Development of Electronic Nose with High Stable Sample Heater to Classify Quality Levels of Local Black Tea

Abstract

an electronic nose (e-nose) based on a gas sensor array equipped with a stable temperature controller has been successfully developed by applying proportional-integral-derivative (PID) controller. This study was motivated due to the dependence of sensor response on the temperature of a sample. Here, the temperature influences the volatile organic compounds (VOC) of the sample. The performance of the e-nose was then evaluated to classify the quality levels of black tea (Q1, Q2, and Q3). The black tea samples were purchased from Tambi Tea Industry in Central Java, Indonesia. Here, the quality is based on the information from the factory. For each quality level, the measurement was repeated 31 times. Therefore, the total of measurements is 93, and only six sensors, i.e. MQ-7, TGS 813, TGS 2602, TGS 826, TGS 2620 and TGS 825 have the high influence on the patterns differentiation. It is found that the e-nose is not able to distinguish the three quality levels of black tea correctly when applying without heating treatment. In this condition, only 88.9% of cross-validated grouped are correctly classified. On the other hand, for the black tea sample with unstable heating, the performance of the e-nose has been improved. In this case, 92.5% of crossvalidated grouped are correctly classified. Moreover, for the black tea sample with stable heating treatment, all samples are separated where 97.8% of cross-validated grouped are correctly classified. The results indicated that the e-nose with the highly stable heater was capable of detecting the quality of black tea.

The Electronic Nose Coupled with Chemometric Tools for Discriminating the Quality of Black Tea Samples In Situ

“…Tea (Camellia sinensis) is the most consumed non-alcoholic beverage in the world, after water [1][2][3][4][5][6][7][8][9][10]. Tea can be made from leaf and bud of Camellia sinensis through a series of production, fixation, withering, rolling, fermentation, polling and drying processes [4,8,9].…”

“…Furthermore, the low number of samples that can be evaluated per day poses an additional limitation. Consequently, this procedure, besides being expensive and time-consuming, may lead to inaccurate tea quality classifications [1,2,13,14]. On the other hand, several analytical techniques may be used for tea analysis such as, gas chromatography (GC), capillary electrophoresis (CE), high-performance liquid chromatography (HPLC) and plasma atomic emission spectrometry.…”

“…Brenet et al used surface plasmon resonance imaging for sensing VOCs that has become a high-selective sensing device [16]. Also, electronic noses (E-nose), that utilize an array of gas sensors to give a fingerprint response to a given odor [17][18][19][20][21], combined with different multivariate statistical tools have been used for tea quality assessment and tea aroma evaluation of green or black teas from different geographical origins [1,2,[22][23][24][25][26][27][28][29][30][31][32][33]. Recently, the possibility of merging different electronic devices (E-nose, E-tongue and/or E-eye), have been studied aiming to improve the overall classification performances of the single devices [3,[34][35][36][37][38].…”

“…Recently, the possibility of merging different electronic devices (E-nose, E-tongue and/or E-eye), have been studied aiming to improve the overall classification performances of the single devices [3,[34][35][36][37][38]. Similarly, E-nose devices, comprising metal oxide semiconductor (MOS) gas sensors have been successfully applied for assessing black tea flavor grade [39] and quality level [1,2,40]. E-Nose have advantages that rapid non-destructive analysis, adequate sensitivity and relatively low cost [41,42] but E-Nose with MOS sensors have disadvantages that sensor drift, susceptible to poisoning, high power consumption, humidity-dependent signal [41].…”

Deteksi Daging Sapi Menggunakan Electronic Nose Berbasis Bidirectional Associative Memory

“…Salah satu implementasi kemampuan dari electronic nose yang sudah dikembangkan adalah digunakan untuk mengklasifikasikan mutu dari teh hitam lokal. Hasil klasifikasi mutu teh hitam didapatkan dari kinerja electronic nose yang telah dievaluasi dengan sampel yang dipanaskan menggunakan suhu tinggi dan stabil [5].…”