Prolay Sharma

Monitoring the Fermentation Process and Detection of Optimum Fermentation Time of Black Tea Using an Electronic Tongue

This paper presents a new methodology to monitor the fermentation process and detect the optimum fermentation time of crush tear curl black tea with a voltammetric electronic tongue. An electronic tongue with an array of five noble metal working electrodes has been developed for this purpose. A suitable large amplitude pulse voltammetric waveform has been employed for probing the chemical changes in tea samples under fermentation. Good correlation between the electronic tongue responses and the biochemical changes has been obtained by principal component analysis (PCA) during various stages of fermentation. The electronic tongue fermentation profile has been derived from PCA analysis and it is observed that such a profile enables detection of optimum fermentation times. Finally, a model based on partial least squares regression technique has been developed for real-time indication of fermentation level. The optimum fermentation times observed from the electronic tongue fermentation profiles derived from PCA and partial least squares regression correlate by a factor of 0.97 and 0.96, respectively, with the reference values obtained from an ultraviolet-visible spectrophotometer-based instrumental analysis.

A Quartz Crystal Microbalance Sensor for Detection of Geraniol in Black Tea

Geraniol is one of the important qualities determining volatile components of black tea. This paper presents a quartz crystal microbalance sensor to detect geraniol from black tea aroma. The sensor is developed using β-cyclodextrin (β-CD). β-CD is a flavor encapsulating material with toroidal bucket-like structure, whose inside-cavity is hydrophobic and the outside is hydrophilic and it is found to be a suitable coating material for detecting geraniol. Extensive experiments have been carried out with the β-CD sensor and it is observed that the sensor offers better sensitivity for geraniol in comparison with other important constituents of black tea such as linalool, linalool oxide, methyl salicylate, and trans-2-hexenal. Experiments with ten Darjeeling orthodox black tea samples have been carried out with the developed sensor and a correlation factor of 0.9925 has been obtained with the corresponding gas chromatography mass spectrometry analysis.

Detection of Optimum Fermentation Time of Black CTC Tea Using a Voltammetric Electronic Tongue

A voltammetric electronic tongue (E-tongue) has been used to detect the optimum fermentation time (OFT) of crush tear curl black tea. An E-tongue with an array of five noble metal working electrodes has been developed for this purpose. A suitable large amplitude pulse voltammetric waveform is used and a simple feature extraction technique based on the charge activity of working electrodes is proposed. The principal component analysis reveals a significant correlation between the E-tongue responses and the biochemical changes during various stages of fermentation. Principal component regression models are developed to assess the effectiveness of the features derived from E-tongue response to model the temporal variations of theaflavins, a key quality compound of tea, produced during the fermentation process. The OFTs detected by the E-tongue correlate by a factor of 0.97 with the estimates obtained from an ultraviolet-visible spectrophotometer-based reference method.

Detection of Methyl Salicylate in Black Tea Using a Quartz Crystal Microbalance Sensor

Methyl salicylate plays an important role in the constitution of black tea aroma. This paper presents a quartz crystal microbalance (QCM) sensor to detect methyl salicylate from the black tea aroma. The sensor is developed using maltodextrin (MDEX). Methyl salicylate is an organic ester, naturally produced by many species of plants. It is used as a fragrance, in foods and beverages, and in ointments. Extensive experiments have been carried out with MDEX-coated QCM sensor and it is observed that the sensor offers better sensitivity for the methyl salicylate in comparison with other important constituents of black tea like linalool, geraniol, linalool oxide, and trans-2-hexenal. Experiments with 32 Darjeeling orthodox black tea samples have been carried out with the developed sensor, which offers 0.982 correlation between the responses of the developed sensor and the concentrations obtained through the reference instrumental technique, i.e., gas chromatography mass spectrometry.

Development of a QCM sensor for detection of trans-2-hexenal in tomatoes

Ripeness monitoring of tomato is very important due to the biosynthesis of a carotenoid Lycopene that increases with the maturity process. The ripening stages of tomato can be estimated by the smell it generates during particular maturity stages. This paper aims the detection of Trans-2-hexenal, an important ripening volatile of tomato with the help of quartz crystal microbalance sensor. A coating material formed by the chemical reaction process of pentafluorobenzyl bromide (PFBBr), polyethylene glycol 6000 (PEG 6000), tri-ethyl amine and chloroform has been developed for this purpose. Moreover different characterization of the sensor has been performed e.g. sensitivity, selectivity, repeatability, reproducibility and the perforamance is verified.

Quartz crystal microbalance sensors for discrimination of black tea

The quality evaluation of black tea is based on organoleptic methods of “Tea- tasters”. However the present quality estimation involving Tea-tasters is not a very reliable method as professional acumen, mood and other personal factors affect the judgment of tea quality. Electronic nose consists of an array of gas sensors with overlapping selectivity patterns, signal handling and classifier modules. An array of quartz crystal microbalance (QCM) sensors has been developed to differentiate among different tea samples. The important volatile components responsible for aroma of tea have been considered and the corresponding sensing materials have been identified. Five AT-cut 10 MHz Quartz crystal blanks coated with different sensing materials have been used to differentiate the aroma of orthodox and cut-tear-curl (CTC) tea samples. The developed sensors can distinguish not only between the orthodox and CTC tea but distinct clusters are also obtained for the four different tea-samples, as visualized through principal component analysis (PCA).