An integrated paper-based optical tongue/nose device combined with chemometrics methods for identification of fermentation degree and aerial parts of Iranian tea

In this research, we proposed an integrated paper-based optical tongue-nose colorimetric sensor array for quality evaluation of tea samples using their chemical constituents in both liquid extracts and volatile organic compounds in their aroma. The integrated device combined the electronic tongue (using 5 reagents) and nose (using 8 indicators) on two sides of a paper that embedded in a chamber. For the electronic tongue phase a flower-like design with eight petals (1mm diameters) and for electronic nose phase, circular areas were designed in 1 mm diameter (deposit sensing elements) around a larger circle in 5 mm diameter (deposit real sample). By placing the electronic tongue and nose on top of each other, the volatile and non-volatile compounds were investigated, simultaneously. Similar to previous studies, the images of the both sensing parts were recorded using a flat-bed scanner and then the imaging data for every reagent spots were extracted in RGB format by ImageJ software [1]. For each sample, the response data of the optical tongue and nose parts of the device were collected in row vectors of length of 15 and 24, respectively. The ability of the developed sensor to distinguish between different types of tea samples according to the degree of fermentation and the type of harvest was evaluated utilizing different chemometrics methods such as principal component analysis (PCA) and linear discrimination analysis (LDA). The accuracy of this proposed device to discriminate tea according to the degree of fermentation and type of harvest was reported as 100% and 92%, respectively. In total, the designed device is portable, rapid and requires low volumes of samples that can be considered a good candidate for simultaneous analysis of volatile and non-volatile compounds of tea samples.