Irreversible Sediment Formation in Green Tea Infusions

Abstract

The formation of irreversible tea sediment (IRS) and its chemical components in green tea infusions were investigated. The results showed that the amounts of IRS in the green tea infusions from various tea cultivars ranged from 0.10 to 1.47 mg/mL. The amount of IRS was influenced remarkably by the chemical components in the green tea infusion. Principal component analysis and regression analysis indicated that gallated catechins, Mn, Ca, caffeine, Na, and (-)-gallocatechin gallate (GCG) were the principal components. IRS (mg/mL) = -4.226 + 0.275 gallated catechins + 79.551 Na + 7.321 Mn + 21.055 Ca + 0.513 caffeine - 0.129 GCG (R2 = 0.697). The contents of the main chemical components in the reversible tea sediment (RTS) and IRS were markedly different, especially the minerals. Large amount of minerals participated in the formation of irreversible green tea sediment. The amount of IRS increased with the extraction temperature.

Stability of co‐crystals of caffeine with gallic acid in presence of coformers

“…A positive value of ΔG portrays that the catechin will not be able to replace gallic acid from the CG co‐crystal. The experiments reveal that catechin neither precipitates out of the solution nor allows the caffeine‐gallic acid co‐crystal to precipitate, because catechin increases the solubility of caffeine and does not allow its precipitation at 300 K. Xu et al () and Chao and Chiang () had shown that the gallated catechins are mostly responsible for tea cream formation as their structures offer more hydroxyl groups for hydrogen bonding, which was thought to be an important force for aggregation of compounds involved in tea cream formation. However, without gallate structure, catechin seem to increase solubility of caffeine in solutions.…”

“…The green tea is prepared with unfermented tea leaves, whereas oolong tea and black tea are prepared using semi‐fermented and fermented tea leaves, respectively. When hot aqueous tea infusion is cooled, solid sediment called “tea cream” precipitates consisting mainly of caffeine, polyphenols, organic acids, and theaflavins (Chao & Chiang, ; Jöbstl, Fairclough, Davies, & Williamson, ; Wickremasinghe & Perera, ; Xu et al, ; Xu, Chen, Yuan, Tang, & Yin, ; Yin, Xu, Yuan, Luo, & Qian, ). The formation of the tea cream depends on temperature, concentration, and chemical composition (Bee, Izzard, Harbron, & Stubbs, ; Jöbstl et al, ; Liang & Xu, ; Xu et al, ; Xu et al, ; Yin et al, ).…”

The major factors influencing the formation of sediments in reconstituted green tea infusion

“…Tea sediment consists of reversible tea sediment (RTS) primarily and irreversible tea sediment (IRS) (Xu et al, 2014). The main chemical composition of RTS is very different from that of IRS, especially the mineral composition (Xu, Chen, Wang, et al, 2012). RTS mainly comprises polyphenols, total sugar, caffeine, flavones and proteins, and IRS consists of oxalates of Ca, Mg, Ga and Mn (Xu et al, 2014).…”

Formation and Characterization of Irreversible Sediment of Ginseng Extract

“…Carbohydrates are the most abundant chemical components in ginseng, followed by protein [9]. Part of the sediment can be reheated and reconstituted into reversible sediment (RS), and the irreversible part is called irreversible sediment (IRS), which is similar to the sediment in green tea [10]. The common phenomenon of turbidity in beverages is a result of polyphenol-protein interactions, which bind noncovalently and are reversible in the early stage of sediment formation [11].…”