# Evaluation of Chongqing Tuo Tea at Different Grades: An Integrated Approach by Artificial and Intelligent Sensory, Non-Volatile, and Volatile Compounds Analysis

## TL;DR

This study evaluates different grades of Tuo tea using sensory and chemical analyses to identify compounds that indicate quality differences.

## Contribution

The study introduces an integrated method combining sensory and analytical techniques to distinguish Tuo tea grades based on volatile and non-volatile compounds.

## Key findings

- Artificial and intelligent sensory methods revealed significant differences in aroma and taste among Tuo tea grades.
- 112 volatile and 44 non-volatile compounds were identified, with 80 key volatile and 22 key non-volatile compounds linked to quality differences.
- PLS-DA models showed strong predictive power for distinguishing tea grades based on compound profiles.

## Abstract

This study aims to investigate the relationship between the grades of Tuo tea and the quality of compounds. A combination of artificial sensory evaluation, intelligent sensory technologies (electronic nose and electronic tongue), gas chromatography–mass spectrometry (GC-MS), high-performance liquid chromatography (HPLC), chemical–physical analysis, and multivariate statistical analysis were employed to examine the differences among three grades of Tuo tea (SG, 1G, and 2G). The results of artificial sensory evaluation, electronic tongue, and electronic nose revealed that the aroma and taste of different grades of Tuo tea varied greatly. A total of 112 volatile compounds and 44 non-volatile compounds were identified. In order to elucidate the key components that cause differences in the quality of Tuo tea, 2 partial least squares discriminant analysis (PLS-DA) models with excellent parameters (volatile, R2Y = 0.999 and Q2 = 0.996; non-volatile, R2Y = 0.992 and Q2 = 0.972) were established. A total of 80 key differential volatile compounds were identified with the double selection criterion of variable importance in projection (VIP) greater than 1 and p < 0.05. Among these, 43 compounds with OAV > 1 were further identified as the odor-active compounds in all three grades of Tuo. Moreover, 22 key non-volatile compounds that contribute to the quality differences have been screened out. This investigation implied that the volatile and non-volatile compounds of Tuo tea could serve as indicators of its quality. The results provided a new approach to distinguish the grades of Tuo tea.