Zest provides a more intense and aromatic citrus flavor compared to juice because it contains the citrus fruit's essential oils.
The zest of a citrus fruit, which is the colored outer layer of the peel, is packed with essential oils. These oils are responsible for the characteristic aroma and flavor of the fruit. When making tea or an infusion, using zest allows you to extract these oils directly into the hot water, resulting in a more potent and fragrant citrus flavor. Juice, while adding some citrus notes, primarily contributes acidity and sweetness. The zest offers a concentrated burst of the fruit's essence without the added liquid volume or potential for sourness that comes with using too much juice. The heat from the water helps to release these oils, maximizing the flavor impact.
When zesting, avoid grating the white pith underneath the colored peel, as it can impart a bitter taste to your tea or infusion. Only zest the outermost layer for the best flavor.