How true is it that hojicha is low in caffeine?

Leaf, water, heat and time

Leaf goes into the pot, water over it, and then a short wait. The caffeine figure moves from source to source because this way of brewing differs from figure to figure.

Every published value is a weight per set volume of tea brewed one particular way. Amount of leaf, amount of water, water temperature, steeping time. Only when those four are fixed does a single figure exist.

Those conditions are set separately for each kind of tea. What the sources support is this much: every figure comes with its own way of brewing. After the conditions comes one line of the national table.

Hojicha and sencha, side by side

Run a finger down the national food table and hojicha and sencha carry the same value. They look alike because two separate ways of brewing happened to land in the same place.

Hojicha is brewed with more leaf and more water, for a short time. Sencha uses less of both, and twice as long. The values do not match because the contents resemble each other.

A government Q&A citing another edition of the table keeps the pair level as well. The sources go no further than this: on the table, the two look the same. After the table comes a tea merchant's page.

Two figures, side by side in a shop

Open a packet of bōcha and the dry, toasty smell of stems rises. On a shop's page, a value taken from the table and a value the shop measured itself sit next to each other.

One merchant gives ordinary hojicha the national table's value. Beside it sits its own bōcha, measured by a prefectural research institute, a little lower. Its brewing uses the same ratio of leaf to water as the table; only the water temperature differs.

The page gives its own reason for the lower figure: the main raw material is stem, not leaf. The sources support the shop's stated reason, and no more. After the shop come the table's own editions.

A new line in a new edition

Take an old food table off the shelf and it smells of dry paper. Some figures did move with the editions, and the one that moved is the line for the leaf itself.

A recent supplement added a new row for hojicha leaf. Most explanations in circulation still cite the edition before it. Under the same words, hojicha caffeine, the value for the leaf and the value for the brewed tea are different things.

Where an explanation does not say which edition it cites, the difference cannot be checked. After the editions comes the question of when things were measured.

A gap in the dates

A finger traces the notes beneath the table, slowly. The values for brewed bancha, hojicha and the rest were set from new analysis and from an old edition together.

That old edition came out a long time ago. Which components were carried over from it is written nowhere in the text.

Lining the figures up by when they were measured is not something the current table allows. The figures and conditions are gathered just below. By the time the steam thins over the cup, the usual brew is ready.

The groups brewed the same way

Run a ruler down the table and, here and there, rows share the same brewing column. Figures compare as they stand only inside a group measured the same way.

In the national food table, just two groups share exactly the same conditions. Hojicha's group holds bancha, genmaicha and oolong tea; sencha's holds kamairicha.

In hojicha's group, hojicha and oolong tea sit on the higher side, bancha and genmaicha on the lower. In sencha's group, sencha is the higher. On the table, hojicha is placed on the higher side.

How far that gap can be read depends on the table's precision. After the groups comes how coarse that precision is.

A table with a coarse mesh

The table's figures are cut off at a very shallow decimal place. At that coarseness hojicha cannot be called equal to sencha, nor double bancha.

Sift sand through a coarse sieve and the small differences between grains do not survive. The table, too, gathers nearby figures onto one mark.

What can be written is that, at the table's precision, they cannot be told apart. After the precision comes dividing by the weight of leaf.

Divided by the weight of leaf

A gyokuro cup is small, and a generous heap of leaf goes into it. Per gram of leaf, the wide gap between gyokuro and hojicha all but disappears.

On the table, gyokuro's caffeine looks many times hojicha's. But gyokuro also puts nearly that much more leaf into the same amount of water. Gyokuro comes out strong because it is brewed strong.

The rearranged values are calculated, not printed in the table. After the rearranging comes the value for the leaf itself.

As leaf, the lowest of all

Dry leaf from the packet rustles between the fingers. As a value for the leaf itself, hojicha sits lowest of all.

The new supplement lists values for the leaf as well. Against gyokuro, matcha, black tea, sencha and bancha, hojicha leaf is the lowest. Low as leaf, level with sencha once brewed. Both hold at once.

What cannot be done is divide the leaf value by the infusion value to see how much came out. The national table does not say the two were measured on the same sample. The figures and conditions are gathered just below. The leaf on the scale goes back to the usual pinch, and into the pot.

No daily limit has been set

The calendar on the kitchen wall is crowded with the child's plans. For caffeine, no upper limit on a safe daily amount has been set.

The national food safety body writes that sensitivity varies greatly between people, which makes the effects on health hard to assess accurately. The health ministry, too, says that largely because of those differences none is set, at home or internationally. The absence does not mean the question was never studied; it means the answer will not sit in one number.

What can be said here goes as far as roughly how much is in one cup. How many cups is not decided in these pages. In place of a limit, what is introduced are the figures of overseas bodies.

A day's total, not a cup's

A tin of coffee and a box of black-tea bags stand on the same shelf. The overseas figures introduced on the ministry pages are amounts taken in across a whole day, from all food and drink.

The figures are set separately for each body and each group of people. None is a national standard; each is introduced as an overseas body's value. Coffee, black tea, soft drinks and medicines containing caffeine all count within the same day.

The adult figures are amounts per day; the children's are per unit of body weight. The units differ, so one cannot serve as a guide for the other.

The consumer agency's page adds that going over the figure does not necessarily mean harm to health. After the daytime comes the cup at night.

One assessment, before bed

At night, a thin thread of steam rises straight from the cup. For the night, only one assessment is introduced.

A hundred milligrams taken in one go just before bed may disturb sleep in some adults, it says. It is an overseas body's assessment, introduced in a national committee's factsheet.

The sources go as far as this single assessment. After the figures comes the cup in hand.

How much in one cup

The usual cup comes out of the cupboard and sits in the palm. The amount in it is the strength of the tea multiplied by the size of the cup.

For hojicha brewed the way the national table brews it, divide the cup's millilitres by five to get milligrams. A bigger cup holds more. With more leaf in the same water, the real cup comes out higher than this.

Whether brewing it weaker brings it down is not covered by any public data measured on hojicha. That brewing can adjust it cannot be written from the material at hand. Pregnancy, children and the cup before bed each have a piece of their own: hojicha in pregnancy and breastfeeding, hojicha for kids and hojicha before bed. The figures and conditions are gathered just below. The flask lid clicks shut, a small sound in the kitchen.

Roasted deep, a little less

As the roaster's drum turns, a thin, toasty smoke drifts out. Within the published trials, roasting does not cut caffeine by much.

In a prefectural tea station's report, the light roast barely fell at all. The dark roast came out a few per cent to just over a tenth lower than before roasting.

What caused that fall, though, cannot be read out of the report. Next comes what the trial actually recorded.

Air and rotation, recorded

Hot air blows out of the roaster's mouth. What was recorded is the temperature of that outgoing air and the speed of the drum, nothing more.

The roasting ran in two stages, and the air at the second stage was the same for light and dark. What separated them was the drum's speed. The slower it turns, the longer the leaf stays inside.

How hot the leaf itself became is written nowhere. After the air comes a record from higher temperatures.

High heat inside an oven

Open an oven door and dry heat meets the face. Even an old record of longer heating at higher temperatures shows caffeine barely changing.

In a report that heated unrefined green tea in a constant-temperature oven, amino acids, vitamin C and sugars fell sharply. Caffeine, by contrast, hardly differed, the text says.

But the air leaving a roaster and the inside of an oven are measured in different places. The two records do not sit on one ruler. Next comes the band of real roasting temperatures.

A band still left open

Where bōcha is roasted, the inside of the drum runs far hotter. No public data has measured caffeine in that band.

An experiment roasting bōcha in a drum set the inner surface to around two hundred degrees, on manufacturers' advice. No public data measuring caffeine at those temperatures turned up in this search.

The sublimation temperature so often quoted is not in the official chemistry database either. The sources go as far as this: the band is still open. Next come stems before roasting, and coffee.

Stems, and coffee's split answer

Shake a packet of kukicha and the thin stems rustle. Unroasted stem tea looks lower than leaf, but the figure was not a like-for-like comparison of leaf and stem.

In the same station's table, unroasted stem tea came to about three quarters of first-flush tea. That table, though, adds one line for stems to a run of tea seasons; it was not built to compare leaf with stem.

For coffee, the same question splits. One study found the darker roast lower with brewing held level, and higher with extraction yield held level. Raw material and brewing differ, so it cannot be carried across to hojicha. Only the shape is shared: change what is held steady, and the answer changes.

Last comes where the missing part went.

Where the missing part went

Spread the roasted leaf on a sieve and fine dust gathers underneath. Where the part lost at the dark roast went is still not known.

Broken down by heat, or crumbled and lost as dust: the report does not say. Through the roasting, it was caffeine that stayed largely still. The other compounds that do move are taken one at a time in the pieces on roast depth.

On the mechanism, the sources go this far and no further. The figures and trial conditions are gathered just below. The leaf on the sieve is still faintly warm.