Nishio “Gokou” tencha: nitrogen assimilation and the green core of aroma
Grown on Aichi's flat tea fields, Gokou takes on a distinctive flower-pistil-like aroma when, after shading, the steaming step heats the leaf evenly to its core. We read the correspondence between its amino-acid profile and volatile compounds from the angles of tasting and headspace analysis.
Gokou is sometimes called a gift of nitrogen assimilation, but the way heat enters during post-shading steaming — reaching all the way to the core — is the key to drawing out its flower-pistil-like aroma. On Nishio's flatlands, the rhythm of morning dew and midday drying evens out the leaf's moisture content, making it easier to suppress aroma loss during post-steaming drying.
In tasting, even within the same Gokou, lots steamed for a long time have a closed aroma, while short, high-heat lots push the top notes too far forward. Without evaluating them alongside the tencha particle size, a label's individuality won't come into view.