Electronic Nose Technologies in Monitoring Black Tea Manufacturing Process

Tharaga Sharmilan,Indika Wanniarachchi,Iresha Premarathne,Sandya Kumari,Dakshika Wanniarachchi

doi:10.1155/2020/3073104

Tharaga Sharmilan, Indika Wanniarachchi + Show 3 more

Open Access

https://doi.org/10.1155/2020/3073104

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Abstract

“Tea” is a beverage which has a unique taste and aroma. The conventional method of tea manufacturing involves several stages. These are plucking, withering, rolling, fermentation, and finally firing. The quality parameters of tea (color, taste, and aroma) are developed during the fermentation stage where polyphenolic compounds are oxidized when exposed to air. Thus, controlling the fermentation stage will result in more consistent production of quality tea. The level of fermentation is often detected by humans as “first” and “second” noses as two distinct smell peaks appear during fermentation. The detection of the “second” aroma peak at the optimum fermentation is less consistent when decided by humans. Thus, an electronic nose is introduced to find the optimum level of fermentation detecting the variation in the aroma level. In this review, it is found that the systems developed are capable of detecting variation of the aroma level using an array of metal oxide semiconductor (MOS) gas sensors using different statistical and neural network techniques (SVD, 2-NM, MDM, PCA, SVM, RBF, SOM, PNN, and Recurrent Elman) successfully.

Highlights

Black tea is the most commonly consumed beverage in the word
Recent studies focused on the combination of electronic eye and electronic nose methods [32,33,34,35] which are aimed at minimizing human intervention of observing color changes and smelling of tea particles
Identification of aroma compounds present in tea is done with gas chromatography mass spectrometry (GCMS) and their characteristics using Gas Chromatography-Olfactometry (GC-O) [37, 38, 40,41,42]

Summary

Introduction

Black tea is the most commonly consumed beverage in the word. The world production of black tea is about 3000 tons per year [1]. The optimum fermentation time is found in almost all tea factories based on the decision of the human detecting aroma and color changes of tea leaves. Recent studies focused on the combination of electronic eye and electronic nose methods [32,33,34,35] which are aimed at minimizing human intervention of observing color changes and smelling of tea particles. Adopting these developed methods into the real factory condition is challenging as most of the studies are conducted in a laboratory scale [36]. Existing e-nose technologies and statistical algorithms which were used in data analysis will be discussed

Tea Quality Evaluation

E-Nose Data Analysis

Findings

Conclusions