Application of Electronic Nose to Predict the Optimum Fermentation Time for Low-Country Sri Lankan Tea

Abstract

The fermentation stage is vital during the black tea manufacturing process to produce the best-quality tea. The oxidation of tea biochemical compounds results in the appearance of characteristic smell peaks during the fermentation stage. These subtle changes in tea aroma are hard to detect unless one is a trained personnel. Here for the first time, we applied e-nose to monitor the fermentation process of Sri Lankan low-country tea. In this study, detection of smell peaks during fermentation was conducted by a custom-made e-nose (Digi-Nose) with four gas sensors. Singular value decomposition (SVD) is applied to eliminate the noise and dimensionality reduction in the sensor responses observed. The prediction of the time of appearance of smell peaks was conducted with a support-vector machine (SVM). Finally, theaflavin content with time was compared to validate the optimum fermentation times observed with an e-nose.

Recent Progress in Electronic Noses for Fermented Foods and Beverages Applications

“…Another emerging direction in the field could be to develop mobile and affordably priced devices for people who suffer from anosmia (loss of smell) [86,87]. With a focus on applications in the food and beverage industry, E-nose systems have been used for both direct/indirect identification via odor analysis for multiple purposes, such as product quality inspection [88], batch-to-batch uniformity studies [89], contamination detection [90], spoilage detection [91][92][93], adulteration detection [13,94], the detection of pathogenic bacteria [95,96], the study of storage conditions/shelf life [97][98][99][100] and the creation of specific sensory profiles [101,102]. In terms of food business competition, they have been used to analyze aromas and compare them with competitor products [103,104], evaluate the impact of changes in the production process and components that affect organoleptic characteristics [105,106] and compare different food formulations [84,107].…”

“…To detect VOCs emitted from fermentation, the MOS is still a popular sensing material in E-nose systems. Based on PCA coupled with CA, they were used to analyze odor substances for quality control in black tea during the fermentation process [178,179] and monitor the fermentation process of Sri Lankan low-country tea [89,180]. Not only MOS but also polymer/CNT gas sensors can be integrated into an E-nose for tracking odors of Thai sweet fermented rice (Khao Mak) during the fermentation process [181].…”

A Gas Sensors Detection System for Real-Time Monitoring of Changes in Volatile Organic Compounds during Oolong Tea Processing

“…However, they may lack specificity and sensitivity compared to more traditional analytical techniques such as liquid chromatography (LC) and gas chromatography (GC). However, their simplicity and speed make them suitable for applications where rapid or on-site analysis is needed [ 16 ]. Gas sensing detection technology, which emerged and developed after the 1990s, utilizes a series of gas-sensitive sensors and recognition algorithms to perceive and identify odors.…”