Studies on the Viscosity of Tea Extracts. part I.

Okada, Fumio; Furuya, Kôzô

doi:10.3136/nskkk1962.12.267

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“…Additionally, WSP is proposed to contribute to the viscosity of infused tea. Okada and Furuya (1965) reported that the viscosity of tea extracts might be associated with the alcohol precipitation characteristics of tea extracts. Moreover, these characteristics are thought to be correlated with the MW of WSP in tea extracts.…”

Section: Resultsmentioning

confidence: 99%

Dynamics of Water-soluble Pectin during Unrefined Tea Processing: Content and Molecular Weight Distribution

Hirono¹

2016

FSTR

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We examined the dynamics of water-soluble pectin (WSP), specifically the content and molecular weight distribution, in tea leaves and tea infusions in relation to steaming time during unrefined tea processing. It was revealed that the fraction of higher-molecular weight (MW) WSP in tea leaves was infused at the beginning of unrefined tea processing at all steaming times, and lower-MW WSP was not infused during any processing steps.Moreover, by increasing steaming time, the increase of higher-MW WSP content in tea leaves was reflected by the increase in WSP content of corresponding size in the tea infusions.Keywords: water-soluble pectin, molecular weight, unrefined tea processing, steaming time IntroductionWater-soluble pectin (WSP) is contained in tea leaves at less than 1.5% (dry weight) (Takayanagi et al., 1987a;Matsuo et al., 2012;Hirono and Uesugi, 2014). It has been shown that the WSP content in both tea leaves and tea infusions alters significantly with steaming time, in contrast to catechins, caffeine and amino acids, the main components of tea (Takayanagi et al., 1987a, b;Matsuo et al., 2012).We recently clarified that when tea leaves were steamed, pectin fractions with a molecular weight (MW) of 1,100 × 10 3 were degraded from water-insoluble pectin and eluted as WSP, resulting in increased WSP content of the steamed tea leaves. Additionally, the longer the steaming time, the greater the degradation of WSP (Hirono and Uesugi, 2014).Green teas are popular beverages that are composed of the infusions of refined tea leaves. Unrefined teas, which possess the fundamental quality of teas and are the base of refined teas, are typically manufactured using drying and rolling processes after the initial steaming process. Therefore, it was necessary to reveal the transition of WSP during the unrefined tea manufacturing processes and the leachability of WSP in tea infusions in order to clarify the properties of WSP in unrefined teas. In this paper, we investigated the dynamics of WSP in both tea leaves and tea infusions, in terms of content and molecular weight distribution, in relation to the duration of unrefined tea steam processing. 60 or 120 seconds using a SD-500 steaming machine (Terada Seisakusho Co., Ltd., Shimada, Japan), and then manufactured into unrefined teas. After the initial steaming process, unrefined tea processing proceeded sequentially from primary drying, tea rolling, secondary drying, to the final rolling; which were all conducted using tea manufacturing machines specified for 2 kg of production (Kawasaki Kiko Co., Ltd., Kakegawa, Japan). For analysis, a small amount of tea leaves from each step in the process was removed and dried to about 5% moisture content using a circulation dryer at 40℃. Manufacturing of each unrefined tea according to steaming H. Hirono 298 time was performed in triplicate. Materials and Methods Preparation of tea leaves Determination of WSP content in tea leaves Dried tea leaveswere powdered using a ZM200 cyclone sample mill (Retsch GmbH, Haan, Germany). Preparation ...

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Section: Resultsmentioning

confidence: 99%

Dynamics of Water-soluble Pectin during Unrefined Tea Processing: Content and Molecular Weight Distribution

Hirono¹

2016

FSTR

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“…This suggests that unrefined teas in the fall-winter crop season are susceptible to β-elimination reaction, and HSP was converted from the hydrochloric acid-insoluble form. Okada and Furuya (1965) reported that the alcohol precipitation It is known that the flavor component in 'sen cha' is affected Roasting time was 3 s after reaching each temperature. Crop seasons were first, second, and fall-winter (i, ii, and iii, respectively).…”

Section: Resultsmentioning

confidence: 99%

Dynamics of Water-soluble Pectin in the Roasting Process during Green Tea Manufacturing

Hirono

Mizukami

2018

FSTR

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We examined changes in water-soluble pectin (WSP) and dilute hydrochloric acid soluble pectin (HSP) contents of tea leaves, and pectin content of tea infusions in the roasting process during refined tea manufacturing by crop season. In all crop seasons, WSP content in tea leaves increased with roasting temperature. HSP content was almost constant or increased with roasting temperature by crop season. Changes in pectin content of tea infusions by roasting temperature were proportional to or lagged slightly behind WSP content changes of tea leaves in all crop seasons. In all crop seasons, the molecular weight (MW) distribution of both WSP in tea leaves and pectin in tea infusions was biased toward the lower-MW range with increasing roasting temperature. In parallel, major peaks in the MW distribution of pectin in tea infusions shifted to the lower-MW range in all crop seasons. It was postulated that β-elimination degradation was involved in WSP production from water-insoluble forms of pectin in HSP and the degradation of WSP itself during the roasting process.

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Studies on the Viscosity of Tea Extracts. part I.

Cited by 2 publications

References 0 publications

Dynamics of Water-soluble Pectin during Unrefined Tea Processing: Content and Molecular Weight Distribution

Dynamics of Water-soluble Pectin during Unrefined Tea Processing: Content and Molecular Weight Distribution

Dynamics of Water-soluble Pectin in the Roasting Process during Green Tea Manufacturing

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