Effect of Leaf Maceration and Withering Duration on Selected Tea Quality Parameters-A Case of Non-aerated Teas from TRFK 306 and TRFK 6/8 Clones

10.37512/1300 ◽  
2021 ◽  
pp. 155-170

Leaf maceration and withering are processing steps that influence tea quality. The current study involved two tea clones, TRFK 306 and TRFK 6/8. Assessment was done on the effects of these steps on total monomeric anthocyanins (TMA), total soluble solids (TSS) and the tasters’ comments. The tea leaves were processed by orthodox (rolling) and Cut, Tear and Curl (CTC) manufacture methods and withered at an interval of 5 hours. TMA were assayed following Giusti and Wrolstad protocol while TSS was determined by weight differential method. Experienced tea tasters participated in the sensory exercise. Data was subjected to general linear model using SAS package version 9.1.3. Both CTC and orthodox non-withered teas had 93 mg/L residual anthocyanins while long withered teas had lower levels averaging 24 mg/L. TRFK 306 non-withered orthodox and CTC teas had 3.2 mg/ mL and 3.43 mg/mL TSS, respectively, while those withered for 20 hours and processed by both methods had 3.5 mg/mL and 3.23 mg/mL TSS, respectively. TRFK 6/8 none withered orthodox and CTC teas had 4.29 mg/mL and 3.62 mg/mL TSS, respectively while those withered for 20 hours had 3.62 mg/mL and 3.51 mg/mL TSS, respectively. The colour score for non-withered TRFK 306 orthodox and TRFK 6/8 teas was 3.33 and 3.00 respectively, while teas withered for 20 hours from both clones had 4.00 and 3.67 colour scores. It was established that leaf maceration style does not affect TMA and long withering duration reduces the levels of anthocyanins. TRFK 6/8 had more TSS than TRFK 306 irrespective of processing method. Rolling and withering improves the liquor colour of teas.

2020 ◽  
Vol 12 (4) ◽  
pp. 657-664
Author(s):  
M. M. Rahman ◽  
M. M. Hossain ◽  
R. Das ◽  
I. Ahmad

Black tea processing consists of four steps, namely withering, CTC, fermentation and drying, while cup quality made tea mostly controlled by fermentation step. This study evaluated biochemical changes at different stages of black tea processing in Bangladesh and determined the optimum fermentation time. Samples were collected from different tea processing stages to measure major phytochemicals and time intervals during fermentation to measure theaflavins and thearubigins ratio. Caffeine content was the least susceptible to processing steps. Biochemical changes started at withering, cell maceration and enzymatic oxidation started at CTC processing, thus the major reduction in the reducing sugar (20.46 to 04.95 ppm), catechin (16.88 to 7.95 ppm) and polyphenol (42.30 to 30.73 ppm) occurred here. The significant changes appeared during fermentation when polyphenol content decreased from 44.66 to 18.23 and catechin from 17.41 to 03.98 ppm due to the breakdown of these compounds to theaflavins (TF) and thearubigins (TR). The TF and TR ratio increased with fermentation time, and the highest of 1:8.4 was found at 50 min, which turned into 1:10 in the final product. The made tea quality parameters were comparable or better at fermentation time of 50 min than the quality of the black tea available in market.


2021 ◽  
Vol 13 (18) ◽  
pp. 3719
Author(s):  
Longyue Chen ◽  
Bo Xu ◽  
Chunjiang Zhao ◽  
Dandan Duan ◽  
Qiong Cao ◽  
...  

The production of high-quality tea by Camellia sinensis (L.) O. Ktze is the goal pursued by both producers and consumers. Rapid, nondestructive, and low-cost monitoring methods for monitoring tea quality could improve the tea quality and the economic benefits associated with tea. This research explored the possibility of monitoring tea leaf quality from multi-spectral images. Threshold segmentation and manual sampling methods were used to eliminate the image background, after which the spectral features were constructed. Based on this, the texture features of the multi-spectral images of the tea canopy were extracted. Three machine learning methods, partial least squares regression, support vector machine regression, and random forest regression (RFR), were used to construct and train multiple monitoring models. Further, the four key quality parameters of tea polyphenols, total sugars, free amino acids, and caffeine content were estimated using these models. Finally, the effects of automatic and manual image background removal methods, different regression methods, and texture features on the model accuracies were compared. The results showed that the spectral characteristics of the canopy of fresh tea leaves were significantly correlated with the tea quality parameters (r ≥ 0.462). Among the sampling methods, the EXG_Ostu sampling method was best for prediction, whereas, among the models, RFR was the best fitted modeling algorithm for three of four quality parameters. The R2 and root-mean-square error values of the built model were 0.85 and 0.16, respectively. In addition, the texture features extracted from the canopy image improved the prediction accuracy of most models. This research confirms the modeling application of a combination of multi-spectral images and chemometrics, as a low-cost, fast, reliable, and nondestructive quality control method, which can effectively monitor the quality of fresh tea leaves. This provides a scientific reference for the research and development of portable tea quality monitoring equipment that has general applicability in the future.


2010 ◽  
Vol 41 (02) ◽  
Author(s):  
J Möhring ◽  
D Coropceanu ◽  
F Möller ◽  
S Wolff ◽  
R Boor ◽  
...  

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