Discriminating the Adulteration of Varieties and Misrepresentation of Vintages of Pu'er Tea based on Fourier Transform Near Infrared Diffuse Reflectance Spectroscopy

Zhenfa Yang ^1* Xiaoping Lu ^2* Lucheng Chen ^2*

• ¹ Shandong University, Jinan, China
• ² Haier Group (China), Qingdao, Shandong Province, China

In the Pu'er tea market, the ubiquity of blending different varieties and the fraudulent representation of vintage years present a persistent challenge. Traditional sensory evaluation and experience are often inadequate for discerning the true variety and vintage of tea, highlighting the need for more sophisticated analytical methods to ensure authenticity and quality. Fourier transform near infrared diffuse reflectance spectroscopy combined with radial basis function neural network (RBFNN) was applied for determination of the varieties and vintages of Pu'er tea. For vintage identification, the accuracy, precision, recall, and F1-score of the RBFNN model for the prediction set were 99.2%, 98.2%, 98.0%, and 98.0%, respectively. For identification of varieties adulteration, the corresponding parameters were 98.9%, 97.2%, 96.7%, and 96.6%, respectively. These results illustrated the feasibility to identify the adulteration of varieties and misrepresentation of vintages of Pu'er tea with near infrared spectra and RBFNN model, proving an efficient alternative for Pu'er tea quality inspection, and offering a robust method for combating the pervasive issues within the market. Keywords：Near infrared spectroscopy; Radial basis function neural network; Pu'er tea; Adulteration of varieties; Misrepresentation of vintages.The escalating pace of contemporary life and the concomitant rise in consumer affluence have led to a burgeoning demand for healthful beverages. Pu'er tea, renowned for its salutary effects including lipid-lowering, weight reduction, and anti-aging properties, is increasingly becoming the beverage of choice for many consumers[1; 2; 3]. There is a price disparity between different varieties of Pu'er tea [4]. Take ancient tree tea and tableland tea for example, ancient tree tea is produced by tea trees older than 100 years that grow on tea hills at higher altitudes, rich in tea polyphenols, catechins, amino acids, caffeine and water leachate, with good quality, low yield, high price, while tableland tea is produced by tea trees grown centrally on plantations using modern tea planting techniques, with poor flavor, high yield and lower price [5; 6]. In