What professional tasters are actually doing
Professional tea tasters are running through the same four checks that an experienced buyer does at home: appearance, dry aroma, wet aroma after infusion, and the cup itself. The difference is speed and vocabulary, not the underlying method.
A trained taster can move through ten or fifteen cups in an hour and form a ranking. An experienced home drinker running two or three side-by-side can reach the same conclusions in fifteen minutes. The professional edge comes from pattern recognition across many teas, not from a different process.
The other thing professional tasters do that home drinkers often miss is hold the cup longer. The third and fourth infusions reveal things the first infusion hides, especially for green tea where the early cup can be misleadingly bright.
Running a useful side-by-side at home means using the same water temperature, the same leaf-to-water ratio, and the same steeping time for each tea. Otherwise you are tasting the brewing method, not the leaf.
Appearance and dry leaf
Appearance covers shape, colour, and uniformity. A Longjing should be flat and even, with no broken pieces. A Biluochun should be tightly spiralled, with no loose buds. A Sencha should be needle-shaped or slightly twisted, with a bright green colour.
Colour tells you about the kill-green and the drying. Bright green means a clean kill-green and a controlled drying. Brown or yellow edges mean the kill-green was off. A greyish leaf means the drying was uneven or the storage was humid.
Uniformity tells you about the grade. A premium lot will be 90 to 95 percent uniform in shape and size. A mid-grade lot will be 70 to eighty percent uniform. A bulk lot will accept anything that came off the line.
Broken pieces are not always a defect. A tea bag is by design broken leaf. For loose-leaf premium teas, more than ten percent broken pieces usually means a downgrade.
Aroma before and after infusion
Dry aroma is what you smell when you open the packet, before any water touches the leaf. It tells you about freshness and about the processing. A fresh green tea has a bright, vegetal aroma. A stale green tea has lost most of it.
Tasting 3 to 5 cups per session keeps the palate sharp. Beyond 5, the sensitivity to sweetness drops by roughly 15 to 20 percent.
Wet aroma is what you smell after the first infusion, with the lid off the gaiwan or the leaves spread on a plate. This is where the more complex notes come through. Longjing smells chestnutty. Biluochun smells fruity and floral. Sencha smells grassy and marine.
Comparing dry and wet aromas reveals what the kill-green preserved and what the rolling released. A tea with a dull dry aroma but a clean wet aroma was probably poorly stored before sale but is still good in the cup.
Aroma is also the easiest dimension to fool with added scent. A genuine green tea aroma dissipates within three or four infusions. A scented tea keeps the aroma strong through six or seven.
Taste, mouthfeel, and finish
Taste is the most important dimension and the one home drinkers usually focus on. Three things matter: sweetness, body, and aftertaste. Sweetness is the amino acid content. Body is the polyphenol and dissolved-solid content. Aftertaste is the lingering flavour after you swallow.
Mouthfeel covers the texture of the cup: smoothness, astringency, and any gritty or papery sensation. A clean green tea feels smooth on the tongue. Astringency from tannins is normal but should soften through the cup.
Premium teas from five of the six main producing regions can be reliably distinguished by dry aroma alone once a taster has trained on one hundred reference samples.
Finish is what you taste thirty seconds after you swallow. A good finish is sweet and lingering. A bad finish is dry, bitter, or metallic. The finish tells you how well the leaf was processed and stored.
Comparing the first and third infusions reveals more than comparing the first and second. The first infusion reads the surface. The third infusion reads what is locked in the leaf. A tea that holds up through the third is well-made.
Across a panel of 10 tasters, agreement on appearance alone runs at 80 percent. Agreement on the cup itself runs closer to 95 percent.