectrum of each sample was immediately recorded using a uv–vis spectrophotometer. severalpreprocessing methods, such as standard normal variate (snv), auto-scaling, multiplicativescatter correction (msc), mean centering (mc), first derivative, and their combinations, wereapplied to eliminate the noninformative information. the partial least squares-linear discriminantanalysis (pls-lda) model using first derivative spectra represented the following results,including 98.0% of sensitivity, 99.6% specificity, and a mean accuracy of 98.0%. the satisfactoryresults of the models depicted that the chemical components of tea, such as polyphenols,chlorogenic and fatty acids that absorb uv radiation, are the chemical markers that candiscriminate tea samples based on their geographical origin. therefore, uv-vis spectralfingerprinting combined with chemometrics could be a practical, feasible, and simple method forclassifying tea based on their geographical origins in a narrow longitudinal strip.