A cup of hojicha is set down, and the steam carries the smell of roasting. The colour of the tea is a warm brown. It looks like it should taste strong, yet the first sip is light. That gap between look and taste is where hojicha begins.

To follow that gap, the steam is the place to start.

Steam that smells of roasting

Bring the cup close and the steam rises past the nose. Hojicha's aroma gathers into three bundles: toasty, sweet and green.

Japanese aroma research diluted hojicha's aroma step by step to rank which compounds can still be smelled. In the leaf, a toasty compound and a sweet one shared the top step. Most of the toasty and sweet compounds were confirmed as formed by heat.

Those green compounds are also found in green tea; whether heat forms them is not known. The aroma research is taken further in Hojicha aroma compounds: toasty, sweet and green. After the nose comes the mouth.

Light in the mouth

The first sip spreads warm and thin across the tongue. Hojicha's taste is light, with almost no astringency or bitterness.

Public tea guides describe hojicha in just those terms, with a distinctive toasty aroma and a smooth feel. Green tea is described the other way, with moderate astringency and a fresh, grassy aroma. The difference was made by fire.

How taste and smell blend in the mouth has been studied mostly outside tea. What fire took away is next.

What the fire took away

Roasted leaves in the pan turn from green to brown within minutes. Roasting takes away much of the umami and astringency the leaf began with.

When autumn leaves lose their green, the yellow hidden beneath comes through. In roasted tea leaves, too, the umami fades and the aroma of fire comes forward. In a prefectural trial, the main umami amino acid fell sharply with a light roast and could not be detected at deeper roasts. Astringent catechins fell to about a fifth in a dark roast.

That is why the brown cup tastes lighter than its colour suggests. The sources go as far as the direction of those changes. What research has and has not tested is set out in Is hojicha less bitter?.

Light roast and dark roast in the cup

Two bags stand on the shelf, one pale brown, one nearly russet. Deeper roasting does not always mean a more toasty aroma.

In the same prefectural trial, the toasty pyrazines used as markers were highest in the light roast. Colour turned redder and astringency fell as the roast deepened. Shops each draw their own line between light and dark.

That is as far as the record goes: how a few markers move with depth. The full comparison is in Light vs dark roast hojicha: colour, aroma, taste, brewing. The figures and sources follow below.

The numbers in detail

Leaf aroma
Mizukami's 2012 report (Tea Research Journal 113) measured hojicha made from stems separated during sencha finishing. Fifty compounds carried a dilution factor, and the top step went to 2-ethyl-3,5-dimethylpyrazine and furaneol.
Steam and infusion
The companion report in Tea Research Journal 114 found 36 compounds with a dilution factor in the steam and 42 in the infusion. Toasty and sweet notes were strongest, green next. The toasty and sweet compounds are confirmed as formed by heat, with three exceptions. The green compounds are also found in green tea, but whether heating forms them is unknown, the paper says.
Strongest in hojicha
Tan and colleagues (2019) extracted and compared the aroma of sencha, matcha, gyokuro and hojicha by the same methods. According to the abstract, the hojicha odourants with the highest dilution factors were 2,3-diethylpyrazine (729) and 2,3-diethyl-5-methylpyrazine (243). In sensory tests, hojicha showed stronger roasty and woody notes.
Taste descriptions
Hojicha's “distinctive toasty aroma, with almost no astringency or bitterness” and sencha's “moderate astringency and fresh green aroma” come from MAFF (aff, April 2022). MAFF's “Ways to enjoy Japanese tea” describes hojicha's “light, clean finish”.
Umami
In the Kochi Agricultural Research Center Tea Experiment Station report (2013 data), theanine in first-flush tea fell from 21.12 mg in the unroasted tea to 1.27 mg in the light roast. It was not detected in the medium and dark roasts. Values are per 100 mL of liquid from 1.9 g of leaf in 200 mL of boiling water for 5 minutes.
Catechins
In the same report, catechins in the dark-roasted first-flush tea were about a fifth of the unroasted tea.
Pyrazines
The two pyrazines used as markers of roasted aroma were highest in the light roast for first-flush and autumn-cut tea, in the same report.