Spontaneously Assembled Nano-aggregates in Clear Green Tea Infusions from Camellia ptilophylla and Camellia sinensis

Abstract

Tea nano-aggregates spontaneously assembled in clear tea infusions are considered as the precursors of tea cream, although their molecular basis remains obscure. Here, we characterized nano-aggregates in green tea infusions from Camellia ptilophylla, a peculiar tea variety with 6.0% of theobromine, and Camellia sinensis as the control for comparative purpose. Numerous negatively charged spherical colloidal particles of 50-100 nm in diameter were primarily found in both green tea infusions. Catechins, proteins, and carbohydrates were confirmed as the dominant components in green tea nano-aggregates. In addition, iron, copper, nickel, proteins, and gallated catechins exhibited higher aggregating affinity than other components, whereas methylxanthines and calcium contributed to the transformation of nano-aggregates into tea cream. Green tea nano-aggregates were partly destroyed by simulated gastrointestinal digestion, and removing theses peculiar particles dramatically attenuated the bioaccessibility of methylxanthines, theanine, and some catechin monomers in green tea infusions. This study enhanced our knowledge of molecular interactions in the formation of green tea cream and provided insight into physicochemical profiles, phytochemical nature, and functional effects of green tea nano-aggregates.

Nanoparticles Isolated From Porcine Bone Soup Ameliorated Dextran Sulfate Sodium-Induced Colitis and Regulated Gut Microbiota in Mice

“…For instance, the proteoglycan–lipid NPs with an average diameter of 50–67 nm were generated during the heating processing of Freshwater Clams ( Corbicula fluminea Muller) soup ( 12 ). Numerous spherical NPs were found in green tea infusions ( 13 ). A large number of self-assembly micro/nanoparticles containing docosahexaenoic acid (DHA) and eicosatetraenoic acid (EPA) have been observed in bigeye tuna ( Thunnus obesus ) head soup ( 14 ).…”

Effects of Tea-Polysaccharide Conjugates and Metal Ions on Precipitate Formation by Epigallocatechin Gallate and Caffeine, the Key Components of Green Tea Infusion

“…To date, several studies have reported on the precipitation of tea infusions, and although the majority of them are focused on analysis of the chemical constitution of the precipitate, − a few study the effects of different tea cultivars, extraction methods (time, temperature, and pH) and storage conditions (temperature and duration) on the components and amount of precipitate. − Generally, green tea infusion precipitate is a negatively charged spherical nanoaggregate with a D H distribution of 106 to 2305 nm and diameters of 50 to 100 nm. − The aggregates have an average zeta-potential value of −14.7 ± 0.3 mV. − The components of the green tea infusion that precipitate include catechins, caffeine, carbohydrates, proteins, amino acids (theanine, aspartic acid, and glutamic acid), and metal ions (Ca 2+ , K + , Mg 2+ , Mn 2+ , Na + , Zn 2+ , and Al 3+ ). Of those, polyphenols (29.86–78.66%), total saccharides (14.47–27.62%), and caffeine (2.35–10.43%) were found to be the dominant components in green tea cream. , In particular, catechins, which are the main components in tea polyphenols (TP), reached a percentage of 12.8–42.5%.…”

Relationship between the turbidity difference and the grade of green tea under Ca2+ acceleration: A preliminary study

“…With the trend of cold brew (Liu et al, 2017 ; Song et al, 2021 ) on the rise, consumers generally use boiling water to brew green tea. The brewing temperature affects the concentration of the components, such as caffeine (Liu et al, 2017 ), in the tea infusion, as well as the aroma and taste of the tea infusion. When a green tea infusion is stood for certain days, the brewing temperature has no effect on its turbidity, as shown in Figure 1 .…”

“…Previous studies have confirmed that caffeine and ester catechins were the principal constituents of green tea cream (Xu & Yin, 2010 ). Amino acids also participated in the formation of tea cream (Lin et al, 2017 ; Xu & Yin, 2010 ), thus, the product of catechin contents and amino acid contents, as well as the product of the ester catechin contents and amino acid contents could be used to distinguish between different grades of the same kind of green tea.…”