When we indulge in the ritual of drinking tea, the experience often begins with the sharp bitterness of the tea leaves.

Yet, as the tea liquid traverses the mouth and throat, a subtle sweetness emerges, growing more pronounced with each sip—a phenomenon aptly termed "returning to sweetness."

Different types of tea exhibit distinct patterns of returning sweetness, with some teas revealing their sweetness swiftly, while others unfurl it gradually, lingering on the palate for an extended duration, and some offer only a fleeting moment of sweetness.

The underlying reason for the sweetness of tea leaves is multifaceted, primarily stemming from the intricate interplay of tea polyphenols, amino acids, flavonoids, organic acids, sugars, and other compounds found in tea.

The aftertaste effect, characterized by a delicate balance of bitterness and sweetness, emerges as a nuanced flavor profile. Initially, bitterness dominates the palate, but over time, sweetness begins to prevail, resulting in a lingering, pleasant aftertaste.

This sensory experience is often described as "slightly bitter at first, but ending with a sweet and refreshing note." Many tea enthusiasts are drawn to this dynamic flavor transition from bitterness to sweetness.

Tea polyphenols, present in tea, possess the ability to bind with proteins, forming a protective membrane in the oral cavity. This membrane triggers a bitter sensation upon contact with the taste buds, creating the perception of initial bitterness upon consuming freshly brewed tea.

However, when the concentration of tea polyphenols is balanced, forming a thin membrane, the initial astringency gradually gives way to sweetness as the membrane dissipates, eliciting salivation and a return to sweetness. In essence, the interaction between tea polyphenols and proteins transforms bitterness into sweetness.

The perception of sweetness and bitterness is relative. When tasting sweet substances like sucrose, water may seem slightly bitter, while bitter compounds such as caffeine or quinine can impart a subtle sweetness to water. This phenomenon underscores the contextual nature of taste perception.

The phenomenon of returning to sweetness is a sensory illusion induced by the initial bitterness of tea. Although the exact mechanism behind this phenomenon remains a subject of debate in the academic community, its mysterious and complex nature adds to the allure and beauty of tea.

Tea polyphenols constitute a significant portion—ranging from 18% to 36%—of the composition of fresh tea leaves, imparting a bitter and astringent taste. This characteristic underscores the adage that "tea without bitterness or astringency is not a true tea."

Notably, research indicates a positive correlation between tea polyphenol content and the intensity of the tea's aftertaste, with some teas boasting stronger bitterness and aftertaste profiles. Tea polyphenols serve as the conduit for these contrasting taste experiences, intertwining bitterness and aftertaste in a symbiotic relationship.

However, the aftertaste alone cannot serve as an absolute criterion for discerning the quality of tea, as taste sensitivity and tolerance to bitterness vary among individuals. Moreover, some lower-quality teas may exhibit a pronounced bitterness, resulting in a more robust aftertaste.

Therefore, while the strength and persistence of a tea's aftertaste are indicative of its quality, they are but one aspect to consider in evaluating tea excellence.