Nori making: insights into a staple of Japanese cuisine

Nori, those paperlike sheets of dried seaweed, are popular in Japan as a tasty snack, as well as featuring in sushi and other famous Japanese dishes.  But the stuff doesn’t grow on trees!  Or does it?

Rows of dark rectangles in the water–telltale signs of seaweed farming are portrayed in Hiroshige woodblock prints of the mid 19th century and aerial photos of Tokyo Bay in the early 20th century.  This form of aquaculture was once a major feature of the shallow areas near the western shore of the upper bay–the areas that are now in Tokyo’s Ota and Shinagawa wards.  Cultivation of seaweed and its use to produce nori is said to have begun in Japan in this area around 1670 and continued for nearly 300 years (until land reclamation and the industrialization of the area rendered aquaculture here unviable).  Although nori is no longer produced in Ota ward, it was once the largest producer of nori in Japan.

Most of the seaweed once grown in Tokyo Bay was was a variety of porphyra (Pyropia tenera), which was then either dried whole or pulped and used to produce nori sheets.  Both of these varieties are popular in Japanese cuisine.  Nori sheets can also be made from other types of seaweed, including another porphyra, Pyropia yezoensis, and wakame (Undaria pinnatifida)

The Omori Nori Museum (in Japanese, Nori no furusato-kan 海苔のふるさと館) has some wonderful displays to help visitors learn about the seaweed cultivation and nori production that was once such a key economic activity here.

P. tenera seedlings naturally attach themselves to rocks or hard surfaces underwater.  Traditional seaweed farming leverages this, using posts and dried bamboo branches as anchors for the plants to control where they grow.  Subsequently, technology was developed to attach seedlings to nets and ropes, boosting production.

The museum displays include examples of the bamboo branches and a diarama showing the use of the branches.  Right at the museum’s front door is a pot in which is growing the kind of reed-like bamboo used.

Currently the museum also has a special exhibit relating to the mid-20th century history of aquaculture (through April 14, 2019), including the professional journals and texts used by seaweed farmers to help them improve production.  This was a time when demand for seaweed products had risen so steeply that supply struggled to meet it, making these documents particularly important.  While most non-Japanese visitors will not be able to read them, the ways in which the documents are organized, printed, illustrated, and bound provide insights into the broader culture of the time.

Twice a month the Omori Nori Museum hosts nori making workshops at which participants can learning more about where nori comes from and have a hands on experience of how it is made.  Participation is free of charge (reservations required–see details at the end).  Each participant gets to make two sheets of nori.

At the beginning of the workshop, participants are asked if they can return in a couple of days to pick up their fully dried nori.  If doing so is inconvenient, participants pay JPY120 and self-address an envelope so their nori can be mailed to them.  Each participant is also asked to write their name and participant number on two labels that they attach by wires to a bamboo or plastic mat similar to the ones used to roll sushi.  These are the mats on which the nori is dried.

When all of this preliminary work is completed, the workshop began with a short explanation of nori’s history and an outline of the growing season and nori production cycle.  Nourished by river sediments and other nutrients found in sea water, porphyras grow through the warm summer months, tended by seaweed farmers.

While much of the crop tending and harvesting is done from small boats, sometimes the farmers need to get into the water to do their work.  In this case, special “platform geta” are used, often weighted with rocks tied to the bottoms.

Harvesting begins once cold weather sets in.

Since nori production requires freshly harvested seaweed, this means the prime nori production season is also the cold winter months.  Yet traditional nori production involves drying the seaweed sheets in fresh air and sunshine.  In order to maximize drying time, the sheets have to have been prepared for drying by sunrise.  This means that much cold, wet work is done in the early morning hours before the sun comes up.

The process begins with fresh seaweed, which must be chopped and minced to a pulp.  Volunteers who are former nori producers explain and demonstrate.  They even let willing participants taste the seaweed before the chopping began.

Using a massive chopping block and some pretty big chopping knives, they commence to chop and mince.

As the chopped pieces get progressively smaller, they used tools with increasing numbers of chopping blades; two, four and more.  Actually, they were just demonstrating the relative efficiency of single blades versus multiple blades.  In fact, the larger tools with multiple blades are more commonly used for commercial production.  (In modern production, of course, machines with multiple blades do this work.)

But the traditional process being demonstrated doesn’t stop with hand chopping.  The hand-pulped sludge is then run through a machine to chop it right down to mush.  In earlier times, this grinder was hand operated, but in modern times, an electric motorized version is used.  The chopped seaweed is put through the machine in small batches with lots of water.  The end product is a mush of seaweed slurry.

Now that the main ingredient of nori is ready, it’s time for all participants to learn just how the nori sheets are produced.

First the experienced volunteers use water to demonstrate the  flick of the wrist necessary to put the seaweed slurry into the form evenly.  The move of a practiced hand was quick and smooth–making it look easy. As each participant also practiced, the phrase “pig on roller skates” came quickly to mind.  It wasn’t as easy as it looked.

Then the volunteer demonstrated with the actual seaweed slurry.  Again, he made it look so easy.

Next it was time for each participant to try things out for real.  Holding the measuring box just so, the slurry is scooped up and poured quickly into the square mold.  The water drains away through the slats of the bamboo or plastic mat, leaving only the solids as a sheet of wet paste.  The square of the mold is lifted away, leave the wet sheet on the mat to be hung out to dry.

Taking turns, each participant got to make two sheets this way.  Hands get covered with bits of chopped seaweed as the slurry is dipped out.  A nearby bucket is used for rinsing off (best to have pack a hankie or small hand towel for this purpose).

The resulting sheets, on their mats, were stacked up to be carried outside to dry in the sun.

Special racks are used to air dry the nori sheets.  Each is made of lightweight pine with hooks positioned for fastening the bamboo mats to the rack.  The volunteers explained how to hook up the mats as well as how to position them.  They stressed that it was important to position the mats to the “outside” and the nori sheets on the “inside”, as the mat side dries slower and therefore needs to be on the side that dries more quickly.

Finally, all the racks were positioned in the sun to allow the nori sheets to dry.

Even once the nori sheets have sun dried, they’re not quite ready for eating.  They still need to be lightly roasted.  Since this last step has to take place letter, a volunteer demonstrated, explaining how to quickly and lightly pass the nori sheets over a heat source (at home a toaster or toaster oven will do).  The sheets will change from nearly black to green.  And then they are ready for eating!

Be sure to take time to walk through the museum itself.  It has some very interesting exhibits.  Although there is little information available in English inside the museum, there is a very good little English pamphlet and a handout sheet explaining the nori-making process that you can get at the reception desk as you enter.  With the help of those documents, the displays are not difficult to understand.

The Omori Nori Museum is a 15 minute walk from Keikyu Heiwajima Station or a 15 minute walk from Ryutsu Center station on the Tokyo Monorail.  It is open daily from 9:00 am to 5:00 pm (closed on the third Monday of the month; third Tuesday if the third Monday is a public holiday).  Admission is free.

Nori making sessions are held twice a month.  To learn the next available date and make a reservation, have a Japanese speaker phone the museum at (03) 5471-0333.

© 2019 Jigsaw-japan.com and Vicki L. Beyer
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