Uncovering the formation of black tea cream: Focusing on the self-assembly process of infusion nanoparticles with different brewing times

Focusing on the self-assembly process of black tea infusion nanoparticles helps elucidate the formation mechanism of tea cream. Brewing times ranging from 1 to 10 min were systematically assessed in this study, and the release pattern of the major components of the tea infusion was followed and related to the dynamic changes of the components of the black tea cream. The mean particle size of nanoparticles in the black tea infusion gradually increased with increasing brewing time, reaching a maximum (269.84 ± 11.25 nm) at 300 s. The results showed that soluble sugars were the most abundant substances of the tea cream at 60 s, and the proportion changed very little during the process. Proteins and flavonoids were rapidly incorporated into the tea cream, maintaining a concentration trend in accordance with the tea infusion. The percentages of caffeine, theobromine, gallic acid, and catechins in tea cream showed a sudden decrease at 240 s, followed by a gradual increase. This formation of tea cream is pH-dependent, with aggregation and precipitation at pH 0–7 and increased dissociation at pH 7–11. The findings will facilitate a more profound comprehension of the formation mechanism of black tea cream.