Influence of withering, including leaf handling, on the manufacturing and quality of black teas — a review

Tomlins, Keith I.; Mashingaidze, A. B.

doi:10.1016/s0308-8146(97)00035-6

Cited by 75 publications

(63 citation statements)

References 32 publications

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“…Chemical withering plays a vital role in increasing the level of caffeine content (Sanderson, 1964), polyphenol oxidase activity (Ullah and Roy, 1982), amino acids, and sugars (Owuor and Orchard, 1989;Tomlins and Mashingaidze, 1997). Chemical withering results in the reduction of chlorophyll content (Wickremasinghe, 1975) and leads to the formation of different kinds of volatile flavor compounds (Mahanta and Baruah, 1989;Ravichandran and Parthiban, 1998).…”

Section: Biochemical Changes During Chemical Witheringmentioning

confidence: 99%

“…Whereas, the effects of unsaturated fatty acids on black tea aroma are much more documented, and the aroma formed from the breakdown of unsaturated fatty acids contributes to a negative odor effect. It has been reported that grassy aroma released from the withering trough is the result of aroma compounds produced from fatty acids (Takeo and Tsushida, 1980;Tomlins and Mashingaidze, 1997).…”

Section: Lipids and Fatty Acidsmentioning

confidence: 99%

“…Although high chlorophyll presence induces inferior liquor quality, degradation of chlorophyll is recommended by proper withering, but high levels of chlorophyll degradation should be avoided. The conversion of chlorophyll to phaeophytin during fermentation and drying results in the black color of the CTC tea (Dev Choudhury and Bajaj, 1980;Taylor et al, 1992;Tomlins and Mashingaidze, 1997;Sanyal, 2011).…”

Section: Chlorophyllmentioning

confidence: 99%

“…Teas with low levels of caffeine content show inefficient creaming properties (Roberts, 1963;Bhatia, 1964;Dev Choudhury and Bajaj, 1980;Tomlins and Mashingaidze, 1997), and these types of teas do not receive good market value. Normally physically withered leaves show comparatively more caffeine concentration than forced physically withered tea leaves (Senderson and Graham, 1973;Dev Choudhury and Bajaj, 1980;Bhuyan and Mahanta, 1989;Tomlins and Mashingaidze, 1997;Sanyal, 2011). Generally, in tea processing factories during rainy days, the withering process is achieved with the application of hot air, and this makes the tea incapable of showing good creaming liquor.…”

Section: Caffeinementioning

confidence: 99%

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A Review of Withering in the Processing of Black Tea

Deb¹,

Pou²

2016

Journal of Biosystems Engineering

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Purpose: Tea is the most frequently consumed drink worldwide, next to water. About 75% of the total world tea production includes black tea, and withering is one of the major processing steps critical for the quality of black tea. There are two types of tea withering methods: physical and chemical withering. Withering can be achieved by using tat, tunnel, drum, and trough withering systems. Of these, the trough withering system is the most commonly used. This study focuses on the different types of withering, their effect on the various quality attributes of tea, and other aspects of withering methods that affect superior quality tea. Results: During physical withering, tea shoots loose moisture content that drops from approximately 70-80% to 60-70% (wet basis). This leads to increased sap concentration in tea leaf cells, and turgid leaves become flaccid. It also prevents tea shoots from damage during maceration or rolling. During chemical withering, complex chemical compounds break down into simpler ones volatile flavor compounds, amino acids, and simple sugars are formed. Withering increases enzymatic activities as well as the concentration of caffeine. Research indicates that about 15% of chlorophyll degradation occurs during withering. It is also reported that during withering lipids break down into simpler compounds and catechin levels decrease. Improper withering can cause adverse effects on subsequent manufacturing operations, such as maceration, rolling, fermentation, drying, and tea storage. Conclusion: Freshly harvested leaves are conditioned physically and chemically for subsequent processing. There is no specified withering duration, but 14-18 h is generally considered the optimum period. Proper and even withering of tea shoots greatly depends on the standards of plucking, handling, transportation, environmental conditions, time, and temperature. Thus, to ensure consumption of high quality tea, the withering step must be monitored carefully.

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Section: Biochemical Changes During Chemical Witheringmentioning

confidence: 99%

Section: Lipids and Fatty Acidsmentioning

confidence: 99%

Section: Chlorophyllmentioning

confidence: 99%

Section: Caffeinementioning

confidence: 99%

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A Review of Withering in the Processing of Black Tea

Deb¹,

Pou²

2016

Journal of Biosystems Engineering

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“…Black tea is a kind of fully fermented tea and is manufactured in four distinct stages, including withering, rolling, fermentation, and drying (Tomlins and Mashingaidze, 1997). The worldwide popularity of black tea has been attributed to its sensory quality, with particular emphasis on its unique aroma and characteristic flavor.…”

Section: Introductionmentioning

confidence: 99%

Aroma changes of black tea prepared from methyl jasmonate treated tea plants

Shi

Wang²,

et al. 2014

J. Zhejiang Univ. Sci. B

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Methyl jasmonate (MeJA) was widely applied in promoting food quality. Aroma is one of the key indicators in judging the quality of tea. This study examined the effect of exogenous MeJA treatment on tea aroma. The aroma components in black tea prepared from MeJA-treated fresh tea leaves were extracted using headspace solid-phase microextraction (HS-SPME) and were analyzed using gas chromatography-mass spectrometry (GC-MS) and GC-olfactometry (GC-O). Forty-five volatile compounds were identified. The results revealed that the MeJA-treated black tea had higher levels of terpene alcohols and hexenyl esters than the untreated tea. Moreover, several newly components, including copaene, cubenol, and indole, were induced by the MeJA treatment. The activities of polyphenol oxidase and β-glucosidase in fresh tea leaves changed after the MeJA treatment. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis indicated that the gene expression levels of polyphenol oxidase and β-primeverosidase were upregulated by two and three folds, respectively, by the MeJA treatment (P<0.01); however, the gene expression of β-glucosidase was downregulated to a half level. In general, the aroma quality of the MeJAtreated black tea was clearly improved.

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Effect of red light on the composition of metabolites in tea leaves during the withering process using untargeted metabolomics

Lin

Liu

Xiao-fen³

et al. 2021

J Sci Food Agric

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BACKGROUND: Red light withering significantly improves the sensory flavor qualities of tea, although changes in metabolites during this process have not been systematically studied until now. The present study comprehensively analyzes metabolites in withered tea leaves at 2-h intervals up to 12 h under red light (630 nm) and dark conditions using ultra performance liquid chromatography-high resolution mass spectrometry (untargeted metabolomics).RESULTS: Ninety-four non-volatile compounds are identified and relatively quantified, including amino acids, catechins, dimeric catechins, flavonol glycosides, glycosidically-bound volatiles, phenolic acids and nucleosides. The results show that amino acids, catechins and dimeric catechins are most affected by red light treatment. Ten free amino acids, theaflavins and theasinensin A increase after red light irradiation, whereas epigallocatechin gallate and catechin fall.CONCLUSION: The present study provides a comprehensive and systematic profile of the dynamic effects of red light on withering tea and a rationale for its use in tea processing quality control.

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Influence of withering, including leaf handling, on the manufacturing and quality of black teas — a review

Cited by 75 publications

References 32 publications

A Review of Withering in the Processing of Black Tea

A Review of Withering in the Processing of Black Tea

Aroma changes of black tea prepared from methyl jasmonate treated tea plants

Effect of red light on the composition of metabolites in tea leaves during the withering process using untargeted metabolomics

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